Understanding ESC Failures in FPV Drone: Causes for smoke, fire and burn out

In recent months, there’s been a startling increase in reports of ESCs (Electronic Speed Controllers) catching fire. Just yesterday, I experienced this firsthand. Amid testing different PID settings, my quadcopter, which had been flying smoothly for over two months, suddenly dropped from the sky after a sharp turn. Approaching the crash site, I was met with smoke and flames. Thankfully, I managed to disconnect the battery quickly, extinguishing the fire with no damage to the quad. This incident led me to investigate the potential causes of such fiery failures in ESCs. Here are the potential causes of ESC fires.

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Running Higher Voltages

With many pilots shifting to 6S LiPo batteries, the stress on ESCs has increased. Even though many ESCs are rated for 6S usage and are generally reliable, the risk of failure is notably higher with these higher voltages compared to 4S setups.

Excessive PID Values, Especially P Gain

High P gain settings in your PID can lead to rapid changes in motor speeds as the quadcopter attempts to stabilize more aggressively. This results in higher current draw by the motors. From analyzing blackbox data from flights before and after adjusting my P gain from 2.0 to 7.0, I noticed significantly more violent fluctuations in motor speeds during maneuvers, even causing overshoots or “bounces” during rolls and flips.

What I found interesting in those blackbox graphs was the motor outputs (The lines at the bottom). The flight with higher P gains, you can clearly see the change of motor speed is more violent, even when the quadcopter isn’t doing much the lines are still jumping quite a bit.

(If you are interested in how blackbox works, stay tune I will put a tutorial on my blog tomorrow night!)

Here I was just flying forward with medium throttle.

And here I was doing a sharp yaw turn.

And here is a roll. Notice there are two rapid changes of motor speed, First one is the actual roll, the second part is the overshoot (as known as “bounce”). The overshoot is huge with high P gain.

And finally here is a flip. The overshoot is dance all over the place! Must be painful for the motors!

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ESC Settings: Damped Light, Motor Timing, and Demag

Motor timing settings can drastically affect ESC performance. Setting the timing too high may cause the motors to draw excessive current, leading to overheating. While Damped Light enhances flight performance by actively braking the props, it also increases pressure on the ESCs.

Firmware Issues: BLHeli vs. SimonK

There have been discussions in the community about whether BLHeli firmware could be contributing to ESC failures more than SimonK. Insights from experienced users would be invaluable here.

Inadequate Cooling

Proper airflow is crucial for keeping ESCs cool. I prefer mounting my ESCs on the arms of the drone, as it’s an effective method to ensure they receive enough air circulation.

Faulty or Poorly Designed ESCs

Sometimes, the ESCs themselves are to blame. Poorly designed or over-rated ESCs are more prone to failure. Compact models like the DYS SN20A and KISS 18A often overheat due to their small size and lack of adequate heat dissipation features like heatsinks.

Conclusion

There are multiple factors that can lead to an ESC catching fire. Understanding these can help you prevent such dangerous situations. If you have experienced similar issues or have insights into other potential causes, I’d love to hear your thoughts. Your experiences can help the community better understand and mitigate these risks.