Regarding pre-pressurizing, I suggest reading these threads:
http://www.chiefdelphi.com/forums/sh...ght=compressor
http://www.chiefdelphi.com/forums/sh...ght=compressor
I believe the net is that using a second battery or even a second compressor is not permitted.
John Vriezen
Team 2530 "Inconceivable"
Mentor, Drive coach, Inspector