I'm now starting to think about the v1.3 firmware, which is intended to add the following: Log charge history Log drive history Sophisticated control of charge time We don't really have TOU metering in Hong Kong, so not much use for me, but part [3] would be fun nevertheless. Most charge control in EVs is pretty basic, and it might be interesting to see how sophisticated this can be made without complications. I don't know if this is workable or not, so put my thoughts out into the open for discussion. For charge time, the consensus seems to be that people want to enter the time to FINISH charge, vs the current time to START charge. To do that, we need an estimate of how long the charge will take. For that, we either need a sophisticated model or a collection of historical data we can lookup to find something approximate. Hence item [1] on my list. Elon talked about the car learning about you. Where you park. Where you charge. etc. So, if always leave home at 7:00am to go to the office on Mondays through Fridays, perhaps the car can learn? Or, at least suggest based on what it has seen... Hence item [2] on my list. For [1], we would store such things as temperatures, SOC start, SOC end, charge mode, charge current, charge voltage and duration. The can bus charge message seem to include this information. For [2], we would store such things as date/time of drive, duration (time, distance, and elevation change), battery usage. We seem limited in this from what we have decoded on the can bus so far. Regardless of the above, [1] and [2] would be useful information for any owner, anyway. Privacy is an issue. Two problems - (a) protection of my charge/drive history, (b) the use of 'shared' charge history for [3]. My suggestion is to keep drive and charge history private. Perhaps it could just be stored as paranoid mode blobs. But, there should be an option to allow anonymised sharing of charge history for the use of [3]. My thinking is that if you share your data anonymously, then your lookup includes the pool of others anonymous charge history. if you choose not to share, then your lookup is only against your own charge history. I did toy with the idea of using the server to control this. So, at 3am the server sends a command to the car to start the charge, etc. That would simplify the firmware in the car, but has a major problem of GPRS connectivity - if the cellular signal was lost the charge wouldn't start. Bad. So, I think it best to have the historical database in the server, the calculations in the App, and the settings downloaded to the car while it has cellular signal (after which it just follows them autonomously). The Tesla Roadster currently offers you a choice of charge on plug-in, or start charge at a particular time. It also allows you to limit charge current and set charge mode. My thinking is to extend this by making it per day-of-the-week for a few defined locations, and to provide an override for the 'current' day/night. If the override is not set, and you are in one of the defined locations, then the system looks up the day of the week and controls charge based on what you have set. The UI for this is quite simple - presumably a screen with tabs/selector for day or the week, and then controls to set charge mode, current limit, and time to start/complete by. One developer also had the good idea that a charge SOC limit would be useful (e.g.; please stop charge when it gets to 70% / 220km ideal). How do we handle night vs day charging? Is this only for overnight, or do we base it on when you plugin? Is this workable? Useful? Really interested in people's feedback on this. Mark.
Great idea. I'm just an end user but for #7: Could you have a backup setting that if the car is plugged in and if the charge is less than a set % SOC, but there is no signal, that it defaults to a standard user defined charge time? Dave On Apr 5, 2012, at 6:45 AM, Mark Webb-Johnson wrote:
I'm now starting to think about the v1.3 firmware, which is intended to add the following:
Log charge history Log drive history Sophisticated control of charge time
We don't really have TOU metering in Hong Kong, so not much use for me, but part [3] would be fun nevertheless. Most charge control in EVs is pretty basic, and it might be interesting to see how sophisticated this can be made without complications.
I don't know if this is workable or not, so put my thoughts out into the open for discussion.
For charge time, the consensus seems to be that people want to enter the time to FINISH charge, vs the current time to START charge. To do that, we need an estimate of how long the charge will take. For that, we either need a sophisticated model or a collection of historical data we can lookup to find something approximate. Hence item [1] on my list.
Elon talked about the car learning about you. Where you park. Where you charge. etc. So, if always leave home at 7:00am to go to the office on Mondays through Fridays, perhaps the car can learn? Or, at least suggest based on what it has seen... Hence item [2] on my list.
For [1], we would store such things as temperatures, SOC start, SOC end, charge mode, charge current, charge voltage and duration. The can bus charge message seem to include this information.
For [2], we would store such things as date/time of drive, duration (time, distance, and elevation change), battery usage. We seem limited in this from what we have decoded on the can bus so far.
Regardless of the above, [1] and [2] would be useful information for any owner, anyway.
Privacy is an issue. Two problems - (a) protection of my charge/drive history, (b) the use of 'shared' charge history for [3]. My suggestion is to keep drive and charge history private. Perhaps it could just be stored as paranoid mode blobs. But, there should be an option to allow anonymised sharing of charge history for the use of [3]. My thinking is that if you share your data anonymously, then your lookup includes the pool of others anonymous charge history. if you choose not to share, then your lookup is only against your own charge history.
I did toy with the idea of using the server to control this. So, at 3am the server sends a command to the car to start the charge, etc. That would simplify the firmware in the car, but has a major problem of GPRS connectivity - if the cellular signal was lost the charge wouldn't start. Bad. So, I think it best to have the historical database in the server, the calculations in the App, and the settings downloaded to the car while it has cellular signal (after which it just follows them autonomously).
The Tesla Roadster currently offers you a choice of charge on plug-in, or start charge at a particular time. It also allows you to limit charge current and set charge mode. My thinking is to extend this by making it per day-of-the-week for a few defined locations, and to provide an override for the 'current' day/night. If the override is not set, and you are in one of the defined locations, then the system looks up the day of the week and controls charge based on what you have set. The UI for this is quite simple - presumably a screen with tabs/selector for day or the week, and then controls to set charge mode, current limit, and time to start/complete by. One developer also had the good idea that a charge SOC limit would be useful (e.g.; please stop charge when it gets to 70% / 220km ideal).
How do we handle night vs day charging? Is this only for overnight, or do we base it on when you plugin?
Is this workable? Useful?
Really interested in people's feedback on this.
Mark.
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David, I think the balance would be ok if we do all the UI and calculations in the App. Then have the server as a data repository (while capability to get a query like 'I need to charge at 29celcius range mode SOC from 30% to 80% at 220v up to 70amp' and get back an approximate charge duration (based on similar charges the server has sen). The car firmware would just have a lookup table to follow and would issue the appropriate commands at the appropriate times. I kind of like the idea that when the car sees park in its defined location, it sends the commands to the VDS to arrange charging. For example, say it needs 3 hours and you scheduled to leave by 7am, when you plug in the VDS will say 'Charging at 4:00am'. That said, I'm not sure if we can do it that way, but it seems the neatest. This can always be overridden in the car by hitting the "Charge Now" button on the VDS. That said, the firmware should have fallback arrangements. It can also try to alert if it can't do what it is told (for example, the car is not plugged in, but it is in a location where it should be). Regards, Mark. On 5 Apr, 2012, at 7:56 PM, David Morse wrote:
Great idea. I'm just an end user but
for #7: Could you have a backup setting that if the car is plugged in and if the charge is less than a set % SOC, but there is no signal, that it defaults to a standard user defined charge time?
Dave
On Apr 5, 2012, at 6:45 AM, Mark Webb-Johnson wrote:
I'm now starting to think about the v1.3 firmware, which is intended to add the following:
Log charge history Log drive history Sophisticated control of charge time
We don't really have TOU metering in Hong Kong, so not much use for me, but part [3] would be fun nevertheless. Most charge control in EVs is pretty basic, and it might be interesting to see how sophisticated this can be made without complications.
I don't know if this is workable or not, so put my thoughts out into the open for discussion.
For charge time, the consensus seems to be that people want to enter the time to FINISH charge, vs the current time to START charge. To do that, we need an estimate of how long the charge will take. For that, we either need a sophisticated model or a collection of historical data we can lookup to find something approximate. Hence item [1] on my list.
Elon talked about the car learning about you. Where you park. Where you charge. etc. So, if always leave home at 7:00am to go to the office on Mondays through Fridays, perhaps the car can learn? Or, at least suggest based on what it has seen... Hence item [2] on my list.
For [1], we would store such things as temperatures, SOC start, SOC end, charge mode, charge current, charge voltage and duration. The can bus charge message seem to include this information.
For [2], we would store such things as date/time of drive, duration (time, distance, and elevation change), battery usage. We seem limited in this from what we have decoded on the can bus so far.
Regardless of the above, [1] and [2] would be useful information for any owner, anyway.
Privacy is an issue. Two problems - (a) protection of my charge/drive history, (b) the use of 'shared' charge history for [3]. My suggestion is to keep drive and charge history private. Perhaps it could just be stored as paranoid mode blobs. But, there should be an option to allow anonymised sharing of charge history for the use of [3]. My thinking is that if you share your data anonymously, then your lookup includes the pool of others anonymous charge history. if you choose not to share, then your lookup is only against your own charge history.
I did toy with the idea of using the server to control this. So, at 3am the server sends a command to the car to start the charge, etc. That would simplify the firmware in the car, but has a major problem of GPRS connectivity - if the cellular signal was lost the charge wouldn't start. Bad. So, I think it best to have the historical database in the server, the calculations in the App, and the settings downloaded to the car while it has cellular signal (after which it just follows them autonomously).
The Tesla Roadster currently offers you a choice of charge on plug-in, or start charge at a particular time. It also allows you to limit charge current and set charge mode. My thinking is to extend this by making it per day-of-the-week for a few defined locations, and to provide an override for the 'current' day/night. If the override is not set, and you are in one of the defined locations, then the system looks up the day of the week and controls charge based on what you have set. The UI for this is quite simple - presumably a screen with tabs/selector for day or the week, and then controls to set charge mode, current limit, and time to start/complete by. One developer also had the good idea that a charge SOC limit would be useful (e.g.; please stop charge when it gets to 70% / 220km ideal).
How do we handle night vs day charging? Is this only for overnight, or do we base it on when you plugin?
Is this workable? Useful?
Really interested in people's feedback on this.
Mark.
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Hi, In response to your points: 1. Setting it based on finish time is what I'd be after, and couldn't you always build in a healthy safety margin so accuracy of only +/- 1 hour might be relatively easy, keeping it simple and getting the function out there, and then building accuracy in later releases. 2. For this to be any use it would have to be very good, but the only place I regularly charge is at home, and location doesn't necessarily mean you have the same charge requirements. Perhaps just a set of saved setups on the app end to choose from would be more useful, and a lot simpler? 3/4/5. It would be great to be able to pull all this data and compare to other cars without fiddling with files and usb sticks. 7. I agree that sounds the best way. 8. Personally I'm not interested in settings based on day of week. It would be nice to be able to specify ideal miles to charge to, and an option to say if it gets to a particular time and you're not fully charged whether to stop or carry on. regards, Tim On 5 Apr 2012, at 12:45, Mark Webb-Johnson wrote:
I'm now starting to think about the v1.3 firmware, which is intended to add the following:
Log charge history Log drive history Sophisticated control of charge time
We don't really have TOU metering in Hong Kong, so not much use for me, but part [3] would be fun nevertheless. Most charge control in EVs is pretty basic, and it might be interesting to see how sophisticated this can be made without complications.
I don't know if this is workable or not, so put my thoughts out into the open for discussion.
For charge time, the consensus seems to be that people want to enter the time to FINISH charge, vs the current time to START charge. To do that, we need an estimate of how long the charge will take. For that, we either need a sophisticated model or a collection of historical data we can lookup to find something approximate. Hence item [1] on my list.
Elon talked about the car learning about you. Where you park. Where you charge. etc. So, if always leave home at 7:00am to go to the office on Mondays through Fridays, perhaps the car can learn? Or, at least suggest based on what it has seen... Hence item [2] on my list.
For [1], we would store such things as temperatures, SOC start, SOC end, charge mode, charge current, charge voltage and duration. The can bus charge message seem to include this information.
For [2], we would store such things as date/time of drive, duration (time, distance, and elevation change), battery usage. We seem limited in this from what we have decoded on the can bus so far.
Regardless of the above, [1] and [2] would be useful information for any owner, anyway.
Privacy is an issue. Two problems - (a) protection of my charge/drive history, (b) the use of 'shared' charge history for [3]. My suggestion is to keep drive and charge history private. Perhaps it could just be stored as paranoid mode blobs. But, there should be an option to allow anonymised sharing of charge history for the use of [3]. My thinking is that if you share your data anonymously, then your lookup includes the pool of others anonymous charge history. if you choose not to share, then your lookup is only against your own charge history.
I did toy with the idea of using the server to control this. So, at 3am the server sends a command to the car to start the charge, etc. That would simplify the firmware in the car, but has a major problem of GPRS connectivity - if the cellular signal was lost the charge wouldn't start. Bad. So, I think it best to have the historical database in the server, the calculations in the App, and the settings downloaded to the car while it has cellular signal (after which it just follows them autonomously).
The Tesla Roadster currently offers you a choice of charge on plug-in, or start charge at a particular time. It also allows you to limit charge current and set charge mode. My thinking is to extend this by making it per day-of-the-week for a few defined locations, and to provide an override for the 'current' day/night. If the override is not set, and you are in one of the defined locations, then the system looks up the day of the week and controls charge based on what you have set. The UI for this is quite simple - presumably a screen with tabs/selector for day or the week, and then controls to set charge mode, current limit, and time to start/complete by. One developer also had the good idea that a charge SOC limit would be useful (e.g.; please stop charge when it gets to 70% / 220km ideal).
How do we handle night vs day charging? Is this only for overnight, or do we base it on when you plugin?
Is this workable? Useful?
Really interested in people's feedback on this.
Mark.
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Mark - those sound like cool features. When I log drives manually, I also record the trip meter energy use, efficiency and drive time numbers. That lets me compare energy from the wall to energy from the battery pack. For charge logging, I log the energy use reported by the car and compare that to the energy use reported by the wall meter so I can see how accurate the car is. I would be great to be able to charge to a lower SOC, since 180 miles of range is just ridiculous for my daily driving. On the other hand, doing that regularly might mess up brick balancing. There's a bunch of info on charge rate here: http://www.saxton.org/tom_saxton/2010/07/tesla-roadster-charging-rates.html I collected that data in early 2010, just before the firmware update that changed how the Roadster calculates battery capacity, which may have also changed charging profiles. All of my data was taken in moderate temperatures, so it needs to be augmented with data on how ambient temperature affects charge rate. Still, I've been using this data to calculate charge times and I do pretty well, both at setting the charge start time to get a range mode charge to end in a certain time window and also to know how long I should charge in the middle of a road trip to maximize charge rate. (For example, if you're at a 70A charging station and your next charge is a 40A outlet, it's a waste of time to keep charging past the point where current tapering is below 40A.) Tom on 4/5/12 4:45 AM, Mark Webb-Johnson wrote:
I'm now starting to think about the v1.3 firmware, which is intended to add the following:
Log charge history Log drive history Sophisticated control of charge time
We don't really have TOU metering in Hong Kong, so not much use for me, but part [3] would be fun nevertheless. Most charge control in EVs is pretty basic, and it might be interesting to see how sophisticated this can be made without complications.
I don't know if this is workable or not, so put my thoughts out into the open for discussion.
For charge time, the consensus seems to be that people want to enter the time to FINISH charge, vs the current time to START charge. To do that, we need an estimate of how long the charge will take. For that, we either need a sophisticated model or a collection of historical data we can lookup to find something approximate. Hence item [1] on my list.
Elon talked about the car learning about you. Where you park. Where you charge. etc. So, if always leave home at 7:00am to go to the office on Mondays through Fridays, perhaps the car can learn? Or, at least suggest based on what it has seen... Hence item [2] on my list.
For [1], we would store such things as temperatures, SOC start, SOC end, charge mode, charge current, charge voltage and duration. The can bus charge message seem to include this information.
For [2], we would store such things as date/time of drive, duration (time, distance, and elevation change), battery usage. We seem limited in this from what we have decoded on the can bus so far.
Regardless of the above, [1] and [2] would be useful information for any owner, anyway.
Privacy is an issue. Two problems - (a) protection of my charge/drive history, (b) the use of 'shared' charge history for [3]. My suggestion is to keep drive and charge history private. Perhaps it could just be stored as paranoid mode blobs. But, there should be an option to allow anonymised sharing of charge history for the use of [3]. My thinking is that if you share your data anonymously, then your lookup includes the pool of others anonymous charge history. if you choose not to share, then your lookup is only against your own charge history.
I did toy with the idea of using the server to control this. So, at 3am the server sends a command to the car to start the charge, etc. That would simplify the firmware in the car, but has a major problem of GPRS connectivity - if the cellular signal was lost the charge wouldn't start. Bad. So, I think it best to have the historical database in the server, the calculations in the App, and the settings downloaded to the car while it has cellular signal (after which it just follows them autonomously).
The Tesla Roadster currently offers you a choice of charge on plug-in, or start charge at a particular time. It also allows you to limit charge current and set charge mode. My thinking is to extend this by making it per day-of-the-week for a few defined locations, and to provide an override for the 'current' day/night. If the override is not set, and you are in one of the defined locations, then the system looks up the day of the week and controls charge based on what you have set. The UI for this is quite simple - presumably a screen with tabs/selector for day or the week, and then controls to set charge mode, current limit, and time to start/complete by. One developer also had the good idea that a charge SOC limit would be useful (e.g.; please stop charge when it gets to 70% / 220km ideal).
How do we handle night vs day charging? Is this only for overnight, or do we base it on when you plugin?
Is this workable? Useful?
Really interested in people's feedback on this.
Mark.
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Bennett Leeds and I have had a discussion off-list (I'm not sure if he is on this list or not), and he brings up a valid point about balancing the pack perhaps not occurring if we cut short the charge with a SOC limit. Looking here: http://www.teslamotorsclub.com/showthread.php/3848-Tesla-Roadster-Battery-Ca... it seems that this approach may be non-optimal. For clarity, let me cut-and-paste the Tesla reply here: For simplicity’s sake, I will refer to all SOC (State Of Charge) numbers as a percentage of a full (100%) charge. I cannot provide exact percentages, as there are many variables which can cause these numbers to vary slightly, however, I will get as close as I can. When plugging in a nearly empty car that is set to Storage mode, the charge will generally stop at around 20%. The car will then settle into its normal Storage mode rhythm, topping up and discharging between 10% and 50% as the car sees fit. Oftentimes it will keep a tighter envelope based on parameters that I am not aware of. Most important to remember is that Storage mode is not intended to be a driving mode. This charge setting is primarily meant to optimize battery life while the car is under storage conditions for two weeks or more. Storage mode does not attempt to balance the pack, and you will cause an imbalance in the pack by driving and charging in this mode regularly. This will penalize you when you do occasionally charge the car fully in the other modes, as you will not have the full range of the car available to you until the car has a chance to balance its battery. Additionally, the car’s range will not be as accurate if driven while in Storage mode vs. having charged it in Standard mode after storing the car, then driving it. Allowing the car to sit plugged in after it has finished charging in Standard mode automatically balances the pack, and it may take a few rounds of this to bring an imbalanced pack back to its full potential after many partial charges. This is one of the major reasons we recommend keeping the car in Standard mode whenever possible. Partial charges in any mode, while not on their own bad for the battery, do not give the car an opportunity to balance its battery, and over time can prevent you from accessing the car’s full range potential. When balanced, Standard mode charges the car to about 87%, with Range and Performance modes getting the car to about 97%. These two percentages are very much affected by the balance between bricks in the battery. An imbalanced pack will not fill up all the way in any mode, nor will it be able to discharge as far. Additionally, the range predictions will not be as accurate. Your voltages are about right. 4.10 volts = full standard mode (187-195 ideal miles) 4.15 volts = full range mode 4.20 volts = maximum of the cells that we never touch As you may know, there is much more to it than just using voltage to calculate range with Lithium batteries. This is something that is incredibly complicated, and not something that I am qualified to discuss in detail, as I do not have the full picture. It is important to remember that SOC is not the only factor in maximizing battery life. For instance most lithium batteries are shipped at around 30-50% SOC in consumer electronics, and part of the reasoning is that they are less susceptible to damage from extreme temperatures at these charge levels. It is also safer to store them at these levels. Part of the benefit of Storage mode is that there is less work required from the HVAC system to keep the batteryhappy and safe, and therefore, less energy is consumed while stored. We chose ~90% as a Standard full charge level because it offers most of the longevity benefit of keeping the car at a lower state of charge, while still allowing a high degree of autonomy. I understand that you are interested in taking extra steps to maximize your battery’s life, so I do have some suggestions for you. I would not recommend that you continue to use Storage mode as a means of maintaining a lower state of charge. As I explained earlier, this mode is not optimized for this type of use. Think of battery degradation this way. It is very much a function of time spent at voltage and temperature. For instance, you do not want to charge a car all the way in performance mode, and then let it sit in the sun all day. Between the higher thermal limits and the high SOC, you are causing the battery a relatively high amount of degradation .In fact, the car will eventually allow itself to discharge to Standard levels if left in Performance mode to prevent inadvertent damage to the battery. If you start driving right away after charging in Performance or Range Mode, and don’t let it sit, you would minimize the damage incurred, as the time spent at these extremes is an important part of the calculation. Similarly, if you top off to full in Standard mode, then jump in the car right away and bring the SOC down quickly, you will minimize the small amount of degradation that occurs at ~90%. If you prefer to keep a lower average SOC in an attempt to maximize the life of your battery, I would instead suggest that you stay in Standard mode and utilize the Roadster’s built in charge timer and current limiting options to find an average SOC that works for you. For instance, try starting your charge at a time that allows the car to top off to a level you are comfortable with right before you need to leave. Alternately, you can use the Current limiting function to adjust the amount of time it takes the car reaches a target SOC, or even a combination of these two options. The car will remember the settings you select based on your location, so once you find something that works for your commute, you can set it and forget it. Just remember that the car does benefit from being allowed to sit fully charged in Standard mode, and should be allowed to do so frequently, especially if being used on a daily basis. Leaving the car plugged in in Standard mode after it is done charging will initiate this balancing program automatically. This doesn’t take much time, 30 minutes or so should do. It may take several of these balancing cycles to bring the car back to a balanced state if it has become imbalanced, which is something that a lack of regular Standard mode top ups and subsequent balancing cycles can induce. It would therefore be a good idea to set the car to “Charge on Plug In” instead of “Charge at X time” in the charge timing menu for at least a few Standard mode charges per week to keep the pack balanced. There are simply too many variables for me to be able to predict how often you would need to do this, and we do not have a recommended procedure for alternate desired average SOC levels. I hope this helps answer your questions, and gives you a better idea of how to maximize battery life under your driving conditions. Regards, Dan Myggen From what he is saying, it appears optimal to time the charge to bring it to full charge in standard mode 30 minutes before you leave. That would leave the car sitting at high charge rate for the least amount of time, but allow enough time for balancing to occur if necessary. This sounds exactly like our finish-charging-by approach. Rather than set the charge start time, you set the finish time, and the system works out how long it should take then adds on a 30-to-60 minute safety margin (which would also allow for battery balancing to occur). Does this make sense? Or is Dan Myggen's advise wrong? Regards, Mark On 5 Apr, 2012, at 7:45 PM, Mark Webb-Johnson wrote:
I'm now starting to think about the v1.3 firmware, which is intended to add the following:
Log charge history Log drive history Sophisticated control of charge time
We don't really have TOU metering in Hong Kong, so not much use for me, but part [3] would be fun nevertheless. Most charge control in EVs is pretty basic, and it might be interesting to see how sophisticated this can be made without complications.
I don't know if this is workable or not, so put my thoughts out into the open for discussion.
For charge time, the consensus seems to be that people want to enter the time to FINISH charge, vs the current time to START charge. To do that, we need an estimate of how long the charge will take. For that, we either need a sophisticated model or a collection of historical data we can lookup to find something approximate. Hence item [1] on my list.
Elon talked about the car learning about you. Where you park. Where you charge. etc. So, if always leave home at 7:00am to go to the office on Mondays through Fridays, perhaps the car can learn? Or, at least suggest based on what it has seen... Hence item [2] on my list.
For [1], we would store such things as temperatures, SOC start, SOC end, charge mode, charge current, charge voltage and duration. The can bus charge message seem to include this information.
For [2], we would store such things as date/time of drive, duration (time, distance, and elevation change), battery usage. We seem limited in this from what we have decoded on the can bus so far.
Regardless of the above, [1] and [2] would be useful information for any owner, anyway.
Privacy is an issue. Two problems - (a) protection of my charge/drive history, (b) the use of 'shared' charge history for [3]. My suggestion is to keep drive and charge history private. Perhaps it could just be stored as paranoid mode blobs. But, there should be an option to allow anonymised sharing of charge history for the use of [3]. My thinking is that if you share your data anonymously, then your lookup includes the pool of others anonymous charge history. if you choose not to share, then your lookup is only against your own charge history.
I did toy with the idea of using the server to control this. So, at 3am the server sends a command to the car to start the charge, etc. That would simplify the firmware in the car, but has a major problem of GPRS connectivity - if the cellular signal was lost the charge wouldn't start. Bad. So, I think it best to have the historical database in the server, the calculations in the App, and the settings downloaded to the car while it has cellular signal (after which it just follows them autonomously).
The Tesla Roadster currently offers you a choice of charge on plug-in, or start charge at a particular time. It also allows you to limit charge current and set charge mode. My thinking is to extend this by making it per day-of-the-week for a few defined locations, and to provide an override for the 'current' day/night. If the override is not set, and you are in one of the defined locations, then the system looks up the day of the week and controls charge based on what you have set. The UI for this is quite simple - presumably a screen with tabs/selector for day or the week, and then controls to set charge mode, current limit, and time to start/complete by. One developer also had the good idea that a charge SOC limit would be useful (e.g.; please stop charge when it gets to 70% / 220km ideal).
How do we handle night vs day charging? Is this only for overnight, or do we base it on when you plugin?
Is this workable? Useful?
Really interested in people's feedback on this.
Mark.
_______________________________________________ OvmsDev mailing list OvmsDev@lists.teslaclub.hk http://lists.teslaclub.hk/mailman/listinfo/ovmsdev
The core question I have here is whether it is possible to build a static table saying that at this temperature, this available voltage+currrent, the charging efficiency is X%? Something accurate enough to give us a charge time prediction (given temperature, kWh needed by the pack, available voltage+current) of +/- 1 hour? I'm assuming the temperature should be ambient, as that is more important overt the duration of a reasonable charge than pack temperature? If we can have such a table, with steps of 5 degrees celcius between -10C and +40C, and say 10 current levels, that is only 100 entries - and we would only need 1 byte for each entry. The module could then put in the current temperature, current/voltage level, and get out an efficiency factor. It could estimate the kWh the pack needs (by mode and SOC/ideal-miles difference), then multiply by efficiency factor, and get out an estimate of how many minutes is required to achieve that. Without this table, we could do the lookup on the server, but that would mean having to set it _every_ night from the App/Server - as it would depend on the SOC% the car was actually at. If we could build this data, where could we get the data from? Regards, Mark. Begin forwarded message:
From: Mark Webb-Johnson <mark@webb-johnson.net> Subject: Re: [Ovmsdev] Charge Control Date: 6 April, 2012 8:25:51 PM GMT+08:00 To: OVMS Developers <ovmsdev@lists.teslaclub.hk>
Bennett Leeds and I have had a discussion off-list (I'm not sure if he is on this list or not), and he brings up a valid point about balancing the pack perhaps not occurring if we cut short the charge with a SOC limit.
Looking here:
http://www.teslamotorsclub.com/showthread.php/3848-Tesla-Roadster-Battery-Ca...
it seems that this approach may be non-optimal. For clarity, let me cut-and-paste the Tesla reply here:
For simplicity’s sake, I will refer to all SOC (State Of Charge) numbers as a percentage of a full (100%) charge. I cannot provide exact percentages, as there are many variables which can cause these numbers to vary slightly, however, I will get as close as I can.
When plugging in a nearly empty car that is set to Storage mode, the charge will generally stop at around 20%. The car will then settle into its normal Storage mode rhythm, topping up and discharging between 10% and 50% as the car sees fit. Oftentimes it will keep a tighter envelope based on parameters that I am not aware of.
Most important to remember is that Storage mode is not intended to be a driving mode. This charge setting is primarily meant to optimize battery life while the car is under storage conditions for two weeks or more.
Storage mode does not attempt to balance the pack, and you will cause an imbalance in the pack by driving and charging in this mode regularly.
This will penalize you when you do occasionally charge the car fully in the other modes, as you will not have the full range of the car available to you until the car has a chance to balance its battery. Additionally, the car’s range will not be as accurate if driven while in Storage mode vs. having charged it in Standard mode after storing the car, then driving it.
Allowing the car to sit plugged in after it has finished charging in Standard mode automatically balances the pack, and it may take a few rounds of this to bring an imbalanced pack back to its full potential after many partial charges. This is one of the major reasons we recommend keeping the car in Standard mode whenever possible. Partial charges in any mode, while not on their own bad for the battery, do not give the car an opportunity to balance its battery, and over time can prevent you from accessing the car’s full range potential.
When balanced, Standard mode charges the car to about 87%, with Range and Performance modes getting the car to about 97%. These two percentages are very much affected by the balance between bricks in the battery. An imbalanced pack will not fill up all the way in any mode, nor will it be able to discharge as far. Additionally, the range predictions will not be as accurate.
Your voltages are about right. 4.10 volts = full standard mode (187-195 ideal miles) 4.15 volts = full range mode 4.20 volts = maximum of the cells that we never touch As you may know, there is much more to it than just using voltage to calculate range with Lithium batteries. This is something that is incredibly complicated, and not something that I am qualified to discuss in detail, as I do not have the full picture.
It is important to remember that SOC is not the only factor in maximizing battery life. For instance most lithium batteries are shipped at around 30-50% SOC in consumer electronics, and part of the reasoning is that they are less susceptible to damage from extreme temperatures at these charge levels. It is also safer to store them at these levels. Part of the benefit of Storage mode is that there is less work required from the HVAC system to keep the batteryhappy and safe, and therefore, less energy is consumed while stored.
We chose ~90% as a Standard full charge level because it offers most of the longevity benefit of keeping the car at a lower state of charge, while still allowing a high degree of autonomy. I understand that you are interested in taking extra steps to maximize your battery’s life, so I do have some suggestions for you.
I would not recommend that you continue to use Storage mode as a means of maintaining a lower state of charge. As I explained earlier, this mode is not optimized for this type of use.
Think of battery degradation this way. It is very much a function of time spent at voltage and temperature. For instance, you do not want to charge a car all the way in performance mode, and then let it sit in the sun all day. Between the higher thermal limits and the high SOC, you are causing the battery a relatively high amount of degradation .In fact, the car will eventually allow itself to discharge to Standard levels if left in Performance mode to prevent inadvertent damage to the battery. If you start driving right away after charging in Performance or Range Mode, and don’t let it sit, you would minimize the damage incurred, as the time spent at these extremes is an important part of the calculation.
Similarly, if you top off to full in Standard mode, then jump in the car right away and bring the SOC down quickly, you will minimize the small amount of degradation that occurs at ~90%.
If you prefer to keep a lower average SOC in an attempt to maximize the life of your battery, I would instead suggest that you stay in Standard mode and utilize the Roadster’s built in charge timer and current limiting options to find an average SOC that works for you. For instance, try starting your charge at a time that allows the car to top off to a level you are comfortable with right before you need to leave. Alternately, you can use the Current limiting function to adjust the amount of time it takes the car reaches a target SOC, or even a combination of these two options. The car will remember the settings you select based on your location, so once you find something that works for your commute, you can set it and forget it.
Just remember that the car does benefit from being allowed to sit fully charged in Standard mode, and should be allowed to do so frequently, especially if being used on a daily basis. Leaving the car plugged in in Standard mode after it is done charging will initiate this balancing program automatically. This doesn’t take much time, 30 minutes or so should do. It may take several of these balancing cycles to bring the car back to a balanced state if it has become imbalanced, which is something that a lack of regular Standard mode top ups and subsequent balancing cycles can induce.
It would therefore be a good idea to set the car to “Charge on Plug In” instead of “Charge at X time” in the charge timing menu for at least a few Standard mode charges per week to keep the pack balanced. There are simply too many variables for me to be able to predict how often you would need to do this, and we do not have a recommended procedure for alternate desired average SOC levels.
I hope this helps answer your questions, and gives you a better idea of how to maximize battery life under your driving conditions.
Regards,
Dan Myggen
From what he is saying, it appears optimal to time the charge to bring it to full charge in standard mode 30 minutes before you leave. That would leave the car sitting at high charge rate for the least amount of time, but allow enough time for balancing to occur if necessary.
