GM recalls 2013 Chevrolet Volts for battery software

Yes looks like this update caused the issue,

In its latest recall notice, GM notes that an update to the hybrid powertrain control module in 2013 Volts may have disabled the cell balancing function.

scottf200 said:

Wonder if this software bug will ruin some Volt batteries or change their lifespan.
Too bad they couldn't fix this potentially dangerous situation with an OTA update.

Click to expand...

This looks right, and with an unbalanced pack, and assuming all cells have equal performance capability, the pack won't charge to 100%, and you can't discharge it fully either. Balancing occurs on a trickle "discharge" basis. Tiny resistors are switched across the high cells to bring them down to match the rest of the pack. It requires time and cycles to bring the pack into balance. This is not an instantaneous thing.