I do this all the time, I've found it best to plug the Empeg into the lighter socket ( With a fuse in line, If the engine's not going you get no interference) and use the line out sockets, using the pre-outs is a bit fiddly getting the sound right. I can't say how long it will play for, but I haven't flattened the battery yet! My headphones say one hundred metre range, but 30 is nearer the truth