[Ovmsdev] MS_V_BAT_SOH

Michael Balzer dexter at expeedo.de
Fri May 25 21:55:11 HKT 2018

Am 25.05.2018 um 03:55 schrieb Mark Webb-Johnson:
> We definitely need some way to make these available in a standard way. I’m not sure that vehicle metrics is the correct way for that, though. Just too many numbers (99 for Tesla Roadster, for example) and maybe not available real-time (need to poll for them). Perhaps a standardised command would be a better approach for this?

Yes, lots of metrics. I know that ;)

OVMS# me li xrt.b.
xrt.b.cell.01.volt.act                   3.995V
xrt.b.cell.01.volt.max                   4.12V
xrt.b.cell.01.volt.maxdev                0.01V
xrt.b.cell.01.volt.min                   3.795V
xrt.b.cell.02.volt.act                   3.985V
xrt.b.cell.02.volt.max                   4.11V
xrt.b.cell.02.volt.maxdev                -0.01V
xrt.b.cell.02.volt.min                   3.785V
xrt.b.cell.03.volt.act                   3.985V
xrt.b.cell.03.volt.max                   4.11V
xrt.b.cell.03.volt.maxdev                -0.005V
xrt.b.cell.03.volt.min                   3.785V
xrt.b.cell.04.volt.act                   3.98V
xrt.b.cell.04.volt.max                   4.105V
xrt.b.cell.04.volt.maxdev                -0.01V
xrt.b.cell.04.volt.min                   3.78V
xrt.b.cell.05.volt.act                   3.985V
xrt.b.cell.05.volt.max                   4.11V
xrt.b.cell.05.volt.maxdev                -0.01V
xrt.b.cell.05.volt.min                   3.78V
xrt.b.cell.06.volt.act                   3.98V
xrt.b.cell.06.volt.max                   4.105V
xrt.b.cell.06.volt.maxdev                -0.01V
xrt.b.cell.06.volt.min                   3.78V
xrt.b.cell.07.volt.act                   3.985V
xrt.b.cell.07.volt.max                   4.105V
xrt.b.cell.07.volt.maxdev                -0.01V
xrt.b.cell.07.volt.min                   3.78V
xrt.b.cell.08.volt.act                   3.985V
xrt.b.cell.08.volt.max                   4.115V
xrt.b.cell.08.volt.maxdev                -0.005V
xrt.b.cell.08.volt.min                   3.785V
xrt.b.cell.09.volt.act                   3.985V
xrt.b.cell.09.volt.max                   4.12V
xrt.b.cell.09.volt.maxdev                0.005V
xrt.b.cell.09.volt.min                   3.785V
xrt.b.cell.10.volt.act                   3.99V
xrt.b.cell.10.volt.max                   4.12V
xrt.b.cell.10.volt.maxdev                0.005V
xrt.b.cell.10.volt.min                   3.785V
xrt.b.cell.11.volt.act                   3.99V
xrt.b.cell.11.volt.max                   4.12V
xrt.b.cell.11.volt.maxdev                0.01V
xrt.b.cell.11.volt.min                   3.79V
xrt.b.cell.12.volt.act                   3.99V
xrt.b.cell.12.volt.max                   4.12V
xrt.b.cell.12.volt.maxdev                0.01V
xrt.b.cell.12.volt.min                   3.785V
xrt.b.cell.13.volt.act                   3.985V
xrt.b.cell.13.volt.max                   4.115V
xrt.b.cell.13.volt.maxdev                0.005V
xrt.b.cell.13.volt.min                   3.785V
xrt.b.cell.14.volt.act                   3.995V
xrt.b.cell.14.volt.max                   4.125V
xrt.b.cell.14.volt.maxdev                0.015V
xrt.b.cell.14.volt.min                   3.795V
xrt.b.cell.15.volt.act                   0V
xrt.b.cell.15.volt.max                   0V
xrt.b.cell.15.volt.maxdev                0V
xrt.b.cell.15.volt.min                   0V
xrt.b.cell.16.volt.act                   0V
xrt.b.cell.16.volt.max                   0V
xrt.b.cell.16.volt.maxdev                0V
xrt.b.cell.16.volt.min                   0V
xrt.b.cell.cnt                           14
xrt.b.cmod.01.temp.act                   17°C
xrt.b.cmod.01.temp.max                   23°C
xrt.b.cmod.01.temp.maxdev                1°C
xrt.b.cmod.01.temp.min                   16°C
xrt.b.cmod.02.temp.act                   16°C
xrt.b.cmod.02.temp.max                   23°C
xrt.b.cmod.02.temp.maxdev                1°C
xrt.b.cmod.02.temp.min                   16°C
xrt.b.cmod.03.temp.act                   17°C
xrt.b.cmod.03.temp.max                   23°C
xrt.b.cmod.03.temp.maxdev                1°C
xrt.b.cmod.03.temp.min                   16°C
xrt.b.cmod.04.temp.act                   16°C
xrt.b.cmod.04.temp.max                   23°C
xrt.b.cmod.04.temp.maxdev                -1°C
xrt.b.cmod.04.temp.min                   16°C
xrt.b.cmod.05.temp.act                   17°C
xrt.b.cmod.05.temp.max                   23°C
xrt.b.cmod.05.temp.maxdev                1°C
xrt.b.cmod.05.temp.min                   16°C
xrt.b.cmod.06.temp.act                   16°C
xrt.b.cmod.06.temp.max                   23°C
xrt.b.cmod.06.temp.maxdev                -1°C
xrt.b.cmod.06.temp.min                   16°C
xrt.b.cmod.07.temp.act                   16°C
xrt.b.cmod.07.temp.max                   23°C
xrt.b.cmod.07.temp.maxdev                -1°C
xrt.b.cmod.07.temp.min                   16°C
xrt.b.cmod.08.temp.act                   -40°C
xrt.b.cmod.08.temp.max                   -40°C
xrt.b.cmod.08.temp.maxdev                0°C
xrt.b.cmod.08.temp.min                   -40°C
xrt.b.cmod.cnt                           7
xrt.b.pack.1.temp.max                    23°C
xrt.b.pack.1.temp.min                    16°C
xrt.b.pack.1.temp.stddev.max             1°C
xrt.b.pack.1.volt.max                    57.6V
xrt.b.pack.1.volt.min                    52.8V
xrt.b.pack.1.volt.stddev.max             0.005V
xrt.b.pack.1.volt.watches                1,2,4,5,6,7,11,12,14
xrt.b.pack.cnt                           1
xrt.b.soc.max                            100%
xrt.b.soc.min                            69.78%

