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 Feb 23, 2012, 01:25 AM Crash and learn United States, PA Joined Dec 2011 2,856 Posts Mini-HowTo Calculate Motor Amps from flying time Motor Amps using battery MAH rating and flying time Calculate motor amps from flying time Motor amps ? If you start with a full battery and get an accurate time how long the battery lasts, you can figure out the average current that the motor drew during those minutes. Amps = (mah) x (1amp/1000ma) x (60minutes/1Hour) / (RunMinutes) Amps = (mah) x (60/1000) / RunMinutes Amps = 0.06 x mah/minutes Example: Amps = 0.06 x mah / Minutes Amps = 0.06 x 1000 / 6 = 10 amps average current Amps = 0.06 x 1000 / 3 = 20 amps average current = 1000mah battery that lasts 3 minutes Amps = 0.06 x 1300 / 3 = 26 amps average current Amps = 0.06 x 1300 / 4 = 19.5 amps average current Amps = 0.06 x 1300 / 5 = 15.6 amps average current Amps = 0.06 x 1300 / 6 = 13 amps average current Amps = 0.06 x 2000 / 6 = 20 amps average current = 2000mah battery that lasts 6 minutes Amps = 0.06 x 2000 / 3 = 40 amps average current Amps = 0.06 x 680 / 6 = 6.8 amps average current Amps = 0.06 x 680 / 3 = 13.6amps average current Amps = 0.06 x 900 / 6 = 9 amps average current Amps = 0.06 x 900 / 3 = 18 amps average current Well, more or less. Pick a ratio of MAIN/TAIL and apportion the total amps A good ratio may be 3/1 where main = 75% and tail gets 25%