Controller Mod: KU123 100V !

Last month I got a 72v 35A controller from china called “Hua Tong”. I wanted to try this controller to push my ebike little motor to the limits and see how much speed I could reach with a 20s li-mn battery (84v fully charged).This controller can take battery packs up to 100V (I checked capacitors and mosfets inside).

Hua Tong mosfets

Unfortunately I think my motor has a broken hall sensor and the “Hua Tong” controller does not work sensorless. I’ve spent and entire evening checking all the possible combinations of phases and hall wires but none of them worked.

My bike uses a KU123 controller, it’s a cheap controller but it can run in both ways sensored and sensorless. It works perfectly with my motor. The only negative thing is that I cannot exceed a voltage of 63v on this controller due to the capacitors limit. The mosfets are good only up to 70-75V (I have been looking for a datasheet but no success).

KU123 Mosfets

Having a spare KU123 controller I decided to go ahead an do some surgery: I transfered the mosfets and capacitors from the Hua Tong to the KU123 controller.

KU123 modded with 100V caps and 100V mosfets


Then I got rid of some wires, I kept the only ones that I need:

Got rid of unused wires


Final result:

KU123 modded 🙂


What are the advantages of the modding?

  • This little controller can run sensorless, so if anything happens to the hall sensors you’re safe and can keep riding. The Hua Thong works only in sensored mode.
  • The Ku123 has a LVC of 35.75V and this allows me to use different combinations of batteries up to 100V. The Hua Thong has a LVC of 60-63V.
  • KU123 has a 3 speed switch that can be used to limit the speed in order to save some power, the Hua Thong hasn’t got this function.
  • KU123 is smaller than Hua Tong.






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