Motor compatibility

Hello, I have two cim motors that I need to hook up to a sabertooth 25a motor controller. With a peak of 50a per channel, would this happen able to handle the startup of a cim motor? It should be able to handle the motors aside from the startup but that’s what I’m worried about. Can I increase the torque or add in resistors to prevent the amperage from being too much?

Oh by the way, on its item description it days that it uses 1.3 milliohm MOSFETs in its bridge (calling it a potential 190a driver, which should handle the motors), does this change anything?


The PDP has 40 amp breakers on the slots dedicated to Motor Controllers, so any throughput higher than 40 amps(for an extended period of time) won’t work. Are you trying to hook up two motors to one motor controller? If so, don’t, because that’s illegal. I guess I don’t fully understand what you’re trying to do.

How heavy of a load will the CIMs be moving? You can find the motor curves for a CIM at the link below, and use that to calculate how much current they will draw at your applied load.

This doesn’t sound like it’s for an FRC application. He’s just curious about the CIM motor.

I’m guessing this is for a non-FIRST project. A CIM motor at stall can pull up to 131A, and under load can exceed the 25A rating.

The speed controllers legal for FRC use are all (as far as I know) rated for 60A continuous and 100A for a 2 second surge. I would strongly hesitate to recommend any controller with lesser specs without knowing a LOT more details about the use case and design.

That dual channel speed control is not a good match for a fully loaded CIM motor. A fully stalled CIM can draw 100A+ and while an inline fuse might save the speed control occasionally I don’t think that’s a great idea. (I assume you don’t have access to current FRC ESC and are looking to test something.)

Consider whatever you move with the CIM will likely have inertia so basically you need to provide that initial rush of power to break free. If your mechanical device has low inertia…or…you can ramp up the output gently it may work but frankly a couple of older FRC approved ESC are likely a better idea.

Since you may not be using an FRC control system look at automotive fuses and the holders for them.

Also review Ohm’s law regarding sizing a resistor inline with a motor. A very small value resistor (< 5 Ohms) in series with a CIM still needs to be a fairly high Wattage resistor because it will heat up as the motor draws the current through it. So that is the first thing that can go wrong there. The second is is that you’d limit the rush of power to break free from inertia possibly making the sizing of said resistor complicated.

Is this the motor controller you are talking about? The CIM seems to have an inrush current of 120A according to this thread so I would be hesitant to use it, mainly since the peak current that is listed is 50A. Granted, those are peaks for a few seconds, so it might be OK since it’s 120A for 70 ms or so.

Personally, I’d be looking at other solutions that were more or less designed with the CIM in mind like the SPARK or Victor SPX. Honestly just looking at the pictures on that guide makes me a bit worried to push 120A through it. If you absolutely MUST use the Sabertooth, please please please look at a motor curve and make sure you’re using it at a point in the curve where it draws less than 25A. Beware of stalls because you will almost certainly fry the controller very quickly at 131A.

Assuming that you’re not doing this for FRC – If you’re on a tight budget, but able to do some coding, you could put a current sensor on the controller’s input, and use a combination of voltage ramping and current limiting to stay within the controller’s specs.