Speed Calculator

[BrianG]

Sounds like you are using the motor's DC resistance value, which is very low.

For simplicity, let's assume the PWM switched DC output of an ESC is AC, because it is.

A coil, being just a relatively short piece of wire, will have very low resistance. But, as soon as you use AC voltage to drive it, the alternating current causes a fluctuating magnetic field to form which counters the current. This looks like resistance to the supply because it is opposing. The amount of this resistance, called impedance, will vary with frequency, specific coil, and mechanical load placed on the motor. This is why getting a current value is near impossible.

The best you could do is get a runtime measurement based on your current setup, and calculate the average current draw using runtime and pack capacity used. The peak or burst current will be around 6-10X that value depending on drivestyle, esc settings, etc, but it gets you in the ballpark.

Or, use the following page once you have that data: http://scriptasylum.com/rc_speed/_power.html