KT-22A Brushless Motor Controller for E-Bikes, 36V 48V 500W

The bike stopped pulling on the hill, and the motor was not the part that failed.

It is almost always the box, not the hub. The controller sits in the frame or under the rack, takes the battery in at one end, and decides how much current goes to the motor. When it goes, the wheel spins freely and the display still lights up, which is the moment most owners find out their bike has a controller at all. This is a replacement for that box: a finned metal shell about the size of a paperback, four screw tabs on the corners, and a loom of leads out of one end.

The white label on the case reads Controller for brushless motor, and lists rated voltage, rated current, a low voltage cut off, a speed set line and a low level brake input. The maker names the model KT-22A, describes it as a square wave controller with nine power tubes, and rates it at DC 36V and 48V for 500 W. The leads end in the sealed round plugs the trade calls waterproof connectors, and one spare connector is packed with it.

Key Benefits

• Covers two battery voltages The maker rates the unit at DC 36V and 48V, so it suits the two systems most mid power e-bikes are built around.
• Nine tube power stage The maker counts nine power tubes on this model, which is what sets it apart from the six tube controllers in the same case family.
• Sealed style connectors The loom ends in waterproof type plugs and one spare connector is included, so a damaged plug does not mean a new controller.
• Protection lines on the label The case label names a low voltage cut off and a low level brake input, both standard e-bike wiring points.
• Finned case with mounting tabs Four screw tabs and a ribbed metal shell, made to bolt into a frame box rather than dangle from cable ties.

Best for: the owner or the shop replacing a dead controller on a 36V or 48V brushless e-bike, who already knows how their existing loom is wired.

Why It Works

A square wave controller switches the three motor phases in blocks rather than shaping a smooth sine, which is why this type is cheap, simple and easy to source as a spare. The number of power tubes is the honest measure of how hard it can be pushed, and the maker gives nine on this one. Everything else is wiring discipline: phase leads, hall leads, throttle, brake cut off and the battery pair all have to land in the right plug. That is also why we will not tell you it is plug and play. The maker does not list a manual or a wiring diagram in the pack, and connector colours vary between builders.

Quick Product Facts: KT-22A square wave controller; case label reads Controller for brushless motor; maker gives rated voltage DC 36V and 48V; maker gives rated power 500 W; nine power tubes as counted by the maker; label lines for low voltage cut off, speed set and low level brake input; leads terminated in waterproof type connectors; ribbed metal case with four screw tabs, case material not stated by the maker; pack holds one controller and one waterproof connector; no manual or wiring diagram listed; no ingress rating published for the case.

How It Fits Your Routine

The first job is not fitting, it is checking. Open the frame box, photograph the existing loom before you unplug anything, and compare plug for plug with what arrives. Ten minutes with a phone camera saves an evening of guessing which yellow lead is which.

Once it is in, the routine is that there is no routine. A controller that is bolted down, sealed at the plugs and running inside its voltage band is a part you never think about again. Keep the spare connector with your tools rather than in the box, because the day you need it will be the day a plug gets crushed by a pannier.

If the bike lives outside, the fixing matters more than the electronics. Bolt it through the tabs, keep the loom pointing down so water runs away from the plugs, and do not leave the case resting on a wet frame member where it can sit in a puddle.

FAQ

Is this for a brushless or a brushed motor? The label printed on the case says brushless, and so does the maker marketing panel. The supplier written sheet says brushed, which contradicts its own label. We are going with the label, and we are telling you about the conflict so you can check your motor before ordering.

Will it fit my bike? The maker names no bike brand and we will not name one for it. It is sold on its ratings, not on a compatibility list. Match the voltage, the power and the plug layout of your existing controller.

Can I fit it myself? Only if you are comfortable identifying phase, hall, throttle and brake leads. The pack has no manual and no wiring diagram, the leads carry battery current, and a wrong connection can destroy the new controller. If any of that is unfamiliar, have a bike shop do it.

Is it waterproof? The maker claims sealed type connectors and nothing more. There is no ingress rating for the case, so treat it as a part that needs to be mounted out of standing water.