MOSFETs overHeating, how to debug/salvage hardware?

I am currently operating the oDrive (v3.6 hardware / 24V power + firmware v0.5.2) at 100% load indefinitely, my application is similar to (ebike, direct drive robot arm etc). Below are couple details about my setup:

  • i am using a very small 5V fan, positioned over the ODrive MOSFETs heatsinks
  • current_lim set = 85A
  • I am not monitoring the motor temp, or the oDrive onboard thermistors temp (big mistake)
  • I am driving Flipsky 6374 190 KV motor
  • requested_current_range = 100 A

Recently my oDrive failed while driving at 100% load, when trying to salvage the oDrive on the bench and running calibration mode the oDrive this happens:

as soon as I sent the command odrv0.axis0.requested_state = AXIS_STATE_MOTOR_CALIBRATION , I heard kind of a spark, and when dump errors i see CURRENT_LIMIT_VIOLATION.

  • My current hypothesis is that some of the MOSFETs have failed due to overheating. Does anyone have another hypothesis of what might be going wrong?
  • It seems that mosfets usually go short, can I use my finger to measure of any is overheating after setting the following mode AXIS_STATE_MOTOR_CALIBRATION? Can the mosfet act like an open circuit instead (how can i debug it if it is open)?

Thank you Community :slight_smile:

Sounds reasonable.

It can but they usually fail short.

Get a thermal camera, it’ll spot hot spots immediately. Alternatively you can dunk the board in 99% isopropyl alochol and see what evaporates first.