Battery question
 

Does increasing the voltage on a brushless motor cause it to use less current?

To achieve the same power output,yes.If geared for 40 mph with the same motor it will take less amps if your voltage increases.

cool, thanks....

If you increase the voltage and do not change the gearing your amp draw will rise due to increased load. Now, you may run into a problem with more voltage. If your current setup is spinning the motor at its most effecient rpm window, raising the voltage may make the motor less effecient, thus causing higher amp draw.

Matching the motor to the voltage and load is an art... Experience really helps.