How to Fix ESC Desync?

by Oscar
Published: Last Updated on

When one of the motors in your quad stops spinning unexpectedly and the quad tumbled out of the air, it might be caused by ESC Desync. Here are some BLHeli and Betaflight settings that might fix ESC Desync.

What’s ESC Desync?

If you look at blackbox log, an ESC desync happens when a motor stalls even though the motor signal goes to maximum. This results in the quad falls out of the sky.

Common causes are excessively high RPM and electrical noise.

When motor RPM is too high, the ESC can miss the “zero crossing” of the motor (commutation). Electrical noise in the signal can worsen the situation.

If the ESC can’t detect the approaching  “zero crossing” accurately, then it will not know when to fire the next pulse (to create the needed magnetic field to push motor) and the motor is stalled eventually.

Solutions to ESC Desync

To fix ESC Desync (or reduce the chances of it from happening), there are some settings in BLHeli and Betaflight you can try changing. One or some of these suggestions could fix your issue, and not necessary all of them are needed at the same time.

Install a low ESR capacitor to the power of your ESC if you haven’t already this will clean up some of the noise.

BLHeli Settings:

  • Rampup Power (or Startup Power) – use lower value like 0.125 for BLHeli_S or 12% for BLHeli_32 ESC
  • Demag Compensation – set to high as it helps the quad from recovering from Desync instead of just drops to the ground at the cost of performance
  • I go into more detail on what these settings do in this post.

Betaflight Settings:

  • Use DShot if you are not already
  • Motor Idle Throttle Value – default is 5.5 which is pretty conservative for smaller quads. Try a slightly higher value like 6.5 or 7

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Mike M 25th July 2021 - 8:55 pm

Thanks Oscar and wondering if you have any thoughts on the FPVCycle 5″ motor and Kebob’s recommendation to INCREASE rampup to prevent desync? I have/like those motors and am using Kebobs settings without problem, but it does seem counterintuitive. Maybe because they are larger than normal 5″ motors?

Oscar 26th July 2021 - 12:01 am

I don’t know under what conditions that one would recommend increasing rampup power to prevent desync as it increases voltage spikes/noise to the ESC signal. It could be a typo, maybe you wanna check with him. Here’s a bit of background on what ramp up power do:
I have not tried that motor so can’t comment.