I am trying to make an electric bike (this is my first electrical project with motors).

To save money, I bought a used electric lawnmower and extracted the motor, as well as two 12V batteries in series (resulting in a 24V battery).

Now, I need to get a controller for this configuration, but I lack knowledge in selecting the correct controller. Someone told me that typical electric bike controllers cannot be used with simple, brushed DC motors like the one I got from a lawnmower machine. Is this true?

This is the controller I had in mind.

Are there different types of controllers that must be used depending on the type of motor you have? Does anyone have a source that describes all the types of controllers?

  • \$\begingroup\$ I think the confusion might stem from the difference between brushed & brushless motors. But you seem to have a 24V brushed motor & a 24V brushed motor controller, so I don't see any problem ... \$\endgroup\$ – brhans Jul 27 '16 at 15:22
  • \$\begingroup\$ No, a brushed (parallel or series magnetized) motor is the easiest to control so there aren't any real types to choose from. I remember my old e-bike with a 750 W 24 V lawnmower motor. The lack of flyback diode burned the MOSFET and we ended up with a simple on-off switch on the frame. At 55 km/hour, you really had to think twice what your optimal survival strategy was, let go with one hand to reach the switch and turn it off or keep both hands on the steering wheel and simply ride it through. Good times. \$\endgroup\$ – winny Jul 27 '16 at 15:30
  • \$\begingroup\$ Haha winny that's pretty funny. So are you saying I can use any brushed controller for my motor (such as the one in the link posted in the original question)? \$\endgroup\$ – user3646493 Jul 27 '16 at 15:58
  • \$\begingroup\$ What power rating is the lawnmower? 350W seems a pretty wimpy controller for a lawnmower motor. \$\endgroup\$ – Brian Drummond Jul 27 '16 at 16:17
  • \$\begingroup\$ We tried different gearing. For more resonable top speeds it would just leave on the back wheel without you and keep going until it crashed into something or batteries ran out, so we limited the torque by gearing it up at the "penalty" of high top speed. Probably. There are many wires going into it and I didn't see any documentation for this one but in general, a brushed DC motor controller is a good beginners power electronics project. Is 350 W enough for you? I would put a suitable diode in reverse straight on the motor if I where you just to be sure. \$\endgroup\$ – winny Jul 27 '16 at 16:17

Brushless motors require controllers that are completely different from controllers for brushed motors.

For any brushed motor:

  1. Select a controller for brushed motors

  2. The controller voltage rating, the motor's maximum operating voltage and the battery voltage should all match. Some variations are acceptable, but need to be understood.

  3. The continuous output current rating of the controller must be not less than the continuous motor current rating.

  4. The controller should have an overload protection adjustment that can be set for the continuous current rating of the motor.

  5. The controller should have a short-term current limit adjustment that can be adjusted to max the short-term current rating of the motor. That will probably be something like 150% of the continuous rating for about 1 minute.

  6. If the motor has a separate field winding, the controller must have a separate output for that. It needs to supply the proper voltage and sufficient current. If the controller has that output and you don't need it, no problem.

  7. The controller may have other inputs and outputs that you may or may not need. For most brushed motors, you don't need speed feedback or anything like that for simple use.

  8. The controller will need a speed setting input that is compatible with the device that will be used for that.

  9. I would highly recommend buying only a controller for which you can download complete specifications, diagrams and instructions before purchase.

Are there different types of controllers that must be used depending on the type of motor you have? Does anyone have a source that describes all the types of controllers?

In addition to brushed and brushless controllers, there are various types within each category, but the differences among brushed motor controllers are probably not too important in this case. For using a lawn mower controller on a bicycle, you should check the range of speed adjustment and acceleration control. We don't usually recommend specific sources of information or products. There is a lot of available information about different controller designs and features. You should study information from bicycle speed controller manufactures. Search the internet for information about unfamiliar terms that you find there.


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