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. Fitting it is a wiring job rather than a plug and play swap, so it rewards someone comfortable matching a loom. Keep a photo of your existing wiring to match plug for plug, since connector colours vary between builders.

Quick Product Facts: KT-22A square wave controller; case label reads Controller for brushless motor; rated voltage DC 36V and 48V; rated power 500 W; nine power tubes; 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; pack holds one controller and one waterproof connector; best matched plug for plug to your existing loom.

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 reads brushless, and that is the spec we follow here. Confirm your own motor is brushless before ordering so the controller matches your build.

Will it fit my bike? It is sold on its ratings, so match it to your bike by voltage, power and the plug layout of your existing controller. Any 36V or 48V brushless build with the same loom is a candidate.

Can I fit it myself? Only if you are comfortable identifying phase, hall, throttle and brake leads. The leads carry battery current, and a wrong connection can destroy the new controller, so if any of that is unfamiliar, have a bike shop do it.

Is it waterproof? The connectors are the sealed, waterproof type. Mount the case out of standing water and keep the loom pointing down so water runs off the plugs.