Size the battery for the aircraft’s total current and each ESC channel for one motor. Use average current for endurance, and the intended maximum load and its duration when checking electrical ratings.
1. Add motor test currents to get aircraft current
The calculator’s current and ESC outputs are preliminary estimates. For component selection, find the required thrust in test data for the actual motor, propeller and voltage. Check that current is measured at the battery input; convert loads on other voltage rails to battery-side power.
The following inputs are illustrative, not product measurements: four identical motors each draw 5 A in hover and 12 A at the intended maximum load. The flight controller, radio and other equipment together draw 1 A at the battery input.
| Operating condition | One motor | Four motors + equipment | Total current |
|---|---|---|---|
| Hover | 5 A | 4 × 5 + 1 | 21 A |
| Maximum load | 12 A | 4 × 12 + 1 | 49 A |
Record how many seconds or minutes the maximum load lasts. If you already measured total aircraft input current, do not multiply it by motor count or add equipment loads again.
2. Check capacity and battery C rating together
Convert capacity to Ah before comparing it with current. A 5,000 mAh pack has a capacity of 5 Ah, so supplying 49 A requires 49 ÷ 5 = 9.8 C.
A 5 Ah pack labeled 20 C continuous has a stated continuous discharge current of 5 × 20 = 100 A. Compare this with the required 49 A, keeping burst and continuous ratings separate. Also check voltage sag and temperature under load, plus connector, wiring and power distribution board ratings.
| Battery capacity | Calculation | Required rate |
|---|---|---|
| 3,000 mAh (3 Ah) | 49 ÷ 3 | About 16.3 C |
| 5,000 mAh (5 Ah) | 49 ÷ 5 | 9.8 C |
This comparison holds the load constant. Changing the battery changes aircraft mass and required thrust, so recalculate current for the actual pack.
Read the battery manufacturer’s capacity and C rating explanation →
3. Check ESC ratings per motor and at the intended voltage
Each ESC channel handles a maximum-load current of 12 A in this example, rather than the aircraft total of 49 A. Check continuous current for the required duration, the allowed burst duration and cooling conditions.
As a specification-reading example, HOBBYWING lists its XRotor 40A 6S BLDC at 40 A continuous / 60 A peak, with 2–6S LiPo support and no BEC. The 60 A figure is not a continuous rating. This illustrates the labels; it is not a component recommendation for the example aircraft.
- Check battery cell count and fully charged voltage against the ESC, motor and power electronics limits.
- For a 4-in-1 ESC, check board-level load and cooling limits as well as per-channel ratings.
- Confirm flight-controller signal compatibility, whether a BEC is included and any separate power supply requirements.
4. Compare flight time using average current
A simple capacity estimate is flight time (minutes) = usable capacity (Ah) ÷ average current (A) × 60. Using 80% of a 5 Ah pack gives 4 Ah; at an assumed average of 21 A, this is about 11.4 minutes. The 80% value is an example assumption, not a universal operating limit.
This result assumes current stays at 21 A. Compare candidates in the flight-time calculator while updating both battery capacity and all-up mass, then refine the estimate with consumption measured under the intended operating conditions.
Related simulation
After reviewing the power system, explore a visualization of a quadcopter airframe, rotors and wakes.
Questions and answers
Does a higher C rating mean longer flight time?
C rating expresses discharge current relative to capacity. Endurance depends on usable capacity and average current. Packs with the same capacity can still produce different results because of mass and voltage under load.
Can I order an ESC directly from the calculator recommendation?
First check test current for the candidate motor–propeller combination and the intended voltage. The estimate alone does not establish operating duration, cooling conditions or control-signal compatibility.