Electric Controllers
Used electric bike controllers are the brain of the system, regulating power from the motor to give you a boost when you need it. Cranxs connects you with sellers offering new and second-hand units from Bafang, Bosch and Shimano, for upgrades, replacements and custom builds.
What does an e-bike controller actually do?
The controller reads your pedal-assist sensor or throttle and decides how much current the motor draws from the battery. It sets how quickly assistance arrives, how smoothly it tapers off, and the limits that stop the motor and battery cooking themselves on a long climb.
Will the controller match my motor?
Match voltage first, since a 36V controller will not safely run a 48V pack, then check the phase and Hall sensor connectors. On Bosch and Shimano systems the controller is built into the sealed drive unit, so replacing it usually means replacing the drive unit; Bafang controllers are more often separate boxes you can swap on their own.
Sine wave or square wave?
Square wave controllers are cheaper and deliver power more sharply, with a bit more motor noise. Sine wave controllers smooth the current fed to the motor for quieter running and a gentler pull away from a standstill, and they are the common choice on newer builds and conversion kits.
What should I check buying used?
Controllers fail from heat and water, so look for swollen or discoloured casings, a burnt smell and corroded pins in the connector block. Ask why the unit was removed — one pulled during a whole-system upgrade is a safer buy than one taken off a bike that had stopped running.
Do I need a new display as well?
Displays talk to the controller over a specific protocol, so a controller from a different family may never communicate with the screen you already own. Confirm the two use the same standard, or pick up a matching display at the same time.