oak3x- He's not just being facetious

You really need a lot of light to detail and I can't imagine getting sufficient illumination from battery powered lights. You'd spend a fortune in batteries in the long run anyhow. IMO most shops don't have enough illumination even with scads of lights.
You might find some battery powered fluorescents, and you could supplement them with a bright battery powered worklight, but IMO it wouldn't work out all that well. No idea where to find the battery powered fluorescents, but I'm sure I've seen them somewhere...
If I were in that situation, and getting the garage wired or using extension cords really was out of the question, I'd get a generator. I consider adequate lighting to be the only thing that rivals a clean work environment when it comes to the essentials.