Syseng68k Post #1012
Total energy for APU starts does not seem to be the problem, because even the Boeing 18kW spec. only needs about 30% of the energy stored an a fully charged battery (though not all that energy is available energy).
Boeing requirement was 18kW x 45 seconds x 3 = 0.675 kWh
Battery stored energy is 75Ah x 32V = 2.4kWh.
Current is the problem.
I should have mentioned that the FAA docket said the APU took only 35 seconds to start, which is less than the 45 seconds in the Boeing SCD.
Just to be sure that I understand your post, are you suggesting that the inverter may have been limited to taking something like 375A max. and was able to start the APU in 35 seconds with this limitation? (I know nothing about APUs.)