Higher voltage and efficiency

[BrianG]

Originally Posted by nuz69

You are taking the problem from the wrong side.
The point is that HV voltage runs not necessarily cooler... For the motor it's pretty much the same, although the ESC is a little cooler with HV setup. So the gain in efficiency can sometimes be negligible...

Even so, an efficiency difference of even a minuscule 0.5% on a 400w average draw is a difference of 2 watts worth of heat. That doesn't sound like a lot, but take a hold of a 5w resistor dissipating 2w and you can get the idea.

No matter what, ANY heat on the motor, ESC, battery, wires, etc is lost power. All those have a given resistance. Current^2 * Resistance=power.
Higher voltage means less current, so less voltage drop and power loss on those components. This means more of your battery is getting to the ground.

Here's some numbers for ya:

If your system is pulling say 300w average, running that on 2s means 40.5A. That 300w on a 4s setup is only 20.3A. 300w average power is pretty typical for a smaller 4WD vehicle.

So, if you have a total resistance of 0.05 ohms for the motor, esc, and wires, that's a loss of 82W on 2s for a system efficiency of 72.67%. But on 4s, that's a loss of 20.6w for a system efficiency of 93%. Big difference there!

So, I really don't understand the argument and confusion here. It seems pretty simple to me.