But if they are available in real time, they provide a very cool battery monitor, that displays per cell voltage breakdowns during driving:

If metrics can use extram, 100 cells would be no problem.


> Regards, Mark.
>> On 24 May 2018, at 10:28 PM, Robin O'Leary <ovmsdev at caederus.org> wrote:
>> On Wed, May 23, 2018 at 10:42:32PM +0800, Mark Webb-Johnson wrote:
>>> What is MS_V_BAT_SOH used for?
>> ...
>>> Which is it?
>>> An overall indication of battery health? 100% being perfect, and 0% a brick?
>>> Or battery capacity (100% being a new car, and 50% being one who’s range is only half that of a new car)?
>> If the car provides its own SOH value, then we should report it, even if
>> we don't know exactly what it means.  In some cases, it may be important
>> for warranty claims.
>> For the Leaf, the BMS-reported SOH seems more complicated than just a
>> percentage of new capacity; e.g. increased internal resistance and cell
>> imbalance are also factors.
>> If the car does not provides its own SOH value directly, then maybe
>> it's better not to fake it; just show whatever values are available.
>> Or perhaps it could be user preference which value best serves their
>> particular purpose: total capacity depletion, cell imbalance ...
>> or some combination.
>> ...
>>> Nissan Leaf uses:
>>> StandardMetrics.ms_v_bat_soh->SetValue(ah / newCarAh * 100);
>> You may recall, we had a recent discussion in favour of changing the
>> Leaf's ms_v_bat_soc and ms_v_bat_soh to report the values directly from
>> the BMS.
>> We do now report SOC as both direct-from-car and scaled-to-new values
>> in Leaf-specific metrics ("m_soc_instrument" and "m_soc_new_car")
>> and we have a config preference for which one to copy to ms_v_bat_soc
>> (defaulting to the instrument value).
>> We have not yet done that for SOH, but hopefully will do so soon, adding
>> "m_soh_instrument" for the BMS value and moving the above calculation to
>> "m_soh_new_car" .
>> ...
>>> Find out the difference between SOC LIM MIN and LIM MAX, and use that as an indication of imbalance in the pack.
>>> Or should we just add SOC_MIN and SOC_MAX if these are used in many cars? Or an imbalance percentage?
>> Having a way to report cell imbalance is a good idea, but trying to
>> express it as two percentage values seems rather crude.  The Leaf can
>> report voltage for every cell, but (as far as I know) does not indicate
>> the nominal voltage value (and I wouldn't be surprised if these differ
>> between the three(?) generations of chemistry already in circulation), so
>> converting each one to a % would be arbitrary.  Also, the distribution of
>> voltage values for the modules is often tightly grouped, with just a few
>> outliers, so just picking the lowest and highest is a bit too simplistic.
>> A better way would be to report all the cell voltage measurements
>> directly, or at least some basic statistics (n, average, stddev).
>> How widely are such detailed values available for other vehicles?
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Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
Fon 02333 / 833 5735 * Handy 0176 / 206 989 26

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