salsa wrote:"8 )
If you have a magic controller, It has a current multiplier (RC circuit) that takes the 5 amps from the 80 volt batteries and changes it to 10 amps before it sends it to the motor. This has been discussed before, but I have not seen a controller that claims to do it.
All PWM controllers do this when they are at partial throttle.
The power needed to go a certain speed is a fixed number of watts.
The current needed by the motor will be the same regardless of pack voltage.
The current drawn from the pack will be roughly half if the voltage is doulbled. 5 amps from the battery will be 10 amps at the motor. At the higher voltage, the throttle setting will be much less to get same speed.
At reduced duty cycles (less than full throttle) the controller / motor work like a buck switching power supply. The current can be multiplied several times when the output voltage is much less than the input. At full throttle, the current input = current output.
Another way to think about it is by looking at the power. To go 20mph, let's say it takes 400W.
80v @ 5a = 400W
40v @ 10a = 400W
Since the controller isn't getting hot and dissipating a bunch of watts, power input = power output. Of course there is some loss, but it's a small percentage.