i use rayovac recharable alkaline. If you use a non rayovac charger, your going to need to set the settings onto ni-cd rather than ni-mh unless you want the battery to leak. The batteries last me about 4 or 5 days, with CONSTANT use, well in the school year it did, there was nothing to do in the last few weeks of school, so we raced
I also use some RC radio AA batteries, that are metal hydrate, and 1600mAh. yes 1600, the best kidn ive seen. I bought em at Fransican hobbies in frisco near stonestown mall. They were usually like 3 or 4 bucks a piece, but then they had a deal when i picked em up. BTW, this was like 3 or 4 years ago when i used to race mini 4WD with some of the people on these boards, lol. You could probably find em somewhere, theyre green and say 1600mAh on em.
If youre not into using your car(s) 24/7 you should use some good alkalines like those energizer titaniums. But if you wanna invest in it, get the rechargable alkaline.