The person on the 787 program with knowledge of the problems said that the electrical-system design makes it commonplace for airline mechanics to inadvertently run the lithium-ion batteries down too low.
Because lithium-ion batteries can be dangerously volatile if undercharged, as well as when overcharged, an automatic cutoff is built into the 787 batteries so that if the charge falls below 15 percent of full, the battery locks.
That's all sensible but I wondered why they don't have two low voltage trips? For example if they had one set to say 20% that would prevent the battery getting low enough that it has to be replaced. Instead it would just need someone to apply ground power, start the APU and "press reset".... or have I missed something?
Obviously you would still need to retain the 15% trip for safety reasons.