[Ovmsdev] i-Miev/C-Zero/iOn

Fri Oct 18 17:08:27 HKT 2013

OK, I've done a bit more testing and it looks promising.

What I have found is the following:

Charger Temperature
I spotted a value in byte 3 of PID 286 that rises gradually during
charging, then falls slowly afterwards. It seems likely this is charger
temperature of some kind. This seems to settle at about 40 higher than the
current outdoor temperature in Celsius. It seems odd to be having a
different offset to the battery temperature values, but the outside air
temperature here is 9.7C and the PID 286 value is 50 with battery sensor
average value 65. This would mean the charger is almost exactly ambient and
the batteries 5C higher.  I have added this as PEM temp.

Motor Temperature
I found that PID 298, which has the suspected motor RPM, has a set of 4
values in a similar range to the possible charger temperature reading.
These seem to rise while driving, the forth of them (byte 3) rises fastest
and highest. I suspect that these are intimately linked to the motor,
either a direct motor temperature, or the motor drive electronics. Again,
they settle to about 40 above ambient in C when not in use.  I have added
this as motor temp.

I have found that the charger temperature rises a little while driving, and
the motor temperature possibly a tad while charging (but not much). This
could simply be because the two are physically close, or the charger could
be involved in regenerative braking.

Rapid/quick charge detection.
During RC the bus has PID 346 messages, but the range in byte 7 is 255
rather than a valid estimated range. I have seen logs showing 255 for a few
samples at startup, so maybe we need to add a test for this 255 being
stable for more than a second or two. Of course the problem now is that we
have lost the predicted range. We have "ideal" range, but that is a bit of
a chocolate teapot as you are never going to get that range and it is not
correctly calculated in my opinion (due to unusable SOC at the bottom of
the battery).

I have studied some of my charging records and it seems that the predicted
range hits 0 at about 10% SOC, and it is roughly linear to 100% from there.
The slope of the line depends on the recent driving style. I have used this
to code a replacement "guess-o-meter" for use during rapid charge. The way
it works is as follows: I constantly record valid SOC and est_range until
either of them gets too low to be reliable (20% SOC or 5 range) - this
gives me an indication of the slope that should be used for the line.
During RC I calculate est_range = (SOC-10%) * Slope,  where Slope =
(Old_Range / (Old_SOC-10%)). This works, but I have only tried one RC with
this code and the ranges it gave me were a bit higher than I expected. This
might need some debugging.

I have attached the revised code. You will see that I have also optimised
the PID filtering a bit to try and reduce load while still capturing the
increased number of PIDs we are now monitoring. I wonder how easy it is to
check how close we are to running out of CPU capacity in the read code.

Matt Beard

On 17 October 2013 07:10, Matt Beard <matt at beard.tv> wrote:

> I hope to be able to do so in the next day or so.
>
> Matt
>
>
> On Wednesday, October 16, 2013, Thomas Bergo wrote:
>
>> Greate work.
>>
>> If you share your discoveries and your code, I can also do some testing.
>>
>> Regards, Thomas
>>
>> onsdag 16. oktober 2013 skrev Matt Beard følgende:
>>
>> I was wrong about the bus being quiet during RC and have figured out how
>> to detect rapid charging.
>>
>> Also I've found the AC charger temperature (which should probably go in
>> PEM temperature) and I'm pretty certain I have found the motor temperature
>> (but I need to do more testing). What I really want is the ambient
>> temperature, but no sign yet. Any ideas?
>>
>> Matt Beard
>>
>>
>> On Friday, September 27, 2013, Matt Beard OVMS wrote:
>>
>> Has anyone seen a CAN log from a rapid charge?
>>
>> Is the OBD port active at all during rapid charge? I found nothing gets
>> reported during RC.
>>
>> Matt
>>
>>
>>
>> On 26 September 2013 10:29, Thomas Bergo <thomas.bergo at gmail.com> wrote:
>>
>> Ok, then you have the same issue.
>>
>> Will look into this later.
>>
>> Regards, Thomas
>>
>>
>> 2013/9/26 Matt Beard OVMS <smvo at mxf.org.uk>
>>
>> My STAT? gives:
>>
>> Not charging
>>  SOC: 100%
>>  Ideal Range: 93 mi
>>  Est. Range 68 mi
>>
>>
>> On 26 September 2013 10:02, Thomas Bergo <thomas.bergo at gmail.com> wrote:
>>
>> Matt:
>> Do you get the ODO in the "STAT?" SMS message?  I did until two days ago,
>> did a cleanup of the code before push to GitHub. After that i haven't got
>> ODO.  Can't see any changes to the code from the previous version ether.
>>
>> Regards, Thomas
>>
>>
>> 2013/9/25 Matt Beard OVMS <smvo at mxf.org.uk>
>>
>> Having disconnected OVMS and power-cycled the car the charge seemed to be
>> going OK, so I connected the unit back up and let it go the last 50% or so
>> with OVMS and it was still fine. So, looks like something set a bad value!
>> Maybe there is a "set max % charge" CAN message and it got set due to noise
>> on the bus. Wish I knew what it was!
>>
>> Matt
>>
>>
>>
>> On 25 September 2013 14:35, Thomas Bergo <thomas.bergo at gmail.com> wrote:
>>
>> How did the rest of the charging go?
>> Any other hick ups?
>>
>> Regards,Thomas
>>
>> onsdag 25. september 2013 skrev Matt Beard følgende:
>>
>> The SOC was about 25%
>>
>> Matt
>>
>>
>> On Tuesday, 24 September 2013, Thomas Bergo wrote:
>>
>> Was the SOC approximately 70% ?
>>
>> The Car takes a pause and stops charging for some time at 70%. I belive
>> this is to level the charge state of the cells. After some time the
>> charging will continue.
>>
>> Regards, Thomas
>>
>> tirsdag 24. september 2013 skrev Matt Beard følgende:
>>
>> More strange behaviour with my C-Zero.
>>
>> Trying to investigate charging current today I discovered that the car
>> would not charge for longer than a couple of minutes with the OVMS
>> connected (with Thomas' image loaded). It would start charging, then the
>> current would drop to zero, but the charge light stayed on. After a while
>> it stopped even trying to charge. Disconnecting the OVMS didn't fix it
>> until I also turned the car on and off again (with the OVMS not connected).
>> Did can noise cause problems again?
>>
>> Matt
>>
>>
>> On Tuesday, September 24, 2013, Thomas Bergo wrote:
>>
>> The first models (2011) was delivered with a 16A cable. This was changed
>> for the later models (2012 ->) to 10A cable do to firesafty.
>> At home i use a 16A cable for charging, but the car only draw 13A.
>>
>> I'm not sure what is the correct info, EVSE limit or the charger limit.
>>
>>
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