This sounds exactly like our finish-charging-by approach. Rather than set the charge start time, you set the finish time, and the system works out how long it should take then adds on a 30-to-60 minute safety margin (which would also allow for battery balancing to occur).
Does this make sense? Or is Dan Myggen's advise wrong?
Regards, Mark
On 5 Apr, 2012, at 7:45 PM, Mark Webb-Johnson wrote:
I'm now starting to think about the v1.3 firmware, which is intended to add the following:
Log charge history Log drive history Sophisticated control of charge time
We don't really have TOU metering in Hong Kong, so not much use for me, but part [3] would be fun nevertheless. Most charge control in EVs is pretty basic, and it might be interesting to see how sophisticated this can be made without complications.
I don't know if this is workable or not, so put my thoughts out into the open for discussion.
For charge time, the consensus seems to be that people want to enter the time to FINISH charge, vs the current time to START charge. To do that, we need an estimate of how long the charge will take. For that, we either need a sophisticated model or a collection of historical data we can lookup to find something approximate. Hence item [1] on my list.
Elon talked about the car learning about you. Where you park. Where you charge. etc. So, if always leave home at 7:00am to go to the office on Mondays through Fridays, perhaps the car can learn? Or, at least suggest based on what it has seen... Hence item [2] on my list.
For [1], we would store such things as temperatures, SOC start, SOC end, charge mode, charge current, charge voltage and duration. The can bus charge message seem to include this information.
For [2], we would store such things as date/time of drive, duration (time, distance, and elevation change), battery usage. We seem limited in this from what we have decoded on the can bus so far.
Regardless of the above, [1] and [2] would be useful information for any owner, anyway.
Privacy is an issue. Two problems - (a) protection of my charge/drive history, (b) the use of 'shared' charge history for [3]. My suggestion is to keep drive and charge history private. Perhaps it could just be stored as paranoid mode blobs. But, there should be an option to allow anonymised sharing of charge history for the use of [3]. My thinking is that if you share your data anonymously, then your lookup includes the pool of others anonymous charge history. if you choose not to share, then your lookup is only against your own charge history.
I did toy with the idea of using the server to control this. So, at 3am the server sends a command to the car to start the charge, etc. That would simplify the firmware in the car, but has a major problem of GPRS connectivity - if the cellular signal was lost the charge wouldn't start. Bad. So, I think it best to have the historical database in the server, the calculations in the App, and the settings downloaded to the car while it has cellular signal (after which it just follows them autonomously).
The Tesla Roadster currently offers you a choice of charge on plug-in, or start charge at a particular time. It also allows you to limit charge current and set charge mode. My thinking is to extend this by making it per day-of-the-week for a few defined locations, and to provide an override for the 'current' day/night. If the override is not set, and you are in one of the defined locations, then the system looks up the day of the week and controls charge based on what you have set. The UI for this is quite simple - presumably a screen with tabs/selector for day or the week, and then controls to set charge mode, current limit, and time to start/complete by. One developer also had the good idea that a charge SOC limit would be useful (e.g.; please stop charge when it gets to 70% / 220km ideal).
How do we handle night vs day charging? Is this only for overnight, or do we base it on when you plugin?
Is this workable? Useful?
Really interested in people's feedback on this.
Mark.
_______________________________________________ OvmsDev mailing list OvmsDev@lists.teslaclub.hk http://lists.teslaclub.hk/mailman/listinfo/ovmsdev
I think your model would work pretty well. To calculate charge time, you also have to take into account the current tapering near the top of the charge. We can get most of the required data from log files. The only tricky bit is getting the ambient temperature, which I don't think anyone has identified in the log files. You could get a good approximating by only considering charge sessions that start a least an hour of the most recent drive and then use the starting temperature of the coolant as a proxy for ambient temperature. Range mode is the trickiest and the most important to time, they are also done less often, so it's harder to get data. I'd be happy to collect logs and extract data if we can get owners to contribute logs for a variety of charging levels and ambient temperatures. Tom on 4/6/12 5:52 PM, Mark Webb-Johnson wrote:
The core question I have here is whether it is possible to build a static table saying that at this temperature, this available voltage+currrent, the charging efficiency is X%? Something accurate enough to give us a charge time prediction (given temperature, kWh needed by the pack, available voltage+current) of +/- 1 hour?
I'm assuming the temperature should be ambient, as that is more important overt the duration of a reasonable charge than pack temperature?
If we can have such a table, with steps of 5 degrees celcius between -10C and +40C, and say 10 current levels, that is only 100 entries - and we would only need 1 byte for each entry. The module could then put in the current temperature, current/voltage level, and get out an efficiency factor. It could estimate the kWh the pack needs (by mode and SOC/ideal-miles difference), then multiply by efficiency factor, and get out an estimate of how many minutes is required to achieve that.
Without this table, we could do the lookup on the server, but that would mean having to set it _every_ night from the App/Server - as it would depend on the SOC% the car was actually at.
If we could build this data, where could we get the data from?
Regards, Mark.
Begin forwarded message:
From: Mark Webb-Johnson <mark@webb-johnson.net> Subject: Re: [Ovmsdev] Charge Control Date: 6 April, 2012 8:25:51 PM GMT+08:00 To: OVMS Developers <ovmsdev@lists.teslaclub.hk>
Bennett Leeds and I have had a discussion off-list (I'm not sure if he is on this list or not), and he brings up a valid point about balancing the pack perhaps not occurring if we cut short the charge with a SOC limit.
Looking here:
http://www.teslamotorsclub.com/showthread.php/3848-Tesla-Roadster-Battery-Ca... e?p=41995&viewfull=1#post41995
it seems that this approach may be non-optimal. For clarity, let me cut-and-paste the Tesla reply here:
For simplicity¹s sake, I will refer to all SOC (State Of Charge) numbers as a percentage of a full (100%) charge. I cannot provide exact percentages, as there are many variables which can cause these numbers to vary slightly, however, I will get as close as I can.
When plugging in a nearly empty car that is set to Storage mode, the charge will generally stop at around 20%. The car will then settle into its normal Storage mode rhythm, topping up and discharging between 10% and 50% as the car sees fit. Oftentimes it will keep a tighter envelope based on parameters that I am not aware of.
Most important to remember is that Storage mode is not intended to be a driving mode. This charge setting is primarily meant to optimize battery life while the car is under storage conditions for two weeks or more.
Storage mode does not attempt to balance the pack, and you will cause an imbalance in the pack by driving and charging in this mode regularly.
This will penalize you when you do occasionally charge the car fully in the other modes, as you will not have the full range of the car available to you until the car has a chance to balance its battery. Additionally, the car¹s range will not be as accurate if driven while in Storage mode vs. having charged it in Standard mode after storing the car, then driving it.
Allowing the car to sit plugged in after it has finished charging in Standard mode automatically balances the pack, and it may take a few rounds of this to bring an imbalanced pack back to its full potential after many partial charges. This is one of the major reasons we recommend keeping the car in Standard mode whenever possible. Partial charges in any mode, while not on their own bad for the battery, do not give the car an opportunity to balance its battery, and over time can prevent you from accessing the car¹s full range potential.
When balanced, Standard mode charges the car to about 87%, with Range and Performance modes getting the car to about 97%. These two percentages are very much affected by the balance between bricks in the battery. An imbalanced pack will not fill up all the way in any mode, nor will it be able to discharge as far. Additionally, the range predictions will not be as accurate.
Your voltages are about right. 4.10 volts = full standard mode (187-195 ideal miles) 4.15 volts = full range mode 4.20 volts = maximum of the cells that we never touch As you may know, there is much more to it than just using voltage to calculate range with Lithium batteries. This is something that is incredibly complicated, and not something that I am qualified to discuss in detail, as I do not have the full picture.
It is important to remember that SOC is not the only factor in maximizing battery life. For instance most lithium batteries are shipped at around 30-50% SOC in consumer electronics, and part of the reasoning is that they are less susceptible to damage from extreme temperatures at these charge levels. It is also safer to store them at these levels. Part of the benefit of Storage mode is that there is less work required from the HVAC system to keep the batteryhappy and safe, and therefore, less energy is consumed while stored.
We chose ~90% as a Standard full charge level because it offers most of the longevity benefit of keeping the car at a lower state of charge, while still allowing a high degree of autonomy. I understand that you are interested in taking extra steps to maximize your battery¹s life, so I do have some suggestions for you.
I would not recommend that you continue to use Storage mode as a means of maintaining a lower state of charge. As I explained earlier, this mode is not optimized for this type of use.
Think of battery degradation this way. It is very much a function of time spent at voltage and temperature. For instance, you do not want to charge a car all the way in performance mode, and then let it sit in the sun all day. Between the higher thermal limits and the high SOC, you are causing the battery a relatively high amount of degradation .In fact, the car will eventually allow itself to discharge to Standard levels if left in Performance mode to prevent inadvertent damage to the battery. If you start driving right away after charging in Performance or Range Mode, and don¹t let it sit, you would minimize the damage incurred, as the time spent at these extremes is an important part of the calculation.
Similarly, if you top off to full in Standard mode, then jump in the car right away and bring the SOC down quickly, you will minimize the small amount of degradation that occurs at ~90%.
If you prefer to keep a lower average SOC in an attempt to maximize the life of your battery, I would instead suggest that you stay in Standard mode and utilize the Roadster¹s built in charge timer and current limiting options to find an average SOC that works for you. For instance, try starting your charge at a time that allows the car to top off to a level you are comfortable with right before you need to leave. Alternately, you can use the Current limiting function to adjust the amount of time it takes the car reaches a target SOC, or even a combination of these two options. The car will remember the settings you select based on your location, so once you find something that works for your commute, you can set it and forget it.
Just remember that the car does benefit from being allowed to sit fully charged in Standard mode, and should be allowed to do so frequently, especially if being used on a daily basis. Leaving the car plugged in in Standard mode after it is done charging will initiate this balancing program automatically. This doesn¹t take much time, 30 minutes or so should do. It may take several of these balancing cycles to bring the car back to a balanced state if it has become imbalanced, which is something that a lack of regular Standard mode top ups and subsequent balancing cycles can induce.
It would therefore be a good idea to set the car to ³Charge on Plug In² instead of ³Charge at X time² in the charge timing menu for at least a few Standard mode charges per week to keep the pack balanced. There are simply too many variables for me to be able to predict how often you would need to do this, and we do not have a recommended procedure for alternate desired average SOC levels.
I hope this helps answer your questions, and gives you a better idea of how to maximize battery life under your driving conditions.
Regards,
Dan Myggen
From what he is saying, it appears optimal to time the charge to bring it to full charge in standard mode 30 minutes before you leave. That would leave the car sitting at high charge rate for the least amount of time, but allow enough time for balancing to occur if necessary.
This sounds exactly like our finish-charging-by approach. Rather than set the charge start time, you set the finish time, and the system works out how long it should take then adds on a 30-to-60 minute safety margin (which would also allow for battery balancing to occur).
Does this make sense? Or is Dan Myggen's advise wrong?
Regards, Mark
On 5 Apr, 2012, at 7:45 PM, Mark Webb-Johnson wrote:
I'm now starting to think about the v1.3 firmware, which is intended to add the following:
Log charge history Log drive history Sophisticated control of charge time
We don't really have TOU metering in Hong Kong, so not much use for me, but part [3] would be fun nevertheless. Most charge control in EVs is pretty basic, and it might be interesting to see how sophisticated this can be made without complications.
I don't know if this is workable or not, so put my thoughts out into the open for discussion.
For charge time, the consensus seems to be that people want to enter the time to FINISH charge, vs the current time to START charge. To do that, we need an estimate of how long the charge will take. For that, we either need a sophisticated model or a collection of historical data we can lookup to find something approximate. Hence item [1] on my list.
Elon talked about the car learning about you. Where you park. Where you charge. etc. So, if always leave home at 7:00am to go to the office on Mondays through Fridays, perhaps the car can learn? Or, at least suggest based on what it has seen... Hence item [2] on my list.
For [1], we would store such things as temperatures, SOC start, SOC end, charge mode, charge current, charge voltage and duration. The can bus charge message seem to include this information.
For [2], we would store such things as date/time of drive, duration (time, distance, and elevation change), battery usage. We seem limited in this from what we have decoded on the can bus so far.
Regardless of the above, [1] and [2] would be useful information for any owner, anyway.
Privacy is an issue. Two problems - (a) protection of my charge/drive history, (b) the use of 'shared' charge history for [3]. My suggestion is to keep drive and charge history private. Perhaps it could just be stored as paranoid mode blobs. But, there should be an option to allow anonymised sharing of charge history for the use of [3]. My thinking is that if you share your data anonymously, then your lookup includes the pool of others anonymous charge history. if you choose not to share, then your lookup is only against your own charge history.
I did toy with the idea of using the server to control this. So, at 3am the server sends a command to the car to start the charge, etc. That would simplify the firmware in the car, but has a major problem of GPRS connectivity - if the cellular signal was lost the charge wouldn't start. Bad. So, I think it best to have the historical database in the server, the calculations in the App, and the settings downloaded to the car while it has cellular signal (after which it just follows them autonomously).
The Tesla Roadster currently offers you a choice of charge on plug-in, or start charge at a particular time. It also allows you to limit charge current and set charge mode. My thinking is to extend this by making it per day-of-the-week for a few defined locations, and to provide an override for the 'current' day/night. If the override is not set, and you are in one of the defined locations, then the system looks up the day of the week and controls charge based on what you have set. The UI for this is quite simple - presumably a screen with tabs/selector for day or the week, and then controls to set charge mode, current limit, and time to start/complete by. One developer also had the good idea that a charge SOC limit would be useful (e.g.; please stop charge when it gets to 70% / 220km ideal).
How do we handle night vs day charging? Is this only for overnight, or do we base it on when you plugin?
Is this workable? Useful?
Really interested in people's feedback on this.
Mark.
_______________________________________________ OvmsDev mailing list OvmsDev@lists.teslaclub.hk http://lists.teslaclub.hk/mailman/listinfo/ovmsdev
_______________________________________________ OvmsDev mailing list OvmsDev@lists.teslaclub.hk http://lists.teslaclub.hk/mailman/listinfo/ovmsdev
I already did some tests calculating the remaining charge time and had it implemented in the iPhone app. First I took the simple approach to linearly estimate the remaining time by taking the charge current and voltage and calculate the energy per sec. Then take the missing energy from the current SOC. This will give you an approximation of the remaining time. If you are looking at +/- 1 hour. This already should work from my experience. I tried to make it better by taking into account that the charging curve is not linear, but more on a logarithmic scale. This worked a bit better. I also figured that there is some loss when charging, which I set to 5% (this probably varies by temperature). What I did not know is the fact that once finished charging the batteries will be rebalanced for 30 minutes. Is this still shown as charging in OVMS? If yes, this would explain, why I've been off for about 30 - 60 minutes with my calculation. I also did not take the age of the battery into account, which should be an important factor, too. I think that it might be better to use a formula which tries to approximate the charging curve instead of using a fixed lookup table. At least it also could be fine tuned a bit easier by just setting a couple of parameters through the app to change the calculation. Greetings Dominik On 08.04.2012, at 06:16, Tom Saxton wrote:
I think your model would work pretty well.
To calculate charge time, you also have to take into account the current tapering near the top of the charge.
We can get most of the required data from log files. The only tricky bit is getting the ambient temperature, which I don't think anyone has identified in the log files. You could get a good approximating by only considering charge sessions that start a least an hour of the most recent drive and then use the starting temperature of the coolant as a proxy for ambient temperature.
Range mode is the trickiest and the most important to time, they are also done less often, so it's harder to get data. I'd be happy to collect logs and extract data if we can get owners to contribute logs for a variety of charging levels and ambient temperatures.
Tom
on 4/6/12 5:52 PM, Mark Webb-Johnson wrote:
The core question I have here is whether it is possible to build a static table saying that at this temperature, this available voltage+currrent, the charging efficiency is X%? Something accurate enough to give us a charge time prediction (given temperature, kWh needed by the pack, available voltage+current) of +/- 1 hour?
I'm assuming the temperature should be ambient, as that is more important overt the duration of a reasonable charge than pack temperature?
If we can have such a table, with steps of 5 degrees celcius between -10C and +40C, and say 10 current levels, that is only 100 entries - and we would only need 1 byte for each entry. The module could then put in the current temperature, current/voltage level, and get out an efficiency factor. It could estimate the kWh the pack needs (by mode and SOC/ideal-miles difference), then multiply by efficiency factor, and get out an estimate of how many minutes is required to achieve that.
Without this table, we could do the lookup on the server, but that would mean having to set it _every_ night from the App/Server - as it would depend on the SOC% the car was actually at.
If we could build this data, where could we get the data from?
Regards, Mark.
Begin forwarded message:
From: Mark Webb-Johnson <mark@webb-johnson.net> Subject: Re: [Ovmsdev] Charge Control Date: 6 April, 2012 8:25:51 PM GMT+08:00 To: OVMS Developers <ovmsdev@lists.teslaclub.hk>
Bennett Leeds and I have had a discussion off-list (I'm not sure if he is on this list or not), and he brings up a valid point about balancing the pack perhaps not occurring if we cut short the charge with a SOC limit.
Looking here:
http://www.teslamotorsclub.com/showthread.php/3848-Tesla-Roadster-Battery-Ca... e?p=41995&viewfull=1#post41995
it seems that this approach may be non-optimal. For clarity, let me cut-and-paste the Tesla reply here:
For simplicity’s sake, I will refer to all SOC (State Of Charge) numbers as a percentage of a full (100%) charge. I cannot provide exact percentages, as there are many variables which can cause these numbers to vary slightly, however, I will get as close as I can.
When plugging in a nearly empty car that is set to Storage mode, the charge will generally stop at around 20%. The car will then settle into its normal Storage mode rhythm, topping up and discharging between 10% and 50% as the car sees fit. Oftentimes it will keep a tighter envelope based on parameters that I am not aware of.
Most important to remember is that Storage mode is not intended to be a driving mode. This charge setting is primarily meant to optimize battery life while the car is under storage conditions for two weeks or more.
Storage mode does not attempt to balance the pack, and you will cause an imbalance in the pack by driving and charging in this mode regularly.
This will penalize you when you do occasionally charge the car fully in the other modes, as you will not have the full range of the car available to you until the car has a chance to balance its battery. Additionally, the car’s range will not be as accurate if driven while in Storage mode vs. having charged it in Standard mode after storing the car, then driving it.
Allowing the car to sit plugged in after it has finished charging in Standard mode automatically balances the pack, and it may take a few rounds of this to bring an imbalanced pack back to its full potential after many partial charges. This is one of the major reasons we recommend keeping the car in Standard mode whenever possible. Partial charges in any mode, while not on their own bad for the battery, do not give the car an opportunity to balance its battery, and over time can prevent you from accessing the car’s full range potential.
When balanced, Standard mode charges the car to about 87%, with Range and Performance modes getting the car to about 97%. These two percentages are very much affected by the balance between bricks in the battery. An imbalanced pack will not fill up all the way in any mode, nor will it be able to discharge as far. Additionally, the range predictions will not be as accurate.
Your voltages are about right. 4.10 volts = full standard mode (187-195 ideal miles) 4.15 volts = full range mode 4.20 volts = maximum of the cells that we never touch As you may know, there is much more to it than just using voltage to calculate range with Lithium batteries. This is something that is incredibly complicated, and not something that I am qualified to discuss in detail, as I do not have the full picture.
It is important to remember that SOC is not the only factor in maximizing battery life. For instance most lithium batteries are shipped at around 30-50% SOC in consumer electronics, and part of the reasoning is that they are less susceptible to damage from extreme temperatures at these charge levels. It is also safer to store them at these levels. Part of the benefit of Storage mode is that there is less work required from the HVAC system to keep the batteryhappy and safe, and therefore, less energy is consumed while stored.
We chose ~90% as a Standard full charge level because it offers most of the longevity benefit of keeping the car at a lower state of charge, while still allowing a high degree of autonomy. I understand that you are interested in taking extra steps to maximize your battery’s life, so I do have some suggestions for you.
I would not recommend that you continue to use Storage mode as a means of maintaining a lower state of charge. As I explained earlier, this mode is not optimized for this type of use.
Think of battery degradation this way. It is very much a function of time spent at voltage and temperature. For instance, you do not want to charge a car all the way in performance mode, and then let it sit in the sun all day. Between the higher thermal limits and the high SOC, you are causing the battery a relatively high amount of degradation .In fact, the car will eventually allow itself to discharge to Standard levels if left in Performance mode to prevent inadvertent damage to the battery. If you start driving right away after charging in Performance or Range Mode, and don’t let it sit, you would minimize the damage incurred, as the time spent at these extremes is an important part of the calculation.
Similarly, if you top off to full in Standard mode, then jump in the car right away and bring the SOC down quickly, you will minimize the small amount of degradation that occurs at ~90%.
If you prefer to keep a lower average SOC in an attempt to maximize the life of your battery, I would instead suggest that you stay in Standard mode and utilize the Roadster’s built in charge timer and current limiting options to find an average SOC that works for you. For instance, try starting your charge at a time that allows the car to top off to a level you are comfortable with right before you need to leave. Alternately, you can use the Current limiting function to adjust the amount of time it takes the car reaches a target SOC, or even a combination of these two options. The car will remember the settings you select based on your location, so once you find something that works for your commute, you can set it and forget it.
Just remember that the car does benefit from being allowed to sit fully charged in Standard mode, and should be allowed to do so frequently, especially if being used on a daily basis. Leaving the car plugged in in Standard mode after it is done charging will initiate this balancing program automatically. This doesn’t take much time, 30 minutes or so should do. It may take several of these balancing cycles to bring the car back to a balanced state if it has become imbalanced, which is something that a lack of regular Standard mode top ups and subsequent balancing cycles can induce.
It would therefore be a good idea to set the car to “Charge on Plug In” instead of “Charge at X time” in the charge timing menu for at least a few Standard mode charges per week to keep the pack balanced. There are simply too many variables for me to be able to predict how often you would need to do this, and we do not have a recommended procedure for alternate desired average SOC levels.
I hope this helps answer your questions, and gives you a better idea of how to maximize battery life under your driving conditions.
Regards,
Dan Myggen
From what he is saying, it appears optimal to time the charge to bring it to full charge in standard mode 30 minutes before you leave. That would leave the car sitting at high charge rate for the least amount of time, but allow enough time for balancing to occur if necessary.
This sounds exactly like our finish-charging-by approach. Rather than set the charge start time, you set the finish time, and the system works out how long it should take then adds on a 30-to-60 minute safety margin (which would also allow for battery balancing to occur).
Does this make sense? Or is Dan Myggen's advise wrong?
Regards, Mark
On 5 Apr, 2012, at 7:45 PM, Mark Webb-Johnson wrote:
I'm now starting to think about the v1.3 firmware, which is intended to add the following:
Log charge history Log drive history Sophisticated control of charge time
We don't really have TOU metering in Hong Kong, so not much use for me, but part [3] would be fun nevertheless. Most charge control in EVs is pretty basic, and it might be interesting to see how sophisticated this can be made without complications.
I don't know if this is workable or not, so put my thoughts out into the open for discussion.
For charge time, the consensus seems to be that people want to enter the time to FINISH charge, vs the current time to START charge. To do that, we need an estimate of how long the charge will take. For that, we either need a sophisticated model or a collection of historical data we can lookup to find something approximate. Hence item [1] on my list.
Elon talked about the car learning about you. Where you park. Where you charge. etc. So, if always leave home at 7:00am to go to the office on Mondays through Fridays, perhaps the car can learn? Or, at least suggest based on what it has seen... Hence item [2] on my list.
For [1], we would store such things as temperatures, SOC start, SOC end, charge mode, charge current, charge voltage and duration. The can bus charge message seem to include this information.
For [2], we would store such things as date/time of drive, duration (time, distance, and elevation change), battery usage. We seem limited in this from what we have decoded on the can bus so far.
Regardless of the above, [1] and [2] would be useful information for any owner, anyway.
Privacy is an issue. Two problems - (a) protection of my charge/drive history, (b) the use of 'shared' charge history for [3]. My suggestion is to keep drive and charge history private. Perhaps it could just be stored as paranoid mode blobs. But, there should be an option to allow anonymised sharing of charge history for the use of [3]. My thinking is that if you share your data anonymously, then your lookup includes the pool of others anonymous charge history. if you choose not to share, then your lookup is only against your own charge history.
I did toy with the idea of using the server to control this. So, at 3am the server sends a command to the car to start the charge, etc. That would simplify the firmware in the car, but has a major problem of GPRS connectivity - if the cellular signal was lost the charge wouldn't start. Bad. So, I think it best to have the historical database in the server, the calculations in the App, and the settings downloaded to the car while it has cellular signal (after which it just follows them autonomously).
The Tesla Roadster currently offers you a choice of charge on plug-in, or start charge at a particular time. It also allows you to limit charge current and set charge mode. My thinking is to extend this by making it per day-of-the-week for a few defined locations, and to provide an override for the 'current' day/night. If the override is not set, and you are in one of the defined locations, then the system looks up the day of the week and controls charge based on what you have set. The UI for this is quite simple - presumably a screen with tabs/selector for day or the week, and then controls to set charge mode, current limit, and time to start/complete by. One developer also had the good idea that a charge SOC limit would be useful (e.g.; please stop charge when it gets to 70% / 220km ideal).
How do we handle night vs day charging? Is this only for overnight, or do we base it on when you plugin?
Is this workable? Useful?
Really interested in people's feedback on this.
Mark.
