Sorry no one is responding to you. This forum seems mostly to focus on flight, not cars.

Do a google for "a123 e-maxx"

Here is one thread I found:
[link=http://www.rcgroups.com/forums/showthread.php?t=707550]http://www.rcgroups.com/forums/showthread.php?t=707550[/link]

It looks like a couple of 6.6v 4600mah packs is what some of them are running.

That is what I want to run in my e-savage, but I'm not sure if I can make them fit onto the car. It sounds like the e-maxx may be more able to accommodate different size packs, but don't take my word on it by any means, I have an e-savage.