Over Volting DC Motors- the “Turbo” of Electric Vehicles

Now that electric vehicles are becoming an ever-present part of transportation systems around the world, people are going to want to know how to modify them and get more power out of existing systems. Fortunately, Brushed DC motors are simple and robust enough to pump more amps and volts through them than their rating would lead you to believe.

Firstly, electric motors aren’t rated at peak power, but at continuous and 1 hour thermal (heat). The continuous rating refers to the amount of power the motor can output without burning up. The 1 hour rating is the power output that the motor can safely perform for… you guessed it, an hour. You may or may not find peak power ratings for these motors, due to the typically predictable duties which they so often perform (industrial settings). In vehicles, there are so many variables that can affect how much power you need in any given situation motors need to be able to put out far more than typical electric motors are “rated” for. Alas, the electric motor’s peak power capability, that unknown amount of power that people like me are destined to find, albeit the hard way if not careful.

One of your main concerns when over-volting an electric motor is the speed of the motor, which is often directly proportional to the voltage applied. You can monitor this with a speed sensor, possibly coupled with a speed switch, which will cut power to the motor in the when a certain speed is reached.  It is important to note the dangers of applying excess voltage to a motor: If the speed becomes too great, the motor will become a large grenade, imparting heavy chunks of steel, copper and aluminum in the air and causing property damage or death. The parts necessary to control/ monitor speed can be purchased from KTA Services Inc                 http://www.kta-ev.com/RPMLimiting_s/1844.htm    there may be other suppliers out there, but I only know of this one.

Though you can often get away with applying higher voltages or higher current to a motor, applying both higher voltage and higher current at the same time will most likely not be tolerated for long and any damage will onset very rapidly. I would suggest sticking with applying small amounts of extra voltage (in increments smaller than 6 volts) incrementally, while observing the brushes on the motor. The brushes will arc excessively and bounce off of the commutator, which will cause quicker brush wear, a build-up of heat and carbon brush dust. The dust can become a major concern if left unchecked and can lead to an event that will damage your motor. Due diligence includes using an air compressor to blow out the area around the brushes on a schedule you’ll have to create (based on the motor and brushes it uses and the amount of excess voltage experienced by the motor).

If abusing your motor, which is technically what I am advising when I say that you can over volt a motor, you should make modifications that allow the motor to shed heat better, like using forced air cooling or better forced air cooling. For those who can fabricate parts, you may be able to come up with a liquid cooling system for your motor (this one may actually take redesigning the motor, but some will go after it anyway), which can easily out-perform the air cooling method and allow even more abuse.

Another very important over-volting precaution that should be observed is the amount of time your motor spins at those higher speeds. Even at rated speeds, some manufacturers recommend not maintaining the rated rpm limit for long periods of time. I have heard no accounts of motors flying apart (well, not in electric vehicles anyway), but you should remember the possibility for it to happen.

Before attempting to modify your motor, please be aware of the dangers discussed herein and any dangers that might surface in your unique situation. Each individual’s experience will be different due to the vast number of variables for which I can’t totally account. Take baby steps and enjoy your electric turbo boost. Other motor types can be over-volted and some of the concerns are similar, though series-wound DC motors are going to be the motor of choice in many DIY projects and will be simple to work with, so, chances are that you’ll be considering applying extra voltage to a brushed DC motor.

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