www.robotmarketplace.com I ran one with 18 cells on my maxx before I switched to brushless. I was very happy with the power of the system but the runtime was shorter than I would have liked. I now run a 9xl with 18 cells and it is barely faster than the 820 on 18 cells. With the 820 I had it geared 21/76 and got about 7-9 mins of runtime on 3300's. With the 9xl I get about 15 mins.