I used Venom Fly 1300mah 30c 11.1v cause it fits snug but with room on both ends to mount nicely. That's about it. You can try a 1500mah 35c 11.1v marine venom but it was a bit tight for my liking. Be sure to use a XT30 connector and a shorty 510 connector as there is VERY little room with that one.