Quote Originally Posted by hays47 View Post
Energy used in an electrical circuit is expressed in watts. Watts is the result of Voltage times current. Thus a 12 Volt motor using 2 amps is using 24 watts. Now a 24 Volt motor only uses 1 amp to produce the same 24 watts. In DC circuitry remember P= I X E

Power is Watts or P in the equation 24 watts= 2 Amps X 12 Volts
Current is Amps or I in the equation
Voltage is Volts or E in the equation 24 watts= 1 Amp X 24 Volts

So in terms of current load for the same power rating 24V is more efficient than 12V.
A 24V system and 12V system have identical efficiency. 24W is 24W whether it's 12V@2A, 24V@1A or [email protected], and the power consumed from the battery is the same (except for some anomalies due to battery physics).

If you have two motors, one 24V and one 12V producing identical thrust, the 24V motor will draw less power due to the lower current in the motor windings. Motor windings are a big problem because the wire has a nasty feature that causes the resistance to increase when it gets hot. Resistance and higher current in the winding are especially bad because power loss in the winding is determined by the current squared times the resistance. So your 24V motor loses 1X1XR Watts while your 12V motor loses 2X2XR Watts.

In English, that translates into a 24V motor has only a fourth the winding loss of a 12V motor. Worse yet, the higher winding current in the 12V motor causes the windings to get hotter, making R bigger and causing the losses to be higher.