[MetalMan]

The motors we use in RC will never run at constant power.

On the previous page you mentioned after BrianG's that Ohm's Law has nothing to do with this. In fact, it does. The motor has a resistance that is constant for the most part. If you do not change the gearing when increasing voltage, then the resistance is constant. You cannot use constant power to determine the amp draw, as the only thing that would be close to determinging the MAX power is the battery, but the only possible way for you to be running at constant power is if you were running at full throttle the entire time and the speed/terrain/acceleration/battery voltage were also constant.

So, since power is not constant, the amp draw will increase as voltage increases (assuming a fixed load, IE same gearing). If you use higher voltage AND the load decreases (smaller pinion or larger spur) then the amp draw decreases.