Posts: 1099
Joined: Sun May 03, 2015 7:15 am
Location: The Heart o' Dixie
Contact: Website

Is this considered Pack Failure?

Sat Feb 15, 2020 6:15 pm

i bought a silver 2012 SE with 40k miles that i thought was in perfect condition since the cells were all within 5mV when fully charged to 16 bars. But it would only go about 25 miles before hitting turtle with 2 bars showing. Cell #27 was 0.6 volts below all the rest, and #20 was 0.4 low. Charged it on L2 and let it balance--Full 16 bars and 36 RR, and all cells within 5mV again. Then i drove it 10 miles and it used 6 bars. Do some more testing tomorrow.

So does this seem like it would qualify for a new pack under warranty even though it charges fully? The seemingly defective cells only manifest as the pack gets drawn down. i can imagine the dealer thinking this was normal wear and tear degradation that is not covered.
kiev = kenny's innovative electric vehicle

Posts: 274
Joined: Mon Mar 20, 2017 4:57 am
Location: Scotland

Re: Is this considered Pack Failure?

Sun Feb 16, 2020 8:18 am

What you're describing is a pack with two cells that have a lot less capacity than the rest.

In that case they will be balanced at 4.1 volts / 100% SoC but the voltage will rapidly diverge from the other cells as the pack discharges. This is to be expected.

This is why I've always said that the cell voltage balance at a high SoC means more or less nothing - all it proves is that the balancing system works! :) It's the voltage balance at a low state of charge after a discharge cycle which started from balanced at 100% that matters.

As for whether you can claim warranty on this - who knows ? My guess is probably not, unless a minimum capacity is guarenteed, however it does seem like a good candidate for a cell swap, and a much better candidate than my car was.

Can you show a Canion voltage graph of the pack at a reported 20% SoC to see how closely matched the other 86 cells are ?
- Simon

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

Return to “Batteries and Battery Management”