I'm a Chemist, not too conversant about electrics and hopefully one of the engineering types will amplify (maybe need to correct this), but basically the controller coordinates the performance of the "e"-system by regulation and protection (things like torque, speed, temperature and low voltage cut off). A 22 amp controller with a 52V battery provides 52V X 22 ah = 1144w while a 30 ah controller 1560w. This is simplistic and there's much more involved. I haven't looked in awhile but maybe the tutorials at ebikesca can help.
Last edited by 2old; 03-02-21 at 10:28 PM.