RC Battery C-Rating & Continuous Current Calculator

To protect the battery and prevent cell damage, LiPos should never be discharged below 20% of their total capacity (the 80% rule). The usable capacity is: Usable Ah = (Capacity (mAh)) / 1000 × 0.80.

Current draw scales non-linearly with throttle. We model average current draw using an exponent of 1.8 to reflect brushless motor efficiency curves: I_avg = I_max_motor × ( (Throttle %) / 100 )^(1.8). The estimated runtime is then: Runtime (minutes) = (Usable Ah) / I_avg × 60. The safety margin is: Margin = I_max - I_max_motor. A positive margin indicates safe operation.

Enter your battery's capacity in mAh and its C-rating (both printed on the battery label), its cell count (S rating), your motor's maximum current draw in Amps, and your average throttle percentage for a typical flight. The calculator returns maximum safe continuous current, energy capacity in Wh, average current draw, estimated flight time, and safety margin.

With the calculator's defaults (a 2200mAh battery rated at 45C, 3S cell count, a motor with a 60A maximum draw, and an average throttle of 50%), the maximum continuous current the battery can safely supply is 99A (2.2Ah × 45C), giving a healthy 39A safety margin over the motor's 60A maximum.

At 50% average throttle, the non-linear power curve means actual average current draw is only about 17.2A (well below the 60A peak), giving an estimated flight time of roughly 6.1 minutes on the battery's 80%-usable capacity of 1.76Ah.

Once you know your flight time, cross-check it against the RC Flight Time & Battery Power Calculator, which models runtime using hover and active-flight current draw instead of a throttle curve.