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From my testing last summer (31 Celsius in Hong Kong), the efficiency loss was much worse than 5%, especially at low charge currents: http://www.teslamotorsclub.com/showthread.php/5655-Charging-in-High-Temperat... Here's were my results at around 31 Celsius: Here is Tom's analysis of my log files, vs his in cool weather, at the time: Bottom line is that ambient temperature is very important to the estimate. Tom: I agree that the log files would give us the best historical data for a jump-start on this. The issues are (a) getting the files, (b) ambient temperature. I don't think (a) would be a problem. I'll submit my logs for inclusion (I've probably got 100 or 200 charges in there at temperatures from 5 Celcius up to 33 Celcius). 99% standard mode. I'm sure, that others would also submit, and we could pretty quickly build up a model. For (b), we either need to find it in the logs files, approximate it from something in the log files, or use something like this to approximate it. For example, I did a charge on my car at 19:31 on 30th March 2012. VMSParser shows: 03/30/2012 19:31:30 | 1333107090 | C1MB | Coolant 30C ESS 28C - 29C charging at 203.7V 0.01A 03/30/2012 19:31:30 | 1333107090 | C30M | range soc = 73%, 70A available 03/30/2012 19:31:31 | 1333107091 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.00A 03/30/2012 19:31:32 | 1333107092 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.02A 03/30/2012 19:31:33 | 1333107093 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.1V 0.00A 03/30/2012 19:31:34 | 1333107094 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.00A 03/30/2012 19:31:35 | 1333107095 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.02A 03/30/2012 19:31:36 | 1333107096 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.01A 03/30/2012 19:31:37 | 1333107097 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.00A 03/30/2012 19:31:38 | 1333107098 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.01A 03/30/2012 19:31:39 | 1333107099 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.00A 03/30/2012 19:31:40 | 1333107100 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.02A 03/30/2012 19:31:41 | 1333107101 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.7V 0.00A 03/30/2012 19:31:42 | 1333107102 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.2V 0.04A 03/30/2012 19:31:43 | 1333107103 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.5V 0.00A 03/30/2012 19:31:44 | 1333107104 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.02A 03/30/2012 19:31:45 | 1333107105 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.3V 0.00A 03/30/2012 19:31:46 | 1333107106 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.02A 03/30/2012 19:31:47 | 1333107107 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.2V 0.00A 03/30/2012 19:31:48 | 1333107108 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.7V 0.01A 03/30/2012 19:31:49 | 1333107109 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.7V 0.00A 03/30/2012 19:31:50 | 1333107110 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.9V 0.01A 03/30/2012 19:31:51 | 1333107111 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.2V 0.00A 03/30/2012 19:31:52 | 1333107112 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.3V 0.23A 03/30/2012 19:31:52 | 1333107112 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.3V 0.23A 03/30/2012 19:31:53 | 1333107113 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.8V 0.18A 03/30/2012 19:31:54 | 1333107114 | C1MB | Coolant 30C ESS 28C - 29C charging at 223.2V 0.19A 03/30/2012 19:31:55 | 1333107115 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.8V 2.23A 03/30/2012 19:31:56 | 1333107116 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.9V 2.52A 03/30/2012 19:31:57 | 1333107117 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.1V 5.71A 03/30/2012 19:31:58 | 1333107118 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 16.96A 03/30/2012 19:31:59 | 1333107119 | C1MB | Coolant 30C ESS 28C - 29C charging at 219.9V 27.05A 03/30/2012 19:32:00 | 1333107120 | C1MB | Coolant 30C ESS 28C - 29C charging at 218.3V 36.99A 03/30/2012 19:32:01 | 1333107121 | C1MB | Coolant 30C ESS 28C - 29C charging at 217.5V 46.94A 03/30/2012 19:32:03 | 1333107123 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.9V 47.74A 03/30/2012 19:32:04 | 1333107124 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.7V 47.75A 03/30/2012 19:32:05 | 1333107125 | C1MB | Coolant 30C ESS 28C - 29C charging at 217.3V 47.79A 03/30/2012 19:33:05 | 1333107185 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.7V 47.84A 03/30/2012 19:34:05 | 1333107245 | C1MB | Coolant 16C ESS 25C - 28C charging at 217.9V 48.12A 03/30/2012 19:35:05 | 1333107305 | C1MB | Coolant 16C ESS 22C - 27C charging at 218.1V 47.96A 03/30/2012 19:36:05 | 1333107365 | C1MB | Coolant 24C ESS 25C - 27C charging at 217.7V 47.97A 03/30/2012 19:37:05 | 1333107425 | C1MB | Coolant 26C ESS 26C - 27C charging at 218.8V 48.11A 03/30/2012 19:38:05 | 1333107485 | C1MB | Coolant 28C ESS 26C - 28C charging at 217.5V 47.92A 03/30/2012 19:39:05 | 1333107545 | C1MB | Coolant 28C ESS 27C - 28C charging at 217.7V 48.06A 03/30/2012 19:40:05 | 1333107605 | C1MB | Coolant 28C ESS 27C - 28C charging at 218.5V 48.11A 03/30/2012 19:41:05 | 1333107665 | C1MB | Coolant 28C ESS 27C - 28C charging at 218.9V 48.14A 03/30/2012 19:42:05 | 1333107725 | C1MB | Coolant 14C ESS 23C - 27C charging at 217.0V 47.81A 03/30/2012 19:43:05 | 1333107785 | C1MB | Coolant 23C ESS 24C - 26C charging at 216.8V 47.74A 03/30/2012 19:44:05 | 1333107845 | C1MB | Coolant 26C ESS 25C - 27C charging at 217.9V 47.98A 03/30/2012 19:45:05 | 1333107905 | C1MB | Coolant 26C ESS 26C - 27C charging at 216.9V 47.78A 03/30/2012 19:46:05 | 1333107965 | C1MB | Coolant 27C ESS 26C - 27C charging at 218.8V 48.14A 03/30/2012 19:47:05 | 1333108025 | C1MB | Coolant 28C ESS 26C - 27C charging at 216.7V 47.77A 03/30/2012 19:48:05 | 1333108085 | C1MB | Coolant 28C ESS 26C - 27C charging at 216.3V 48.09A 03/30/2012 19:49:05 | 1333108145 | C1MB | Coolant 17C ESS 24C - 27C charging at 216.4V 47.76A 03/30/2012 19:50:06 | 1333108206 | C1MB | Coolant 22C ESS 23C - 26C charging at 218.4V 48.26A 03/30/2012 19:51:06 | 1333108266 | C1MB | Coolant 24C ESS 24C - 26C charging at 218.4V 48.26A 03/30/2012 19:52:07 | 1333108327 | C1MB | Coolant 26C ESS 25C - 26C charging at 217.7V 48.16A 03/30/2012 19:53:08 | 1333108388 | C1MB | Coolant 26C ESS 25C - 26C charging at 219.1V 48.25A 03/30/2012 19:54:08 | 1333108448 | C1MB | Coolant 27C ESS 25C - 27C charging at 218.3V 48.27A 03/30/2012 19:55:09 | 1333108509 | C1MB | Coolant 27C ESS 26C - 27C charging at 217.0V 47.95A 03/30/2012 19:56:10 | 1333108570 | C1MB | Coolant 28C ESS 26C - 27C charging at 217.0V 48.03A 03/30/2012 19:57:10 | 1333108630 | C1MB | Coolant 14C ESS 23C - 26C charging at 218.0V 48.02A 03/30/2012 19:58:11 | 1333108691 | C1MB | Coolant 24C ESS 24C - 26C charging at 217.4V 47.98A 03/30/2012 19:59:12 | 1333108752 | C1MB | Coolant 25C ESS 24C - 26C charging at 216.6V 47.78A 03/30/2012 20:00:13 | 1333108813 | C1MB | Coolant 26C ESS 25C - 26C charging at 216.9V 47.81A 03/30/2012 20:01:13 | 1333108873 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.7V 48.27A 03/30/2012 20:01:30 | 1333108890 | C30M | range soc = 79%, 70A available 03/30/2012 20:02:14 | 1333108934 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.4V 48.16A 03/30/2012 20:03:15 | 1333108995 | C1MB | Coolant 27C ESS 25C - 26C charging at 217.5V 47.79A 03/30/2012 20:04:15 | 1333109055 | C1MB | Coolant 17C ESS 24C - 26C charging at 217.3V 47.79A 03/30/2012 20:05:16 | 1333109116 | C1MB | Coolant 21C ESS 22C - 25C charging at 218.2V 47.85A 03/30/2012 20:06:17 | 1333109177 | C1MB | Coolant 24C ESS 24C - 25C charging at 217.3V 49.34A 03/30/2012 20:07:17 | 1333109237 | C1MB | Coolant 25C ESS 24C - 25C charging at 218.4V 45.78A 03/30/2012 20:08:18 | 1333109298 | C1MB | Coolant 26C ESS 24C - 26C charging at 220.4V 42.43A 03/30/2012 20:09:19 | 1333109359 | C1MB | Coolant 26C ESS 25C - 26C charging at 220.0V 43.13A 03/30/2012 20:10:19 | 1333109419 | C1MB | Coolant 26C ESS 25C - 26C charging at 219.6V 42.09A 03/30/2012 20:11:20 | 1333109480 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.3V 43.46A 03/30/2012 20:12:21 | 1333109541 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.6V 41.73A 03/30/2012 20:13:22 | 1333109602 | C1MB | Coolant 14C ESS 22C - 25C charging at 220.4V 40.81A 03/30/2012 20:14:22 | 1333109662 | C1MB | Coolant 23C ESS 23C - 25C charging at 219.5V 33.66A 03/30/2012 20:15:23 | 1333109723 | C1MB | Coolant 24C ESS 24C - 25C charging at 218.9V 36.06A 03/30/2012 20:16:24 | 1333109784 | C1MB | Coolant 25C ESS 24C - 25C charging at 220.4V 35.36A 03/30/2012 20:17:24 | 1333109844 | C1MB | Coolant 26C ESS 24C - 25C charging at 221.0V 32.97A 03/30/2012 20:18:25 | 1333109905 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.9V 32.17A 03/30/2012 20:19:26 | 1333109966 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.4V 33.65A 03/30/2012 20:20:26 | 1333110026 | C1MB | Coolant 13C ESS 22C - 25C charging at 218.9V 37.86A 03/30/2012 20:21:27 | 1333110087 | C1MB | Coolant 22C ESS 22C - 24C charging at 219.2V 28.58A 03/30/2012 20:22:28 | 1333110148 | C1MB | Coolant 24C ESS 23C - 24C charging at 220.6V 27.84A 03/30/2012 20:23:28 | 1333110208 | C1MB | Coolant 24C ESS 23C - 25C charging at 219.7V 27.55A 03/30/2012 20:24:29 | 1333110269 | C1MB | Coolant 25C ESS 24C - 25C charging at 221.3V 28.81A 03/30/2012 20:25:30 | 1333110330 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.6V 24.53A 03/30/2012 20:26:30 | 1333110390 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.1V 26.89A 03/30/2012 20:27:31 | 1333110451 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.6V 26.35A 03/30/2012 20:28:32 | 1333110512 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.5V 24.03A 03/30/2012 20:29:13 | 1333110553 | IDLE | range soc = 84% ESS 23C - 25C, 2.691V min, 1.205V max and OVMS reported: 2012-03-30 18:24:07.142047 +0800 info main: #10 C EV915 rx msg S 81,K,-1,0,done,standard,250,219,48,67,100,10,7,4,0 2012-03-30 18:24:07.144289 +0800 info main: #10 C EV915 rx msg D 136,32,3,42,78,29,3272,65163,45,0,25,2,113,113 ==> Driving PEM:42, MOTOR:78, BATTERY:29, AMBIENT:25 2012-03-30 19:23:57.730154 +0800 info main: #10 C EV915 rx msg S 81,K,-1,0,done,standard,250,234,48,67,100,10,7,4,0 2012-03-30 19:23:57.732294 +0800 info main: #10 C EV915 rx msg D 104,8,4,34,56,29,3284,65175,0,3379,24,2,102,113 ==> Stopped PEM:34, MOTOR:56, BATTERY:29, AMBIENT:24 2012-03-30 19:33:57.348051 +0800 info main: #10 C EV915 rx msg S 82,K,217,48,charging,standard,253,237,48,2,100,0,5,1,0 2012-03-30 19:33:57.374906 +0800 info main: #10 C EV915 rx msg D 124,8,4,42,55,28,3284,65175,0,3986,25,2,120,120 ==> Charging PEM:42, MOTOR:55, BATTERY:28, AMBIENT:25 2012-03-30 19:44:11.802571 +0800 info main: #10 C EV915 rx msg S 84,K,217,48,charging,standard,262,245,48,12,100,2,5,1,0 2012-03-30 19:44:11.805104 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,53,27,3284,65175,0,4581,29,2,118,118 ==> Charging PEM:43, MOTOR:53, BATTERY:27, AMBIENT:29 2012-03-30 19:53:11.578629 +0800 info main: #10 C EV915 rx msg S 87,K,219,48,charging,standard,270,253,48,21,100,4,5,1,0 2012-03-30 19:53:11.582720 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,52,26,3284,65175,0,5142,28,2,120,120 ==> Charging PEM:43, MOTOR:52, BATTERY:26, AMBIENT:28 2012-03-30 20:03:55.020585 +0800 info main: #10 C EV915 rx msg S 91,K,218,48,charging,standard,282,262,48,32,100,6,5,1,0 2012-03-30 20:03:55.022789 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,51,26,3284,65175,0,5777,27,2,114,114 ==> Charging PEM:43, MOTOR:51, BATTERY:26, AMBIENT:27 2012-03-30 20:14:03.376116 +0800 info main: #10 C EV915 rx msg S 93,K,220,37,charging,standard,290,270,48,42,100,7,5,1,0 2012-03-30 20:14:03.378258 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,49,25,3284,65175,0,6374,29,2,112,112 ==> Charging PEM:43, MOTOR:49, BATTERY:25, AMBIENT:29 2012-03-30 20:24:01.668658 +0800 info main: #10 C EV915 rx msg S 95,K,221,28,charging,standard,296,277,48,52,100,8,5,1,0 2012-03-30 20:24:01.681265 +0800 info main: #10 C EV915 rx msg D 124,8,4,42,48,25,3284,65175,0,6980,29,2,120,120 ==> Charging PEM:42, MOTOR:48, BATTERY:25, AMBIENT:29 2012-03-30 20:33:59.497056 +0800 info main: #10 C EV915 rx msg S 96,K,0,0,done,standard,299,280,48,57,100,9,9,4,0 2012-03-30 20:33:59.505736 +0800 info main: #10 C EV915 rx msg D 108,8,4,34,47,25,3284,65175,0,7577,27,2,119,119 ==> Charged PEM:34, MOTOR:47, BATTERY: 25, AMBIENT:27 I reckon the actual ambient temperature was probably 24 or 25 Celcius. It goes up during the charge, presumably because the HVAC is spewing out hot air around the ambient sensor at the front of the car (which is in the garage so will build up heat). I think my data above is not a very good example, as I wasn't driving hard so the battery temperature was unusually low. My first instinct was that it would be good to use as an approximation for ambient, but actually not. The theory is that when the ambient temperature is hot or cold, the car has to use HVAC/heater to keep the battery at the temperature it needs, and that uses power which reduces charging efficiency. Battery temperature is a side-effect, and won't help to predict energy usage. So, I still think ambient temperature is the correct thing to use as a predictor for charging efficiency (along with current+voltage). The question is, looking at historical logs how can we approximate that? Only looking at charges that occurred an hour after a drive would work, but would remove 95% of my charges, like anyone else who plugs in when they get home ;-) Regards, Mark. On 8 Apr, 2012, at 4:22 PM, Dominik Westner wrote:
I already did some tests calculating the remaining charge time and had it implemented in the iPhone app.
First I took the simple approach to linearly estimate the remaining time by taking the charge current and voltage and calculate the energy per sec. Then take the missing energy from the current SOC. This will give you an approximation of the remaining time.
If you are looking at +/- 1 hour. This already should work from my experience.
I tried to make it better by taking into account that the charging curve is not linear, but more on a logarithmic scale. This worked a bit better. I also figured that there is some loss when charging, which I set to 5% (this probably varies by temperature).
What I did not know is the fact that once finished charging the batteries will be rebalanced for 30 minutes. Is this still shown as charging in OVMS? If yes, this would explain, why I've been off for about 30 - 60 minutes with my calculation.
I also did not take the age of the battery into account, which should be an important factor, too.
I think that it might be better to use a formula which tries to approximate the charging curve instead of using a fixed lookup table. At least it also could be fine tuned a bit easier by just setting a couple of parameters through the app to change the calculation.
Greetings
Dominik
On 08.04.2012, at 06:16, Tom Saxton wrote:
I think your model would work pretty well.
To calculate charge time, you also have to take into account the current tapering near the top of the charge.
We can get most of the required data from log files. The only tricky bit is getting the ambient temperature, which I don't think anyone has identified in the log files. You could get a good approximating by only considering charge sessions that start a least an hour of the most recent drive and then use the starting temperature of the coolant as a proxy for ambient temperature.
Range mode is the trickiest and the most important to time, they are also done less often, so it's harder to get data. I'd be happy to collect logs and extract data if we can get owners to contribute logs for a variety of charging levels and ambient temperatures.
Tom
on 4/6/12 5:52 PM, Mark Webb-Johnson wrote:
The core question I have here is whether it is possible to build a static table saying that at this temperature, this available voltage+currrent, the charging efficiency is X%? Something accurate enough to give us a charge time prediction (given temperature, kWh needed by the pack, available voltage+current) of +/- 1 hour?
I'm assuming the temperature should be ambient, as that is more important overt the duration of a reasonable charge than pack temperature?
If we can have such a table, with steps of 5 degrees celcius between -10C and +40C, and say 10 current levels, that is only 100 entries - and we would only need 1 byte for each entry. The module could then put in the current temperature, current/voltage level, and get out an efficiency factor. It could estimate the kWh the pack needs (by mode and SOC/ideal-miles difference), then multiply by efficiency factor, and get out an estimate of how many minutes is required to achieve that.
Without this table, we could do the lookup on the server, but that would mean having to set it _every_ night from the App/Server - as it would depend on the SOC% the car was actually at.
If we could build this data, where could we get the data from?
Regards, Mark.
Begin forwarded message:
From: Mark Webb-Johnson <mark@webb-johnson.net> Subject: Re: [Ovmsdev] Charge Control Date: 6 April, 2012 8:25:51 PM GMT+08:00 To: OVMS Developers <ovmsdev@lists.teslaclub.hk>
Bennett Leeds and I have had a discussion off-list (I'm not sure if he is on this list or not), and he brings up a valid point about balancing the pack perhaps not occurring if we cut short the charge with a SOC limit.
Looking here:
http://www.teslamotorsclub.com/showthread.php/3848-Tesla-Roadster-Battery-Ca... e?p=41995&viewfull=1#post41995
it seems that this approach may be non-optimal. For clarity, let me cut-and-paste the Tesla reply here:
For simplicity’s sake, I will refer to all SOC (State Of Charge) numbers as a percentage of a full (100%) charge. I cannot provide exact percentages, as there are many variables which can cause these numbers to vary slightly, however, I will get as close as I can.
When plugging in a nearly empty car that is set to Storage mode, the charge will generally stop at around 20%. The car will then settle into its normal Storage mode rhythm, topping up and discharging between 10% and 50% as the car sees fit. Oftentimes it will keep a tighter envelope based on parameters that I am not aware of.
Most important to remember is that Storage mode is not intended to be a driving mode. This charge setting is primarily meant to optimize battery life while the car is under storage conditions for two weeks or more.
Storage mode does not attempt to balance the pack, and you will cause an imbalance in the pack by driving and charging in this mode regularly.
This will penalize you when you do occasionally charge the car fully in the other modes, as you will not have the full range of the car available to you until the car has a chance to balance its battery. Additionally, the car’s range will not be as accurate if driven while in Storage mode vs. having charged it in Standard mode after storing the car, then driving it.
Allowing the car to sit plugged in after it has finished charging in Standard mode automatically balances the pack, and it may take a few rounds of this to bring an imbalanced pack back to its full potential after many partial charges. This is one of the major reasons we recommend keeping the car in Standard mode whenever possible. Partial charges in any mode, while not on their own bad for the battery, do not give the car an opportunity to balance its battery, and over time can prevent you from accessing the car’s full range potential.
When balanced, Standard mode charges the car to about 87%, with Range and Performance modes getting the car to about 97%. These two percentages are very much affected by the balance between bricks in the battery. An imbalanced pack will not fill up all the way in any mode, nor will it be able to discharge as far. Additionally, the range predictions will not be as accurate.
Your voltages are about right. 4.10 volts = full standard mode (187-195 ideal miles) 4.15 volts = full range mode 4.20 volts = maximum of the cells that we never touch As you may know, there is much more to it than just using voltage to calculate range with Lithium batteries. This is something that is incredibly complicated, and not something that I am qualified to discuss in detail, as I do not have the full picture.
It is important to remember that SOC is not the only factor in maximizing battery life. For instance most lithium batteries are shipped at around 30-50% SOC in consumer electronics, and part of the reasoning is that they are less susceptible to damage from extreme temperatures at these charge levels. It is also safer to store them at these levels. Part of the benefit of Storage mode is that there is less work required from the HVAC system to keep the batteryhappy and safe, and therefore, less energy is consumed while stored.
We chose ~90% as a Standard full charge level because it offers most of the longevity benefit of keeping the car at a lower state of charge, while still allowing a high degree of autonomy. I understand that you are interested in taking extra steps to maximize your battery’s life, so I do have some suggestions for you.
I would not recommend that you continue to use Storage mode as a means of maintaining a lower state of charge. As I explained earlier, this mode is not optimized for this type of use.
Think of battery degradation this way. It is very much a function of time spent at voltage and temperature. For instance, you do not want to charge a car all the way in performance mode, and then let it sit in the sun all day. Between the higher thermal limits and the high SOC, you are causing the battery a relatively high amount of degradation .In fact, the car will eventually allow itself to discharge to Standard levels if left in Performance mode to prevent inadvertent damage to the battery. If you start driving right away after charging in Performance or Range Mode, and don’t let it sit, you would minimize the damage incurred, as the time spent at these extremes is an important part of the calculation.
Similarly, if you top off to full in Standard mode, then jump in the car right away and bring the SOC down quickly, you will minimize the small amount of degradation that occurs at ~90%.
If you prefer to keep a lower average SOC in an attempt to maximize the life of your battery, I would instead suggest that you stay in Standard mode and utilize the Roadster’s built in charge timer and current limiting options to find an average SOC that works for you. For instance, try starting your charge at a time that allows the car to top off to a level you are comfortable with right before you need to leave. Alternately, you can use the Current limiting function to adjust the amount of time it takes the car reaches a target SOC, or even a combination of these two options. The car will remember the settings you select based on your location, so once you find something that works for your commute, you can set it and forget it.
Just remember that the car does benefit from being allowed to sit fully charged in Standard mode, and should be allowed to do so frequently, especially if being used on a daily basis. Leaving the car plugged in in Standard mode after it is done charging will initiate this balancing program automatically. This doesn’t take much time, 30 minutes or so should do. It may take several of these balancing cycles to bring the car back to a balanced state if it has become imbalanced, which is something that a lack of regular Standard mode top ups and subsequent balancing cycles can induce.
It would therefore be a good idea to set the car to “Charge on Plug In” instead of “Charge at X time” in the charge timing menu for at least a few Standard mode charges per week to keep the pack balanced. There are simply too many variables for me to be able to predict how often you would need to do this, and we do not have a recommended procedure for alternate desired average SOC levels.
I hope this helps answer your questions, and gives you a better idea of how to maximize battery life under your driving conditions.
Regards,
Dan Myggen
From what he is saying, it appears optimal to time the charge to bring it to full charge in standard mode 30 minutes before you leave. That would leave the car sitting at high charge rate for the least amount of time, but allow enough time for balancing to occur if necessary.
This sounds exactly like our finish-charging-by approach. Rather than set the charge start time, you set the finish time, and the system works out how long it should take then adds on a 30-to-60 minute safety margin (which would also allow for battery balancing to occur).
Does this make sense? Or is Dan Myggen's advise wrong?
Regards, Mark
On 5 Apr, 2012, at 7:45 PM, Mark Webb-Johnson wrote:
I'm now starting to think about the v1.3 firmware, which is intended to add the following:
Log charge history Log drive history Sophisticated control of charge time
We don't really have TOU metering in Hong Kong, so not much use for me, but part [3] would be fun nevertheless. Most charge control in EVs is pretty basic, and it might be interesting to see how sophisticated this can be made without complications.
I don't know if this is workable or not, so put my thoughts out into the open for discussion.
For charge time, the consensus seems to be that people want to enter the time to FINISH charge, vs the current time to START charge. To do that, we need an estimate of how long the charge will take. For that, we either need a sophisticated model or a collection of historical data we can lookup to find something approximate. Hence item [1] on my list.
Elon talked about the car learning about you. Where you park. Where you charge. etc. So, if always leave home at 7:00am to go to the office on Mondays through Fridays, perhaps the car can learn? Or, at least suggest based on what it has seen... Hence item [2] on my list.
For [1], we would store such things as temperatures, SOC start, SOC end, charge mode, charge current, charge voltage and duration. The can bus charge message seem to include this information.
For [2], we would store such things as date/time of drive, duration (time, distance, and elevation change), battery usage. We seem limited in this from what we have decoded on the can bus so far.
Regardless of the above, [1] and [2] would be useful information for any owner, anyway.
Privacy is an issue. Two problems - (a) protection of my charge/drive history, (b) the use of 'shared' charge history for [3]. My suggestion is to keep drive and charge history private. Perhaps it could just be stored as paranoid mode blobs. But, there should be an option to allow anonymised sharing of charge history for the use of [3]. My thinking is that if you share your data anonymously, then your lookup includes the pool of others anonymous charge history. if you choose not to share, then your lookup is only against your own charge history.
I did toy with the idea of using the server to control this. So, at 3am the server sends a command to the car to start the charge, etc. That would simplify the firmware in the car, but has a major problem of GPRS connectivity - if the cellular signal was lost the charge wouldn't start. Bad. So, I think it best to have the historical database in the server, the calculations in the App, and the settings downloaded to the car while it has cellular signal (after which it just follows them autonomously).
The Tesla Roadster currently offers you a choice of charge on plug-in, or start charge at a particular time. It also allows you to limit charge current and set charge mode. My thinking is to extend this by making it per day-of-the-week for a few defined locations, and to provide an override for the 'current' day/night. If the override is not set, and you are in one of the defined locations, then the system looks up the day of the week and controls charge based on what you have set. The UI for this is quite simple - presumably a screen with tabs/selector for day or the week, and then controls to set charge mode, current limit, and time to start/complete by. One developer also had the good idea that a charge SOC limit would be useful (e.g.; please stop charge when it gets to 70% / 220km ideal).
How do we handle night vs day charging? Is this only for overnight, or do we base it on when you plugin?
Is this workable? Useful?
Really interested in people's feedback on this.
Mark.
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Let's see if we can find the ambient temp in the log. On your log file, do this command: VMSParser -v -r C1MB -s "03/30/2012 19:31:30" -e "03/30/2012 20:29:13" That will dump out all of the bytes in the v2.0 1-minute charge records, C1MB, so we can correlate with what OVMS says. It might also be worth dumping out some of the 1-minute drive records from a drive segment with matching OVMS reports to look for the ambient temperature there as well. VMSParser -v -r DR1M If you want to look at it, I've attached the C snippet that decodes the relevant records. cbRecordHeader skips over the header bytes so that the first byte shown after the last vertical bar in the log output is at offset "cbRecordHeader + 0". Otherwise, you can send me the log output and I'll take a look. Is there a way I can get the OVMS records from my car so I can look for the ambient temperature in the v1.5 1-minute charge records? When charging at home, I use a timer so I'm charging off-peak and when there aren't any other big loads on our panel. Also, all of our cars are EVs, so we stagger times to avoid charging two (or possibly even three) at once. I hope most owners who can charge at 240V/32A or higher are also using the timer to charge off-peak. Tom on 4/9/12 7:48 AM, Mark Webb-Johnson wrote:
From my testing last summer (31 Celsius in Hong Kong), the efficiency loss was much worse than 5%, especially at low charge currents:
http://www.teslamotorsclub.com/showthread.php/5655-Charging-in-High-Temperat... e-environments-13A-vs-32A-vs-70A-cost-of-air-conditioning
Here's were my results at around 31 Celsius:
Here is Tom's analysis of my log files, vs his in cool weather, at the time:
Bottom line is that ambient temperature is very important to the estimate.
Tom:
I agree that the log files would give us the best historical data for a jump-start on this. The issues are (a) getting the files, (b) ambient temperature.
I don't think (a) would be a problem. I'll submit my logs for inclusion (I've probably got 100 or 200 charges in there at temperatures from 5 Celcius up to 33 Celcius). 99% standard mode. I'm sure, that others would also submit, and we could pretty quickly build up a model.
For (b), we either need to find it in the logs files, approximate it from something in the log files, or use something like this to approximate it.
For example, I did a charge on my car at 19:31 on 30th March 2012. VMSParser shows:
03/30/2012 19:31:30 | 1333107090 | C1MB | Coolant 30C ESS 28C - 29C charging at 203.7V 0.01A 03/30/2012 19:31:30 | 1333107090 | C30M | range soc = 73%, 70A available 03/30/2012 19:31:31 | 1333107091 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.00A 03/30/2012 19:31:32 | 1333107092 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.02A 03/30/2012 19:31:33 | 1333107093 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.1V 0.00A 03/30/2012 19:31:34 | 1333107094 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.00A 03/30/2012 19:31:35 | 1333107095 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.02A 03/30/2012 19:31:36 | 1333107096 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.01A 03/30/2012 19:31:37 | 1333107097 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.00A 03/30/2012 19:31:38 | 1333107098 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.01A 03/30/2012 19:31:39 | 1333107099 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.00A 03/30/2012 19:31:40 | 1333107100 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.02A 03/30/2012 19:31:41 | 1333107101 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.7V 0.00A 03/30/2012 19:31:42 | 1333107102 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.2V 0.04A 03/30/2012 19:31:43 | 1333107103 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.5V 0.00A 03/30/2012 19:31:44 | 1333107104 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.02A 03/30/2012 19:31:45 | 1333107105 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.3V 0.00A 03/30/2012 19:31:46 | 1333107106 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.02A 03/30/2012 19:31:47 | 1333107107 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.2V 0.00A 03/30/2012 19:31:48 | 1333107108 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.7V 0.01A 03/30/2012 19:31:49 | 1333107109 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.7V 0.00A 03/30/2012 19:31:50 | 1333107110 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.9V 0.01A 03/30/2012 19:31:51 | 1333107111 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.2V 0.00A 03/30/2012 19:31:52 | 1333107112 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.3V 0.23A 03/30/2012 19:31:52 | 1333107112 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.3V 0.23A 03/30/2012 19:31:53 | 1333107113 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.8V 0.18A 03/30/2012 19:31:54 | 1333107114 | C1MB | Coolant 30C ESS 28C - 29C charging at 223.2V 0.19A 03/30/2012 19:31:55 | 1333107115 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.8V 2.23A 03/30/2012 19:31:56 | 1333107116 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.9V 2.52A 03/30/2012 19:31:57 | 1333107117 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.1V 5.71A 03/30/2012 19:31:58 | 1333107118 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 16.96A 03/30/2012 19:31:59 | 1333107119 | C1MB | Coolant 30C ESS 28C - 29C charging at 219.9V 27.05A 03/30/2012 19:32:00 | 1333107120 | C1MB | Coolant 30C ESS 28C - 29C charging at 218.3V 36.99A 03/30/2012 19:32:01 | 1333107121 | C1MB | Coolant 30C ESS 28C - 29C charging at 217.5V 46.94A 03/30/2012 19:32:03 | 1333107123 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.9V 47.74A 03/30/2012 19:32:04 | 1333107124 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.7V 47.75A 03/30/2012 19:32:05 | 1333107125 | C1MB | Coolant 30C ESS 28C - 29C charging at 217.3V 47.79A 03/30/2012 19:33:05 | 1333107185 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.7V 47.84A 03/30/2012 19:34:05 | 1333107245 | C1MB | Coolant 16C ESS 25C - 28C charging at 217.9V 48.12A 03/30/2012 19:35:05 | 1333107305 | C1MB | Coolant 16C ESS 22C - 27C charging at 218.1V 47.96A 03/30/2012 19:36:05 | 1333107365 | C1MB | Coolant 24C ESS 25C - 27C charging at 217.7V 47.97A 03/30/2012 19:37:05 | 1333107425 | C1MB | Coolant 26C ESS 26C - 27C charging at 218.8V 48.11A 03/30/2012 19:38:05 | 1333107485 | C1MB | Coolant 28C ESS 26C - 28C charging at 217.5V 47.92A 03/30/2012 19:39:05 | 1333107545 | C1MB | Coolant 28C ESS 27C - 28C charging at 217.7V 48.06A 03/30/2012 19:40:05 | 1333107605 | C1MB | Coolant 28C ESS 27C - 28C charging at 218.5V 48.11A 03/30/2012 19:41:05 | 1333107665 | C1MB | Coolant 28C ESS 27C - 28C charging at 218.9V 48.14A 03/30/2012 19:42:05 | 1333107725 | C1MB | Coolant 14C ESS 23C - 27C charging at 217.0V 47.81A 03/30/2012 19:43:05 | 1333107785 | C1MB | Coolant 23C ESS 24C - 26C charging at 216.8V 47.74A 03/30/2012 19:44:05 | 1333107845 | C1MB | Coolant 26C ESS 25C - 27C charging at 217.9V 47.98A 03/30/2012 19:45:05 | 1333107905 | C1MB | Coolant 26C ESS 26C - 27C charging at 216.9V 47.78A 03/30/2012 19:46:05 | 1333107965 | C1MB | Coolant 27C ESS 26C - 27C charging at 218.8V 48.14A 03/30/2012 19:47:05 | 1333108025 | C1MB | Coolant 28C ESS 26C - 27C charging at 216.7V 47.77A 03/30/2012 19:48:05 | 1333108085 | C1MB | Coolant 28C ESS 26C - 27C charging at 216.3V 48.09A 03/30/2012 19:49:05 | 1333108145 | C1MB | Coolant 17C ESS 24C - 27C charging at 216.4V 47.76A 03/30/2012 19:50:06 | 1333108206 | C1MB | Coolant 22C ESS 23C - 26C charging at 218.4V 48.26A 03/30/2012 19:51:06 | 1333108266 | C1MB | Coolant 24C ESS 24C - 26C charging at 218.4V 48.26A 03/30/2012 19:52:07 | 1333108327 | C1MB | Coolant 26C ESS 25C - 26C charging at 217.7V 48.16A 03/30/2012 19:53:08 | 1333108388 | C1MB | Coolant 26C ESS 25C - 26C charging at 219.1V 48.25A 03/30/2012 19:54:08 | 1333108448 | C1MB | Coolant 27C ESS 25C - 27C charging at 218.3V 48.27A 03/30/2012 19:55:09 | 1333108509 | C1MB | Coolant 27C ESS 26C - 27C charging at 217.0V 47.95A 03/30/2012 19:56:10 | 1333108570 | C1MB | Coolant 28C ESS 26C - 27C charging at 217.0V 48.03A 03/30/2012 19:57:10 | 1333108630 | C1MB | Coolant 14C ESS 23C - 26C charging at 218.0V 48.02A 03/30/2012 19:58:11 | 1333108691 | C1MB | Coolant 24C ESS 24C - 26C charging at 217.4V 47.98A 03/30/2012 19:59:12 | 1333108752 | C1MB | Coolant 25C ESS 24C - 26C charging at 216.6V 47.78A 03/30/2012 20:00:13 | 1333108813 | C1MB | Coolant 26C ESS 25C - 26C charging at 216.9V 47.81A 03/30/2012 20:01:13 | 1333108873 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.7V 48.27A 03/30/2012 20:01:30 | 1333108890 | C30M | range soc = 79%, 70A available 03/30/2012 20:02:14 | 1333108934 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.4V 48.16A 03/30/2012 20:03:15 | 1333108995 | C1MB | Coolant 27C ESS 25C - 26C charging at 217.5V 47.79A 03/30/2012 20:04:15 | 1333109055 | C1MB | Coolant 17C ESS 24C - 26C charging at 217.3V 47.79A 03/30/2012 20:05:16 | 1333109116 | C1MB | Coolant 21C ESS 22C - 25C charging at 218.2V 47.85A 03/30/2012 20:06:17 | 1333109177 | C1MB | Coolant 24C ESS 24C - 25C charging at 217.3V 49.34A 03/30/2012 20:07:17 | 1333109237 | C1MB | Coolant 25C ESS 24C - 25C charging at 218.4V 45.78A 03/30/2012 20:08:18 | 1333109298 | C1MB | Coolant 26C ESS 24C - 26C charging at 220.4V 42.43A 03/30/2012 20:09:19 | 1333109359 | C1MB | Coolant 26C ESS 25C - 26C charging at 220.0V 43.13A 03/30/2012 20:10:19 | 1333109419 | C1MB | Coolant 26C ESS 25C - 26C charging at 219.6V 42.09A 03/30/2012 20:11:20 | 1333109480 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.3V 43.46A 03/30/2012 20:12:21 | 1333109541 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.6V 41.73A 03/30/2012 20:13:22 | 1333109602 | C1MB | Coolant 14C ESS 22C - 25C charging at 220.4V 40.81A 03/30/2012 20:14:22 | 1333109662 | C1MB | Coolant 23C ESS 23C - 25C charging at 219.5V 33.66A 03/30/2012 20:15:23 | 1333109723 | C1MB | Coolant 24C ESS 24C - 25C charging at 218.9V 36.06A 03/30/2012 20:16:24 | 1333109784 | C1MB | Coolant 25C ESS 24C - 25C charging at 220.4V 35.36A 03/30/2012 20:17:24 | 1333109844 | C1MB | Coolant 26C ESS 24C - 25C charging at 221.0V 32.97A 03/30/2012 20:18:25 | 1333109905 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.9V 32.17A 03/30/2012 20:19:26 | 1333109966 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.4V 33.65A 03/30/2012 20:20:26 | 1333110026 | C1MB | Coolant 13C ESS 22C - 25C charging at 218.9V 37.86A 03/30/2012 20:21:27 | 1333110087 | C1MB | Coolant 22C ESS 22C - 24C charging at 219.2V 28.58A 03/30/2012 20:22:28 | 1333110148 | C1MB | Coolant 24C ESS 23C - 24C charging at 220.6V 27.84A 03/30/2012 20:23:28 | 1333110208 | C1MB | Coolant 24C ESS 23C - 25C charging at 219.7V 27.55A 03/30/2012 20:24:29 | 1333110269 | C1MB | Coolant 25C ESS 24C - 25C charging at 221.3V 28.81A 03/30/2012 20:25:30 | 1333110330 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.6V 24.53A 03/30/2012 20:26:30 | 1333110390 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.1V 26.89A 03/30/2012 20:27:31 | 1333110451 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.6V 26.35A 03/30/2012 20:28:32 | 1333110512 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.5V 24.03A 03/30/2012 20:29:13 | 1333110553 | IDLE | range soc = 84% ESS 23C - 25C, 2.691V min, 1.205V max
and OVMS reported:
2012-03-30 18:24:07.142047 +0800 info main: #10 C EV915 rx msg S 81,K,-1,0,done,standard,250,219,48,67,100,10,7,4,0 2012-03-30 18:24:07.144289 +0800 info main: #10 C EV915 rx msg D 136,32,3,42,78,29,3272,65163,45,0,25,2,113,113 ==> Driving PEM:42, MOTOR:78, BATTERY:29, AMBIENT:25
2012-03-30 19:23:57.730154 +0800 info main: #10 C EV915 rx msg S 81,K,-1,0,done,standard,250,234,48,67,100,10,7,4,0 2012-03-30 19:23:57.732294 +0800 info main: #10 C EV915 rx msg D 104,8,4,34,56,29,3284,65175,0,3379,24,2,102,113 ==> Stopped PEM:34, MOTOR:56, BATTERY:29, AMBIENT:24
2012-03-30 19:33:57.348051 +0800 info main: #10 C EV915 rx msg S 82,K,217,48,charging,standard,253,237,48,2,100,0,5,1,0 2012-03-30 19:33:57.374906 +0800 info main: #10 C EV915 rx msg D 124,8,4,42,55,28,3284,65175,0,3986,25,2,120,120 ==> Charging PEM:42, MOTOR:55, BATTERY:28, AMBIENT:25
2012-03-30 19:44:11.802571 +0800 info main: #10 C EV915 rx msg S 84,K,217,48,charging,standard,262,245,48,12,100,2,5,1,0 2012-03-30 19:44:11.805104 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,53,27,3284,65175,0,4581,29,2,118,118 ==> Charging PEM:43, MOTOR:53, BATTERY:27, AMBIENT:29
2012-03-30 19:53:11.578629 +0800 info main: #10 C EV915 rx msg S 87,K,219,48,charging,standard,270,253,48,21,100,4,5,1,0 2012-03-30 19:53:11.582720 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,52,26,3284,65175,0,5142,28,2,120,120 ==> Charging PEM:43, MOTOR:52, BATTERY:26, AMBIENT:28
2012-03-30 20:03:55.020585 +0800 info main: #10 C EV915 rx msg S 91,K,218,48,charging,standard,282,262,48,32,100,6,5,1,0 2012-03-30 20:03:55.022789 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,51,26,3284,65175,0,5777,27,2,114,114 ==> Charging PEM:43, MOTOR:51, BATTERY:26, AMBIENT:27
2012-03-30 20:14:03.376116 +0800 info main: #10 C EV915 rx msg S 93,K,220,37,charging,standard,290,270,48,42,100,7,5,1,0 2012-03-30 20:14:03.378258 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,49,25,3284,65175,0,6374,29,2,112,112 ==> Charging PEM:43, MOTOR:49, BATTERY:25, AMBIENT:29
2012-03-30 20:24:01.668658 +0800 info main: #10 C EV915 rx msg S 95,K,221,28,charging,standard,296,277,48,52,100,8,5,1,0 2012-03-30 20:24:01.681265 +0800 info main: #10 C EV915 rx msg D 124,8,4,42,48,25,3284,65175,0,6980,29,2,120,120 ==> Charging PEM:42, MOTOR:48, BATTERY:25, AMBIENT:29
2012-03-30 20:33:59.497056 +0800 info main: #10 C EV915 rx msg S 96,K,0,0,done,standard,299,280,48,57,100,9,9,4,0 2012-03-30 20:33:59.505736 +0800 info main: #10 C EV915 rx msg D 108,8,4,34,47,25,3284,65175,0,7577,27,2,119,119 ==> Charged PEM:34, MOTOR:47, BATTERY: 25, AMBIENT:27
I reckon the actual ambient temperature was probably 24 or 25 Celcius. It goes up during the charge, presumably because the HVAC is spewing out hot air around the ambient sensor at the front of the car (which is in the garage so will build up heat).
