18v to AFmotor and 37D motor

I’m running a pair of Pololu 12v 37D 131:1 motors through an Adafruit Arduino motor controller on a Mega ADK board, power separated. I’ve been running them at 12v, great little motors. I get that they are 12v motors and I hope this question isn’t as dumb as it sounds now that I’m actually writing it out. I need the 12v battery for the kinect and monitor for the raspberry pi. I have an 18v NiCd from a drill laying about. Can I run these motors with an 18v battery, or will that fry them? I CAN reduce the voltage to 12v, I’ve got a 7812 laying around here somewhere, but my bot is a wee bit heavy and I’d rather run at 18v.

So what say you forum gurus?

regards, Richard

Hi, Richard.

In general, you can operate DC motors over a range of voltages with the trade-off being between performance and motor life, but 18 V strikes me as high. I think the simplest solution for you (if you want to play it safe) is to power them at 18 V but cap your motor driver duty cycle at something like 70%. Note that you would need a relatively beefy and expensive voltage regulator to power those motors; I do not expect your 7812 to be sufficient.

- Ben

Be aware an 18v nicad might be much more than 18v straight off the charger.

You can buy decent DC-DC step-downs, super cheap, that can do 1-2A (rated 3A) from ebay. There’s a common design used all over the place, which some specific regulator chip. If you expect >1.3A draw, your best bet is to step-down to the highest safe voltage for your driver, and then limit your drivers max PWM (this is essentially a two-stage stepdown. If you input 12V 1A to your driver and limit pwm to 50%, you can get 6V 2A going to your motor)