Suddenly loose 12KWh of battery capacity

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Aug 29, 2022
I got a 2017 and been logging battery capacity for its whole life. In June 2022, the car still have around 24Kwh usable capacity (from the original 29.2KWh usable). 2nd week of September I start to see a huge degradation ( I was able to use around 12Kwh). Dealer diagnose unable to balance battery cell : they change the onboard charger early January ... And still got only 12kWh of usable capacity but the wrench (that indicate a problem) has disappear.
Dealer said that I still can see all of the cell in the battery report, has anyone ever heard of this kind of problem?
Any hint is welcome since the battery capacity is not guaranty by Ford ....

The car has around 141000Km, the modem upgrade has been done and I drove it until it stop near my house to exclude a bad guessometer.
I think your dealer is an idiot. I can't imagine a reason to replace the onboard charger because of a loss in battery capacity. Its a 2017, the dealer should have fast charged it and seen how many kw went in. That would let them know if it is a battery issue or not. You are under the 8 year warranty, 100k miles, right? That is not normal degradation. If there is a bad cell in the pack, then I would not think you would have the problem you are having, Unless the BMS is not charging up the the entire pack past the bad cell. I would also think it would be possible to tell the BMS to ignore that cell.
Do you have any diagnostic information to share with us? Any DTC codes? You have been logging degradation. That is a great tool to show that something went wrong. If the warranty does not cover battery degradation, then that would be a catch all to deny any battery repair. So Ford must have something in writing that specifies an amount of degradation that is acceptable or warrantable .
I am sorry you are having problems with your 2017. Right now I am knocking on wood for mine.
I think you need to call up Ford regional.
The pack stops discharging when the lowest cell hits the lower voltage limit and stops charging when the highest cell hits the upper voltage limit. So if one cell is really bad, it can and will keep you from fully discharging the pack.

When it's "empty", what is the total pack voltage?

If you leave it plugged into L2 for several days, the battery management is supposed to isolate cells and recondition them, but it can only do so much.
I dont have OBD2 code reader to know the voltage when empty, maybe this is my first step to debug this issue!
I will post the dealer code later (Still at work). Thank you for quick reply.
My dealer sold 3 of those cars, I usually know a lot more than they do about that car.
Here the code written on the dealer invoice :
0880 for check engine light
code P0560, u3003 DCDC done test i1 to i4

I got each cell voltage and capacity from the BECM it seem like cell 25 has only 3.642volts (and 18.049Ah) all the other cell are between 3.892 and 3.901 volts
That'll do it.

So you lost the bottom 12kWh, which is the most likely failure mode.

Not sure how easy it is to track down modules. Pretty sure the raw cells are not sold outside OEMs, so it will just be salvage offerings.
The car have less than 6 years and have not reach 160K km, should this problem be covered by ford battery warranty?
When you said the bottom 12Kwh, it is indicate by the cell number?
I meant bottom in that you have lost the ability to draw the cells down fully, but they likely still charge up to the correct voltage.

Not sure what your warranty terms are but if it's still in warranty it seems like something that should be covered. I don't know if they ever noted some specific capacity loss as qualifying for warranty replacement, but the fact that you've lost the capacity from something other than natural degradation of the entire pack is compelling.
Thank again,

great amount of information on this site even if there is a few contributors.

Continue providing useful information on this forum, this is greatly appreciate.
I was reading this forum for 5 years (golden years of the FFE 2017) and never had any problems with the car before.
Reading about 12V battery and other useful topic might be the reason why I never encounter those issues.