Re: Operation: Nightlight My recommendation is a marine deep cycle battery. it's the type favoured by the GRL in NYC. I'd go with something like this Image:Grl laser bike.jpg - Wikipedia, the free encyclopedia info here DEEP CYCLE BATTERY FREQUENTLY ASKED QUESTIONS etc To run a good laser or projector we'd also need an inverter. With a charge controller we could charge the thing from any car battery. Actually we could just run it from a car.