How to Size an ESC for a Drone Motor

An undersized ESC overheats or fails. An oversized one adds weight and cost. Here is how to pick the right one.

1. Look at the motor’s peak current

The motor datasheet lists a peak current. For example, the RD8015 115KV lists 46.58 A, the RD6218 160KV lists 50 A, and the RD8030 160KV lists 135 A. Your ESC’s rated current should comfortably cover that value.

2. Compare continuous and peak ratings

ESC ratings come as two numbers. The continuous rating is the current the ESC can carry indefinitely with cooling. The peak rating is the current it can carry for a short time, such as 30 or 120 seconds. Naming can be based on the peak figure. In our A-Series, for example, the RD A-Series ESC 150A has a 150 A peak for under 30 seconds and a 75 A continuous rating.

3. Check the cooling conditions

Ratings only apply under the stated conditions. Our A-Series ESCs are tested at about 30 °C ambient with 12.5 m/s of airflow, and several trapezoidal models state that active cooling is needed for the rated current. If your ESC sits inside a closed fuselage, derate it.

4. Match the voltage

The ESC must support your battery’s cell count. The RD A-Series ESC 60A supports 6S to 12S, the RD A-Series ESC 120A 4S to 12S, and the RD S-Series ESC 25A 2S to 6S. See our guide to KV and cell count.

5. Choose the control type and signal

Decide between FOC and trapezoidal (see FOC vs trapezoidal ESC) and make sure your flight controller supports the input: PWM, DShot or CAN. Browse our UAV ESCs, or use the recommended ESC listed on each motor page.

6. Leave margin

A common practice is to leave at least 20 % headroom above the highest current you expect. Make sure the power distribution board can carry the combined current (see what a PDB does).

Need help choosing? Email [email protected] with your take-off weight, battery voltage and number of motors, and the Reflex Drive team will suggest a matching set. Reflex Drive is a brand of Sunmint Electronics LLP, and all of our products are designed and manufactured in India.

Amrit RD