3.2 update. Battery passed inspection but deltaV is 11.9v.

[DraxxMenvone]

Hi folks. I bought a used 2020 id3 business pro last week privately. I insisted the seller have the software updated from 2.1 to 3.2 and get the 12v recall addressed before I bought it which he did. VW says the battery passed the test and no modules needed to be replaced. I’m checking with Carscanner and seeing a deltaV of 11.9mv, with one specific cell looking like the culprit.
Does this look like it’s just within operational limits and likely to cause issues soon? I’ve heard of the 3.2 update not showing HV battery warnings for a year afterwards. Thanks for any help.

[sidehaas]

On the face of it that looks like a small anomaly, but 11.9mv in itself is not a big problem. In some makes of cars that's entirely normal. You can find old degraded Leafs with deltas an order of magnitude more.
However I am pretty sure the VW software is more complex than just a voltage delta. It's trying to work out which cells might have defects. Based on my own experience (what I observed from analysing carscanner data with our ID3 in the few months between it failing the battery check and having a module replaced) I would advise looking at the bar chart at a range of different SoCs and seeing:
- is the delta sometimes much more than 11.9mv (ours ranged from almost nothing to about 18, but was mostly 10-15mv).
- is the same cell always the lowest in the pack?

If this cell is always the lowest and the delta changes as a function of SoC (non linear) and is sometimes more than 11mv, that would be like what our car had, which failed the battery check and did eventually trigger the dashboard warning (which was when I expedited getting it fixed).

[DraxxMenvone]

Many thanks for your detailed reply. I’ve only tested the car stationary snd cell #55 has consistently been the problematic cell. I was asking Chat GPT this morning about it and it suggested something similar to your advice. Check deltaV at different SOC but also to check under load. I’ll try screen grabbing while accelerating uphill but also at different SOC and report back.
I’m guessing VW don’t make moves to replace modules until warnings appear on the dash? I’ve got three years left on the battery warranty so here’s hoping it pops before then!

[DraxxMenvone]

So I just tried testing the deltaV while accelerating up a steep hill and it came out as 27.1mV. For what’s it’s worth, Chat GPT is telling me that it’s well within operational limits and that a deltaV consistently over 30 to 50mV would indicate a problem. I realise I’m reaching the upper limit there so I’ll definitely keep an eye on it. Tests during regenerative braking and charging were much less pronounced. I’m going to test it after a balance charge tonight and during rapid charging tomorrow and see if anything else shows up.

[sidehaas]

The carscanner data only seems to update every couple of seconds and not at the same time for every cell, so I don't think you'll get an accurate reading under load (when the voltages are changing). Definitely worth checking over a wide SoC range though. Once you understand how it seems to behave, you can keep an occasional eye on it to be confident it isn't getting worse.

[DraxxMenvone]

That’s really helpful. Thanks sidehaas. Will do.

[Midgex]

So I just tried testing the deltaV while accelerating up a steep hill and it came out as 27.1mV. For what’s it’s worth, Chat GPT is telling me that it’s well within operational limits and that a deltaV consistently over 30 to 50mV would indicate a problem. I realise I’m reaching the upper limit there so I’ll definitely keep an eye on it. Tests during regenerative braking and charging were much less pronounced. I’m going to test it after a balance charge tonight and during rapid charging tomorrow and see if anything else shows up.

I'd suggest having the navigator do the screen grabbing, while driving, please.
Chat GPT and all of its ilk make things up, there isn't reasoning going on in there.
Personally I'd find 12mV hard to get very worried about, and I'd remind myself that in any set of cells, one will always be the lowest voltage, and one the highest. I'd look for progressive change.

I suspect that as time goes on the job of replacing a module will become cheaper and more local, and the cost will tend downward rather than upward.

[DraxxMenvone]

So I just tried testing the deltaV while accelerating up a steep hill and it came out as 27.1mV. For what’s it’s worth, Chat GPT is telling me that it’s well within operational limits and that a deltaV consistently over 30 to 50mV would indicate a problem. I realise I’m reaching the upper limit there so I’ll definitely keep an eye on it. Tests during regenerative braking and charging were much less pronounced. I’m going to test it after a balance charge tonight and during rapid charging tomorrow and see if anything else shows up.

I'd suggest having the navigator do the screen grabbing, while driving, please.
Chat GPT and all of its ilk make things up, there isn't reasoning going on in there.
Personally I'd find 12mV hard to get very worried about, and I'd remind myself that in any set of cells, one will always be the lowest voltage, and one the highest. I'd look for progressive change.

I suspect that as time goes on the job of replacing a module will become cheaper and more local, and the cost will tend downward rather than upward.

Thank you. I’ve just driven to Scotland doing a few rapids to high SOC and it’s survived so far. I’m trying to relax into the car but I’m always trepidatious with new (used) cars!