Motor controller + motor question

since the 18v25 motor controller accepts voltage ranging from 5.5v to 30v, can I use a 12VDC battery on this motor controller to power the motors of the Dagu Wild Thumper 6WD All-Terrain Chassis ? will it know those motors need 7.2v to operate and adjust or will it burn the motors by sending 12vdc from the battery?

Hello.

The motor controller has no way of knowing the suggested operating voltage of the connected motor, so it will supply the full 12 V to the motor if you command it to do so, and that would likely shorten the lifetime of the motors (and potentially burn them out or cause damage to the gearbox if they are stalled).

However, you could safely use a 12 V battery if you are careful to restrict the maximum motor speed to around 60% (so the motors never see more than an average voltage of 7.2 V). The SMC has a configurable “Max speed” setting that you can use for this, or you can just make sure your control source never requests a speed above 60%.

- Ben

how about using a 12vdc battery with a voltage regulator strong enough to support the maximum stall current amperage? so 12vdc -> 7vdc using a voltage regulator and then connect the 7.2v to the motor controller :slight_smile:

There is nothing wrong with that general concept (e.g. the motors on our 3pi robots are powered from voltage regulators), but I think that is impractical for this particular application given the high currents involved. Using a different, more appropriate battery seems like a much simpler (and cheaper) solution.

- Ben

how is that a better solution? think about it. you need 7.2v battery for the motors, a 12vdc pack for the motherboard, and other battery packs for other subsystems that use different voltages, why not use 1 voltage to simplify charging and then distribute that power at different voltages as needed?

I’m not advocating you use multiple battery packs, I’m suggesting you choose a battery voltage appropriate for your motors and use regulators to power other, low-current elements of your system. If it is not obvious to you that this is a much simpler approach, can you tell me what you were planning on using to get your regulated motor voltage? By the way, what are you using for your robot controller?

- Ben

Hello, starguy.

I don’t understand why you aren’t totally happy with the solution of setting the max speed to 60%. Is there something about your application that requires a lot of resolution in speed?

- Ryan