How-to Recalibrate your SoH.

[SergeyIndy]

Thanks for the quick answer!

Mainly I am charging AC with 8kW at home in the range of 25-80% SoC. Austria has mild summers up to 33°C and mediocre winters to -6°C. I'd say less than 10% is DC charging.

I suspect highly varying SoH bc I see highly varying SoC per cell of up to 3-4% at low SoC, combined with high voltage delta.

My method already seems to show success:
-Yesterday night 3% SoC and about 50mV voltage delta.
-10h letting it sit without plugged in only gained to ~45mV (this shows that there is nothing happening at these low SoCs, just like the Audi paper says)
-having it charged at only 1,3kW for 2h shows already only 23mV delta at 6% SoC, This is already the best delta I have ever had at these low SoCs.

Good to hear. I just want to be sure you are following the procedure that we have here in the TSB that would apply the same way to your Audi E-Tron. I am not sure why in this thread some do not follow it as stated and it is not that hard. Also, charging back up to 100% at that low of speed is NOT good, I charge it by setting my EVSE to a lower 36Amp vs. 48Amp max, but 1,3kW is way too low.

Sponsored

 

[Scandinavian]

Hi,

been following this issue as an Etron GT driver bc I too have low SoH and therefore also low capacity. 3yo, 25000miles, 86 SoH, 76kWh tops.

Trying to do the routine from the OP. What I did find out after letting it sit for 8h at 20% and 3% SoC, there is no rebalancing happening at these SoCs. Delta is like 30mV and 50mV and it barely tightens.

This is also suggested in this paper from Audi:
https://github.com/electrichasgoneaudi/etron-issues/issues/86

Now trying to charge at the lowest rate(1.3kW), see if it balances at these low SoCs and with these low rate it has more time.
Hope to hear from my Taycan brothers what they think of these findings

Sounds like your process is right. I have done similar process on both our Taycan and BMW. I also found that there is little of any rebalancing done at low SoC. However once I charged the car to 95% in both cases, the delta in the cells was quite reduced. From about 50 mV to 6 mV.

However I question why you use such a low charging rate. I reduced my rate from 11 kW to around 6 kW and that should be fine. It took some time but I felt that the losses when charging at lower rates were far too high.

Here is the recommended procedure for Taycan and I guess the same is valid for Audi.

https://static.nhtsa.gov/odi/tsbs/2024/MC-11005773-0001.pdf

 

[Berti123]

Sounds like your process is right. I have done similar process on both our Taycan and BMW. I also found that there is little of any rebalancing done at low SoC. However once I charged the car to 95% in both cases, the delta in the cells was quite reduced. From about 50 mV to 6 mV.

Easy to have little delta at high SoCs. You either just charged or are at >30% SoC where it self balances (check the Audi paper I linked in prior post).
Low Delta at low SoC is much harder to achieve. You either never discharge it to these levels and if, there is only little time to balance since charging (where balancing can be done) lets you escape these SoCs quickly.

However I question why you use such a low charging rate. I reduced my rate from 11 kW to around 6 kW and that should be fine. It took some time but I felt that the losses when charging at lower rates were far too high.

Low charge rate so it has actually time to balance at these low SoCs. It took 4h to go from 45mV to 7mV and this was at 9% SoC. With normal charge rates you would already be in the 30s SoC.


Here is the recommended procedure for Taycan and I guess the same is valid for Audi.

https://static.nhtsa.gov/odi/tsbs/2024/MC-11005773-0001.pdf

I always had ~7mV delta at high SoCs, but discharging always shows 50mV at low SoCs. Lets see what happens after also being balanced at low SoC.

 

[Sace]

I also found that there is little of any rebalancing done at low SoC. However once I charged the car to 95% in both cases, the delta in the cells was quite reduced. From about 50 mV to 6 mV.

