I've ran 14 cells on brushed 550's and 700's................16.8v. If your talkin about modified 540's you need to stay more in the 6 or 7 cell range. I think a wheely king has like a 27t in it..............heck i wouldnt be afraid to go 8...........maybe 9 cells on it. Its a $13 motor...........i would try it, but thats just me.