I've got a nice outdoor spot where I want to play music and I'd like to power two amps (one guitar, one bass). The bass amp I would like to use is a TC Electronic BG250 combo amp. I've read that I can use an old car battery and a power inverter to do the trick but am not sure exactly how to do it. Any help as far as power inverter specs, setup, etc would be appreciated. Edit-- I'm not opposed to the idea of using a portable power supply either... It just seems like I might need a few of them as they drain quickly, and that would be more pricey.