I think my data above is not a very good example, as I wasn't driving hard so the battery temperature was unusually low. My first instinct was that it would be good to use as an approximation for ambient, but actually not. The theory is that when the ambient temperature is hot or cold, the car has to use HVAC/heater to keep the battery at the temperature it needs, and that uses power which reduces charging efficiency. Battery temperature is a side-effect, and won't help to predict energy usage.
So, I still think ambient temperature is the correct thing to use as a predictor for charging efficiency (along with current+voltage).
The question is, looking at historical logs how can we approximate that? Only looking at charges that occurred an hour after a drive would work, but would remove 95% of my charges, like anyone else who plugs in when they get home ;-)
Regards, Mark.
On 8 Apr, 2012, at 4:22 PM, Dominik Westner wrote:
I already did some tests calculating the remaining charge time and had it implemented in the iPhone app.
First I took the simple approach to linearly estimate the remaining time by taking the charge current and voltage and calculate the energy per sec. Then take the missing energy from the current SOC. This will give you an approximation of the remaining time.
If you are looking at +/- 1 hour. This already should work from my experience.
I tried to make it better by taking into account that the charging curve is not linear, but more on a logarithmic scale. This worked a bit better. I also figured that there is some loss when charging, which I set to 5% (this probably varies by temperature).
What I did not know is the fact that once finished charging the batteries will be rebalanced for 30 minutes. Is this still shown as charging in OVMS? If yes, this would explain, why I've been off for about 30 - 60 minutes with my calculation.
I also did not take the age of the battery into account, which should be an important factor, too.
I think that it might be better to use a formula which tries to approximate the charging curve instead of using a fixed lookup table. At least it also could be fine tuned a bit easier by just setting a couple of parameters through the app to change the calculation.
Greetings
Dominik
On 08.04.2012, at 06:16, Tom Saxton wrote:
I think your model would work pretty well.
To calculate charge time, you also have to take into account the current tapering near the top of the charge.
We can get most of the required data from log files. The only tricky bit is getting the ambient temperature, which I don't think anyone has identified in the log files. You could get a good approximating by only considering charge sessions that start a least an hour of the most recent drive and then use the starting temperature of the coolant as a proxy for ambient temperature.
Range mode is the trickiest and the most important to time, they are also done less often, so it's harder to get data. I'd be happy to collect logs and extract data if we can get owners to contribute logs for a variety of charging levels and ambient temperatures.
Tom
on 4/6/12 5:52 PM, Mark Webb-Johnson wrote:
The core question I have here is whether it is possible to build a static table saying that at this temperature, this available voltage+currrent, the charging efficiency is X%? Something accurate enough to give us a charge time prediction (given temperature, kWh needed by the pack, available voltage+current) of +/- 1 hour?
I'm assuming the temperature should be ambient, as that is more important overt the duration of a reasonable charge than pack temperature?
If we can have such a table, with steps of 5 degrees celcius between -10C and +40C, and say 10 current levels, that is only 100 entries - and we would only need 1 byte for each entry. The module could then put in the current temperature, current/voltage level, and get out an efficiency factor. It could estimate the kWh the pack needs (by mode and SOC/ideal-miles difference), then multiply by efficiency factor, and get out an estimate of how many minutes is required to achieve that.
Without this table, we could do the lookup on the server, but that would mean having to set it _every_ night from the App/Server - as it would depend on the SOC% the car was actually at.
If we could build this data, where could we get the data from?
Regards, Mark.
Begin forwarded message:
From: Mark Webb-Johnson <mark@webb-johnson.net> Subject: Re: [Ovmsdev] Charge Control Date: 6 April, 2012 8:25:51 PM GMT+08:00 To: OVMS Developers <ovmsdev@lists.teslaclub.hk>
Bennett Leeds and I have had a discussion off-list (I'm not sure if he is on this list or not), and he brings up a valid point about balancing the pack perhaps not occurring if we cut short the charge with a SOC limit.
Looking here:
http://www.teslamotorsclub.com/showthread.php/3848-Tesla-Roadster-Battery- Car e?p=41995&viewfull=1#post41995
it seems that this approach may be non-optimal. For clarity, let me cut-and-paste the Tesla reply here:
For simplicity¹s sake, I will refer to all SOC (State Of Charge) numbers as a percentage of a full (100%) charge. I cannot provide exact percentages, as there are many variables which can cause these numbers to vary slightly, however, I will get as close as I can.
When plugging in a nearly empty car that is set to Storage mode, the charge will generally stop at around 20%. The car will then settle into its normal Storage mode rhythm, topping up and discharging between 10% and 50% as the car sees fit. Oftentimes it will keep a tighter envelope based on parameters that I am not aware of.
Most important to remember is that Storage mode is not intended to be a driving mode. This charge setting is primarily meant to optimize battery life while the car is under storage conditions for two weeks or more.
Storage mode does not attempt to balance the pack, and you will cause an imbalance in the pack by driving and charging in this mode regularly.
This will penalize you when you do occasionally charge the car fully in the other modes, as you will not have the full range of the car available to you until the car has a chance to balance its battery. Additionally, the car¹s range will not be as accurate if driven while in Storage mode vs. having charged it in Standard mode after storing the car, then driving it.
Allowing the car to sit plugged in after it has finished charging in Standard mode automatically balances the pack, and it may take a few rounds of this to bring an imbalanced pack back to its full potential after many partial charges. This is one of the major reasons we recommend keeping the car in Standard mode whenever possible. Partial charges in any mode, while not on their own bad for the battery, do not give the car an opportunity to balance its battery, and over time can prevent you from accessing the car¹s full range potential.
When balanced, Standard mode charges the car to about 87%, with Range and Performance modes getting the car to about 97%. These two percentages are very much affected by the balance between bricks in the battery. An imbalanced pack will not fill up all the way in any mode, nor will it be able to discharge as far. Additionally, the range predictions will not be as accurate.
Your voltages are about right. 4.10 volts = full standard mode (187-195 ideal miles) 4.15 volts = full range mode 4.20 volts = maximum of the cells that we never touch As you may know, there is much more to it than just using voltage to calculate range with Lithium batteries. This is something that is incredibly complicated, and not something that I am qualified to discuss in detail, as I do not have the full picture.
It is important to remember that SOC is not the only factor in maximizing battery life. For instance most lithium batteries are shipped at around 30-50% SOC in consumer electronics, and part of the reasoning is that they are less susceptible to damage from extreme temperatures at these charge levels. It is also safer to store them at these levels. Part of the benefit of Storage mode is that there is less work required from the HVAC system to keep the batteryhappy and safe, and therefore, less energy is consumed while stored.
We chose ~90% as a Standard full charge level because it offers most of the longevity benefit of keeping the car at a lower state of charge, while still allowing a high degree of autonomy. I understand that you are interested in taking extra steps to maximize your battery¹s life, so I do have some suggestions for you.
I would not recommend that you continue to use Storage mode as a means of maintaining a lower state of charge. As I explained earlier, this mode is not optimized for this type of use.
Think of battery degradation this way. It is very much a function of time spent at voltage and temperature. For instance, you do not want to charge a car all the way in performance mode, and then let it sit in the sun all day. Between the higher thermal limits and the high SOC, you are causing the battery a relatively high amount of degradation .In fact, the car will eventually allow itself to discharge to Standard levels if left in Performance mode to prevent inadvertent damage to the battery. If you start driving right away after charging in Performance or Range Mode, and don¹t let it sit, you would minimize the damage incurred, as the time spent at these extremes is an important part of the calculation.
Similarly, if you top off to full in Standard mode, then jump in the car right away and bring the SOC down quickly, you will minimize the small amount of degradation that occurs at ~90%.
If you prefer to keep a lower average SOC in an attempt to maximize the life of your battery, I would instead suggest that you stay in Standard mode and utilize the Roadster¹s built in charge timer and current limiting options to find an average SOC that works for you. For instance, try starting your charge at a time that allows the car to top off to a level you are comfortable with right before you need to leave. Alternately, you can use the Current limiting function to adjust the amount of time it takes the car reaches a target SOC, or even a combination of these two options. The car will remember the settings you select based on your location, so once you find something that works for your commute, you can set it and forget it.
Just remember that the car does benefit from being allowed to sit fully charged in Standard mode, and should be allowed to do so frequently, especially if being used on a daily basis. Leaving the car plugged in in Standard mode after it is done charging will initiate this balancing program automatically. This doesn¹t take much time, 30 minutes or so should do. It may take several of these balancing cycles to bring the car back to a balanced state if it has become imbalanced, which is something that a lack of regular Standard mode top ups and subsequent balancing cycles can induce.
It would therefore be a good idea to set the car to ³Charge on Plug In² instead of ³Charge at X time² in the charge timing menu for at least a few Standard mode charges per week to keep the pack balanced. There are simply too many variables for me to be able to predict how often you would need to do this, and we do not have a recommended procedure for alternate desired average SOC levels.
I hope this helps answer your questions, and gives you a better idea of how to maximize battery life under your driving conditions.
Regards,
Dan Myggen
From what he is saying, it appears optimal to time the charge to bring it to full charge in standard mode 30 minutes before you leave. That would leave the car sitting at high charge rate for the least amount of time, but allow enough time for balancing to occur if necessary.
This sounds exactly like our finish-charging-by approach. Rather than set the charge start time, you set the finish time, and the system works out how long it should take then adds on a 30-to-60 minute safety margin (which would also allow for battery balancing to occur).
Does this make sense? Or is Dan Myggen's advise wrong?
Regards, Mark
On 5 Apr, 2012, at 7:45 PM, Mark Webb-Johnson wrote:
I'm now starting to think about the v1.3 firmware, which is intended to add the following:
Log charge history Log drive history Sophisticated control of charge time
We don't really have TOU metering in Hong Kong, so not much use for me, but part [3] would be fun nevertheless. Most charge control in EVs is pretty basic, and it might be interesting to see how sophisticated this can be made without complications.
I don't know if this is workable or not, so put my thoughts out into the open for discussion.
For charge time, the consensus seems to be that people want to enter the time to FINISH charge, vs the current time to START charge. To do that, we need an estimate of how long the charge will take. For that, we either need a sophisticated model or a collection of historical data we can lookup to find something approximate. Hence item [1] on my list.
Elon talked about the car learning about you. Where you park. Where you charge. etc. So, if always leave home at 7:00am to go to the office on Mondays through Fridays, perhaps the car can learn? Or, at least suggest based on what it has seen... Hence item [2] on my list.
For [1], we would store such things as temperatures, SOC start, SOC end, charge mode, charge current, charge voltage and duration. The can bus charge message seem to include this information.
For [2], we would store such things as date/time of drive, duration (time, distance, and elevation change), battery usage. We seem limited in this from what we have decoded on the can bus so far.
Regardless of the above, [1] and [2] would be useful information for any owner, anyway.
Privacy is an issue. Two problems - (a) protection of my charge/drive history, (b) the use of 'shared' charge history for [3]. My suggestion is to keep drive and charge history private. Perhaps it could just be stored as paranoid mode blobs. But, there should be an option to allow anonymised sharing of charge history for the use of [3]. My thinking is that if you share your data anonymously, then your lookup includes the pool of others anonymous charge history. if you choose not to share, then your lookup is only against your own charge history.
I did toy with the idea of using the server to control this. So, at 3am the server sends a command to the car to start the charge, etc. That would simplify the firmware in the car, but has a major problem of GPRS connectivity - if the cellular signal was lost the charge wouldn't start. Bad. So, I think it best to have the historical database in the server, the calculations in the App, and the settings downloaded to the car while it has cellular signal (after which it just follows them autonomously).
The Tesla Roadster currently offers you a choice of charge on plug-in, or start charge at a particular time. It also allows you to limit charge current and set charge mode. My thinking is to extend this by making it per day-of-the-week for a few defined locations, and to provide an override for the 'current' day/night. If the override is not set, and you are in one of the defined locations, then the system looks up the day of the week and controls charge based on what you have set. The UI for this is quite simple - presumably a screen with tabs/selector for day or the week, and then controls to set charge mode, current limit, and time to start/complete by. One developer also had the good idea that a charge SOC limit would be useful (e.g.; please stop charge when it gets to 70% / 220km ideal).
How do we handle night vs day charging? Is this only for overnight, or do we base it on when you plugin?
Is this workable? Useful?
Really interested in people's feedback on this.
Mark.
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hi mark, how are you doing on the UI development? no stress! just wondering if there is anything I can help with.........? best felix b. Sent from my iPad somewhere in our beautiful universe....... On 9 Apr, 2012, at 22:48, Mark Webb-Johnson <mark@webb-johnson.net> wrote:
From my testing last summer (31 Celsius in Hong Kong), the efficiency loss was much worse than 5%, especially at low charge currents:
http://www.teslamotorsclub.com/showthread.php/5655-Charging-in-High-Temperat...
Here's were my results at around 31 Celsius:
<attachment.php.png>
Here is Tom's analysis of my log files, vs his in cool weather, at the time:
<Hot-Weather-Charging-Stats.png>
Bottom line is that ambient temperature is very important to the estimate.
Tom:
I agree that the log files would give us the best historical data for a jump-start on this. The issues are (a) getting the files, (b) ambient temperature.
I don't think (a) would be a problem. I'll submit my logs for inclusion (I've probably got 100 or 200 charges in there at temperatures from 5 Celcius up to 33 Celcius). 99% standard mode. I'm sure, that others would also submit, and we could pretty quickly build up a model.
For (b), we either need to find it in the logs files, approximate it from something in the log files, or use something like this to approximate it.
For example, I did a charge on my car at 19:31 on 30th March 2012. VMSParser shows:
03/30/2012 19:31:30 | 1333107090 | C1MB | Coolant 30C ESS 28C - 29C charging at 203.7V 0.01A 03/30/2012 19:31:30 | 1333107090 | C30M | range soc = 73%, 70A available 03/30/2012 19:31:31 | 1333107091 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.00A 03/30/2012 19:31:32 | 1333107092 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.02A 03/30/2012 19:31:33 | 1333107093 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.1V 0.00A 03/30/2012 19:31:34 | 1333107094 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.00A 03/30/2012 19:31:35 | 1333107095 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.02A 03/30/2012 19:31:36 | 1333107096 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.01A 03/30/2012 19:31:37 | 1333107097 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.00A 03/30/2012 19:31:38 | 1333107098 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.01A 03/30/2012 19:31:39 | 1333107099 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.00A 03/30/2012 19:31:40 | 1333107100 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.02A 03/30/2012 19:31:41 | 1333107101 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.7V 0.00A 03/30/2012 19:31:42 | 1333107102 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.2V 0.04A 03/30/2012 19:31:43 | 1333107103 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.5V 0.00A 03/30/2012 19:31:44 | 1333107104 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.02A 03/30/2012 19:31:45 | 1333107105 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.3V 0.00A 03/30/2012 19:31:46 | 1333107106 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.02A 03/30/2012 19:31:47 | 1333107107 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.2V 0.00A 03/30/2012 19:31:48 | 1333107108 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.7V 0.01A 03/30/2012 19:31:49 | 1333107109 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.7V 0.00A 03/30/2012 19:31:50 | 1333107110 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.9V 0.01A 03/30/2012 19:31:51 | 1333107111 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.2V 0.00A 03/30/2012 19:31:52 | 1333107112 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.3V 0.23A 03/30/2012 19:31:52 | 1333107112 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.3V 0.23A 03/30/2012 19:31:53 | 1333107113 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.8V 0.18A 03/30/2012 19:31:54 | 1333107114 | C1MB | Coolant 30C ESS 28C - 29C charging at 223.2V 0.19A 03/30/2012 19:31:55 | 1333107115 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.8V 2.23A 03/30/2012 19:31:56 | 1333107116 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.9V 2.52A 03/30/2012 19:31:57 | 1333107117 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.1V 5.71A 03/30/2012 19:31:58 | 1333107118 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 16.96A 03/30/2012 19:31:59 | 1333107119 | C1MB | Coolant 30C ESS 28C - 29C charging at 219.9V 27.05A 03/30/2012 19:32:00 | 1333107120 | C1MB | Coolant 30C ESS 28C - 29C charging at 218.3V 36.99A 03/30/2012 19:32:01 | 1333107121 | C1MB | Coolant 30C ESS 28C - 29C charging at 217.5V 46.94A 03/30/2012 19:32:03 | 1333107123 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.9V 47.74A 03/30/2012 19:32:04 | 1333107124 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.7V 47.75A 03/30/2012 19:32:05 | 1333107125 | C1MB | Coolant 30C ESS 28C - 29C charging at 217.3V 47.79A 03/30/2012 19:33:05 | 1333107185 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.7V 47.84A 03/30/2012 19:34:05 | 1333107245 | C1MB | Coolant 16C ESS 25C - 28C charging at 217.9V 48.12A 03/30/2012 19:35:05 | 1333107305 | C1MB | Coolant 16C ESS 22C - 27C charging at 218.1V 47.96A 03/30/2012 19:36:05 | 1333107365 | C1MB | Coolant 24C ESS 25C - 27C charging at 217.7V 47.97A 03/30/2012 19:37:05 | 1333107425 | C1MB | Coolant 26C ESS 26C - 27C charging at 218.8V 48.11A 03/30/2012 19:38:05 | 1333107485 | C1MB | Coolant 28C ESS 26C - 28C charging at 217.5V 47.92A 03/30/2012 19:39:05 | 1333107545 | C1MB | Coolant 28C ESS 27C - 28C charging at 217.7V 48.06A 03/30/2012 19:40:05 | 1333107605 | C1MB | Coolant 28C ESS 27C - 28C charging at 218.5V 48.11A 03/30/2012 19:41:05 | 1333107665 | C1MB | Coolant 28C ESS 27C - 28C charging at 218.9V 48.14A 03/30/2012 19:42:05 | 1333107725 | C1MB | Coolant 14C ESS 23C - 27C charging at 217.0V 47.81A 03/30/2012 19:43:05 | 1333107785 | C1MB | Coolant 23C ESS 24C - 26C charging at 216.8V 47.74A 03/30/2012 19:44:05 | 1333107845 | C1MB | Coolant 26C ESS 25C - 27C charging at 217.9V 47.98A 03/30/2012 19:45:05 | 1333107905 | C1MB | Coolant 26C ESS 26C - 27C charging at 216.9V 47.78A 03/30/2012 19:46:05 | 1333107965 | C1MB | Coolant 27C ESS 26C - 27C charging at 218.8V 48.14A 03/30/2012 19:47:05 | 1333108025 | C1MB | Coolant 28C ESS 26C - 27C charging at 216.7V 47.77A 03/30/2012 19:48:05 | 1333108085 | C1MB | Coolant 28C ESS 26C - 27C charging at 216.3V 48.09A 03/30/2012 19:49:05 | 1333108145 | C1MB | Coolant 17C ESS 24C - 27C charging at 216.4V 47.76A 03/30/2012 19:50:06 | 1333108206 | C1MB | Coolant 22C ESS 23C - 26C charging at 218.4V 48.26A 03/30/2012 19:51:06 | 1333108266 | C1MB | Coolant 24C ESS 24C - 26C charging at 218.4V 48.26A 03/30/2012 19:52:07 | 1333108327 | C1MB | Coolant 26C ESS 25C - 26C charging at 217.7V 48.16A 03/30/2012 19:53:08 | 1333108388 | C1MB | Coolant 26C ESS 25C - 26C charging at 219.1V 48.25A 03/30/2012 19:54:08 | 1333108448 | C1MB | Coolant 27C ESS 25C - 27C charging at 218.3V 48.27A 03/30/2012 19:55:09 | 1333108509 | C1MB | Coolant 27C ESS 26C - 27C charging at 217.0V 47.95A 03/30/2012 19:56:10 | 1333108570 | C1MB | Coolant 28C ESS 26C - 27C charging at 217.0V 48.03A 03/30/2012 19:57:10 | 1333108630 | C1MB | Coolant 14C ESS 23C - 26C charging at 218.0V 48.02A 03/30/2012 19:58:11 | 1333108691 | C1MB | Coolant 24C ESS 24C - 26C charging at 217.4V 47.98A 03/30/2012 19:59:12 | 1333108752 | C1MB | Coolant 25C ESS 24C - 26C charging at 216.6V 47.78A 03/30/2012 20:00:13 | 1333108813 | C1MB | Coolant 26C ESS 25C - 26C charging at 216.9V 47.81A 03/30/2012 20:01:13 | 1333108873 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.7V 48.27A 03/30/2012 20:01:30 | 1333108890 | C30M | range soc = 79%, 70A available 03/30/2012 20:02:14 | 1333108934 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.4V 48.16A 03/30/2012 20:03:15 | 1333108995 | C1MB | Coolant 27C ESS 25C - 26C charging at 217.5V 47.79A 03/30/2012 20:04:15 | 1333109055 | C1MB | Coolant 17C ESS 24C - 26C charging at 217.3V 47.79A 03/30/2012 20:05:16 | 1333109116 | C1MB | Coolant 21C ESS 22C - 25C charging at 218.2V 47.85A 03/30/2012 20:06:17 | 1333109177 | C1MB | Coolant 24C ESS 24C - 25C charging at 217.3V 49.34A 03/30/2012 20:07:17 | 1333109237 | C1MB | Coolant 25C ESS 24C - 25C charging at 218.4V 45.78A 03/30/2012 20:08:18 | 1333109298 | C1MB | Coolant 26C ESS 24C - 26C charging at 220.4V 42.43A 03/30/2012 20:09:19 | 1333109359 | C1MB | Coolant 26C ESS 25C - 26C charging at 220.0V 43.13A 03/30/2012 20:10:19 | 1333109419 | C1MB | Coolant 26C ESS 25C - 26C charging at 219.6V 42.09A 03/30/2012 20:11:20 | 1333109480 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.3V 43.46A 03/30/2012 20:12:21 | 1333109541 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.6V 41.73A 03/30/2012 20:13:22 | 1333109602 | C1MB | Coolant 14C ESS 22C - 25C charging at 220.4V 40.81A 03/30/2012 20:14:22 | 1333109662 | C1MB | Coolant 23C ESS 23C - 25C charging at 219.5V 33.66A 03/30/2012 20:15:23 | 1333109723 | C1MB | Coolant 24C ESS 24C - 25C charging at 218.9V 36.06A 03/30/2012 20:16:24 | 1333109784 | C1MB | Coolant 25C ESS 24C - 25C charging at 220.4V 35.36A 03/30/2012 20:17:24 | 1333109844 | C1MB | Coolant 26C ESS 24C - 25C charging at 221.0V 32.97A 03/30/2012 20:18:25 | 1333109905 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.9V 32.17A 03/30/2012 20:19:26 | 1333109966 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.4V 33.65A 03/30/2012 20:20:26 | 1333110026 | C1MB | Coolant 13C ESS 22C - 25C charging at 218.9V 37.86A 03/30/2012 20:21:27 | 1333110087 | C1MB | Coolant 22C ESS 22C - 24C charging at 219.2V 28.58A 03/30/2012 20:22:28 | 1333110148 | C1MB | Coolant 24C ESS 23C - 24C charging at 220.6V 27.84A 03/30/2012 20:23:28 | 1333110208 | C1MB | Coolant 24C ESS 23C - 25C charging at 219.7V 27.55A 03/30/2012 20:24:29 | 1333110269 | C1MB | Coolant 25C ESS 24C - 25C charging at 221.3V 28.81A 03/30/2012 20:25:30 | 1333110330 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.6V 24.53A 03/30/2012 20:26:30 | 1333110390 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.1V 26.89A 03/30/2012 20:27:31 | 1333110451 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.6V 26.35A 03/30/2012 20:28:32 | 1333110512 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.5V 24.03A 03/30/2012 20:29:13 | 1333110553 | IDLE | range soc = 84% ESS 23C - 25C, 2.691V min, 1.205V max
and OVMS reported:
2012-03-30 18:24:07.142047 +0800 info main: #10 C EV915 rx msg S 81,K,-1,0,done,standard,250,219,48,67,100,10,7,4,0 2012-03-30 18:24:07.144289 +0800 info main: #10 C EV915 rx msg D 136,32,3,42,78,29,3272,65163,45,0,25,2,113,113 ==> Driving PEM:42, MOTOR:78, BATTERY:29, AMBIENT:25
2012-03-30 19:23:57.730154 +0800 info main: #10 C EV915 rx msg S 81,K,-1,0,done,standard,250,234,48,67,100,10,7,4,0 2012-03-30 19:23:57.732294 +0800 info main: #10 C EV915 rx msg D 104,8,4,34,56,29,3284,65175,0,3379,24,2,102,113 ==> Stopped PEM:34, MOTOR:56, BATTERY:29, AMBIENT:24
2012-03-30 19:33:57.348051 +0800 info main: #10 C EV915 rx msg S 82,K,217,48,charging,standard,253,237,48,2,100,0,5,1,0 2012-03-30 19:33:57.374906 +0800 info main: #10 C EV915 rx msg D 124,8,4,42,55,28,3284,65175,0,3986,25,2,120,120 ==> Charging PEM:42, MOTOR:55, BATTERY:28, AMBIENT:25
2012-03-30 19:44:11.802571 +0800 info main: #10 C EV915 rx msg S 84,K,217,48,charging,standard,262,245,48,12,100,2,5,1,0 2012-03-30 19:44:11.805104 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,53,27,3284,65175,0,4581,29,2,118,118 ==> Charging PEM:43, MOTOR:53, BATTERY:27, AMBIENT:29
2012-03-30 19:53:11.578629 +0800 info main: #10 C EV915 rx msg S 87,K,219,48,charging,standard,270,253,48,21,100,4,5,1,0 2012-03-30 19:53:11.582720 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,52,26,3284,65175,0,5142,28,2,120,120 ==> Charging PEM:43, MOTOR:52, BATTERY:26, AMBIENT:28
2012-03-30 20:03:55.020585 +0800 info main: #10 C EV915 rx msg S 91,K,218,48,charging,standard,282,262,48,32,100,6,5,1,0 2012-03-30 20:03:55.022789 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,51,26,3284,65175,0,5777,27,2,114,114 ==> Charging PEM:43, MOTOR:51, BATTERY:26, AMBIENT:27
2012-03-30 20:14:03.376116 +0800 info main: #10 C EV915 rx msg S 93,K,220,37,charging,standard,290,270,48,42,100,7,5,1,0 2012-03-30 20:14:03.378258 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,49,25,3284,65175,0,6374,29,2,112,112 ==> Charging PEM:43, MOTOR:49, BATTERY:25, AMBIENT:29
2012-03-30 20:24:01.668658 +0800 info main: #10 C EV915 rx msg S 95,K,221,28,charging,standard,296,277,48,52,100,8,5,1,0 2012-03-30 20:24:01.681265 +0800 info main: #10 C EV915 rx msg D 124,8,4,42,48,25,3284,65175,0,6980,29,2,120,120 ==> Charging PEM:42, MOTOR:48, BATTERY:25, AMBIENT:29
2012-03-30 20:33:59.497056 +0800 info main: #10 C EV915 rx msg S 96,K,0,0,done,standard,299,280,48,57,100,9,9,4,0 2012-03-30 20:33:59.505736 +0800 info main: #10 C EV915 rx msg D 108,8,4,34,47,25,3284,65175,0,7577,27,2,119,119 ==> Charged PEM:34, MOTOR:47, BATTERY: 25, AMBIENT:27
I reckon the actual ambient temperature was probably 24 or 25 Celcius. It goes up during the charge, presumably because the HVAC is spewing out hot air around the ambient sensor at the front of the car (which is in the garage so will build up heat).
I think my data above is not a very good example, as I wasn't driving hard so the battery temperature was unusually low. My first instinct was that it would be good to use as an approximation for ambient, but actually not. The theory is that when the ambient temperature is hot or cold, the car has to use HVAC/heater to keep the battery at the temperature it needs, and that uses power which reduces charging efficiency. Battery temperature is a side-effect, and won't help to predict energy usage.
So, I still think ambient temperature is the correct thing to use as a predictor for charging efficiency (along with current+voltage).
The question is, looking at historical logs how can we approximate that? Only looking at charges that occurred an hour after a drive would work, but would remove 95% of my charges, like anyone else who plugs in when they get home ;-)
Regards, Mark.
On 8 Apr, 2012, at 4:22 PM, Dominik Westner wrote:
I already did some tests calculating the remaining charge time and had it implemented in the iPhone app.
First I took the simple approach to linearly estimate the remaining time by taking the charge current and voltage and calculate the energy per sec. Then take the missing energy from the current SOC. This will give you an approximation of the remaining time.
If you are looking at +/- 1 hour. This already should work from my experience.
I tried to make it better by taking into account that the charging curve is not linear, but more on a logarithmic scale. This worked a bit better. I also figured that there is some loss when charging, which I set to 5% (this probably varies by temperature).
What I did not know is the fact that once finished charging the batteries will be rebalanced for 30 minutes. Is this still shown as charging in OVMS? If yes, this would explain, why I've been off for about 30 - 60 minutes with my calculation.
I also did not take the age of the battery into account, which should be an important factor, too.
I think that it might be better to use a formula which tries to approximate the charging curve instead of using a fixed lookup table. At least it also could be fine tuned a bit easier by just setting a couple of parameters through the app to change the calculation.
