What Matt said is basically all you need to know to get started though i'm by no means an expert i've just done my research. Lipos are fine and safe to use as long as you're smart with them, over discharging damages them and will most likely end in a fire which is why it's better to go for a bigger pack than you need just to be on the safe side. I shouldn't think you need a capacity more than 2000mah, for a single fight it should be plenty but try and find something with say a 35 or higher c rating, that means you'll be able to pull 70amps continuously which should be fine.