We are often asked whether 12v or 24v is best for a battery powered motor system [the short answer is 24v]. For a more reasoned explanation lets think about power, putting it in car terms, if you want to accelerate harder or have a higher top speed then you need more horsepower.
In an electric vehicle the power usually comes from the battery, and is converted by the motor into energy. Electrical power is volts multiplied by amps so that 40 amps from a 12v battery is 480 watts. But 480 watts can also come from a 24v battery at a current of only 20 amps; so for any particular power, the higher the voltage, the lower the current will be.
Now electrical current causes heating. The motor, wiring and controller will all get hot which wastes power. The heat wasted is proportional to the square of the current multiplied by the resistance. Other things being equal, that would cause losses on 24v to be half those on 12v.
It is clear from this that a 24v system is always better than a 12v system – provided you can physically fit two batteries. By the same token 36 or 48v would be even better [there is a page about using our controllers at 48v and above here].
Really heavy current systems (milk floats, electric cars, fork lift trucks) often use 72v or even 96v to reduce heating. We’re designing our new Pro-160 to work up to 84v.
The amount of energy in the batteries is amps x hours x volts. Consider a 12v 60 Ampere Hour battery. Clearly this is exactly the same as two smaller 12v 30 AH batteries in parallel. But the total amount of energy in these two will not change whether we connect them in parallel or in series. So a 12v 60 AH battery can store exactly the same energy as a 24v 30 AH battery.
There is another factor against 12v stepper motor or 24v stepper motor operation, MOSFETs need a good voltage to fully turn them on, so most of 4QD’s controllers use an internal 9v supply rail, which is adequate to ensure proper turn-on. However, there is not much difference between 9v and 12v. It does not take much current to be drawn from the battery before it drops 2v at its terminals.
For this reason, we would generally not advise 12v operation if the peak motor current is likely to be more than around 30-50 amps.
See more:
http://christ282.inube.com/blog/8523971/how-to-drive-a-brushless-dc-motor/
