[Ovmsdev] Volt/Ampera CAN Logs

Sat Jun 2 02:34:45 HKT 2012

I'm not a Volt owner, but I've been logging EV drive and charge data for
four years across three different production EVs.

It's great that the Volt is giving an energy number, not an SOC. The Leaf's
factory SOC gauge is relative to the battery's current capacity.
Fortunately, the CAN bus provides an energy number.

The RAV4-EV, Roadster and Leaf all show SOC relative to the usable portion
of the battery, not the full rated capacity. I think it makes sense to set
0% to the bottom of the normal usable range and 100% at the top.

If the battery pack gets outside those bounds in some unusual circumstance,
it should show negative or above 100% so that net battery use can be
computed by subtracting two SOC values. (That doesn't give energy use, but
rather use of energy capacity, which can be different.)

To compute ideal miles do what Tesla does: multiply the SOC by the EPA-rated
electric range. If you want to be really nice, let the user set the full
range number to something other than the EPA number if they like.

Personally, I think estimated miles is rarely useful and often worse than
useless. We live in an area with lots of hills, so estimated miles are
constantly jumping up and down. Alternative, the estimated miles could be on
a wider driving window, but then it becomes too unresponsive to be useful. I
wouldn't bother to go to a lot of trouble to create an estimated miles
algorithm that's only going to be useful in a steady speed and flat road
situation.

    Tom

on 6/1/12 7:46 AM, Mark Webb-Johnson wrote:

