Get some NiMH or LiPO batteries. 3800 is a good size battery-you really don't need anything higher if you're racing because the race is only 6 minutes. A LiPo is great for bashing because it has such a long run time. The higher the number the longer it will last and the more punch it will have. Keep in mind that a LiPO is much lighter than a NiMH. I prefer to use a 3800 NiMH when I race because my T4 handles better with the weight and it is easier to drive.