We are looking for application where we need sometimes backdrive DC-motor manually. In order to protect motor driver and rest of the electronics we're thinking of electrically disconnecting motor leads from the motor driver using FETs or relays. Is there something else you should worry about? E.g. if rotating motor shaft too fast will produce too much voltage and we damage something inside motor or damage FETs isolating it? Is answer different for brushed and brushless motor?

Motor is rated for 24V, 5A continuous, 10A peak for 2 seconds. It's geared 50:1, so we can potentially backdrive it quite fast.

  • \$\begingroup\$ How can you backdrive a disconnected motor? Backdriving, is AFAIK, rotating the motor in the opposite direction of the electrically induced rotation. \$\endgroup\$
    – Eugene Sh.
    Nov 25, 2015 at 21:26
  • 1
    \$\begingroup\$ @EugeneSh. I think this term is usually used when you rotate motor shaft externally. I.e. from wiki "backdrive is a component used in reverse to obtain its input from its output... A DC electrical generator can be implemented by backdriving a DC electric motor" \$\endgroup\$
    – DikobrAz
    Nov 25, 2015 at 21:39

1 Answer 1


Don't backdrive it any faster than its nominal run speed on 24V. This means that the back voltage won't be any more than 24V and the commutator won't fly apart. Now you can be confident that your isolation MOSFETs won't blow up.


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