Amusingly, I encountered the same sort of problem on a vastly smaller scale: An electric car with a fully charged 400 V, 64 kWh battery that I could not start f

Amusingly, I encountered the same sort of problem on a vastly smaller scale: An electric car with a fully charged 400 V, 64 kWh battery that I could not start for lack of electric power. Said electric power normally to be delivered by a small conventional 12 V car battery that was, unfortunately, almost completely discharged. To get my car started, that battery has to provide power to some electronics and to close a relay connecting the 400 V battery to a power inverter providing power to the car – including power to charge that 12 V battery. The owner of a gas car that I asked to help me jumpstart my car would not believe me at first, but I got the help I needed, thus saving the Christmas party I was going to on that occassion.