> 
> For OVMS, is it best to leave this as 'real' soc, or 'normalise' to the
> 'standard' range like the Tesla does?
> 
> For example, say the top 10% and bottom 10% is never used, so only numbers
> between 10 and 90 are seen (in a 0 to 100 range). For example, if the value is
> 40, is that 40% SOC or 37.5%?
> 
> It is going to be interesting coming up with estimates for ideal and estimated
> miles in the Volt...
> 
> Mark.
> 
> On 1 Jun, 2012, at 9:47 PM, R. Scott Perry wrote:
> 
>> Hi Michael,
>> 
>> I believe the SOC is correct.  The SOC number is the actual amount of
>> electricity in the battery, not the usable amount.  Only about 70% of the
>> actual battery power is ever used.  So this number is normally between about
>> 3,5kwh and 14,4kwh.
>>                     -Scott
>> 
>> 
>> On 6/1/2012 8:35 AM, Michael Jochum wrote:
>>> Hi,
>>> 
>>> in the mean time in can confirm:
>>> 
>>>> The VIN can be constructed by taking the number "1" and converting the CAN
>>>> IDs 4E9 and 514 to ASCII.  So with "4E1 4255313032363839" and "514
>>>> 4731524436453436", you would end up with 42 55 31 30 32 36 38 39 47 31 52
>>>> 44 36 45 34 36, where 42 is ASCII for B, 55 is U, etc.
>>> 
>>> "1" . 514 .  4E1 converted to ascii IS the VIN!
>>> 
>>>> For the SOC, the "206 3 69 C3 00" capture indicates CAN ID 206, with 3
>>>> bytes of data.  The SOC data only uses the first two bytes, so this would
>>>> be 0x69C3, or 27075d.  Dividing by 4,000 gets 6.769kWh in the battery, or
>>>> about 42% of the total battery capacity, which should be 4 bars on the
>>>> display. 
>>>> http://gm-volt.com/forum/showthread.php?5328-Volt-Diagnostic-Tool&p=91868#p
>>>> ost91868 correlates the SOC number here with the bars displayed.
>>> 
>>> 
>>> could be the SOC. But in my case it goes only to 14,14kwh and that it falls
>>> down. Car is still connected AND Battery is full (Green Light is flashing).
>>> 
>>> Bye
>>> michael
>>> 
>>> 
>>> Am 31.05.2012 um 15:34 schrieb R. Scott Perry:
>>> 
>>>> Hi everyone,
>>>> 
>>>> I'm the RScott from gm-volt.com, and I wrote the page at evtools.info about
>>>> the Volt and OBD2 data (which I haven't updated in quite some time).  I've
>>>> read the recent posts to the list about the Volt, and thought I would
>>>> provide information here in response.
>>>> 
>>>> First, if it would be helpful, I have written a program for Windows to
>>>> record data from an OBD2 scanner.  It is designed to work with scanners
>>>> that use the ELM327 chip (or are compatible).  It saves the timestamp, and
>>>> saves the data in the format "11:48:45.829: 206 639600".  It is run from a
>>>> command prompt, and not very user friendly.
>>>> 
>>>> For the SOC, the "206 3 69 C3 00" capture indicates CAN ID 206, with 3
>>>> bytes of data.  The SOC data only uses the first two bytes, so this would
>>>> be 0x69C3, or 27075d.  Dividing by 4,000 gets 6.769kWh in the battery, or
>>>> about 42% of the total battery capacity, which should be 4 bars on the
>>>> display. 
>>>> http://gm-volt.com/forum/showthread.php?5328-Volt-Diagnostic-Tool&p=91868#p
>>>> ost91868 correlates the SOC number here with the bars displayed.
>>>> 
>>>> The VIN can be constructed by taking the number "1" and converting the CAN
>>>> IDs 4E9 and 514 to ASCII.  So with "4E1 4255313032363839" and "514
>>>> 4731524436453436", you would end up with 42 55 31 30 32 36 38 39 47 31 52
>>>> 44 36 45 34 36, where 42 is ASCII for B, 55 is U, etc.
>>>> 
>>>> The latitude/longitude conversion is almost the same as what you have for
>>>> the Tesla, with two exceptions -- changing the 2048 to 1000, as noted, and
>>>> the accounting for negative numbers is different.  It seems that the number
>>>> the Volt supplies is a 31-bit signed integer.  The easiest way to handle
>>>> that, I think, would be to add "latlon = latlon<<  1;" before checking
>>>> for<0, and then "latlon = latlon>>  1;" afterwards.  Running the code you
>>>> have with those two changes seems to work fine.
>>>> 
>>>> The bad news is that I have checked all my log files (I have been logging
>>>> almost all the time I have driven for about 8 months now), and the CAN ID
>>>> 32A (latitude/longitude) has never shown all zeroes.  If the GPS data is
>>>> unobtainable, I believe the car reports the most recent reading.  The GPS
>>>> data comes from the OnStar system, so I am thinking it may only provide the
>>>> data if the OnStar service has been activated, which could be a problem for
>>>> owners outside of U.S/Canada.
>>>> 
>>>> For charging, all I have found so far are some numbers that appear to show
>>>> electricity flow to/from the battery.  If they are positive, electricity is
>>>> going to the battery; if negative, electricity is leaving the battery.  But
>>>> this will also be positive if the gas engine is on and charging the
>>>> battery, as well as if the car is going downhill and the regenerative
>>>> braking is being used.
>>>>                       -Scott
>>>> _______________________________________________
>>>> OvmsDev mailing list
>>>> OvmsDev at lists.teslaclub.hk
>>>> http://lists.teslaclub.hk/mailman/listinfo/ovmsdev
>>> 
>>> _______________________________________________
>>> OvmsDev mailing list
>>> OvmsDev at lists.teslaclub.hk
>>> http://lists.teslaclub.hk/mailman/listinfo/ovmsdev
>>> 
>> _______________________________________________
>> OvmsDev mailing list
>> OvmsDev at lists.teslaclub.hk
>> http://lists.teslaclub.hk/mailman/listinfo/ovmsdev
> 
> _______________________________________________
> OvmsDev mailing list
> OvmsDev at lists.teslaclub.hk
> http://lists.teslaclub.hk/mailman/listinfo/ovmsdev
> 