One ESC gets extremely hot, others are fine


I noticed this behaviour when I was testing some code on the RPi. The drone was connected to the battery and then just stood there doing nothing. It wasn’t even armed.
All the ESC’s were maintaining a temperature slightly above room temperature, but one quickly got very hot (around 50 deg. C within a minute on the heatsink surface).
Does anybody know this problem? Luckily, I have some spare ESC’s (not my first issue with this brand) but maybe there is an alternative to rewiring and recalibrating everything again.

Best regards


Was this the esc furnishing power to the fc? If so, try removing the power (red wire) and see if it makes a difference.


Thanks, It was the one. I made another ESC the single UBEC supplier and now this one gets hot instead. So much for the problem source.
After some more research, I found out that the problem was the Raspberry. I had some undervoltage problems once and lost confidence in the telemetry port as a power source as described in the course videos. So I attached the RPI directly to one of the main outs of the Pixhawk. I removed that line and restored the original setup. The ESC still gets cozy (around 32 deg. celsius), but I guess that is normal for the UBEC supplier, isn’t it?

Two more questions, if you don’t mind:

  1. What exactly is the purpose of that one UBEC line? Would the main and aux outs on the Pixhawk stop delivering any power if the UBEC wasn’t there?
  2. Did I have a problem at all? The RPI’s max current draw roughly equals the ESC’s max current delivery. Is a temperature of 50 deg. maybe normal in that case and well within the ESC’s comfort zone?

Thanks and best regards


You can fly w/o the esc ubec feed to the fc. Normally the purpose for it is 1] to supply a backup power source to the fc in case something happens to the normal power supply, and 2] to provide a powered rail that you can use for other devices.

That said, as of late I use an independent ubec from the pdb and not the esc. I use it to power other devices such as range finders, LEDs, optical flow, etc. I still use the fc telemetry to power the RPi and so far haven’t had an issue, but I recognize an undervoltage could occur.

I cannot understand why your RPi would draw max amps for simple flight missions unless you also had some special devices on it.

I once had one of these escs catch fire on a hard landing, presumably because it was putting a lot of current through to manage the motors and fc. 50C is close to where it can burn flesh but normally not close to ignition temperatures. Once airborne I would assume it cools off - you can put a temperature sensor on it and see. But these escs are cheaply made but low price. So always keep a fire extinguisher around when you fly.