Greetings
Dominik
On 08.04.2012, at 06:16, Tom Saxton wrote:
I think your model would work pretty well.
To calculate charge time, you also have to take into account the current tapering near the top of the charge.
We can get most of the required data from log files. The only tricky bit is getting the ambient temperature, which I don't think anyone has identified in the log files. You could get a good approximating by only considering charge sessions that start a least an hour of the most recent drive and then use the starting temperature of the coolant as a proxy for ambient temperature.
Range mode is the trickiest and the most important to time, they are also done less often, so it's harder to get data. I'd be happy to collect logs and extract data if we can get owners to contribute logs for a variety of charging levels and ambient temperatures.
Tom
on 4/6/12 5:52 PM, Mark Webb-Johnson wrote:
The core question I have here is whether it is possible to build a static table saying that at this temperature, this available voltage+currrent, the charging efficiency is X%? Something accurate enough to give us a charge time prediction (given temperature, kWh needed by the pack, available voltage+current) of +/- 1 hour?
I'm assuming the temperature should be ambient, as that is more important overt the duration of a reasonable charge than pack temperature?
If we can have such a table, with steps of 5 degrees celcius between -10C and +40C, and say 10 current levels, that is only 100 entries - and we would only need 1 byte for each entry. The module could then put in the current temperature, current/voltage level, and get out an efficiency factor. It could estimate the kWh the pack needs (by mode and SOC/ideal-miles difference), then multiply by efficiency factor, and get out an estimate of how many minutes is required to achieve that.
Without this table, we could do the lookup on the server, but that would mean having to set it _every_ night from the App/Server - as it would depend on the SOC% the car was actually at.
If we could build this data, where could we get the data from?
Regards, Mark.
Begin forwarded message:
From: Mark Webb-Johnson <mark@webb-johnson.net> Subject: Re: [Ovmsdev] Charge Control Date: 6 April, 2012 8:25:51 PM GMT+08:00 To: OVMS Developers <ovmsdev@lists.teslaclub.hk>
Bennett Leeds and I have had a discussion off-list (I'm not sure if he is on this list or not), and he brings up a valid point about balancing the pack perhaps not occurring if we cut short the charge with a SOC limit.
Looking here:
http://www.teslamotorsclub.com/showthread.php/3848-Tesla-Roadster-Battery-Ca... e?p=41995&viewfull=1#post41995
it seems that this approach may be non-optimal. For clarity, let me cut-and-paste the Tesla reply here:
For simplicity’s sake, I will refer to all SOC (State Of Charge) numbers as a percentage of a full (100%) charge. I cannot provide exact percentages, as there are many variables which can cause these numbers to vary slightly, however, I will get as close as I can.
When plugging in a nearly empty car that is set to Storage mode, the charge will generally stop at around 20%. The car will then settle into its normal Storage mode rhythm, topping up and discharging between 10% and 50% as the car sees fit. Oftentimes it will keep a tighter envelope based on parameters that I am not aware of.
Most important to remember is that Storage mode is not intended to be a driving mode. This charge setting is primarily meant to optimize battery life while the car is under storage conditions for two weeks or more.
Storage mode does not attempt to balance the pack, and you will cause an imbalance in the pack by driving and charging in this mode regularly.
This will penalize you when you do occasionally charge the car fully in the other modes, as you will not have the full range of the car available to you until the car has a chance to balance its battery. Additionally, the car’s range will not be as accurate if driven while in Storage mode vs. having charged it in Standard mode after storing the car, then driving it.
Allowing the car to sit plugged in after it has finished charging in Standard mode automatically balances the pack, and it may take a few rounds of this to bring an imbalanced pack back to its full potential after many partial charges. This is one of the major reasons we recommend keeping the car in Standard mode whenever possible. Partial charges in any mode, while not on their own bad for the battery, do not give the car an opportunity to balance its battery, and over time can prevent you from accessing the car’s full range potential.
When balanced, Standard mode charges the car to about 87%, with Range and Performance modes getting the car to about 97%. These two percentages are very much affected by the balance between bricks in the battery. An imbalanced pack will not fill up all the way in any mode, nor will it be able to discharge as far. Additionally, the range predictions will not be as accurate.
Your voltages are about right. 4.10 volts = full standard mode (187-195 ideal miles) 4.15 volts = full range mode 4.20 volts = maximum of the cells that we never touch As you may know, there is much more to it than just using voltage to calculate range with Lithium batteries. This is something that is incredibly complicated, and not something that I am qualified to discuss in detail, as I do not have the full picture.
It is important to remember that SOC is not the only factor in maximizing battery life. For instance most lithium batteries are shipped at around 30-50% SOC in consumer electronics, and part of the reasoning is that they are less susceptible to damage from extreme temperatures at these charge levels. It is also safer to store them at these levels. Part of the benefit of Storage mode is that there is less work required from the HVAC system to keep the batteryhappy and safe, and therefore, less energy is consumed while stored.
We chose ~90% as a Standard full charge level because it offers most of the longevity benefit of keeping the car at a lower state of charge, while still allowing a high degree of autonomy. I understand that you are interested in taking extra steps to maximize your battery’s life, so I do have some suggestions for you.
I would not recommend that you continue to use Storage mode as a means of maintaining a lower state of charge. As I explained earlier, this mode is not optimized for this type of use.
Think of battery degradation this way. It is very much a function of time spent at voltage and temperature. For instance, you do not want to charge a car all the way in performance mode, and then let it sit in the sun all day. Between the higher thermal limits and the high SOC, you are causing the battery a relatively high amount of degradation .In fact, the car will eventually allow itself to discharge to Standard levels if left in Performance mode to prevent inadvertent damage to the battery. If you start driving right away after charging in Performance or Range Mode, and don’t let it sit, you would minimize the damage incurred, as the time spent at these extremes is an important part of the calculation.
Similarly, if you top off to full in Standard mode, then jump in the car right away and bring the SOC down quickly, you will minimize the small amount of degradation that occurs at ~90%.
If you prefer to keep a lower average SOC in an attempt to maximize the life of your battery, I would instead suggest that you stay in Standard mode and utilize the Roadster’s built in charge timer and current limiting options to find an average SOC that works for you. For instance, try starting your charge at a time that allows the car to top off to a level you are comfortable with right before you need to leave. Alternately, you can use the Current limiting function to adjust the amount of time it takes the car reaches a target SOC, or even a combination of these two options. The car will remember the settings you select based on your location, so once you find something that works for your commute, you can set it and forget it.
Just remember that the car does benefit from being allowed to sit fully charged in Standard mode, and should be allowed to do so frequently, especially if being used on a daily basis. Leaving the car plugged in in Standard mode after it is done charging will initiate this balancing program automatically. This doesn’t take much time, 30 minutes or so should do. It may take several of these balancing cycles to bring the car back to a balanced state if it has become imbalanced, which is something that a lack of regular Standard mode top ups and subsequent balancing cycles can induce.
It would therefore be a good idea to set the car to “Charge on Plug In” instead of “Charge at X time” in the charge timing menu for at least a few Standard mode charges per week to keep the pack balanced. There are simply too many variables for me to be able to predict how often you would need to do this, and we do not have a recommended procedure for alternate desired average SOC levels.
I hope this helps answer your questions, and gives you a better idea of how to maximize battery life under your driving conditions.
Regards,
Dan Myggen
From what he is saying, it appears optimal to time the charge to bring it to full charge in standard mode 30 minutes before you leave. That would leave the car sitting at high charge rate for the least amount of time, but allow enough time for balancing to occur if necessary.
This sounds exactly like our finish-charging-by approach. Rather than set the charge start time, you set the finish time, and the system works out how long it should take then adds on a 30-to-60 minute safety margin (which would also allow for battery balancing to occur).
Does this make sense? Or is Dan Myggen's advise wrong?
Regards, Mark
On 5 Apr, 2012, at 7:45 PM, Mark Webb-Johnson wrote:
I'm now starting to think about the v1.3 firmware, which is intended to add the following:
Log charge history Log drive history Sophisticated control of charge time
We don't really have TOU metering in Hong Kong, so not much use for me, but part [3] would be fun nevertheless. Most charge control in EVs is pretty basic, and it might be interesting to see how sophisticated this can be made without complications.
I don't know if this is workable or not, so put my thoughts out into the open for discussion.
For charge time, the consensus seems to be that people want to enter the time to FINISH charge, vs the current time to START charge. To do that, we need an estimate of how long the charge will take. For that, we either need a sophisticated model or a collection of historical data we can lookup to find something approximate. Hence item [1] on my list.
Elon talked about the car learning about you. Where you park. Where you charge. etc. So, if always leave home at 7:00am to go to the office on Mondays through Fridays, perhaps the car can learn? Or, at least suggest based on what it has seen... Hence item [2] on my list.
For [1], we would store such things as temperatures, SOC start, SOC end, charge mode, charge current, charge voltage and duration. The can bus charge message seem to include this information.
For [2], we would store such things as date/time of drive, duration (time, distance, and elevation change), battery usage. We seem limited in this from what we have decoded on the can bus so far.
Regardless of the above, [1] and [2] would be useful information for any owner, anyway.
Privacy is an issue. Two problems - (a) protection of my charge/drive history, (b) the use of 'shared' charge history for [3]. My suggestion is to keep drive and charge history private. Perhaps it could just be stored as paranoid mode blobs. But, there should be an option to allow anonymised sharing of charge history for the use of [3]. My thinking is that if you share your data anonymously, then your lookup includes the pool of others anonymous charge history. if you choose not to share, then your lookup is only against your own charge history.
I did toy with the idea of using the server to control this. So, at 3am the server sends a command to the car to start the charge, etc. That would simplify the firmware in the car, but has a major problem of GPRS connectivity - if the cellular signal was lost the charge wouldn't start. Bad. So, I think it best to have the historical database in the server, the calculations in the App, and the settings downloaded to the car while it has cellular signal (after which it just follows them autonomously).
The Tesla Roadster currently offers you a choice of charge on plug-in, or start charge at a particular time. It also allows you to limit charge current and set charge mode. My thinking is to extend this by making it per day-of-the-week for a few defined locations, and to provide an override for the 'current' day/night. If the override is not set, and you are in one of the defined locations, then the system looks up the day of the week and controls charge based on what you have set. The UI for this is quite simple - presumably a screen with tabs/selector for day or the week, and then controls to set charge mode, current limit, and time to start/complete by. One developer also had the good idea that a charge SOC limit would be useful (e.g.; please stop charge when it gets to 70% / 220km ideal).
How do we handle night vs day charging? Is this only for overnight, or do we base it on when you plugin?
Is this workable? Useful?
Really interested in people's feedback on this.
Mark.
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Felix, It is progressing. I got the car and battery screens tidied up. Now supporting suppression of the TPMS boxes if there is no TPMS installed, and grayed-out figures for those that are not currently being recently updated by the car. I even got the throbbing animation working on the charge port - very nice. Now working on moving the Info and Control screens around as we discussed. After that will be the MAP screen and social group support. Regards, Mark. On 10 Apr 2012, at 1:44 PM, felix bonnier wrote:
hi mark,
how are you doing on the UI development? no stress! just wondering if there is anything I can help with.........?
best
felix b.
Sent from my iPad somewhere in our beautiful universe.......
On 9 Apr, 2012, at 22:48, Mark Webb-Johnson <mark@webb-johnson.net> wrote:
From my testing last summer (31 Celsius in Hong Kong), the efficiency loss was much worse than 5%, especially at low charge currents:
http://www.teslamotorsclub.com/showthread.php/5655-Charging-in-High-Temperat...
Here's were my results at around 31 Celsius:
<attachment.php.png>
Here is Tom's analysis of my log files, vs his in cool weather, at the time:
<Hot-Weather-Charging-Stats.png>
Bottom line is that ambient temperature is very important to the estimate.
Tom:
I agree that the log files would give us the best historical data for a jump-start on this. The issues are (a) getting the files, (b) ambient temperature.
I don't think (a) would be a problem. I'll submit my logs for inclusion (I've probably got 100 or 200 charges in there at temperatures from 5 Celcius up to 33 Celcius). 99% standard mode. I'm sure, that others would also submit, and we could pretty quickly build up a model.
For (b), we either need to find it in the logs files, approximate it from something in the log files, or use something like this to approximate it.
For example, I did a charge on my car at 19:31 on 30th March 2012. VMSParser shows:
03/30/2012 19:31:30 | 1333107090 | C1MB | Coolant 30C ESS 28C - 29C charging at 203.7V 0.01A 03/30/2012 19:31:30 | 1333107090 | C30M | range soc = 73%, 70A available 03/30/2012 19:31:31 | 1333107091 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.00A 03/30/2012 19:31:32 | 1333107092 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.02A 03/30/2012 19:31:33 | 1333107093 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.1V 0.00A 03/30/2012 19:31:34 | 1333107094 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.00A 03/30/2012 19:31:35 | 1333107095 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.02A 03/30/2012 19:31:36 | 1333107096 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.01A 03/30/2012 19:31:37 | 1333107097 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.00A 03/30/2012 19:31:38 | 1333107098 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.01A 03/30/2012 19:31:39 | 1333107099 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.00A 03/30/2012 19:31:40 | 1333107100 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.02A 03/30/2012 19:31:41 | 1333107101 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.7V 0.00A 03/30/2012 19:31:42 | 1333107102 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.2V 0.04A 03/30/2012 19:31:43 | 1333107103 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.5V 0.00A 03/30/2012 19:31:44 | 1333107104 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.02A 03/30/2012 19:31:45 | 1333107105 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.3V 0.00A 03/30/2012 19:31:46 | 1333107106 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.02A 03/30/2012 19:31:47 | 1333107107 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.2V 0.00A 03/30/2012 19:31:48 | 1333107108 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.7V 0.01A 03/30/2012 19:31:49 | 1333107109 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.7V 0.00A 03/30/2012 19:31:50 | 1333107110 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.9V 0.01A 03/30/2012 19:31:51 | 1333107111 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.2V 0.00A 03/30/2012 19:31:52 | 1333107112 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.3V 0.23A 03/30/2012 19:31:52 | 1333107112 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.3V 0.23A 03/30/2012 19:31:53 | 1333107113 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.8V 0.18A 03/30/2012 19:31:54 | 1333107114 | C1MB | Coolant 30C ESS 28C - 29C charging at 223.2V 0.19A 03/30/2012 19:31:55 | 1333107115 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.8V 2.23A 03/30/2012 19:31:56 | 1333107116 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.9V 2.52A 03/30/2012 19:31:57 | 1333107117 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.1V 5.71A 03/30/2012 19:31:58 | 1333107118 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 16.96A 03/30/2012 19:31:59 | 1333107119 | C1MB | Coolant 30C ESS 28C - 29C charging at 219.9V 27.05A 03/30/2012 19:32:00 | 1333107120 | C1MB | Coolant 30C ESS 28C - 29C charging at 218.3V 36.99A 03/30/2012 19:32:01 | 1333107121 | C1MB | Coolant 30C ESS 28C - 29C charging at 217.5V 46.94A 03/30/2012 19:32:03 | 1333107123 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.9V 47.74A 03/30/2012 19:32:04 | 1333107124 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.7V 47.75A 03/30/2012 19:32:05 | 1333107125 | C1MB | Coolant 30C ESS 28C - 29C charging at 217.3V 47.79A 03/30/2012 19:33:05 | 1333107185 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.7V 47.84A 03/30/2012 19:34:05 | 1333107245 | C1MB | Coolant 16C ESS 25C - 28C charging at 217.9V 48.12A 03/30/2012 19:35:05 | 1333107305 | C1MB | Coolant 16C ESS 22C - 27C charging at 218.1V 47.96A 03/30/2012 19:36:05 | 1333107365 | C1MB | Coolant 24C ESS 25C - 27C charging at 217.7V 47.97A 03/30/2012 19:37:05 | 1333107425 | C1MB | Coolant 26C ESS 26C - 27C charging at 218.8V 48.11A 03/30/2012 19:38:05 | 1333107485 | C1MB | Coolant 28C ESS 26C - 28C charging at 217.5V 47.92A 03/30/2012 19:39:05 | 1333107545 | C1MB | Coolant 28C ESS 27C - 28C charging at 217.7V 48.06A 03/30/2012 19:40:05 | 1333107605 | C1MB | Coolant 28C ESS 27C - 28C charging at 218.5V 48.11A 03/30/2012 19:41:05 | 1333107665 | C1MB | Coolant 28C ESS 27C - 28C charging at 218.9V 48.14A 03/30/2012 19:42:05 | 1333107725 | C1MB | Coolant 14C ESS 23C - 27C charging at 217.0V 47.81A 03/30/2012 19:43:05 | 1333107785 | C1MB | Coolant 23C ESS 24C - 26C charging at 216.8V 47.74A 03/30/2012 19:44:05 | 1333107845 | C1MB | Coolant 26C ESS 25C - 27C charging at 217.9V 47.98A 03/30/2012 19:45:05 | 1333107905 | C1MB | Coolant 26C ESS 26C - 27C charging at 216.9V 47.78A 03/30/2012 19:46:05 | 1333107965 | C1MB | Coolant 27C ESS 26C - 27C charging at 218.8V 48.14A 03/30/2012 19:47:05 | 1333108025 | C1MB | Coolant 28C ESS 26C - 27C charging at 216.7V 47.77A 03/30/2012 19:48:05 | 1333108085 | C1MB | Coolant 28C ESS 26C - 27C charging at 216.3V 48.09A 03/30/2012 19:49:05 | 1333108145 | C1MB | Coolant 17C ESS 24C - 27C charging at 216.4V 47.76A 03/30/2012 19:50:06 | 1333108206 | C1MB | Coolant 22C ESS 23C - 26C charging at 218.4V 48.26A 03/30/2012 19:51:06 | 1333108266 | C1MB | Coolant 24C ESS 24C - 26C charging at 218.4V 48.26A 03/30/2012 19:52:07 | 1333108327 | C1MB | Coolant 26C ESS 25C - 26C charging at 217.7V 48.16A 03/30/2012 19:53:08 | 1333108388 | C1MB | Coolant 26C ESS 25C - 26C charging at 219.1V 48.25A 03/30/2012 19:54:08 | 1333108448 | C1MB | Coolant 27C ESS 25C - 27C charging at 218.3V 48.27A 03/30/2012 19:55:09 | 1333108509 | C1MB | Coolant 27C ESS 26C - 27C charging at 217.0V 47.95A 03/30/2012 19:56:10 | 1333108570 | C1MB | Coolant 28C ESS 26C - 27C charging at 217.0V 48.03A 03/30/2012 19:57:10 | 1333108630 | C1MB | Coolant 14C ESS 23C - 26C charging at 218.0V 48.02A 03/30/2012 19:58:11 | 1333108691 | C1MB | Coolant 24C ESS 24C - 26C charging at 217.4V 47.98A 03/30/2012 19:59:12 | 1333108752 | C1MB | Coolant 25C ESS 24C - 26C charging at 216.6V 47.78A 03/30/2012 20:00:13 | 1333108813 | C1MB | Coolant 26C ESS 25C - 26C charging at 216.9V 47.81A 03/30/2012 20:01:13 | 1333108873 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.7V 48.27A 03/30/2012 20:01:30 | 1333108890 | C30M | range soc = 79%, 70A available 03/30/2012 20:02:14 | 1333108934 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.4V 48.16A 03/30/2012 20:03:15 | 1333108995 | C1MB | Coolant 27C ESS 25C - 26C charging at 217.5V 47.79A 03/30/2012 20:04:15 | 1333109055 | C1MB | Coolant 17C ESS 24C - 26C charging at 217.3V 47.79A 03/30/2012 20:05:16 | 1333109116 | C1MB | Coolant 21C ESS 22C - 25C charging at 218.2V 47.85A 03/30/2012 20:06:17 | 1333109177 | C1MB | Coolant 24C ESS 24C - 25C charging at 217.3V 49.34A 03/30/2012 20:07:17 | 1333109237 | C1MB | Coolant 25C ESS 24C - 25C charging at 218.4V 45.78A 03/30/2012 20:08:18 | 1333109298 | C1MB | Coolant 26C ESS 24C - 26C charging at 220.4V 42.43A 03/30/2012 20:09:19 | 1333109359 | C1MB | Coolant 26C ESS 25C - 26C charging at 220.0V 43.13A 03/30/2012 20:10:19 | 1333109419 | C1MB | Coolant 26C ESS 25C - 26C charging at 219.6V 42.09A 03/30/2012 20:11:20 | 1333109480 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.3V 43.46A 03/30/2012 20:12:21 | 1333109541 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.6V 41.73A 03/30/2012 20:13:22 | 1333109602 | C1MB | Coolant 14C ESS 22C - 25C charging at 220.4V 40.81A 03/30/2012 20:14:22 | 1333109662 | C1MB | Coolant 23C ESS 23C - 25C charging at 219.5V 33.66A 03/30/2012 20:15:23 | 1333109723 | C1MB | Coolant 24C ESS 24C - 25C charging at 218.9V 36.06A 03/30/2012 20:16:24 | 1333109784 | C1MB | Coolant 25C ESS 24C - 25C charging at 220.4V 35.36A 03/30/2012 20:17:24 | 1333109844 | C1MB | Coolant 26C ESS 24C - 25C charging at 221.0V 32.97A 03/30/2012 20:18:25 | 1333109905 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.9V 32.17A 03/30/2012 20:19:26 | 1333109966 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.4V 33.65A 03/30/2012 20:20:26 | 1333110026 | C1MB | Coolant 13C ESS 22C - 25C charging at 218.9V 37.86A 03/30/2012 20:21:27 | 1333110087 | C1MB | Coolant 22C ESS 22C - 24C charging at 219.2V 28.58A 03/30/2012 20:22:28 | 1333110148 | C1MB | Coolant 24C ESS 23C - 24C charging at 220.6V 27.84A 03/30/2012 20:23:28 | 1333110208 | C1MB | Coolant 24C ESS 23C - 25C charging at 219.7V 27.55A 03/30/2012 20:24:29 | 1333110269 | C1MB | Coolant 25C ESS 24C - 25C charging at 221.3V 28.81A 03/30/2012 20:25:30 | 1333110330 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.6V 24.53A 03/30/2012 20:26:30 | 1333110390 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.1V 26.89A 03/30/2012 20:27:31 | 1333110451 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.6V 26.35A 03/30/2012 20:28:32 | 1333110512 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.5V 24.03A 03/30/2012 20:29:13 | 1333110553 | IDLE | range soc = 84% ESS 23C - 25C, 2.691V min, 1.205V max
and OVMS reported:
2012-03-30 18:24:07.142047 +0800 info main: #10 C EV915 rx msg S 81,K,-1,0,done,standard,250,219,48,67,100,10,7,4,0 2012-03-30 18:24:07.144289 +0800 info main: #10 C EV915 rx msg D 136,32,3,42,78,29,3272,65163,45,0,25,2,113,113 ==> Driving PEM:42, MOTOR:78, BATTERY:29, AMBIENT:25
2012-03-30 19:23:57.730154 +0800 info main: #10 C EV915 rx msg S 81,K,-1,0,done,standard,250,234,48,67,100,10,7,4,0 2012-03-30 19:23:57.732294 +0800 info main: #10 C EV915 rx msg D 104,8,4,34,56,29,3284,65175,0,3379,24,2,102,113 ==> Stopped PEM:34, MOTOR:56, BATTERY:29, AMBIENT:24
2012-03-30 19:33:57.348051 +0800 info main: #10 C EV915 rx msg S 82,K,217,48,charging,standard,253,237,48,2,100,0,5,1,0 2012-03-30 19:33:57.374906 +0800 info main: #10 C EV915 rx msg D 124,8,4,42,55,28,3284,65175,0,3986,25,2,120,120 ==> Charging PEM:42, MOTOR:55, BATTERY:28, AMBIENT:25
2012-03-30 19:44:11.802571 +0800 info main: #10 C EV915 rx msg S 84,K,217,48,charging,standard,262,245,48,12,100,2,5,1,0 2012-03-30 19:44:11.805104 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,53,27,3284,65175,0,4581,29,2,118,118 ==> Charging PEM:43, MOTOR:53, BATTERY:27, AMBIENT:29
2012-03-30 19:53:11.578629 +0800 info main: #10 C EV915 rx msg S 87,K,219,48,charging,standard,270,253,48,21,100,4,5,1,0 2012-03-30 19:53:11.582720 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,52,26,3284,65175,0,5142,28,2,120,120 ==> Charging PEM:43, MOTOR:52, BATTERY:26, AMBIENT:28
2012-03-30 20:03:55.020585 +0800 info main: #10 C EV915 rx msg S 91,K,218,48,charging,standard,282,262,48,32,100,6,5,1,0 2012-03-30 20:03:55.022789 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,51,26,3284,65175,0,5777,27,2,114,114 ==> Charging PEM:43, MOTOR:51, BATTERY:26, AMBIENT:27
2012-03-30 20:14:03.376116 +0800 info main: #10 C EV915 rx msg S 93,K,220,37,charging,standard,290,270,48,42,100,7,5,1,0 2012-03-30 20:14:03.378258 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,49,25,3284,65175,0,6374,29,2,112,112 ==> Charging PEM:43, MOTOR:49, BATTERY:25, AMBIENT:29
2012-03-30 20:24:01.668658 +0800 info main: #10 C EV915 rx msg S 95,K,221,28,charging,standard,296,277,48,52,100,8,5,1,0 2012-03-30 20:24:01.681265 +0800 info main: #10 C EV915 rx msg D 124,8,4,42,48,25,3284,65175,0,6980,29,2,120,120 ==> Charging PEM:42, MOTOR:48, BATTERY:25, AMBIENT:29
2012-03-30 20:33:59.497056 +0800 info main: #10 C EV915 rx msg S 96,K,0,0,done,standard,299,280,48,57,100,9,9,4,0 2012-03-30 20:33:59.505736 +0800 info main: #10 C EV915 rx msg D 108,8,4,34,47,25,3284,65175,0,7577,27,2,119,119 ==> Charged PEM:34, MOTOR:47, BATTERY: 25, AMBIENT:27
I reckon the actual ambient temperature was probably 24 or 25 Celcius. It goes up during the charge, presumably because the HVAC is spewing out hot air around the ambient sensor at the front of the car (which is in the garage so will build up heat).
I think my data above is not a very good example, as I wasn't driving hard so the battery temperature was unusually low. My first instinct was that it would be good to use as an approximation for ambient, but actually not. The theory is that when the ambient temperature is hot or cold, the car has to use HVAC/heater to keep the battery at the temperature it needs, and that uses power which reduces charging efficiency. Battery temperature is a side-effect, and won't help to predict energy usage.
So, I still think ambient temperature is the correct thing to use as a predictor for charging efficiency (along with current+voltage).
The question is, looking at historical logs how can we approximate that? Only looking at charges that occurred an hour after a drive would work, but would remove 95% of my charges, like anyone else who plugs in when they get home ;-)
Regards, Mark.
On 8 Apr, 2012, at 4:22 PM, Dominik Westner wrote:
I already did some tests calculating the remaining charge time and had it implemented in the iPhone app.
First I took the simple approach to linearly estimate the remaining time by taking the charge current and voltage and calculate the energy per sec. Then take the missing energy from the current SOC. This will give you an approximation of the remaining time.
If you are looking at +/- 1 hour. This already should work from my experience.
I tried to make it better by taking into account that the charging curve is not linear, but more on a logarithmic scale. This worked a bit better. I also figured that there is some loss when charging, which I set to 5% (this probably varies by temperature).
What I did not know is the fact that once finished charging the batteries will be rebalanced for 30 minutes. Is this still shown as charging in OVMS? If yes, this would explain, why I've been off for about 30 - 60 minutes with my calculation.
I also did not take the age of the battery into account, which should be an important factor, too.
I think that it might be better to use a formula which tries to approximate the charging curve instead of using a fixed lookup table. At least it also could be fine tuned a bit easier by just setting a couple of parameters through the app to change the calculation.
Greetings
Dominik
On 08.04.2012, at 06:16, Tom Saxton wrote:
I think your model would work pretty well.
To calculate charge time, you also have to take into account the current tapering near the top of the charge.
We can get most of the required data from log files. The only tricky bit is getting the ambient temperature, which I don't think anyone has identified in the log files. You could get a good approximating by only considering charge sessions that start a least an hour of the most recent drive and then use the starting temperature of the coolant as a proxy for ambient temperature.
Range mode is the trickiest and the most important to time, they are also done less often, so it's harder to get data. I'd be happy to collect logs and extract data if we can get owners to contribute logs for a variety of charging levels and ambient temperatures.
Tom
on 4/6/12 5:52 PM, Mark Webb-Johnson wrote:
The core question I have here is whether it is possible to build a static table saying that at this temperature, this available voltage+currrent, the charging efficiency is X%? Something accurate enough to give us a charge time prediction (given temperature, kWh needed by the pack, available voltage+current) of +/- 1 hour?
I'm assuming the temperature should be ambient, as that is more important overt the duration of a reasonable charge than pack temperature?
If we can have such a table, with steps of 5 degrees celcius between -10C and +40C, and say 10 current levels, that is only 100 entries - and we would only need 1 byte for each entry. The module could then put in the current temperature, current/voltage level, and get out an efficiency factor. It could estimate the kWh the pack needs (by mode and SOC/ideal-miles difference), then multiply by efficiency factor, and get out an estimate of how many minutes is required to achieve that.
Without this table, we could do the lookup on the server, but that would mean having to set it _every_ night from the App/Server - as it would depend on the SOC% the car was actually at.
If we could build this data, where could we get the data from?
Regards, Mark.
Begin forwarded message:
From: Mark Webb-Johnson <mark@webb-johnson.net> Subject: Re: [Ovmsdev] Charge Control Date: 6 April, 2012 8:25:51 PM GMT+08:00 To: OVMS Developers <ovmsdev@lists.teslaclub.hk>
Bennett Leeds and I have had a discussion off-list (I'm not sure if he is on this list or not), and he brings up a valid point about balancing the pack perhaps not occurring if we cut short the charge with a SOC limit.
Looking here:
http://www.teslamotorsclub.com/showthread.php/3848-Tesla-Roadster-Battery-Ca... e?p=41995&viewfull=1#post41995
it seems that this approach may be non-optimal. For clarity, let me cut-and-paste the Tesla reply here:
For simplicity’s sake, I will refer to all SOC (State Of Charge) numbers as a percentage of a full (100%) charge. I cannot provide exact percentages, as there are many variables which can cause these numbers to vary slightly, however, I will get as close as I can.
When plugging in a nearly empty car that is set to Storage mode, the charge will generally stop at around 20%. The car will then settle into its normal Storage mode rhythm, topping up and discharging between 10% and 50% as the car sees fit. Oftentimes it will keep a tighter envelope based on parameters that I am not aware of.
Most important to remember is that Storage mode is not intended to be a driving mode. This charge setting is primarily meant to optimize battery life while the car is under storage conditions for two weeks or more.
Storage mode does not attempt to balance the pack, and you will cause an imbalance in the pack by driving and charging in this mode regularly.
This will penalize you when you do occasionally charge the car fully in the other modes, as you will not have the full range of the car available to you until the car has a chance to balance its battery. Additionally, the car’s range will not be as accurate if driven while in Storage mode vs. having charged it in Standard mode after storing the car, then driving it.
Allowing the car to sit plugged in after it has finished charging in Standard mode automatically balances the pack, and it may take a few rounds of this to bring an imbalanced pack back to its full potential after many partial charges. This is one of the major reasons we recommend keeping the car in Standard mode whenever possible. Partial charges in any mode, while not on their own bad for the battery, do not give the car an opportunity to balance its battery, and over time can prevent you from accessing the car’s full range potential.
When balanced, Standard mode charges the car to about 87%, with Range and Performance modes getting the car to about 97%. These two percentages are very much affected by the balance between bricks in the battery. An imbalanced pack will not fill up all the way in any mode, nor will it be able to discharge as far. Additionally, the range predictions will not be as accurate.
Your voltages are about right. 4.10 volts = full standard mode (187-195 ideal miles) 4.15 volts = full range mode 4.20 volts = maximum of the cells that we never touch As you may know, there is much more to it than just using voltage to calculate range with Lithium batteries. This is something that is incredibly complicated, and not something that I am qualified to discuss in detail, as I do not have the full picture.
It is important to remember that SOC is not the only factor in maximizing battery life. For instance most lithium batteries are shipped at around 30-50% SOC in consumer electronics, and part of the reasoning is that they are less susceptible to damage from extreme temperatures at these charge levels. It is also safer to store them at these levels. Part of the benefit of Storage mode is that there is less work required from the HVAC system to keep the batteryhappy and safe, and therefore, less energy is consumed while stored.
