a DC electric motor moving a car. will it experience the same torque with current provided from a 4V battery with a capacity of 1000 Ah as with current provided from a 400V battery with a capacity of 100 Ah? according to math, P=V x A it should be the same, but would 4V be enough to move that car, even though it is supposedly moving so much more current (same C rates)? i have read about "energy efficiency" where higher voltage batteries are more efficient deliverers of energy as opposed to higher capacity ones, but don't understand why.
Is a higher voltage battery a more efficient energy deliverer than a lower voltage battery
battery-chemistry
Best Answer
Any given motor will develop torque proportional to current. However, within some reasonable power range motors can be built with considerable latitude in their voltage versus current tradeoff. For example, a 1 kW motor could be made for 100 V 10 A operation, or 200 V 5 A operation. Once the motor has been chosen though, you're stuck with that tradeoff.
This tradeoff doesn't go infinitely in both directions due to practical limitations. If you use too low of a voltage, then the current becomes so high that conductors need to be thick and expensive. Note the losses is wires goes with the square of the current, or put another way, for the same power loss you need copper proportional to the square of the current with DC. With AC skin effect gets in the way and makes things more complicated.
At the other end, high voltages become difficult to handle and keep safe. Above a few 100 Volts, electronic components get a lot more expensive and you have significant safety issues.