Interesting finding about the 12V battery from page 21 of the test report,
In the early stages of the project when charging stations were being commissioned, and the LEAFs were not being fully used as fleet vehicles, LBNL discovered that when the LEAFs were connected to their charging stations and not driven for at least 1-2 weeks, the 12-volt accessory batteries would be drained to the point of inoperability. LBNL devised a protocol to maintain the charge of the 12-volt batteries that was performed every 1-2 weeks by LAAFB fleet operations staff. The process consisted of disconnecting the charging connector, pressing the Start button, turning off all accessories and leaving for 30 minutes before switching off and re-connecting to the charging station.
And for the HV traction battery,
Charging station faults, on several occasions, led to deep discharges of the LEAF drivetrain battery. In one early case, the discharge was so deep that the battery in LEAF 12B80023 could not be recovered and had to be replaced with a new battery.