Originally Posted by k_bojar

the Mah of the lipo won't matter, but you'll want one of the lipo that are in the shape of a stick pack, like this:

there are ones from different battery makers, this is just an example - and they are approximately the same price

that chassis is really designed for stick packs, any of the more square lipo packs will require you to dremel the battery compartment some so that they sit nice and flat on the chassis