- How to choose the power rating of your e-bike motor?
In the Power Standards of EN15194, the maximum rated power of an e-bike is 250 w. Operating power will normally be less as assistance is cut off above a speed of 25 km/h or when the rider stops pedaling.
Power at the driving wheel (or wheels) for the whole e-bike will be less than the motor’s rated output due to transmission losses, wheel-spoke distortion, tyres and so on.
If the e-bike’s maximum output power is 250 w, the motor’s maximum output power should be about 320 w. The motor’s maximum output power is thus related to the e-bike’s design; so transmission losses should be reduced as far as possible, allowing limited battery resources to be used efficiently.
When you have the following conditions: speed of 25 km/h, flat road, rider’s weight approx. 75 kg, wind speed Force 3 or less, the motor power is between 150 w and 250 w – as determined by the rider’s pedaling power and the controller’s setting. When going uphill or with an increased weight or stronger headwind, the motor draws more power.
- What is the difference between torque sensor and speed sensor?
A torque sensor detects the rider’s pedaling force, while a speed sensor detects the rider’s pedaling speed. Both sensors need to transmit this information to the controller. The controller adjusts the motor’s torque or power according to the information input and adjusts the assist rate. This kind of design saves power and produces a better driving feel.
- Reason for motor noise and vibration?
There may be two kinds of motor noise: mechanical noise and electromagnetic noise.
- Bearing failure
- Excessive gear friction or gear failure
- Rotor imbalance or poor gear positioning due to construction inaccuracies
- Water or other ingress into motor housing
- Resonance of motor and frame
The main reason is bad matching of motor and controller. A sine-wave current from the controller is better than a square wave, and induces less noise.
- What is the difference between mid motor and hub motor?