One ESC gets extremely hot, others are fine


#1

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


#2

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


#3

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


#4

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.