Pololu Simple High-Power Motor Controller 24v23

I have these motor controllers and they seem to work fine with my motors, but I am worried that the motors might at some point pull more amps than the controller will be able to handle. Should I add an inline fuse to the motor power line? If so, how many amps should it be?

Hello.

Can you tell me a bit about your motors? Do you know what their stall current is, and will they ever come close to stalling in your application?

- Ben

Peak current is 18.7A. Stall current is 130A, but in this application, they should never be stalling. But just in case, I was thinking I should put in a fuse just to prevent any damage to the control boards if they happened to stall at some point.

Given that your motors can draw up to 130 A, I’m not sure what a “peak current” of 18.7 A means. Do you mean that you don’t expect your motors to draw more than 18.7 A in your particular application?

- Ben

I am running these motors at close to their peak efficiency where they deliver 13.99 oz-in of torque and pull 18.7A. The application is not required to stress them beyond that, although it could happen by accident, and I don’t want to damage the controller boards if it does.

If you want to be totally safe, you can use a slow-blow 25A fuse, which would hopefully tolerate the short current spikes that can occur when you try to rapidly accelerate your motor. If you find that the fuse is constantly tripping, you will have some good feedback that your motor is often exceeding the continuous current rating of the driver for non-negligible durations (i.e. your application might be too demanding for this motor controller), and you can consider the more risky proposition of trying a higher-value fuse, like 40 or 50 A. Note that you might find the SMC’s built-in acceleration-limiting features helpful with limiting the magnitude of current spikes, which might in turn help keep your fuses from tripping unexpectedly during normal operation.

In general, picking a good fuse is not necessarily easy given how much variation there can be in motor current draw. For example, your motor might briefly draw close to the stall current when you start driving it from rest, and the SMC 24v23 can generally tolerate short spikes like this. The situation you want to avoid is drawing excessive current for longer periods of time, which might damage the board before the thermal protection has a chance to kick in.

- Ben