If the car was new at that date, it's a hardware change and needs to be swapped out for the 72 Amp version at a Service Center. The option seems to have evaporated from the online catalog but we've seen that 'some' SC's will still do it. The story seems to be that you ask nicely and if they want to do it, they will. Very puzzling why it's hit or miss. It used to be a normal 'after sales' upgrade.