Should have read all the way before answering. But my truck has a 120v ac power supply. Yea, I know, another cable. But, you could also charge the battery from solar. Hmm, as anyone ever rigged a wind powered generator on a moving vehicle. I should shut up now, because I'm getting all sorts of fun things to figure out.
That the problem with retired engineers, we get bored not solving problems so we invent them.