We chose ~90% as a Standard full charge level because it offers most of the longevity benefit of keeping the car at a lower state of charge, while still allowing a high degree of autonomy. I understand that you are interested in taking extra steps to maximize your battery’s life, so I do have some suggestions for you.
I would not recommend that you continue to use Storage mode as a means of maintaining a lower state of charge. As I explained earlier, this mode is not optimized for this type of use.
Think of battery degradation this way. It is very much a function of time spent at voltage and temperature. For instance, you do not want to charge a car all the way in performance mode, and then let it sit in the sun all day. Between the higher thermal limits and the high SOC, you are causing the battery a relatively high amount of degradation .In fact, the car will eventually allow itself to discharge to Standard levels if left in Performance mode to prevent inadvertent damage to the battery. If you start driving right away after charging in Performance or Range Mode, and don’t let it sit, you would minimize the damage incurred, as the time spent at these extremes is an important part of the calculation.
Similarly, if you top off to full in Standard mode, then jump in the car right away and bring the SOC down quickly, you will minimize the small amount of degradation that occurs at ~90%.
If you prefer to keep a lower average SOC in an attempt to maximize the life of your battery, I would instead suggest that you stay in Standard mode and utilize the Roadster’s built in charge timer and current limiting options to find an average SOC that works for you. For instance, try starting your charge at a time that allows the car to top off to a level you are comfortable with right before you need to leave. Alternately, you can use the Current limiting function to adjust the amount of time it takes the car reaches a target SOC, or even a combination of these two options. The car will remember the settings you select based on your location, so once you find something that works for your commute, you can set it and forget it.
Just remember that the car does benefit from being allowed to sit fully charged in Standard mode, and should be allowed to do so frequently, especially if being used on a daily basis. Leaving the car plugged in in Standard mode after it is done charging will initiate this balancing program automatically. This doesn’t take much time, 30 minutes or so should do. It may take several of these balancing cycles to bring the car back to a balanced state if it has become imbalanced, which is something that a lack of regular Standard mode top ups and subsequent balancing cycles can induce.
It would therefore be a good idea to set the car to “Charge on Plug In” instead of “Charge at X time” in the charge timing menu for at least a few Standard mode charges per week to keep the pack balanced. There are simply too many variables for me to be able to predict how often you would need to do this, and we do not have a recommended procedure for alternate desired average SOC levels.
I hope this helps answer your questions, and gives you a better idea of how to maximize battery life under your driving conditions.
Regards,
Dan Myggen
From what he is saying, it appears optimal to time the charge to bring it to full charge in standard mode 30 minutes before you leave. That would leave the car sitting at high charge rate for the least amount of time, but allow enough time for balancing to occur if necessary.
This sounds exactly like our finish-charging-by approach. Rather than set the charge start time, you set the finish time, and the system works out how long it should take then adds on a 30-to-60 minute safety margin (which would also allow for battery balancing to occur).
Does this make sense? Or is Dan Myggen's advise wrong?
Regards, Mark
On 5 Apr, 2012, at 7:45 PM, Mark Webb-Johnson wrote:
> > I'm now starting to think about the v1.3 firmware, which is intended to add > the following: > > Log charge history > Log drive history > Sophisticated control of charge time > > We don't really have TOU metering in Hong Kong, so not much use for me, but > part [3] would be fun nevertheless. Most charge control in EVs is pretty > basic, and it might be interesting to see how sophisticated this can be made > without complications. > > I don't know if this is workable or not, so put my thoughts out into the > open for discussion. > > For charge time, the consensus seems to be that people want to enter the > time to FINISH charge, vs the current time to START charge. To do that, we > need an estimate of how long the charge will take. For that, we either need > a sophisticated model or a collection of historical data we can lookup to > find something approximate. Hence item [1] on my list. > > Elon talked about the car learning about you. Where you park. Where you > charge. etc. So, if always leave home at 7:00am to go to the office on > Mondays through Fridays, perhaps the car can learn? Or, at least suggest > based on what it has seen... Hence item [2] on my list. > > For [1], we would store such things as temperatures, SOC start, SOC end, > charge mode, charge current, charge voltage and duration. The can bus charge > message seem to include this information. > > For [2], we would store such things as date/time of drive, duration (time, > distance, and elevation change), battery usage. We seem limited in this from > what we have decoded on the can bus so far. > > Regardless of the above, [1] and [2] would be useful information for any > owner, anyway. > > Privacy is an issue. Two problems - (a) protection of my charge/drive > history, (b) the use of 'shared' charge history for [3]. My suggestion is to > keep drive and charge history private. Perhaps it could just be stored as > paranoid mode blobs. But, there should be an option to allow anonymised > sharing of charge history for the use of [3]. My thinking is that if you > share your data anonymously, then your lookup includes the pool of others > anonymous charge history. if you choose not to share, then your lookup is > only against your own charge history. > > I did toy with the idea of using the server to control this. So, at 3am the > server sends a command to the car to start the charge, etc. That would > simplify the firmware in the car, but has a major problem of GPRS > connectivity - if the cellular signal was lost the charge wouldn't start. > Bad. So, I think it best to have the historical database in the server, the > calculations in the App, and the settings downloaded to the car while it has > cellular signal (after which it just follows them autonomously). > > The Tesla Roadster currently offers you a choice of charge on plug-in, or > start charge at a particular time. It also allows you to limit charge > current and set charge mode. My thinking is to extend this by making it per > day-of-the-week for a few defined locations, and to provide an override for > the 'current' day/night. If the override is not set, and you are in one of > the defined locations, then the system looks up the day of the week and > controls charge based on what you have set. The UI for this is quite simple > - presumably a screen with tabs/selector for day or the week, and then > controls to set charge mode, current limit, and time to start/complete by. > One developer also had the good idea that a charge SOC limit would be useful > (e.g.; please stop charge when it gets to 70% / 220km ideal). > > How do we handle night vs day charging? Is this only for overnight, or do we > base it on when you plugin? > > Is this workable? Useful? > > Really interested in people's feedback on this. > > Mark. > > _______________________________________________ > OvmsDev mailing list > OvmsDev@lists.teslaclub.hk > http://lists.teslaclub.hk/mailman/listinfo/ovmsdev
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hi mark, just had another idea. could we tweak the park-timer so that after 48 or so it begins to count in days with half day increments?...... I park my roadster for extended periods when I'm in asia. so to know that it's been parked for 286hrs is not that useful days would be better at this point thanks /fb Sent from somewhere in our beautiful universe. On 10 Apr, 2012, at 14:03, Mark Webb-Johnson <mark@webb-johnson.net> wrote:
Felix,
It is progressing. I got the car and battery screens tidied up. Now supporting suppression of the TPMS boxes if there is no TPMS installed, and grayed-out figures for those that are not currently being recently updated by the car. I even got the throbbing animation working on the charge port - very nice.
Now working on moving the Info and Control screens around as we discussed.
After that will be the MAP screen and social group support.
Regards, Mark.
On 10 Apr 2012, at 1:44 PM, felix bonnier wrote:
hi mark,
how are you doing on the UI development? no stress! just wondering if there is anything I can help with.........?
best
felix b.
Sent from my iPad somewhere in our beautiful universe.......
On 9 Apr, 2012, at 22:48, Mark Webb-Johnson <mark@webb-johnson.net> wrote:
From my testing last summer (31 Celsius in Hong Kong), the efficiency loss was much worse than 5%, especially at low charge currents:
http://www.teslamotorsclub.com/showthread.php/5655-Charging-in-High-Temperat...
Here's were my results at around 31 Celsius:
<attachment.php.png>
Here is Tom's analysis of my log files, vs his in cool weather, at the time:
<Hot-Weather-Charging-Stats.png>
Bottom line is that ambient temperature is very important to the estimate.
Tom:
I agree that the log files would give us the best historical data for a jump-start on this. The issues are (a) getting the files, (b) ambient temperature.
I don't think (a) would be a problem. I'll submit my logs for inclusion (I've probably got 100 or 200 charges in there at temperatures from 5 Celcius up to 33 Celcius). 99% standard mode. I'm sure, that others would also submit, and we could pretty quickly build up a model.
For (b), we either need to find it in the logs files, approximate it from something in the log files, or use something like this to approximate it.
For example, I did a charge on my car at 19:31 on 30th March 2012. VMSParser shows:
03/30/2012 19:31:30 | 1333107090 | C1MB | Coolant 30C ESS 28C - 29C charging at 203.7V 0.01A 03/30/2012 19:31:30 | 1333107090 | C30M | range soc = 73%, 70A available 03/30/2012 19:31:31 | 1333107091 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.00A 03/30/2012 19:31:32 | 1333107092 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.02A 03/30/2012 19:31:33 | 1333107093 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.1V 0.00A 03/30/2012 19:31:34 | 1333107094 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.00A 03/30/2012 19:31:35 | 1333107095 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.02A 03/30/2012 19:31:36 | 1333107096 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.01A 03/30/2012 19:31:37 | 1333107097 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.00A 03/30/2012 19:31:38 | 1333107098 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.01A 03/30/2012 19:31:39 | 1333107099 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.00A 03/30/2012 19:31:40 | 1333107100 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.02A 03/30/2012 19:31:41 | 1333107101 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.7V 0.00A 03/30/2012 19:31:42 | 1333107102 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.2V 0.04A 03/30/2012 19:31:43 | 1333107103 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.5V 0.00A 03/30/2012 19:31:44 | 1333107104 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.02A 03/30/2012 19:31:45 | 1333107105 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.3V 0.00A 03/30/2012 19:31:46 | 1333107106 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.02A 03/30/2012 19:31:47 | 1333107107 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.2V 0.00A 03/30/2012 19:31:48 | 1333107108 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.7V 0.01A 03/30/2012 19:31:49 | 1333107109 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.7V 0.00A 03/30/2012 19:31:50 | 1333107110 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.9V 0.01A 03/30/2012 19:31:51 | 1333107111 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.2V 0.00A 03/30/2012 19:31:52 | 1333107112 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.3V 0.23A 03/30/2012 19:31:52 | 1333107112 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.3V 0.23A 03/30/2012 19:31:53 | 1333107113 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.8V 0.18A 03/30/2012 19:31:54 | 1333107114 | C1MB | Coolant 30C ESS 28C - 29C charging at 223.2V 0.19A 03/30/2012 19:31:55 | 1333107115 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.8V 2.23A 03/30/2012 19:31:56 | 1333107116 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.9V 2.52A 03/30/2012 19:31:57 | 1333107117 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.1V 5.71A 03/30/2012 19:31:58 | 1333107118 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 16.96A 03/30/2012 19:31:59 | 1333107119 | C1MB | Coolant 30C ESS 28C - 29C charging at 219.9V 27.05A 03/30/2012 19:32:00 | 1333107120 | C1MB | Coolant 30C ESS 28C - 29C charging at 218.3V 36.99A 03/30/2012 19:32:01 | 1333107121 | C1MB | Coolant 30C ESS 28C - 29C charging at 217.5V 46.94A 03/30/2012 19:32:03 | 1333107123 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.9V 47.74A 03/30/2012 19:32:04 | 1333107124 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.7V 47.75A 03/30/2012 19:32:05 | 1333107125 | C1MB | Coolant 30C ESS 28C - 29C charging at 217.3V 47.79A 03/30/2012 19:33:05 | 1333107185 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.7V 47.84A 03/30/2012 19:34:05 | 1333107245 | C1MB | Coolant 16C ESS 25C - 28C charging at 217.9V 48.12A 03/30/2012 19:35:05 | 1333107305 | C1MB | Coolant 16C ESS 22C - 27C charging at 218.1V 47.96A 03/30/2012 19:36:05 | 1333107365 | C1MB | Coolant 24C ESS 25C - 27C charging at 217.7V 47.97A 03/30/2012 19:37:05 | 1333107425 | C1MB | Coolant 26C ESS 26C - 27C charging at 218.8V 48.11A 03/30/2012 19:38:05 | 1333107485 | C1MB | Coolant 28C ESS 26C - 28C charging at 217.5V 47.92A 03/30/2012 19:39:05 | 1333107545 | C1MB | Coolant 28C ESS 27C - 28C charging at 217.7V 48.06A 03/30/2012 19:40:05 | 1333107605 | C1MB | Coolant 28C ESS 27C - 28C charging at 218.5V 48.11A 03/30/2012 19:41:05 | 1333107665 | C1MB | Coolant 28C ESS 27C - 28C charging at 218.9V 48.14A 03/30/2012 19:42:05 | 1333107725 | C1MB | Coolant 14C ESS 23C - 27C charging at 217.0V 47.81A 03/30/2012 19:43:05 | 1333107785 | C1MB | Coolant 23C ESS 24C - 26C charging at 216.8V 47.74A 03/30/2012 19:44:05 | 1333107845 | C1MB | Coolant 26C ESS 25C - 27C charging at 217.9V 47.98A 03/30/2012 19:45:05 | 1333107905 | C1MB | Coolant 26C ESS 26C - 27C charging at 216.9V 47.78A 03/30/2012 19:46:05 | 1333107965 | C1MB | Coolant 27C ESS 26C - 27C charging at 218.8V 48.14A 03/30/2012 19:47:05 | 1333108025 | C1MB | Coolant 28C ESS 26C - 27C charging at 216.7V 47.77A 03/30/2012 19:48:05 | 1333108085 | C1MB | Coolant 28C ESS 26C - 27C charging at 216.3V 48.09A 03/30/2012 19:49:05 | 1333108145 | C1MB | Coolant 17C ESS 24C - 27C charging at 216.4V 47.76A 03/30/2012 19:50:06 | 1333108206 | C1MB | Coolant 22C ESS 23C - 26C charging at 218.4V 48.26A 03/30/2012 19:51:06 | 1333108266 | C1MB | Coolant 24C ESS 24C - 26C charging at 218.4V 48.26A 03/30/2012 19:52:07 | 1333108327 | C1MB | Coolant 26C ESS 25C - 26C charging at 217.7V 48.16A 03/30/2012 19:53:08 | 1333108388 | C1MB | Coolant 26C ESS 25C - 26C charging at 219.1V 48.25A 03/30/2012 19:54:08 | 1333108448 | C1MB | Coolant 27C ESS 25C - 27C charging at 218.3V 48.27A 03/30/2012 19:55:09 | 1333108509 | C1MB | Coolant 27C ESS 26C - 27C charging at 217.0V 47.95A 03/30/2012 19:56:10 | 1333108570 | C1MB | Coolant 28C ESS 26C - 27C charging at 217.0V 48.03A 03/30/2012 19:57:10 | 1333108630 | C1MB | Coolant 14C ESS 23C - 26C charging at 218.0V 48.02A 03/30/2012 19:58:11 | 1333108691 | C1MB | Coolant 24C ESS 24C - 26C charging at 217.4V 47.98A 03/30/2012 19:59:12 | 1333108752 | C1MB | Coolant 25C ESS 24C - 26C charging at 216.6V 47.78A 03/30/2012 20:00:13 | 1333108813 | C1MB | Coolant 26C ESS 25C - 26C charging at 216.9V 47.81A 03/30/2012 20:01:13 | 1333108873 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.7V 48.27A 03/30/2012 20:01:30 | 1333108890 | C30M | range soc = 79%, 70A available 03/30/2012 20:02:14 | 1333108934 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.4V 48.16A 03/30/2012 20:03:15 | 1333108995 | C1MB | Coolant 27C ESS 25C - 26C charging at 217.5V 47.79A 03/30/2012 20:04:15 | 1333109055 | C1MB | Coolant 17C ESS 24C - 26C charging at 217.3V 47.79A 03/30/2012 20:05:16 | 1333109116 | C1MB | Coolant 21C ESS 22C - 25C charging at 218.2V 47.85A 03/30/2012 20:06:17 | 1333109177 | C1MB | Coolant 24C ESS 24C - 25C charging at 217.3V 49.34A 03/30/2012 20:07:17 | 1333109237 | C1MB | Coolant 25C ESS 24C - 25C charging at 218.4V 45.78A 03/30/2012 20:08:18 | 1333109298 | C1MB | Coolant 26C ESS 24C - 26C charging at 220.4V 42.43A 03/30/2012 20:09:19 | 1333109359 | C1MB | Coolant 26C ESS 25C - 26C charging at 220.0V 43.13A 03/30/2012 20:10:19 | 1333109419 | C1MB | Coolant 26C ESS 25C - 26C charging at 219.6V 42.09A 03/30/2012 20:11:20 | 1333109480 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.3V 43.46A 03/30/2012 20:12:21 | 1333109541 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.6V 41.73A 03/30/2012 20:13:22 | 1333109602 | C1MB | Coolant 14C ESS 22C - 25C charging at 220.4V 40.81A 03/30/2012 20:14:22 | 1333109662 | C1MB | Coolant 23C ESS 23C - 25C charging at 219.5V 33.66A 03/30/2012 20:15:23 | 1333109723 | C1MB | Coolant 24C ESS 24C - 25C charging at 218.9V 36.06A 03/30/2012 20:16:24 | 1333109784 | C1MB | Coolant 25C ESS 24C - 25C charging at 220.4V 35.36A 03/30/2012 20:17:24 | 1333109844 | C1MB | Coolant 26C ESS 24C - 25C charging at 221.0V 32.97A 03/30/2012 20:18:25 | 1333109905 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.9V 32.17A 03/30/2012 20:19:26 | 1333109966 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.4V 33.65A 03/30/2012 20:20:26 | 1333110026 | C1MB | Coolant 13C ESS 22C - 25C charging at 218.9V 37.86A 03/30/2012 20:21:27 | 1333110087 | C1MB | Coolant 22C ESS 22C - 24C charging at 219.2V 28.58A 03/30/2012 20:22:28 | 1333110148 | C1MB | Coolant 24C ESS 23C - 24C charging at 220.6V 27.84A 03/30/2012 20:23:28 | 1333110208 | C1MB | Coolant 24C ESS 23C - 25C charging at 219.7V 27.55A 03/30/2012 20:24:29 | 1333110269 | C1MB | Coolant 25C ESS 24C - 25C charging at 221.3V 28.81A 03/30/2012 20:25:30 | 1333110330 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.6V 24.53A 03/30/2012 20:26:30 | 1333110390 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.1V 26.89A 03/30/2012 20:27:31 | 1333110451 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.6V 26.35A 03/30/2012 20:28:32 | 1333110512 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.5V 24.03A 03/30/2012 20:29:13 | 1333110553 | IDLE | range soc = 84% ESS 23C - 25C, 2.691V min, 1.205V max
and OVMS reported:
2012-03-30 18:24:07.142047 +0800 info main: #10 C EV915 rx msg S 81,K,-1,0,done,standard,250,219,48,67,100,10,7,4,0 2012-03-30 18:24:07.144289 +0800 info main: #10 C EV915 rx msg D 136,32,3,42,78,29,3272,65163,45,0,25,2,113,113 ==> Driving PEM:42, MOTOR:78, BATTERY:29, AMBIENT:25
2012-03-30 19:23:57.730154 +0800 info main: #10 C EV915 rx msg S 81,K,-1,0,done,standard,250,234,48,67,100,10,7,4,0 2012-03-30 19:23:57.732294 +0800 info main: #10 C EV915 rx msg D 104,8,4,34,56,29,3284,65175,0,3379,24,2,102,113 ==> Stopped PEM:34, MOTOR:56, BATTERY:29, AMBIENT:24
2012-03-30 19:33:57.348051 +0800 info main: #10 C EV915 rx msg S 82,K,217,48,charging,standard,253,237,48,2,100,0,5,1,0 2012-03-30 19:33:57.374906 +0800 info main: #10 C EV915 rx msg D 124,8,4,42,55,28,3284,65175,0,3986,25,2,120,120 ==> Charging PEM:42, MOTOR:55, BATTERY:28, AMBIENT:25
2012-03-30 19:44:11.802571 +0800 info main: #10 C EV915 rx msg S 84,K,217,48,charging,standard,262,245,48,12,100,2,5,1,0 2012-03-30 19:44:11.805104 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,53,27,3284,65175,0,4581,29,2,118,118 ==> Charging PEM:43, MOTOR:53, BATTERY:27, AMBIENT:29
2012-03-30 19:53:11.578629 +0800 info main: #10 C EV915 rx msg S 87,K,219,48,charging,standard,270,253,48,21,100,4,5,1,0 2012-03-30 19:53:11.582720 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,52,26,3284,65175,0,5142,28,2,120,120 ==> Charging PEM:43, MOTOR:52, BATTERY:26, AMBIENT:28
2012-03-30 20:03:55.020585 +0800 info main: #10 C EV915 rx msg S 91,K,218,48,charging,standard,282,262,48,32,100,6,5,1,0 2012-03-30 20:03:55.022789 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,51,26,3284,65175,0,5777,27,2,114,114 ==> Charging PEM:43, MOTOR:51, BATTERY:26, AMBIENT:27
2012-03-30 20:14:03.376116 +0800 info main: #10 C EV915 rx msg S 93,K,220,37,charging,standard,290,270,48,42,100,7,5,1,0 2012-03-30 20:14:03.378258 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,49,25,3284,65175,0,6374,29,2,112,112 ==> Charging PEM:43, MOTOR:49, BATTERY:25, AMBIENT:29
2012-03-30 20:24:01.668658 +0800 info main: #10 C EV915 rx msg S 95,K,221,28,charging,standard,296,277,48,52,100,8,5,1,0 2012-03-30 20:24:01.681265 +0800 info main: #10 C EV915 rx msg D 124,8,4,42,48,25,3284,65175,0,6980,29,2,120,120 ==> Charging PEM:42, MOTOR:48, BATTERY:25, AMBIENT:29
2012-03-30 20:33:59.497056 +0800 info main: #10 C EV915 rx msg S 96,K,0,0,done,standard,299,280,48,57,100,9,9,4,0 2012-03-30 20:33:59.505736 +0800 info main: #10 C EV915 rx msg D 108,8,4,34,47,25,3284,65175,0,7577,27,2,119,119 ==> Charged PEM:34, MOTOR:47, BATTERY: 25, AMBIENT:27
I reckon the actual ambient temperature was probably 24 or 25 Celcius. It goes up during the charge, presumably because the HVAC is spewing out hot air around the ambient sensor at the front of the car (which is in the garage so will build up heat).
I think my data above is not a very good example, as I wasn't driving hard so the battery temperature was unusually low. My first instinct was that it would be good to use as an approximation for ambient, but actually not. The theory is that when the ambient temperature is hot or cold, the car has to use HVAC/heater to keep the battery at the temperature it needs, and that uses power which reduces charging efficiency. Battery temperature is a side-effect, and won't help to predict energy usage.
So, I still think ambient temperature is the correct thing to use as a predictor for charging efficiency (along with current+voltage).
The question is, looking at historical logs how can we approximate that? Only looking at charges that occurred an hour after a drive would work, but would remove 95% of my charges, like anyone else who plugs in when they get home ;-)
Regards, Mark.
On 8 Apr, 2012, at 4:22 PM, Dominik Westner wrote:
I already did some tests calculating the remaining charge time and had it implemented in the iPhone app.
First I took the simple approach to linearly estimate the remaining time by taking the charge current and voltage and calculate the energy per sec. Then take the missing energy from the current SOC. This will give you an approximation of the remaining time.
If you are looking at +/- 1 hour. This already should work from my experience.
I tried to make it better by taking into account that the charging curve is not linear, but more on a logarithmic scale. This worked a bit better. I also figured that there is some loss when charging, which I set to 5% (this probably varies by temperature).
What I did not know is the fact that once finished charging the batteries will be rebalanced for 30 minutes. Is this still shown as charging in OVMS? If yes, this would explain, why I've been off for about 30 - 60 minutes with my calculation.
I also did not take the age of the battery into account, which should be an important factor, too.
I think that it might be better to use a formula which tries to approximate the charging curve instead of using a fixed lookup table. At least it also could be fine tuned a bit easier by just setting a couple of parameters through the app to change the calculation.
Greetings
Dominik
On 08.04.2012, at 06:16, Tom Saxton wrote:
I think your model would work pretty well.
To calculate charge time, you also have to take into account the current tapering near the top of the charge.
We can get most of the required data from log files. The only tricky bit is getting the ambient temperature, which I don't think anyone has identified in the log files. You could get a good approximating by only considering charge sessions that start a least an hour of the most recent drive and then use the starting temperature of the coolant as a proxy for ambient temperature.
Range mode is the trickiest and the most important to time, they are also done less often, so it's harder to get data. I'd be happy to collect logs and extract data if we can get owners to contribute logs for a variety of charging levels and ambient temperatures.
Tom
on 4/6/12 5:52 PM, Mark Webb-Johnson wrote:
The core question I have here is whether it is possible to build a static table saying that at this temperature, this available voltage+currrent, the charging efficiency is X%? Something accurate enough to give us a charge time prediction (given temperature, kWh needed by the pack, available voltage+current) of +/- 1 hour?
I'm assuming the temperature should be ambient, as that is more important overt the duration of a reasonable charge than pack temperature?
If we can have such a table, with steps of 5 degrees celcius between -10C and +40C, and say 10 current levels, that is only 100 entries - and we would only need 1 byte for each entry. The module could then put in the current temperature, current/voltage level, and get out an efficiency factor. It could estimate the kWh the pack needs (by mode and SOC/ideal-miles difference), then multiply by efficiency factor, and get out an estimate of how many minutes is required to achieve that.
Without this table, we could do the lookup on the server, but that would mean having to set it _every_ night from the App/Server - as it would depend on the SOC% the car was actually at.
If we could build this data, where could we get the data from?
Regards, Mark.
Begin forwarded message:
> From: Mark Webb-Johnson <mark@webb-johnson.net> > Subject: Re: [Ovmsdev] Charge Control > Date: 6 April, 2012 8:25:51 PM GMT+08:00 > To: OVMS Developers <ovmsdev@lists.teslaclub.hk> > > > Bennett Leeds and I have had a discussion off-list (I'm not sure if he is on > this list or not), and he brings up a valid point about balancing the pack > perhaps not occurring if we cut short the charge with a SOC limit. > > Looking here: > > http://www.teslamotorsclub.com/showthread.php/3848-Tesla-Roadster-Battery-Ca... > e?p=41995&viewfull=1#post41995 > > it seems that this approach may be non-optimal. For clarity, let me > cut-and-paste the Tesla reply here: > > For simplicity’s sake, I will refer to all SOC (State Of Charge) numbers as a > percentage of a full (100%) charge. I cannot provide exact percentages, as > there are many variables which can cause these numbers to vary slightly, > however, I will get as close as I can. > > When plugging in a nearly empty car that is set to Storage mode, the charge > will generally stop at around 20%. The car will then settle into its normal > Storage mode rhythm, topping up and discharging between 10% and 50% as the > car sees fit. Oftentimes it will keep a tighter envelope based on parameters > that I am not aware of. > > Most important to remember is that Storage mode is not intended to be a > driving mode. This charge setting is primarily meant to optimize battery life > while the car is under storage conditions for two weeks or more. > > Storage mode does not attempt to balance the pack, and you will cause an > imbalance in the pack by driving and charging in this mode regularly. > > This will penalize you when you do occasionally charge the car fully in the > other modes, as you will not have the full range of the car available to you > until the car has a chance to balance its battery. Additionally, the car’s > range will not be as accurate if driven while in Storage mode vs. having > charged it in Standard mode after storing the car, then driving it. > > Allowing the car to sit plugged in after it has finished charging in Standard > mode automatically balances the pack, and it may take a few rounds of this to > bring an imbalanced pack back to its full potential after many partial > charges. This is one of the major reasons we recommend keeping the car in > Standard mode whenever possible. Partial charges in any mode, while not on > their own bad for the battery, do not give the car an opportunity to balance > its battery, and over time can prevent you from accessing the car’s full > range potential. > > When balanced, Standard mode charges the car to about 87%, with Range and > Performance modes getting the car to about 97%. These two percentages are > very much affected by the balance between bricks in the battery. An > imbalanced pack will not fill up all the way in any mode, nor will it be able > to discharge as far. Additionally, the range predictions will not be as > accurate. > > Your voltages are about right. > 4.10 volts = full standard mode (187-195 ideal miles) > 4.15 volts = full range mode > 4.20 volts = maximum of the cells that we never touch > As you may know, there is much more to it than just using voltage to > calculate range with Lithium batteries. This is something that is incredibly > complicated, and not something that I am qualified to discuss in detail, as I > do not have the full picture. > > It is important to remember that SOC is not the only factor in maximizing > battery life. For instance most lithium batteries are shipped at around > 30-50% SOC in consumer electronics, and part of the reasoning is that they > are less susceptible to damage from extreme temperatures at these charge > levels. It is also safer to store them at these levels. Part of the benefit > of Storage mode is that there is less work required from the HVAC system to > keep the batteryhappy and safe, and therefore, less energy is consumed while > stored. > > We chose ~90% as a Standard full charge level because it offers most of the > longevity benefit of keeping the car at a lower state of charge, while still > allowing a high degree of autonomy. I understand that you are interested in > taking extra steps to maximize your battery’s life, so I do have some > suggestions for you. > > I would not recommend that you continue to use Storage mode as a means of > maintaining a lower state of charge. As I explained earlier, this mode is not > optimized for this type of use. > > Think of battery degradation this way. It is very much a function of time > spent at voltage and temperature. For instance, you do not want to charge a > car all the way in performance mode, and then let it sit in the sun all day. > Between the higher thermal limits and the high SOC, you are causing the > battery a relatively high amount of degradation .In fact, the car will > eventually allow itself to discharge to Standard levels if left in > Performance mode to prevent inadvertent damage to the battery. If you start > driving right away after charging in Performance or Range Mode, and don’t let > it sit, you would minimize the damage incurred, as the time spent at these > extremes is an important part of the calculation. > > Similarly, if you top off to full in Standard mode, then jump in the car > right away and bring the SOC down quickly, you will minimize the small amount > of degradation that occurs at ~90%. > > If you prefer to keep a lower average SOC in an attempt to maximize the life > of your battery, I would instead suggest that you stay in Standard mode and > utilize the Roadster’s built in charge timer and current limiting options to > find an average SOC that works for you. For instance, try starting your > charge at a time that allows the car to top off to a level you are > comfortable with right before you need to leave. Alternately, you can use the > Current limiting function to adjust the amount of time it takes the car > reaches a target SOC, or even a combination of these two options. The car > will remember the settings you select based on your location, so once you > find something that works for your commute, you can set it and forget it. > > Just remember that the car does benefit from being allowed to sit fully > charged in Standard mode, and should be allowed to do so frequently, > especially if being used on a daily basis. Leaving the car plugged in in > Standard mode after it is done charging will initiate this balancing program > automatically. This doesn’t take much time, 30 minutes or so should do. It > may take several of these balancing cycles to bring the car back to a > balanced state if it has become imbalanced, which is something that a lack of > regular Standard mode top ups and subsequent balancing cycles can induce. > > It would therefore be a good idea to set the car to “Charge on Plug In” > instead of “Charge at X time” in the charge timing menu for at least a few > Standard mode charges per week to keep the pack balanced. There are simply > too many variables for me to be able to predict how often you would need to > do this, and we do not have a recommended procedure for alternate desired > average SOC levels. > > I hope this helps answer your questions, and gives you a better idea of how > to maximize battery life under your driving conditions. > > Regards, > > Dan Myggen > > From what he is saying, it appears optimal to time the charge to bring it to > full charge in standard mode 30 minutes before you leave. That would leave > the car sitting at high charge rate for the least amount of time, but allow > enough time for balancing to occur if necessary. > > This sounds exactly like our finish-charging-by approach. Rather than set the > charge start time, you set the finish time, and the system works out how long > it should take then adds on a 30-to-60 minute safety margin (which would also > allow for battery balancing to occur). > > Does this make sense? Or is Dan Myggen's advise wrong? > > Regards, Mark > > On 5 Apr, 2012, at 7:45 PM, Mark Webb-Johnson wrote: > >> >> I'm now starting to think about the v1.3 firmware, which is intended to add >> the following: >> >> Log charge history >> Log drive history >> Sophisticated control of charge time >> >> We don't really have TOU metering in Hong Kong, so not much use for me, but >> part [3] would be fun nevertheless. Most charge control in EVs is pretty >> basic, and it might be interesting to see how sophisticated this can be made >> without complications. >> >> I don't know if this is workable or not, so put my thoughts out into the >> open for discussion. >> >> For charge time, the consensus seems to be that people want to enter the >> time to FINISH charge, vs the current time to START charge. To do that, we >> need an estimate of how long the charge will take. For that, we either need >> a sophisticated model or a collection of historical data we can lookup to >> find something approximate. Hence item [1] on my list. >> >> Elon talked about the car learning about you. Where you park. Where you >> charge. etc. So, if always leave home at 7:00am to go to the office on >> Mondays through Fridays, perhaps the car can learn? Or, at least suggest >> based on what it has seen... Hence item [2] on my list. >> >> For [1], we would store such things as temperatures, SOC start, SOC end, >> charge mode, charge current, charge voltage and duration. The can bus charge >> message seem to include this information. >> >> For [2], we would store such things as date/time of drive, duration (time, >> distance, and elevation change), battery usage. We seem limited in this from >> what we have decoded on the can bus so far. >> >> Regardless of the above, [1] and [2] would be useful information for any >> owner, anyway. >> >> Privacy is an issue. Two problems - (a) protection of my charge/drive >> history, (b) the use of 'shared' charge history for [3]. My suggestion is to >> keep drive and charge history private. Perhaps it could just be stored as >> paranoid mode blobs. But, there should be an option to allow anonymised >> sharing of charge history for the use of [3]. My thinking is that if you >> share your data anonymously, then your lookup includes the pool of others >> anonymous charge history. if you choose not to share, then your lookup is >> only against your own charge history. >> >> I did toy with the idea of using the server to control this. So, at 3am the >> server sends a command to the car to start the charge, etc. That would >> simplify the firmware in the car, but has a major problem of GPRS >> connectivity - if the cellular signal was lost the charge wouldn't start. >> Bad. So, I think it best to have the historical database in the server, the >> calculations in the App, and the settings downloaded to the car while it has >> cellular signal (after which it just follows them autonomously). >> >> The Tesla Roadster currently offers you a choice of charge on plug-in, or >> start charge at a particular time. It also allows you to limit charge >> current and set charge mode. My thinking is to extend this by making it per >> day-of-the-week for a few defined locations, and to provide an override for >> the 'current' day/night. If the override is not set, and you are in one of >> the defined locations, then the system looks up the day of the week and >> controls charge based on what you have set. The UI for this is quite simple >> - presumably a screen with tabs/selector for day or the week, and then >> controls to set charge mode, current limit, and time to start/complete by. >> One developer also had the good idea that a charge SOC limit would be useful >> (e.g.; please stop charge when it gets to 70% / 220km ideal). >> >> How do we handle night vs day charging? Is this only for overnight, or do we >> base it on when you plugin? >> >> Is this workable? Useful? >> >> Really interested in people's feedback on this. >> >> Mark. >> >> _______________________________________________ >> OvmsDev mailing list >> OvmsDev@lists.teslaclub.hk >> http://lists.teslaclub.hk/mailman/listinfo/ovmsdev >
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Felix, For iOS App, the current logic is: <120 seconds: show as "just now". <2 hours: show as "MM minutes". <24 hours: show as "HH:MM" hours and minutes. otherwise: show as "HH hours". I think it best to change the last case to restrict it to <48 hours, and then add a final case of >=48 hours as "DD days". That avoids having to deal with 'day' vs 'days'. I'll handle this for the next update. Regards, Mark. On 12 Apr 2012, at 10:21 AM, felix bonnier wrote:
hi mark,
just had another idea. could we tweak the park-timer so that after 48 or so it begins to count in days with half day increments?......
