There have been so many reports of ESC catching fire the past 3, 4 months, it’s unreal! And I burnt an ESC yesterday, there was so much smoke and flame it was horrifying! I am trying to find out why this is happening so frequently.
A bit of background from yesterday: I was experimenting with different PID. The quad flew happily for 30 mins, but after a sharp turn, the quad just fell out of the sky. As I walked closer to the quad I saw lots and lots of smoke, and fire! I rushed to the crash site, immediately unplug the lipo battery, few seconds later the fire went out. Luckily no damaged was done to the quad.
This mini quad flew reliably and beautifully for the last 2 months, and you know what I did before that crash? I almost doubled my P gain for both roll and pitch (I was testing the effect of high P gain, it was changed from 3.8 to 7)
I also written a guide on how to choose ESC you should check out.
So here are my theory what could potentially cause ESC set on fire:
Running Higher Voltages
More and more people run 6S LiPo. Although some ESC’s are rated for 6S, and a good proportion of them are reliable, there is a higher chance of burning the ESC than 4S. Higher voltage is just more risky.
Excessive PID value, especially P gain?
When your P is high, the quadcopter will try to change motor speed more rapidly and stabilize the aircraft harder, therefore motors will draw more current.
This is what I think was responsible for my last ESC fire. Luckily I was running blackbox and I got some data of the flights. I am comparing the data of two different flights, first one with P gain of 2.0, and the other with P gain of 7.0 (both roll and pitch), all other PID values and rates are identical.
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!
ESC setting – Damped Light / Motor Timing / Demag
Pretty sure motor timing has an effect on how the motor runs. I have heard when motor timing is set to too high, some motors just draw excessive amount of current, gets hot or simply don’t work well. I think for most motors the default “medium” is pretty good. Some prefer “med-high” for Cobra 2204 2300KV motors, and seem to have good result.
Does Damped light put more pressure on the motors and ESCs? I think it does, as it uses more power to actively brakes the prop and motor from spinning when you slow down. But this feature really improves flight performance.
BLHeli in general?
I have heard more than once that people accuse BLHeli firmware for burning ESC in general, and said SimonK doesn’t have this issue as often. Hope someone with experience with these firmware to shed some light on it!
Bad Air Flow to Cool ESC Down
Whatever you do, always have good air flow to help ESCs cool down. I personally prefer mounting ESCs on the arms, cheapest and most effective way to avoid overheat.
Simply Bad ESC
Badly designed or over-rated ESCs are likely to catch fire. Also I think the reason for miniture ESCs like DYS SN20A and KISS 18A to catch fire so often is due to the tiny size, insufficient surface area will make heat dissipation slower, and they don’t even come with heat-sink. You probably don’t want to push the limit with these ESCs.
What else could set your ESCs on Fire?
Let me know if you think some the above factors are the ESC killer, or anything else I have not mentioned.