battery current
In a previous role i carried out a lot of research into aircraft batteries, and did a number of tests with various batteries and their performance at various temperatures during APU starts. The instantaneous current drawn the moment the starter is energised and the APU begins to turn during the start sequence will be around the 1200-1800amp mark. It will fall away fairly rapidly (2-5 secs) to around 400 amps and will continue to decrease as the APU accelerates towards starter cut-out. A typical APU start will draw about 4% of available battery capacity at 20 deg C.
I have some actual curves at home somewhere, but none for the 777 i'm afraid.
high-flyer