[MetalMan]

If you want max. runtimes then you'll want to maximize available energy - 6s 5000mah is a good size battery without weighing too much, and they can still be gotten for pretty cheap. But you won't be able to properly gear your XST with that battery and the 2200 motor, so that means 5s is pretty much the maximum. The capacity you get will depend on how much weight your care for your truggy to carry around, and how deep your pockets are. 5s 5000mah is my personal choice.