Yes, normally that would be a problem with a higher voltage supply. But my code turns off the coils between steps, you choose the duty cycle. The coolest of all for very slow speeds is when it's off the whole time between steps. You cannot turn it off when you're running at full speed or there would be zero torque to the point where it can't run at all at that speed. This motor is different from your traditional motor because of the gear box, and smaller steps than 1.8 deg. If you turn a big motor off between steps even half the time it would go backward with any load at all.