Here is what I came up with:
It could be the same reason why 2 batteries are required to start the APU, APU starter motors draw significant current and with a GPU only thats supplying the full network it would probably overload it so batteries are required to be paralleled with the GPU to assist in the start operation.
Thats as far as I understand, I couldn't find a specific answer though.
Lets wait and see if anyone out here has an answer.
Last edited by flame_bringer; 7th Jun 2012 at 18:10.