Correct. There is not automatic balancing when you are below 30% SoC which is described here:
https://www.taycanforum.com/forum/threads/is-this-normal-for-cells.21213/post-325103

I found that the recalibration procedure helped a lot on my SoH reading. After letting the car rest for a few hours at 2% the cells had recovered enough to now show 4% SoC. I then discharged them a bit more and let it rest (and followed the rest of the procedure).

 

[Berti123]

After letting the car rest for a few hours at 2% the cells had recovered enough to now show 4% SoC. I then discharged them a bit more and let it rest (and followed the rest of the procedure).

This recovery has nothing to do with the procedure or any BMS activity, this is normal behaviour of any battery cell after being discharged. The more the load that was applied the more the "regain" of cell voltage at no load.
This regain of cell voltage appears in "more" SoC.

 

[Sace]

This recovery has nothing to do with the procedure or any BMS activity, this is normal behaviour of any battery cell after being discharged. The more the load that was applied the more the "regain" of cell voltage at no load.
This regain of cell voltage appears in "more" SoC.

I am fully aware that it has nothing to do with the BMS. It was just an observation about how the cells behave when you let them rest (that some might misinterpret as active cell balancing).

 

[Berti123]

This is the result, quite Happy with it. Gained 2.3kWh, or 3% less "degradation".

Before:

After:

This is inbetween, how I was able to get Delta down at very low SoC:
3%:

8%:

 

[Berti123]

I noticed completely flat voltage readings combined with wobbly SoC cell readings.
Anyone know whats going on Here? Can it be fixed?

SoC readings were flat at high SoCs though.

 

[SergeyIndy]

I noticed completely flat voltage readings combined with wobbly SoC cell readings.
Anyone know whats going on Here? Can it be fixed?

SoC readings were flat at high SoCs though.

I do not see anything unusual about SoC deviations as I have the same thing after recalibration and BMS is managing it the way it sees fit. I am more concerned about voltage, which is an indication of potentially failed module if one is out of line by a big deviation.

 

[Scandinavian]

Your battery looks absolutely fine. More worrying when your battery looks like this!

I believe I am in for another battery failure

 

[Dee]

Your battery looks absolutely fine. More worrying when your battery looks like this!

I believe I am in for another battery failure

Only one bad cell! Nice! ??
This is such a "good" failure, very clear.

 

[Sace]

Your battery looks absolutely fine. More worrying when your battery looks like this!

I believe I am in for another battery failure

You have had a few cellblocks replaced previously and not the entire pack, right? Surely that does not look good unless you have zoomed to a crazy scale.

I noticed completely flat voltage readings combined with wobbly SoC cell readings.
Anyone know whats going on Here? Can it be fixed?

I see the same on mine and believe it's completely normal. Had the voltage curve been completely linear each 1% SoC would equal 8mV or someting like that. So that 5-6mV difference shows up as a small difference in SoC sounds reasonable when factoring in that the curve is not completely flat.

 

[SergeyIndy]

Your battery looks absolutely fine. More worrying when your battery looks like this!

I believe I am in for another battery failure

The way the modules are wired, if one goes bad the car goes into a Red Circle of death and cannot be moved.

 

[whitex]

The way the modules are wired, if one goes bad the car goes into a Red Circle of death and cannot be moved.

Definitely not designed with redundancy in mind. They could have just allowed individual modules to take themselves out of the loop (short circuit the positive and negative terminals) while informing the owner battery needs service. So the battery ends up with slightly lower voltage, at least the car can still move and get to the dealer on its own power, probably continue driving with reduced max performance while Porsche gets around to replacing the module (cheaper than a loaner, and even with reduced power Taycan still beats a Macan loaner).

 

[Scandinavian]

You have had a few cellblocks replaced previously and not the entire pack, right? Surely that does not look good unless you have zoomed to a crazy scale.

It is the same scale as CarScanner always shows, but I do not know why the photo became so different.
’I have had two modules replaced before and now it looks bad again.
’Here is another attempt at showing the normal picture scale

Sponsored