I park my roadster for extended periods when I'm in asia. so to know that it's been parked for 286hrs is not that useful days would be better at this point
thanks
/fb
Sent from somewhere in our beautiful universe.
On 10 Apr, 2012, at 14:03, Mark Webb-Johnson <mark@webb-johnson.net> wrote:
Felix,
It is progressing. I got the car and battery screens tidied up. Now supporting suppression of the TPMS boxes if there is no TPMS installed, and grayed-out figures for those that are not currently being recently updated by the car. I even got the throbbing animation working on the charge port - very nice.
Now working on moving the Info and Control screens around as we discussed.
After that will be the MAP screen and social group support.
Regards, Mark.
On 10 Apr 2012, at 1:44 PM, felix bonnier wrote:
hi mark,
how are you doing on the UI development? no stress! just wondering if there is anything I can help with.........?
best
felix b.
Sent from my iPad somewhere in our beautiful universe.......
On 9 Apr, 2012, at 22:48, Mark Webb-Johnson <mark@webb-johnson.net> wrote:
From my testing last summer (31 Celsius in Hong Kong), the efficiency loss was much worse than 5%, especially at low charge currents:
http://www.teslamotorsclub.com/showthread.php/5655-Charging-in-High-Temperat...
Here's were my results at around 31 Celsius:
<attachment.php.png>
Here is Tom's analysis of my log files, vs his in cool weather, at the time:
<Hot-Weather-Charging-Stats.png>
Bottom line is that ambient temperature is very important to the estimate.
Tom:
I agree that the log files would give us the best historical data for a jump-start on this. The issues are (a) getting the files, (b) ambient temperature.
I don't think (a) would be a problem. I'll submit my logs for inclusion (I've probably got 100 or 200 charges in there at temperatures from 5 Celcius up to 33 Celcius). 99% standard mode. I'm sure, that others would also submit, and we could pretty quickly build up a model.
For (b), we either need to find it in the logs files, approximate it from something in the log files, or use something like this to approximate it.
For example, I did a charge on my car at 19:31 on 30th March 2012. VMSParser shows:
03/30/2012 19:31:30 | 1333107090 | C1MB | Coolant 30C ESS 28C - 29C charging at 203.7V 0.01A 03/30/2012 19:31:30 | 1333107090 | C30M | range soc = 73%, 70A available 03/30/2012 19:31:31 | 1333107091 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.00A 03/30/2012 19:31:32 | 1333107092 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.02A 03/30/2012 19:31:33 | 1333107093 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.1V 0.00A 03/30/2012 19:31:34 | 1333107094 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.00A 03/30/2012 19:31:35 | 1333107095 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.02A 03/30/2012 19:31:36 | 1333107096 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.01A 03/30/2012 19:31:37 | 1333107097 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.00A 03/30/2012 19:31:38 | 1333107098 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.01A 03/30/2012 19:31:39 | 1333107099 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.00A 03/30/2012 19:31:40 | 1333107100 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.02A 03/30/2012 19:31:41 | 1333107101 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.7V 0.00A 03/30/2012 19:31:42 | 1333107102 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.2V 0.04A 03/30/2012 19:31:43 | 1333107103 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.5V 0.00A 03/30/2012 19:31:44 | 1333107104 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.02A 03/30/2012 19:31:45 | 1333107105 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.3V 0.00A 03/30/2012 19:31:46 | 1333107106 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.02A 03/30/2012 19:31:47 | 1333107107 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.2V 0.00A 03/30/2012 19:31:48 | 1333107108 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.7V 0.01A 03/30/2012 19:31:49 | 1333107109 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.7V 0.00A 03/30/2012 19:31:50 | 1333107110 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.9V 0.01A 03/30/2012 19:31:51 | 1333107111 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.2V 0.00A 03/30/2012 19:31:52 | 1333107112 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.3V 0.23A 03/30/2012 19:31:52 | 1333107112 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.3V 0.23A 03/30/2012 19:31:53 | 1333107113 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.8V 0.18A 03/30/2012 19:31:54 | 1333107114 | C1MB | Coolant 30C ESS 28C - 29C charging at 223.2V 0.19A 03/30/2012 19:31:55 | 1333107115 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.8V 2.23A 03/30/2012 19:31:56 | 1333107116 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.9V 2.52A 03/30/2012 19:31:57 | 1333107117 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.1V 5.71A 03/30/2012 19:31:58 | 1333107118 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 16.96A 03/30/2012 19:31:59 | 1333107119 | C1MB | Coolant 30C ESS 28C - 29C charging at 219.9V 27.05A 03/30/2012 19:32:00 | 1333107120 | C1MB | Coolant 30C ESS 28C - 29C charging at 218.3V 36.99A 03/30/2012 19:32:01 | 1333107121 | C1MB | Coolant 30C ESS 28C - 29C charging at 217.5V 46.94A 03/30/2012 19:32:03 | 1333107123 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.9V 47.74A 03/30/2012 19:32:04 | 1333107124 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.7V 47.75A 03/30/2012 19:32:05 | 1333107125 | C1MB | Coolant 30C ESS 28C - 29C charging at 217.3V 47.79A 03/30/2012 19:33:05 | 1333107185 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.7V 47.84A 03/30/2012 19:34:05 | 1333107245 | C1MB | Coolant 16C ESS 25C - 28C charging at 217.9V 48.12A 03/30/2012 19:35:05 | 1333107305 | C1MB | Coolant 16C ESS 22C - 27C charging at 218.1V 47.96A 03/30/2012 19:36:05 | 1333107365 | C1MB | Coolant 24C ESS 25C - 27C charging at 217.7V 47.97A 03/30/2012 19:37:05 | 1333107425 | C1MB | Coolant 26C ESS 26C - 27C charging at 218.8V 48.11A 03/30/2012 19:38:05 | 1333107485 | C1MB | Coolant 28C ESS 26C - 28C charging at 217.5V 47.92A 03/30/2012 19:39:05 | 1333107545 | C1MB | Coolant 28C ESS 27C - 28C charging at 217.7V 48.06A 03/30/2012 19:40:05 | 1333107605 | C1MB | Coolant 28C ESS 27C - 28C charging at 218.5V 48.11A 03/30/2012 19:41:05 | 1333107665 | C1MB | Coolant 28C ESS 27C - 28C charging at 218.9V 48.14A 03/30/2012 19:42:05 | 1333107725 | C1MB | Coolant 14C ESS 23C - 27C charging at 217.0V 47.81A 03/30/2012 19:43:05 | 1333107785 | C1MB | Coolant 23C ESS 24C - 26C charging at 216.8V 47.74A 03/30/2012 19:44:05 | 1333107845 | C1MB | Coolant 26C ESS 25C - 27C charging at 217.9V 47.98A 03/30/2012 19:45:05 | 1333107905 | C1MB | Coolant 26C ESS 26C - 27C charging at 216.9V 47.78A 03/30/2012 19:46:05 | 1333107965 | C1MB | Coolant 27C ESS 26C - 27C charging at 218.8V 48.14A 03/30/2012 19:47:05 | 1333108025 | C1MB | Coolant 28C ESS 26C - 27C charging at 216.7V 47.77A 03/30/2012 19:48:05 | 1333108085 | C1MB | Coolant 28C ESS 26C - 27C charging at 216.3V 48.09A 03/30/2012 19:49:05 | 1333108145 | C1MB | Coolant 17C ESS 24C - 27C charging at 216.4V 47.76A 03/30/2012 19:50:06 | 1333108206 | C1MB | Coolant 22C ESS 23C - 26C charging at 218.4V 48.26A 03/30/2012 19:51:06 | 1333108266 | C1MB | Coolant 24C ESS 24C - 26C charging at 218.4V 48.26A 03/30/2012 19:52:07 | 1333108327 | C1MB | Coolant 26C ESS 25C - 26C charging at 217.7V 48.16A 03/30/2012 19:53:08 | 1333108388 | C1MB | Coolant 26C ESS 25C - 26C charging at 219.1V 48.25A 03/30/2012 19:54:08 | 1333108448 | C1MB | Coolant 27C ESS 25C - 27C charging at 218.3V 48.27A 03/30/2012 19:55:09 | 1333108509 | C1MB | Coolant 27C ESS 26C - 27C charging at 217.0V 47.95A 03/30/2012 19:56:10 | 1333108570 | C1MB | Coolant 28C ESS 26C - 27C charging at 217.0V 48.03A 03/30/2012 19:57:10 | 1333108630 | C1MB | Coolant 14C ESS 23C - 26C charging at 218.0V 48.02A 03/30/2012 19:58:11 | 1333108691 | C1MB | Coolant 24C ESS 24C - 26C charging at 217.4V 47.98A 03/30/2012 19:59:12 | 1333108752 | C1MB | Coolant 25C ESS 24C - 26C charging at 216.6V 47.78A 03/30/2012 20:00:13 | 1333108813 | C1MB | Coolant 26C ESS 25C - 26C charging at 216.9V 47.81A 03/30/2012 20:01:13 | 1333108873 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.7V 48.27A 03/30/2012 20:01:30 | 1333108890 | C30M | range soc = 79%, 70A available 03/30/2012 20:02:14 | 1333108934 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.4V 48.16A 03/30/2012 20:03:15 | 1333108995 | C1MB | Coolant 27C ESS 25C - 26C charging at 217.5V 47.79A 03/30/2012 20:04:15 | 1333109055 | C1MB | Coolant 17C ESS 24C - 26C charging at 217.3V 47.79A 03/30/2012 20:05:16 | 1333109116 | C1MB | Coolant 21C ESS 22C - 25C charging at 218.2V 47.85A 03/30/2012 20:06:17 | 1333109177 | C1MB | Coolant 24C ESS 24C - 25C charging at 217.3V 49.34A 03/30/2012 20:07:17 | 1333109237 | C1MB | Coolant 25C ESS 24C - 25C charging at 218.4V 45.78A 03/30/2012 20:08:18 | 1333109298 | C1MB | Coolant 26C ESS 24C - 26C charging at 220.4V 42.43A 03/30/2012 20:09:19 | 1333109359 | C1MB | Coolant 26C ESS 25C - 26C charging at 220.0V 43.13A 03/30/2012 20:10:19 | 1333109419 | C1MB | Coolant 26C ESS 25C - 26C charging at 219.6V 42.09A 03/30/2012 20:11:20 | 1333109480 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.3V 43.46A 03/30/2012 20:12:21 | 1333109541 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.6V 41.73A 03/30/2012 20:13:22 | 1333109602 | C1MB | Coolant 14C ESS 22C - 25C charging at 220.4V 40.81A 03/30/2012 20:14:22 | 1333109662 | C1MB | Coolant 23C ESS 23C - 25C charging at 219.5V 33.66A 03/30/2012 20:15:23 | 1333109723 | C1MB | Coolant 24C ESS 24C - 25C charging at 218.9V 36.06A 03/30/2012 20:16:24 | 1333109784 | C1MB | Coolant 25C ESS 24C - 25C charging at 220.4V 35.36A 03/30/2012 20:17:24 | 1333109844 | C1MB | Coolant 26C ESS 24C - 25C charging at 221.0V 32.97A 03/30/2012 20:18:25 | 1333109905 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.9V 32.17A 03/30/2012 20:19:26 | 1333109966 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.4V 33.65A 03/30/2012 20:20:26 | 1333110026 | C1MB | Coolant 13C ESS 22C - 25C charging at 218.9V 37.86A 03/30/2012 20:21:27 | 1333110087 | C1MB | Coolant 22C ESS 22C - 24C charging at 219.2V 28.58A 03/30/2012 20:22:28 | 1333110148 | C1MB | Coolant 24C ESS 23C - 24C charging at 220.6V 27.84A 03/30/2012 20:23:28 | 1333110208 | C1MB | Coolant 24C ESS 23C - 25C charging at 219.7V 27.55A 03/30/2012 20:24:29 | 1333110269 | C1MB | Coolant 25C ESS 24C - 25C charging at 221.3V 28.81A 03/30/2012 20:25:30 | 1333110330 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.6V 24.53A 03/30/2012 20:26:30 | 1333110390 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.1V 26.89A 03/30/2012 20:27:31 | 1333110451 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.6V 26.35A 03/30/2012 20:28:32 | 1333110512 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.5V 24.03A 03/30/2012 20:29:13 | 1333110553 | IDLE | range soc = 84% ESS 23C - 25C, 2.691V min, 1.205V max
and OVMS reported:
2012-03-30 18:24:07.142047 +0800 info main: #10 C EV915 rx msg S 81,K,-1,0,done,standard,250,219,48,67,100,10,7,4,0 2012-03-30 18:24:07.144289 +0800 info main: #10 C EV915 rx msg D 136,32,3,42,78,29,3272,65163,45,0,25,2,113,113 ==> Driving PEM:42, MOTOR:78, BATTERY:29, AMBIENT:25
2012-03-30 19:23:57.730154 +0800 info main: #10 C EV915 rx msg S 81,K,-1,0,done,standard,250,234,48,67,100,10,7,4,0 2012-03-30 19:23:57.732294 +0800 info main: #10 C EV915 rx msg D 104,8,4,34,56,29,3284,65175,0,3379,24,2,102,113 ==> Stopped PEM:34, MOTOR:56, BATTERY:29, AMBIENT:24
2012-03-30 19:33:57.348051 +0800 info main: #10 C EV915 rx msg S 82,K,217,48,charging,standard,253,237,48,2,100,0,5,1,0 2012-03-30 19:33:57.374906 +0800 info main: #10 C EV915 rx msg D 124,8,4,42,55,28,3284,65175,0,3986,25,2,120,120 ==> Charging PEM:42, MOTOR:55, BATTERY:28, AMBIENT:25
2012-03-30 19:44:11.802571 +0800 info main: #10 C EV915 rx msg S 84,K,217,48,charging,standard,262,245,48,12,100,2,5,1,0 2012-03-30 19:44:11.805104 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,53,27,3284,65175,0,4581,29,2,118,118 ==> Charging PEM:43, MOTOR:53, BATTERY:27, AMBIENT:29
2012-03-30 19:53:11.578629 +0800 info main: #10 C EV915 rx msg S 87,K,219,48,charging,standard,270,253,48,21,100,4,5,1,0 2012-03-30 19:53:11.582720 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,52,26,3284,65175,0,5142,28,2,120,120 ==> Charging PEM:43, MOTOR:52, BATTERY:26, AMBIENT:28
2012-03-30 20:03:55.020585 +0800 info main: #10 C EV915 rx msg S 91,K,218,48,charging,standard,282,262,48,32,100,6,5,1,0 2012-03-30 20:03:55.022789 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,51,26,3284,65175,0,5777,27,2,114,114 ==> Charging PEM:43, MOTOR:51, BATTERY:26, AMBIENT:27
2012-03-30 20:14:03.376116 +0800 info main: #10 C EV915 rx msg S 93,K,220,37,charging,standard,290,270,48,42,100,7,5,1,0 2012-03-30 20:14:03.378258 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,49,25,3284,65175,0,6374,29,2,112,112 ==> Charging PEM:43, MOTOR:49, BATTERY:25, AMBIENT:29
2012-03-30 20:24:01.668658 +0800 info main: #10 C EV915 rx msg S 95,K,221,28,charging,standard,296,277,48,52,100,8,5,1,0 2012-03-30 20:24:01.681265 +0800 info main: #10 C EV915 rx msg D 124,8,4,42,48,25,3284,65175,0,6980,29,2,120,120 ==> Charging PEM:42, MOTOR:48, BATTERY:25, AMBIENT:29
2012-03-30 20:33:59.497056 +0800 info main: #10 C EV915 rx msg S 96,K,0,0,done,standard,299,280,48,57,100,9,9,4,0 2012-03-30 20:33:59.505736 +0800 info main: #10 C EV915 rx msg D 108,8,4,34,47,25,3284,65175,0,7577,27,2,119,119 ==> Charged PEM:34, MOTOR:47, BATTERY: 25, AMBIENT:27
I reckon the actual ambient temperature was probably 24 or 25 Celcius. It goes up during the charge, presumably because the HVAC is spewing out hot air around the ambient sensor at the front of the car (which is in the garage so will build up heat).
I think my data above is not a very good example, as I wasn't driving hard so the battery temperature was unusually low. My first instinct was that it would be good to use as an approximation for ambient, but actually not. The theory is that when the ambient temperature is hot or cold, the car has to use HVAC/heater to keep the battery at the temperature it needs, and that uses power which reduces charging efficiency. Battery temperature is a side-effect, and won't help to predict energy usage.
So, I still think ambient temperature is the correct thing to use as a predictor for charging efficiency (along with current+voltage).
The question is, looking at historical logs how can we approximate that? Only looking at charges that occurred an hour after a drive would work, but would remove 95% of my charges, like anyone else who plugs in when they get home ;-)
Regards, Mark.
On 8 Apr, 2012, at 4:22 PM, Dominik Westner wrote:
I already did some tests calculating the remaining charge time and had it implemented in the iPhone app.
First I took the simple approach to linearly estimate the remaining time by taking the charge current and voltage and calculate the energy per sec. Then take the missing energy from the current SOC. This will give you an approximation of the remaining time.
If you are looking at +/- 1 hour. This already should work from my experience.
I tried to make it better by taking into account that the charging curve is not linear, but more on a logarithmic scale. This worked a bit better. I also figured that there is some loss when charging, which I set to 5% (this probably varies by temperature).
What I did not know is the fact that once finished charging the batteries will be rebalanced for 30 minutes. Is this still shown as charging in OVMS? If yes, this would explain, why I've been off for about 30 - 60 minutes with my calculation.
I also did not take the age of the battery into account, which should be an important factor, too.
I think that it might be better to use a formula which tries to approximate the charging curve instead of using a fixed lookup table. At least it also could be fine tuned a bit easier by just setting a couple of parameters through the app to change the calculation.
Greetings
Dominik
On 08.04.2012, at 06:16, Tom Saxton wrote:
I think your model would work pretty well.
To calculate charge time, you also have to take into account the current tapering near the top of the charge.
We can get most of the required data from log files. The only tricky bit is getting the ambient temperature, which I don't think anyone has identified in the log files. You could get a good approximating by only considering charge sessions that start a least an hour of the most recent drive and then use the starting temperature of the coolant as a proxy for ambient temperature.
Range mode is the trickiest and the most important to time, they are also done less often, so it's harder to get data. I'd be happy to collect logs and extract data if we can get owners to contribute logs for a variety of charging levels and ambient temperatures.
Tom
on 4/6/12 5:52 PM, Mark Webb-Johnson wrote:
> The core question I have here is whether it is possible to build a static > table saying that at this temperature, this available voltage+currrent, the > charging efficiency is X%? Something accurate enough to give us a charge time > prediction (given temperature, kWh needed by the pack, available > voltage+current) of +/- 1 hour? > > I'm assuming the temperature should be ambient, as that is more important > overt the duration of a reasonable charge than pack temperature? > > If we can have such a table, with steps of 5 degrees celcius between -10C and > +40C, and say 10 current levels, that is only 100 entries - and we would only > need 1 byte for each entry. The module could then put in the current > temperature, current/voltage level, and get out an efficiency factor. It could > estimate the kWh the pack needs (by mode and SOC/ideal-miles difference), then > multiply by efficiency factor, and get out an estimate of how many minutes is > required to achieve that. > > Without this table, we could do the lookup on the server, but that would mean > having to set it _every_ night from the App/Server - as it would depend on the > SOC% the car was actually at. > > If we could build this data, where could we get the data from? > > Regards, Mark. > > Begin forwarded message: > >> From: Mark Webb-Johnson <mark@webb-johnson.net> >> Subject: Re: [Ovmsdev] Charge Control >> Date: 6 April, 2012 8:25:51 PM GMT+08:00 >> To: OVMS Developers <ovmsdev@lists.teslaclub.hk> >> >> >> Bennett Leeds and I have had a discussion off-list (I'm not sure if he is on >> this list or not), and he brings up a valid point about balancing the pack >> perhaps not occurring if we cut short the charge with a SOC limit. >> >> Looking here: >> >> http://www.teslamotorsclub.com/showthread.php/3848-Tesla-Roadster-Battery-Ca... >> e?p=41995&viewfull=1#post41995 >> >> it seems that this approach may be non-optimal. For clarity, let me >> cut-and-paste the Tesla reply here: >> >> For simplicity’s sake, I will refer to all SOC (State Of Charge) numbers as a >> percentage of a full (100%) charge. I cannot provide exact percentages, as >> there are many variables which can cause these numbers to vary slightly, >> however, I will get as close as I can. >> >> When plugging in a nearly empty car that is set to Storage mode, the charge >> will generally stop at around 20%. The car will then settle into its normal >> Storage mode rhythm, topping up and discharging between 10% and 50% as the >> car sees fit. Oftentimes it will keep a tighter envelope based on parameters >> that I am not aware of. >> >> Most important to remember is that Storage mode is not intended to be a >> driving mode. This charge setting is primarily meant to optimize battery life >> while the car is under storage conditions for two weeks or more. >> >> Storage mode does not attempt to balance the pack, and you will cause an >> imbalance in the pack by driving and charging in this mode regularly. >> >> This will penalize you when you do occasionally charge the car fully in the >> other modes, as you will not have the full range of the car available to you >> until the car has a chance to balance its battery. Additionally, the car’s >> range will not be as accurate if driven while in Storage mode vs. having >> charged it in Standard mode after storing the car, then driving it. >> >> Allowing the car to sit plugged in after it has finished charging in Standard >> mode automatically balances the pack, and it may take a few rounds of this to >> bring an imbalanced pack back to its full potential after many partial >> charges. This is one of the major reasons we recommend keeping the car in >> Standard mode whenever possible. Partial charges in any mode, while not on >> their own bad for the battery, do not give the car an opportunity to balance >> its battery, and over time can prevent you from accessing the car’s full >> range potential. >> >> When balanced, Standard mode charges the car to about 87%, with Range and >> Performance modes getting the car to about 97%. These two percentages are >> very much affected by the balance between bricks in the battery. An >> imbalanced pack will not fill up all the way in any mode, nor will it be able >> to discharge as far. Additionally, the range predictions will not be as >> accurate. >> >> Your voltages are about right. >> 4.10 volts = full standard mode (187-195 ideal miles) >> 4.15 volts = full range mode >> 4.20 volts = maximum of the cells that we never touch >> As you may know, there is much more to it than just using voltage to >> calculate range with Lithium batteries. This is something that is incredibly >> complicated, and not something that I am qualified to discuss in detail, as I >> do not have the full picture. >> >> It is important to remember that SOC is not the only factor in maximizing >> battery life. For instance most lithium batteries are shipped at around >> 30-50% SOC in consumer electronics, and part of the reasoning is that they >> are less susceptible to damage from extreme temperatures at these charge >> levels. It is also safer to store them at these levels. Part of the benefit >> of Storage mode is that there is less work required from the HVAC system to >> keep the batteryhappy and safe, and therefore, less energy is consumed while >> stored. >> >> We chose ~90% as a Standard full charge level because it offers most of the >> longevity benefit of keeping the car at a lower state of charge, while still >> allowing a high degree of autonomy. I understand that you are interested in >> taking extra steps to maximize your battery’s life, so I do have some >> suggestions for you. >> >> I would not recommend that you continue to use Storage mode as a means of >> maintaining a lower state of charge. As I explained earlier, this mode is not >> optimized for this type of use. >> >> Think of battery degradation this way. It is very much a function of time >> spent at voltage and temperature. For instance, you do not want to charge a >> car all the way in performance mode, and then let it sit in the sun all day. >> Between the higher thermal limits and the high SOC, you are causing the >> battery a relatively high amount of degradation .In fact, the car will >> eventually allow itself to discharge to Standard levels if left in >> Performance mode to prevent inadvertent damage to the battery. If you start >> driving right away after charging in Performance or Range Mode, and don’t let >> it sit, you would minimize the damage incurred, as the time spent at these >> extremes is an important part of the calculation. >> >> Similarly, if you top off to full in Standard mode, then jump in the car >> right away and bring the SOC down quickly, you will minimize the small amount >> of degradation that occurs at ~90%. >> >> If you prefer to keep a lower average SOC in an attempt to maximize the life >> of your battery, I would instead suggest that you stay in Standard mode and >> utilize the Roadster’s built in charge timer and current limiting options to >> find an average SOC that works for you. For instance, try starting your >> charge at a time that allows the car to top off to a level you are >> comfortable with right before you need to leave. Alternately, you can use the >> Current limiting function to adjust the amount of time it takes the car >> reaches a target SOC, or even a combination of these two options. The car >> will remember the settings you select based on your location, so once you >> find something that works for your commute, you can set it and forget it. >> >> Just remember that the car does benefit from being allowed to sit fully >> charged in Standard mode, and should be allowed to do so frequently, >> especially if being used on a daily basis. Leaving the car plugged in in >> Standard mode after it is done charging will initiate this balancing program >> automatically. This doesn’t take much time, 30 minutes or so should do. It >> may take several of these balancing cycles to bring the car back to a >> balanced state if it has become imbalanced, which is something that a lack of >> regular Standard mode top ups and subsequent balancing cycles can induce. >> >> It would therefore be a good idea to set the car to “Charge on Plug In” >> instead of “Charge at X time” in the charge timing menu for at least a few >> Standard mode charges per week to keep the pack balanced. There are simply >> too many variables for me to be able to predict how often you would need to >> do this, and we do not have a recommended procedure for alternate desired >> average SOC levels. >> >> I hope this helps answer your questions, and gives you a better idea of how >> to maximize battery life under your driving conditions. >> >> Regards, >> >> Dan Myggen >> >> From what he is saying, it appears optimal to time the charge to bring it to >> full charge in standard mode 30 minutes before you leave. That would leave >> the car sitting at high charge rate for the least amount of time, but allow >> enough time for balancing to occur if necessary. >> >> This sounds exactly like our finish-charging-by approach. Rather than set the >> charge start time, you set the finish time, and the system works out how long >> it should take then adds on a 30-to-60 minute safety margin (which would also >> allow for battery balancing to occur). >> >> Does this make sense? Or is Dan Myggen's advise wrong? >> >> Regards, Mark >> >> On 5 Apr, 2012, at 7:45 PM, Mark Webb-Johnson wrote: >> >>> >>> I'm now starting to think about the v1.3 firmware, which is intended to add >>> the following: >>> >>> Log charge history >>> Log drive history >>> Sophisticated control of charge time >>> >>> We don't really have TOU metering in Hong Kong, so not much use for me, but >>> part [3] would be fun nevertheless. Most charge control in EVs is pretty >>> basic, and it might be interesting to see how sophisticated this can be made >>> without complications. >>> >>> I don't know if this is workable or not, so put my thoughts out into the >>> open for discussion. >>> >>> For charge time, the consensus seems to be that people want to enter the >>> time to FINISH charge, vs the current time to START charge. To do that, we >>> need an estimate of how long the charge will take. For that, we either need >>> a sophisticated model or a collection of historical data we can lookup to >>> find something approximate. Hence item [1] on my list. >>> >>> Elon talked about the car learning about you. Where you park. Where you >>> charge. etc. So, if always leave home at 7:00am to go to the office on >>> Mondays through Fridays, perhaps the car can learn? Or, at least suggest >>> based on what it has seen... Hence item [2] on my list. >>> >>> For [1], we would store such things as temperatures, SOC start, SOC end, >>> charge mode, charge current, charge voltage and duration. The can bus charge >>> message seem to include this information. >>> >>> For [2], we would store such things as date/time of drive, duration (time, >>> distance, and elevation change), battery usage. We seem limited in this from >>> what we have decoded on the can bus so far. >>> >>> Regardless of the above, [1] and [2] would be useful information for any >>> owner, anyway. >>> >>> Privacy is an issue. Two problems - (a) protection of my charge/drive >>> history, (b) the use of 'shared' charge history for [3]. My suggestion is to >>> keep drive and charge history private. Perhaps it could just be stored as >>> paranoid mode blobs. But, there should be an option to allow anonymised >>> sharing of charge history for the use of [3]. My thinking is that if you >>> share your data anonymously, then your lookup includes the pool of others >>> anonymous charge history. if you choose not to share, then your lookup is >>> only against your own charge history. >>> >>> I did toy with the idea of using the server to control this. So, at 3am the >>> server sends a command to the car to start the charge, etc. That would >>> simplify the firmware in the car, but has a major problem of GPRS >>> connectivity - if the cellular signal was lost the charge wouldn't start. >>> Bad. So, I think it best to have the historical database in the server, the >>> calculations in the App, and the settings downloaded to the car while it has >>> cellular signal (after which it just follows them autonomously). >>> >>> The Tesla Roadster currently offers you a choice of charge on plug-in, or >>> start charge at a particular time. It also allows you to limit charge >>> current and set charge mode. My thinking is to extend this by making it per >>> day-of-the-week for a few defined locations, and to provide an override for >>> the 'current' day/night. If the override is not set, and you are in one of >>> the defined locations, then the system looks up the day of the week and >>> controls charge based on what you have set. The UI for this is quite simple >>> - presumably a screen with tabs/selector for day or the week, and then >>> controls to set charge mode, current limit, and time to start/complete by. >>> One developer also had the good idea that a charge SOC limit would be useful >>> (e.g.; please stop charge when it gets to 70% / 220km ideal). >>> >>> How do we handle night vs day charging? Is this only for overnight, or do we >>> base it on when you plugin? >>> >>> Is this workable? Useful? >>> >>> Really interested in people's feedback on this. >>> >>> Mark. >>> >>> _______________________________________________ >>> OvmsDev mailing list >>> OvmsDev@lists.teslaclub.hk >>> http://lists.teslaclub.hk/mailman/listinfo/ovmsdev >> > > _______________________________________________ > OvmsDev mailing list > OvmsDev@lists.teslaclub.hk > http://lists.teslaclub.hk/mailman/listinfo/ovmsdev
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Sounds perfect!!! THANKS :-) /fb On Apr 12, 2012, at 10:30 AM, Mark Webb-Johnson wrote:
Felix,
For iOS App, the current logic is:
<120 seconds: show as "just now". <2 hours: show as "MM minutes". <24 hours: show as "HH:MM" hours and minutes. otherwise: show as "HH hours".
