I have used both lithium poly and li-ion batteries to moderate success with xmods. The main issue comes from charging them. I use an appache 2030 charger that can charge 1-3 cell li-on or li-poly. I talso charges 1-8 cells nicad or nimh. I believe the store that carries this online is bisship power productions. The charger does need a 12V DC source. Once you have a way of charging batteries, you're set. They carry much more charge per weight than any other chemistry. You cannother overly discharge them or they won't charge again. WHenever one of my li-po cars slows down, I know it's time for a charge.

Two cells with li-ion or li-po will be around7.4V (equivalent of a 6 cell)as well. Poly batteries also have higher discharge cababilities.