How to spot faulty battery cells

[DanishFamilyMan]

Hi.

I need some advice on how to use an OBD2 adapter to track down faulty high voltages battery cells.
I'm planning to use the car scanner app and the icar pro adapter.
The case is, that my Enyaq self-discharge. Often by 3% within a couple of hours while being parked in garage.
My local dealer tells me that the car's VIN is not affected by the known “Bad battery cell issue” and because of that, they won't test the battery. Furthermore, they claim that self-discharge in that range is normal and should be expected
Have anyone else seen a discharge like that on their Enyaq?
I would like to test the battery myself.
Does anybody know a bulletproof method to determine if some of my high voltages battery cells are faulty.

[snalbansed]

I have no idea as to if this helps, but with Car Scanner on Android I have the following data that might be useful:

[8C.BMS] Battery max SoC cell # ()
[8C.BMS] Battery max SoC cell % (%)
[8C.BMS] Battery min SoC cell # ()
[8C.BMS] Battery min SoC cell % (%)
[8C.BMS] HV Battery cell # with highest voltage ()
[8C.BMS] HV Battery cell # with lowest voltage ()
[8C.BMS] HV Battery cell voltage #001 (V)
[8C.BMS] HV Battery cell voltage #002 (V)
...
[8C.BMS] HV Battery cell voltage #045 (V)
[8C.BMS] HV Battery cell with highest voltage (V)

I don't know how you would monitor over a period of hours though - with Car Scanner if I connect it to the ODB-II dongle and leave it for a while (I don't know if looking at the live data makes any difference, I suspect not), I can then export the csv of the data afterwards. I think in your situation I might be tempted to periodically go back to the car, wake it up, connect it again, leave it running for ten minutes then do it all again 30 minutes later or something.

If you leave Car Scanner connected to the ODB whilst the car is locked, it will set the car alarm off. If you disconnect it, it won't.

[snalbansed]

I should add that I would not expect any change to SoC in a few hours on my car.

The other thing that might be interesting is to see whether you are seeing the same change in SoC for the BMS figures and for the display figures - you might have seen in my thread about charting OBD charging data that they are not the same and don't have a fixed offset either.

[snalbansed]

This post in particular regarding SoC figures:

How about this then? My preferred 150 kW charger was in use, so as I was on ~13% I went to the next charger which was 50 kW. After a while on that charger, the other one was free and I wouldn't be stuck if someone else got there first, so I went back to it.

Battery power with State of Charge:
PowerSOC.png

Battery power with battery temperature - this time I used minimum and maximum battery temperature values:
PowerTemp.png

[orrery]

It is possible that the SOC changes with temperature - when the batteries cool, the SOC shows as lower than it was even though there is no change in the actual charge level.

[Goaty]

It is possible that the SOC changes with temperature - when the batteries cool, the SOC shows as lower than it was even though there is no change in the actual charge level.

Absolutely - I was about to say the same thing. The predicted range can go up, too, if the ambient temperature increases while it’s parked. I’ve seen that happen a few times.

[Stripy]

Not seen that in my iV60

You can disable the alarm, when you engage the parking brake, on the screen, if you want to keep your OBDII running - or don’t lock the car, if garaged