I think it best to change the last case to restrict it to <48 hours, and then add a final case of >=48 hours as "DD days". That avoids having to deal with 'day' vs 'days'.
I'll handle this for the next update.
Regards, Mark.
On 12 Apr 2012, at 10:21 AM, felix bonnier wrote:
hi mark,
just had another idea. could we tweak the park-timer so that after 48 or so it begins to count in days with half day increments?......
I park my roadster for extended periods when I'm in asia. so to know that it's been parked for 286hrs is not that useful days would be better at this point
thanks
/fb
Sent from somewhere in our beautiful universe.
On 10 Apr, 2012, at 14:03, Mark Webb-Johnson <mark@webb-johnson.net> wrote:
Felix,
It is progressing. I got the car and battery screens tidied up. Now supporting suppression of the TPMS boxes if there is no TPMS installed, and grayed-out figures for those that are not currently being recently updated by the car. I even got the throbbing animation working on the charge port - very nice.
Now working on moving the Info and Control screens around as we discussed.
After that will be the MAP screen and social group support.
Regards, Mark.
On 10 Apr 2012, at 1:44 PM, felix bonnier wrote:
hi mark,
how are you doing on the UI development? no stress! just wondering if there is anything I can help with.........?
best
felix b.
Sent from my iPad somewhere in our beautiful universe.......
On 9 Apr, 2012, at 22:48, Mark Webb-Johnson <mark@webb-johnson.net> wrote:
From my testing last summer (31 Celsius in Hong Kong), the efficiency loss was much worse than 5%, especially at low charge currents:
http://www.teslamotorsclub.com/showthread.php/5655-Charging-in-High-Temperat...
Here's were my results at around 31 Celsius:
<attachment.php.png>
Here is Tom's analysis of my log files, vs his in cool weather, at the time:
<Hot-Weather-Charging-Stats.png>
Bottom line is that ambient temperature is very important to the estimate.
Tom:
I agree that the log files would give us the best historical data for a jump-start on this. The issues are (a) getting the files, (b) ambient temperature.
I don't think (a) would be a problem. I'll submit my logs for inclusion (I've probably got 100 or 200 charges in there at temperatures from 5 Celcius up to 33 Celcius). 99% standard mode. I'm sure, that others would also submit, and we could pretty quickly build up a model.
For (b), we either need to find it in the logs files, approximate it from something in the log files, or use something like this to approximate it.
For example, I did a charge on my car at 19:31 on 30th March 2012. VMSParser shows:
03/30/2012 19:31:30 | 1333107090 | C1MB | Coolant 30C ESS 28C - 29C charging at 203.7V 0.01A 03/30/2012 19:31:30 | 1333107090 | C30M | range soc = 73%, 70A available 03/30/2012 19:31:31 | 1333107091 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.00A 03/30/2012 19:31:32 | 1333107092 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.02A 03/30/2012 19:31:33 | 1333107093 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.1V 0.00A 03/30/2012 19:31:34 | 1333107094 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.00A 03/30/2012 19:31:35 | 1333107095 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.02A 03/30/2012 19:31:36 | 1333107096 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.01A 03/30/2012 19:31:37 | 1333107097 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.00A 03/30/2012 19:31:38 | 1333107098 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 0.01A 03/30/2012 19:31:39 | 1333107099 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.00A 03/30/2012 19:31:40 | 1333107100 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.02A 03/30/2012 19:31:41 | 1333107101 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.7V 0.00A 03/30/2012 19:31:42 | 1333107102 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.2V 0.04A 03/30/2012 19:31:43 | 1333107103 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.5V 0.00A 03/30/2012 19:31:44 | 1333107104 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.0V 0.02A 03/30/2012 19:31:45 | 1333107105 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.3V 0.00A 03/30/2012 19:31:46 | 1333107106 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.9V 0.02A 03/30/2012 19:31:47 | 1333107107 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.2V 0.00A 03/30/2012 19:31:48 | 1333107108 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.7V 0.01A 03/30/2012 19:31:49 | 1333107109 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.7V 0.00A 03/30/2012 19:31:50 | 1333107110 | C1MB | Coolant 30C ESS 28C - 29C charging at 221.9V 0.01A 03/30/2012 19:31:51 | 1333107111 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.2V 0.00A 03/30/2012 19:31:52 | 1333107112 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.3V 0.23A 03/30/2012 19:31:52 | 1333107112 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.3V 0.23A 03/30/2012 19:31:53 | 1333107113 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.8V 0.18A 03/30/2012 19:31:54 | 1333107114 | C1MB | Coolant 30C ESS 28C - 29C charging at 223.2V 0.19A 03/30/2012 19:31:55 | 1333107115 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.8V 2.23A 03/30/2012 19:31:56 | 1333107116 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.9V 2.52A 03/30/2012 19:31:57 | 1333107117 | C1MB | Coolant 30C ESS 28C - 29C charging at 222.1V 5.71A 03/30/2012 19:31:58 | 1333107118 | C1MB | Coolant 30C ESS 28C - 29C charging at 220.8V 16.96A 03/30/2012 19:31:59 | 1333107119 | C1MB | Coolant 30C ESS 28C - 29C charging at 219.9V 27.05A 03/30/2012 19:32:00 | 1333107120 | C1MB | Coolant 30C ESS 28C - 29C charging at 218.3V 36.99A 03/30/2012 19:32:01 | 1333107121 | C1MB | Coolant 30C ESS 28C - 29C charging at 217.5V 46.94A 03/30/2012 19:32:03 | 1333107123 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.9V 47.74A 03/30/2012 19:32:04 | 1333107124 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.7V 47.75A 03/30/2012 19:32:05 | 1333107125 | C1MB | Coolant 30C ESS 28C - 29C charging at 217.3V 47.79A 03/30/2012 19:33:05 | 1333107185 | C1MB | Coolant 30C ESS 28C - 29C charging at 216.7V 47.84A 03/30/2012 19:34:05 | 1333107245 | C1MB | Coolant 16C ESS 25C - 28C charging at 217.9V 48.12A 03/30/2012 19:35:05 | 1333107305 | C1MB | Coolant 16C ESS 22C - 27C charging at 218.1V 47.96A 03/30/2012 19:36:05 | 1333107365 | C1MB | Coolant 24C ESS 25C - 27C charging at 217.7V 47.97A 03/30/2012 19:37:05 | 1333107425 | C1MB | Coolant 26C ESS 26C - 27C charging at 218.8V 48.11A 03/30/2012 19:38:05 | 1333107485 | C1MB | Coolant 28C ESS 26C - 28C charging at 217.5V 47.92A 03/30/2012 19:39:05 | 1333107545 | C1MB | Coolant 28C ESS 27C - 28C charging at 217.7V 48.06A 03/30/2012 19:40:05 | 1333107605 | C1MB | Coolant 28C ESS 27C - 28C charging at 218.5V 48.11A 03/30/2012 19:41:05 | 1333107665 | C1MB | Coolant 28C ESS 27C - 28C charging at 218.9V 48.14A 03/30/2012 19:42:05 | 1333107725 | C1MB | Coolant 14C ESS 23C - 27C charging at 217.0V 47.81A 03/30/2012 19:43:05 | 1333107785 | C1MB | Coolant 23C ESS 24C - 26C charging at 216.8V 47.74A 03/30/2012 19:44:05 | 1333107845 | C1MB | Coolant 26C ESS 25C - 27C charging at 217.9V 47.98A 03/30/2012 19:45:05 | 1333107905 | C1MB | Coolant 26C ESS 26C - 27C charging at 216.9V 47.78A 03/30/2012 19:46:05 | 1333107965 | C1MB | Coolant 27C ESS 26C - 27C charging at 218.8V 48.14A 03/30/2012 19:47:05 | 1333108025 | C1MB | Coolant 28C ESS 26C - 27C charging at 216.7V 47.77A 03/30/2012 19:48:05 | 1333108085 | C1MB | Coolant 28C ESS 26C - 27C charging at 216.3V 48.09A 03/30/2012 19:49:05 | 1333108145 | C1MB | Coolant 17C ESS 24C - 27C charging at 216.4V 47.76A 03/30/2012 19:50:06 | 1333108206 | C1MB | Coolant 22C ESS 23C - 26C charging at 218.4V 48.26A 03/30/2012 19:51:06 | 1333108266 | C1MB | Coolant 24C ESS 24C - 26C charging at 218.4V 48.26A 03/30/2012 19:52:07 | 1333108327 | C1MB | Coolant 26C ESS 25C - 26C charging at 217.7V 48.16A 03/30/2012 19:53:08 | 1333108388 | C1MB | Coolant 26C ESS 25C - 26C charging at 219.1V 48.25A 03/30/2012 19:54:08 | 1333108448 | C1MB | Coolant 27C ESS 25C - 27C charging at 218.3V 48.27A 03/30/2012 19:55:09 | 1333108509 | C1MB | Coolant 27C ESS 26C - 27C charging at 217.0V 47.95A 03/30/2012 19:56:10 | 1333108570 | C1MB | Coolant 28C ESS 26C - 27C charging at 217.0V 48.03A 03/30/2012 19:57:10 | 1333108630 | C1MB | Coolant 14C ESS 23C - 26C charging at 218.0V 48.02A 03/30/2012 19:58:11 | 1333108691 | C1MB | Coolant 24C ESS 24C - 26C charging at 217.4V 47.98A 03/30/2012 19:59:12 | 1333108752 | C1MB | Coolant 25C ESS 24C - 26C charging at 216.6V 47.78A 03/30/2012 20:00:13 | 1333108813 | C1MB | Coolant 26C ESS 25C - 26C charging at 216.9V 47.81A 03/30/2012 20:01:13 | 1333108873 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.7V 48.27A 03/30/2012 20:01:30 | 1333108890 | C30M | range soc = 79%, 70A available 03/30/2012 20:02:14 | 1333108934 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.4V 48.16A 03/30/2012 20:03:15 | 1333108995 | C1MB | Coolant 27C ESS 25C - 26C charging at 217.5V 47.79A 03/30/2012 20:04:15 | 1333109055 | C1MB | Coolant 17C ESS 24C - 26C charging at 217.3V 47.79A 03/30/2012 20:05:16 | 1333109116 | C1MB | Coolant 21C ESS 22C - 25C charging at 218.2V 47.85A 03/30/2012 20:06:17 | 1333109177 | C1MB | Coolant 24C ESS 24C - 25C charging at 217.3V 49.34A 03/30/2012 20:07:17 | 1333109237 | C1MB | Coolant 25C ESS 24C - 25C charging at 218.4V 45.78A 03/30/2012 20:08:18 | 1333109298 | C1MB | Coolant 26C ESS 24C - 26C charging at 220.4V 42.43A 03/30/2012 20:09:19 | 1333109359 | C1MB | Coolant 26C ESS 25C - 26C charging at 220.0V 43.13A 03/30/2012 20:10:19 | 1333109419 | C1MB | Coolant 26C ESS 25C - 26C charging at 219.6V 42.09A 03/30/2012 20:11:20 | 1333109480 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.3V 43.46A 03/30/2012 20:12:21 | 1333109541 | C1MB | Coolant 26C ESS 25C - 26C charging at 218.6V 41.73A 03/30/2012 20:13:22 | 1333109602 | C1MB | Coolant 14C ESS 22C - 25C charging at 220.4V 40.81A 03/30/2012 20:14:22 | 1333109662 | C1MB | Coolant 23C ESS 23C - 25C charging at 219.5V 33.66A 03/30/2012 20:15:23 | 1333109723 | C1MB | Coolant 24C ESS 24C - 25C charging at 218.9V 36.06A 03/30/2012 20:16:24 | 1333109784 | C1MB | Coolant 25C ESS 24C - 25C charging at 220.4V 35.36A 03/30/2012 20:17:24 | 1333109844 | C1MB | Coolant 26C ESS 24C - 25C charging at 221.0V 32.97A 03/30/2012 20:18:25 | 1333109905 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.9V 32.17A 03/30/2012 20:19:26 | 1333109966 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.4V 33.65A 03/30/2012 20:20:26 | 1333110026 | C1MB | Coolant 13C ESS 22C - 25C charging at 218.9V 37.86A 03/30/2012 20:21:27 | 1333110087 | C1MB | Coolant 22C ESS 22C - 24C charging at 219.2V 28.58A 03/30/2012 20:22:28 | 1333110148 | C1MB | Coolant 24C ESS 23C - 24C charging at 220.6V 27.84A 03/30/2012 20:23:28 | 1333110208 | C1MB | Coolant 24C ESS 23C - 25C charging at 219.7V 27.55A 03/30/2012 20:24:29 | 1333110269 | C1MB | Coolant 25C ESS 24C - 25C charging at 221.3V 28.81A 03/30/2012 20:25:30 | 1333110330 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.6V 24.53A 03/30/2012 20:26:30 | 1333110390 | C1MB | Coolant 26C ESS 24C - 25C charging at 219.1V 26.89A 03/30/2012 20:27:31 | 1333110451 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.6V 26.35A 03/30/2012 20:28:32 | 1333110512 | C1MB | Coolant 26C ESS 24C - 25C charging at 220.5V 24.03A 03/30/2012 20:29:13 | 1333110553 | IDLE | range soc = 84% ESS 23C - 25C, 2.691V min, 1.205V max
and OVMS reported:
2012-03-30 18:24:07.142047 +0800 info main: #10 C EV915 rx msg S 81,K,-1,0,done,standard,250,219,48,67,100,10,7,4,0 2012-03-30 18:24:07.144289 +0800 info main: #10 C EV915 rx msg D 136,32,3,42,78,29,3272,65163,45,0,25,2,113,113 ==> Driving PEM:42, MOTOR:78, BATTERY:29, AMBIENT:25
2012-03-30 19:23:57.730154 +0800 info main: #10 C EV915 rx msg S 81,K,-1,0,done,standard,250,234,48,67,100,10,7,4,0 2012-03-30 19:23:57.732294 +0800 info main: #10 C EV915 rx msg D 104,8,4,34,56,29,3284,65175,0,3379,24,2,102,113 ==> Stopped PEM:34, MOTOR:56, BATTERY:29, AMBIENT:24
2012-03-30 19:33:57.348051 +0800 info main: #10 C EV915 rx msg S 82,K,217,48,charging,standard,253,237,48,2,100,0,5,1,0 2012-03-30 19:33:57.374906 +0800 info main: #10 C EV915 rx msg D 124,8,4,42,55,28,3284,65175,0,3986,25,2,120,120 ==> Charging PEM:42, MOTOR:55, BATTERY:28, AMBIENT:25
2012-03-30 19:44:11.802571 +0800 info main: #10 C EV915 rx msg S 84,K,217,48,charging,standard,262,245,48,12,100,2,5,1,0 2012-03-30 19:44:11.805104 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,53,27,3284,65175,0,4581,29,2,118,118 ==> Charging PEM:43, MOTOR:53, BATTERY:27, AMBIENT:29
2012-03-30 19:53:11.578629 +0800 info main: #10 C EV915 rx msg S 87,K,219,48,charging,standard,270,253,48,21,100,4,5,1,0 2012-03-30 19:53:11.582720 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,52,26,3284,65175,0,5142,28,2,120,120 ==> Charging PEM:43, MOTOR:52, BATTERY:26, AMBIENT:28
2012-03-30 20:03:55.020585 +0800 info main: #10 C EV915 rx msg S 91,K,218,48,charging,standard,282,262,48,32,100,6,5,1,0 2012-03-30 20:03:55.022789 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,51,26,3284,65175,0,5777,27,2,114,114 ==> Charging PEM:43, MOTOR:51, BATTERY:26, AMBIENT:27
2012-03-30 20:14:03.376116 +0800 info main: #10 C EV915 rx msg S 93,K,220,37,charging,standard,290,270,48,42,100,7,5,1,0 2012-03-30 20:14:03.378258 +0800 info main: #10 C EV915 rx msg D 124,8,4,43,49,25,3284,65175,0,6374,29,2,112,112 ==> Charging PEM:43, MOTOR:49, BATTERY:25, AMBIENT:29
2012-03-30 20:24:01.668658 +0800 info main: #10 C EV915 rx msg S 95,K,221,28,charging,standard,296,277,48,52,100,8,5,1,0 2012-03-30 20:24:01.681265 +0800 info main: #10 C EV915 rx msg D 124,8,4,42,48,25,3284,65175,0,6980,29,2,120,120 ==> Charging PEM:42, MOTOR:48, BATTERY:25, AMBIENT:29
2012-03-30 20:33:59.497056 +0800 info main: #10 C EV915 rx msg S 96,K,0,0,done,standard,299,280,48,57,100,9,9,4,0 2012-03-30 20:33:59.505736 +0800 info main: #10 C EV915 rx msg D 108,8,4,34,47,25,3284,65175,0,7577,27,2,119,119 ==> Charged PEM:34, MOTOR:47, BATTERY: 25, AMBIENT:27
I reckon the actual ambient temperature was probably 24 or 25 Celcius. It goes up during the charge, presumably because the HVAC is spewing out hot air around the ambient sensor at the front of the car (which is in the garage so will build up heat).
I think my data above is not a very good example, as I wasn't driving hard so the battery temperature was unusually low. My first instinct was that it would be good to use as an approximation for ambient, but actually not. The theory is that when the ambient temperature is hot or cold, the car has to use HVAC/heater to keep the battery at the temperature it needs, and that uses power which reduces charging efficiency. Battery temperature is a side-effect, and won't help to predict energy usage.
So, I still think ambient temperature is the correct thing to use as a predictor for charging efficiency (along with current+voltage).
The question is, looking at historical logs how can we approximate that? Only looking at charges that occurred an hour after a drive would work, but would remove 95% of my charges, like anyone else who plugs in when they get home ;-)
Regards, Mark.
On 8 Apr, 2012, at 4:22 PM, Dominik Westner wrote:
I already did some tests calculating the remaining charge time and had it implemented in the iPhone app.
First I took the simple approach to linearly estimate the remaining time by taking the charge current and voltage and calculate the energy per sec. Then take the missing energy from the current SOC. This will give you an approximation of the remaining time.
If you are looking at +/- 1 hour. This already should work from my experience.
I tried to make it better by taking into account that the charging curve is not linear, but more on a logarithmic scale. This worked a bit better. I also figured that there is some loss when charging, which I set to 5% (this probably varies by temperature).
What I did not know is the fact that once finished charging the batteries will be rebalanced for 30 minutes. Is this still shown as charging in OVMS? If yes, this would explain, why I've been off for about 30 - 60 minutes with my calculation.
I also did not take the age of the battery into account, which should be an important factor, too.
I think that it might be better to use a formula which tries to approximate the charging curve instead of using a fixed lookup table. At least it also could be fine tuned a bit easier by just setting a couple of parameters through the app to change the calculation.
Greetings
Dominik
On 08.04.2012, at 06:16, Tom Saxton wrote:
> I think your model would work pretty well. > > To calculate charge time, you also have to take into account the current > tapering near the top of the charge. > > We can get most of the required data from log files. The only tricky bit is > getting the ambient temperature, which I don't think anyone has identified > in the log files. You could get a good approximating by only considering > charge sessions that start a least an hour of the most recent drive and then > use the starting temperature of the coolant as a proxy for ambient > temperature. > > Range mode is the trickiest and the most important to time, they are also > done less often, so it's harder to get data. I'd be happy to collect logs > and extract data if we can get owners to contribute logs for a variety of > charging levels and ambient temperatures. > > Tom > > on 4/6/12 5:52 PM, Mark Webb-Johnson wrote: > >> The core question I have here is whether it is possible to build a static >> table saying that at this temperature, this available voltage+currrent, the >> charging efficiency is X%? Something accurate enough to give us a charge time >> prediction (given temperature, kWh needed by the pack, available >> voltage+current) of +/- 1 hour? >> >> I'm assuming the temperature should be ambient, as that is more important >> overt the duration of a reasonable charge than pack temperature? >> >> If we can have such a table, with steps of 5 degrees celcius between -10C and >> +40C, and say 10 current levels, that is only 100 entries - and we would only >> need 1 byte for each entry. The module could then put in the current >> temperature, current/voltage level, and get out an efficiency factor. It could >> estimate the kWh the pack needs (by mode and SOC/ideal-miles difference), then >> multiply by efficiency factor, and get out an estimate of how many minutes is >> required to achieve that. >> >> Without this table, we could do the lookup on the server, but that would mean >> having to set it _every_ night from the App/Server - as it would depend on the >> SOC% the car was actually at. >> >> If we could build this data, where could we get the data from? >> >> Regards, Mark. >> >> Begin forwarded message: >> >>> From: Mark Webb-Johnson <mark@webb-johnson.net> >>> Subject: Re: [Ovmsdev] Charge Control >>> Date: 6 April, 2012 8:25:51 PM GMT+08:00 >>> To: OVMS Developers <ovmsdev@lists.teslaclub.hk> >>> >>> >>> Bennett Leeds and I have had a discussion off-list (I'm not sure if he is on >>> this list or not), and he brings up a valid point about balancing the pack >>> perhaps not occurring if we cut short the charge with a SOC limit. >>> >>> Looking here: >>> >>> http://www.teslamotorsclub.com/showthread.php/3848-Tesla-Roadster-Battery-Ca... >>> e?p=41995&viewfull=1#post41995 >>> >>> it seems that this approach may be non-optimal. For clarity, let me >>> cut-and-paste the Tesla reply here: >>> >>> For simplicity’s sake, I will refer to all SOC (State Of Charge) numbers as a >>> percentage of a full (100%) charge. I cannot provide exact percentages, as >>> there are many variables which can cause these numbers to vary slightly, >>> however, I will get as close as I can. >>> >>> When plugging in a nearly empty car that is set to Storage mode, the charge >>> will generally stop at around 20%. The car will then settle into its normal >>> Storage mode rhythm, topping up and discharging between 10% and 50% as the >>> car sees fit. Oftentimes it will keep a tighter envelope based on parameters >>> that I am not aware of. >>> >>> Most important to remember is that Storage mode is not intended to be a >>> driving mode. This charge setting is primarily meant to optimize battery life >>> while the car is under storage conditions for two weeks or more. >>> >>> Storage mode does not attempt to balance the pack, and you will cause an >>> imbalance in the pack by driving and charging in this mode regularly. >>> >>> This will penalize you when you do occasionally charge the car fully in the >>> other modes, as you will not have the full range of the car available to you >>> until the car has a chance to balance its battery. Additionally, the car’s >>> range will not be as accurate if driven while in Storage mode vs. having >>> charged it in Standard mode after storing the car, then driving it. >>> >>> Allowing the car to sit plugged in after it has finished charging in Standard >>> mode automatically balances the pack, and it may take a few rounds of this to >>> bring an imbalanced pack back to its full potential after many partial >>> charges. This is one of the major reasons we recommend keeping the car in >>> Standard mode whenever possible. Partial charges in any mode, while not on >>> their own bad for the battery, do not give the car an opportunity to balance >>> its battery, and over time can prevent you from accessing the car’s full >>> range potential. >>> >>> When balanced, Standard mode charges the car to about 87%, with Range and >>> Performance modes getting the car to about 97%. These two percentages are >>> very much affected by the balance between bricks in the battery. An >>> imbalanced pack will not fill up all the way in any mode, nor will it be able >>> to discharge as far. Additionally, the range predictions will not be as >>> accurate. >>> >>> Your voltages are about right. >>> 4.10 volts = full standard mode (187-195 ideal miles) >>> 4.15 volts = full range mode >>> 4.20 volts = maximum of the cells that we never touch >>> As you may know, there is much more to it than just using voltage to >>> calculate range with Lithium batteries. This is something that is incredibly >>> complicated, and not something that I am qualified to discuss in detail, as I >>> do not have the full picture. >>> >>> It is important to remember that SOC is not the only factor in maximizing >>> battery life. For instance most lithium batteries are shipped at around >>> 30-50% SOC in consumer electronics, and part of the reasoning is that they >>> are less susceptible to damage from extreme temperatures at these charge >>> levels. It is also safer to store them at these levels. Part of the benefit >>> of Storage mode is that there is less work required from the HVAC system to >>> keep the batteryhappy and safe, and therefore, less energy is consumed while >>> stored. >>> >>> We chose ~90% as a Standard full charge level because it offers most of the >>> longevity benefit of keeping the car at a lower state of charge, while still >>> allowing a high degree of autonomy. I understand that you are interested in >>> taking extra steps to maximize your battery’s life, so I do have some >>> suggestions for you. >>> >>> I would not recommend that you continue to use Storage mode as a means of >>> maintaining a lower state of charge. As I explained earlier, this mode is not >>> optimized for this type of use. >>> >>> Think of battery degradation this way. It is very much a function of time >>> spent at voltage and temperature. For instance, you do not want to charge a >>> car all the way in performance mode, and then let it sit in the sun all day. >>> Between the higher thermal limits and the high SOC, you are causing the >>> battery a relatively high amount of degradation .In fact, the car will >>> eventually allow itself to discharge to Standard levels if left in >>> Performance mode to prevent inadvertent damage to the battery. If you start >>> driving right away after charging in Performance or Range Mode, and don’t let >>> it sit, you would minimize the damage incurred, as the time spent at these >>> extremes is an important part of the calculation. >>> >>> Similarly, if you top off to full in Standard mode, then jump in the car >>> right away and bring the SOC down quickly, you will minimize the small amount >>> of degradation that occurs at ~90%. >>> >>> If you prefer to keep a lower average SOC in an attempt to maximize the life >>> of your battery, I would instead suggest that you stay in Standard mode and >>> utilize the Roadster’s built in charge timer and current limiting options to >>> find an average SOC that works for you. For instance, try starting your >>> charge at a time that allows the car to top off to a level you are >>> comfortable with right before you need to leave. Alternately, you can use the >>> Current limiting function to adjust the amount of time it takes the car >>> reaches a target SOC, or even a combination of these two options. The car >>> will remember the settings you select based on your location, so once you >>> find something that works for your commute, you can set it and forget it. >>> >>> Just remember that the car does benefit from being allowed to sit fully >>> charged in Standard mode, and should be allowed to do so frequently, >>> especially if being used on a daily basis. Leaving the car plugged in in >>> Standard mode after it is done charging will initiate this balancing program >>> automatically. This doesn’t take much time, 30 minutes or so should do. It >>> may take several of these balancing cycles to bring the car back to a >>> balanced state if it has become imbalanced, which is something that a lack of >>> regular Standard mode top ups and subsequent balancing cycles can induce. >>> >>> It would therefore be a good idea to set the car to “Charge on Plug In” >>> instead of “Charge at X time” in the charge timing menu for at least a few >>> Standard mode charges per week to keep the pack balanced. There are simply >>> too many variables for me to be able to predict how often you would need to >>> do this, and we do not have a recommended procedure for alternate desired >>> average SOC levels. >>> >>> I hope this helps answer your questions, and gives you a better idea of how >>> to maximize battery life under your driving conditions. >>> >>> Regards, >>> >>> Dan Myggen >>> >>> From what he is saying, it appears optimal to time the charge to bring it to >>> full charge in standard mode 30 minutes before you leave. That would leave >>> the car sitting at high charge rate for the least amount of time, but allow >>> enough time for balancing to occur if necessary. >>> >>> This sounds exactly like our finish-charging-by approach. Rather than set the >>> charge start time, you set the finish time, and the system works out how long >>> it should take then adds on a 30-to-60 minute safety margin (which would also >>> allow for battery balancing to occur). >>> >>> Does this make sense? Or is Dan Myggen's advise wrong? >>> >>> Regards, Mark >>> >>> On 5 Apr, 2012, at 7:45 PM, Mark Webb-Johnson wrote: >>> >>>> >>>> I'm now starting to think about the v1.3 firmware, which is intended to add >>>> the following: >>>> >>>> Log charge history >>>> Log drive history >>>> Sophisticated control of charge time >>>> >>>> We don't really have TOU metering in Hong Kong, so not much use for me, but >>>> part [3] would be fun nevertheless. Most charge control in EVs is pretty >>>> basic, and it might be interesting to see how sophisticated this can be made >>>> without complications. >>>> >>>> I don't know if this is workable or not, so put my thoughts out into the >>>> open for discussion. >>>> >>>> For charge time, the consensus seems to be that people want to enter the >>>> time to FINISH charge, vs the current time to START charge. To do that, we >>>> need an estimate of how long the charge will take. For that, we either need >>>> a sophisticated model or a collection of historical data we can lookup to >>>> find something approximate. Hence item [1] on my list. >>>> >>>> Elon talked about the car learning about you. Where you park. Where you >>>> charge. etc. So, if always leave home at 7:00am to go to the office on >>>> Mondays through Fridays, perhaps the car can learn? Or, at least suggest >>>> based on what it has seen... Hence item [2] on my list. >>>> >>>> For [1], we would store such things as temperatures, SOC start, SOC end, >>>> charge mode, charge current, charge voltage and duration. The can bus charge >>>> message seem to include this information. >>>> >>>> For [2], we would store such things as date/time of drive, duration (time, >>>> distance, and elevation change), battery usage. We seem limited in this from >>>> what we have decoded on the can bus so far. >>>> >>>> Regardless of the above, [1] and [2] would be useful information for any >>>> owner, anyway. >>>> >>>> Privacy is an issue. Two problems - (a) protection of my charge/drive >>>> history, (b) the use of 'shared' charge history for [3]. My suggestion is to >>>> keep drive and charge history private. Perhaps it could just be stored as >>>> paranoid mode blobs. But, there should be an option to allow anonymised >>>> sharing of charge history for the use of [3]. My thinking is that if you >>>> share your data anonymously, then your lookup includes the pool of others >>>> anonymous charge history. if you choose not to share, then your lookup is >>>> only against your own charge history. >>>> >>>> I did toy with the idea of using the server to control this. So, at 3am the >>>> server sends a command to the car to start the charge, etc. That would >>>> simplify the firmware in the car, but has a major problem of GPRS >>>> connectivity - if the cellular signal was lost the charge wouldn't start. >>>> Bad. So, I think it best to have the historical database in the server, the >>>> calculations in the App, and the settings downloaded to the car while it has >>>> cellular signal (after which it just follows them autonomously). >>>> >>>> The Tesla Roadster currently offers you a choice of charge on plug-in, or >>>> start charge at a particular time. It also allows you to limit charge >>>> current and set charge mode. My thinking is to extend this by making it per >>>> day-of-the-week for a few defined locations, and to provide an override for >>>> the 'current' day/night. If the override is not set, and you are in one of >>>> the defined locations, then the system looks up the day of the week and >>>> controls charge based on what you have set. The UI for this is quite simple >>>> - presumably a screen with tabs/selector for day or the week, and then >>>> controls to set charge mode, current limit, and time to start/complete by. >>>> One developer also had the good idea that a charge SOC limit would be useful >>>> (e.g.; please stop charge when it gets to 70% / 220km ideal). >>>> >>>> How do we handle night vs day charging? Is this only for overnight, or do we >>>> base it on when you plugin? >>>> >>>> Is this workable? Useful? >>>> >>>> Really interested in people's feedback on this. >>>> >>>> Mark. >>>> >>>> _______________________________________________ >>>> OvmsDev mailing list >>>> OvmsDev@lists.teslaclub.hk >>>> http://lists.teslaclub.hk/mailman/listinfo/ovmsdev >>> >> >> _______________________________________________ >> OvmsDev mailing list >> OvmsDev@lists.teslaclub.hk >> http://lists.teslaclub.hk/mailman/listinfo/ovmsdev > > > _______________________________________________ > OvmsDev mailing list > OvmsDev@lists.teslaclub.hk > http://lists.teslaclub.hk/mailman/listinfo/ovmsdev
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participants (6)
-
David Morse -
Dominik Westner -
felix bonnier -
Mark Webb-Johnson -
Tim Putnam -
Tom Saxton