problem is that even if nothing else is running your convertor is and that draws a lot of power. i actually put a switch on mine so the battery would not charge when thrown. I had to do that as my microwave only just barely runs off my Honda 2000.
I am wanting to put a switch on my converter also. Could you post some instructions on how you did yours? Northwood said just pull the fuses but they are a pain to get to in my AF1150.