[Daox]

I think you have some things mixed up. Running at a higher voltage does not increase heat. Amperage is what creates heat. Going to a higher voltage allows more power at the same amperage. So, you can either get more power for the same heat generated, or the same power for less heat generated. Going too high over the rated voltage can be a problem and your brushes may spark and wear out faster. Of course, that all depends on the design of the motor. Many of the electric car guys are running their 24-36V forklift motors at 72, 96, even 144 volts without problems.