B3 - 25Nm direct drive compact motor

The Motor for light, urban bikes.

The B3 motor is the latest addition to our suite of motors. We started the development process in early 2016 with the target to engineer a very lightweight and compact direct drive motor for minimalistic city and urban bikes.

Compact rear motors are already on the market but none have an internal torque sensor requiring a sensor in the BB shell meaning less flexibility. With the sensor being inside the B3 motor, the BB can be equipped with the Kappstein Doppio, making it possible to build a very light eBike with two gears. A comfortable Set-up for urban requirements.

Furthermore, most compact motors are geared motors which are generally more noisy. The B3 motor is direct drive and therefore very quiet and maintenance free. The motor has similar dimensions to an internal gear hub and can be used with 6-bolt disc brakes. We will provide this motor in two different versions: the first version is for 25 km/h pedelecs and the second version is for faster 45 km/h s-pedelecs.

performance characteristics

  • nominal voltage: 36V
  • nominal capacity: 150W / 350W
  • maximum output: 400W
  • weight: 2,7 kg (2,3 kg light version)
  • diameter (PCD): 110 mm
  • torque: 20 Nm - 25 Nm
  • type: BLDC direct drive hub motor
  • spokes: 28, 32, 36
  • protection class: IP55
  • efficiency: 86%
  • brake: Kappstein disc brake adapter
  • axle: M10 bolt on or thru axle
  • sensors: internal (torque, heat) & internal controller
  • communication: CAN Bus
  • AOB: no screws, very clean, nearly noiseless (silent freewheel)
  • color: black, silver


Almost each eBike has it´s own characteristics and geometry as well as a special set up of configuration, this is why our specifications aren't cut in stone, they rather can be customized collaborative. Kappstein offers this service for the possibility of finding a solution for nearly any e-bike project. Engraving, color and the driving mode are adjustable too. Our motors are produced in China in-house production, this is why we can invent every process and part. We are open for supplier audits and visits. Our headquater in Gotha ensures a quick and easy communication between bike manufacturer and series production, it´s also suitable for more logistical flexibility. Meetings and agreements can settled fast and customer oriented.


In this special segment Kappstein is selling exclusively B2B. We do not offer retrofit sets. 

You would like to know more about our E-Mobility products? Please contact our Technical Sales Team and we are looking forward to arrange a meeting with you.


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