Several motors not spinning during one specific ARM sequence

ArduCopter Copter 4.2
,
1

Hi everyone! Weird event yesterday: During an ARM sequence, three motors didn’t spin.

Context:

  • This drone has done two flights a few hours before, completely normal;
  • There was no beeping and the armset LEDs were on, so both signal and power were there;
  • Without any reboot, we tried to ARM again and the same three motors didn’t spin;
  • After a hard reboot, not even touching the rest of the drone , they worked normally.
  • After the successful ARM test, we did a short flight. All nominal

SETUP

  • Cube Orange+
  • Kore carrier board
  • Armset T-Motor MN705 + ESC Alpha 80A HV

Considerations:

  • We had similar thing after getting some water inside the armset. However, three motors at the same time is lottery-unlikely to happen.
  • After the event, the battery was put in the charger and it was saying “Cells Voltage High”
  • We know that the ESC can protect itself from some electrical abnormalities;
  • I really don’t think it is a damaged cable because, again, three motors at the same time.
  • Checking the log, PWM was also there.

Questions:

  • Have you seen something like that?
  • Could a battery issue cause such a behavior?

LOG

2

You have the correct MOT_PWM values, so that’s good. Usually the ALpha ESCs have MOT_THST_EXPO,0.6 but that wont be the cause of the issue you see now.
You will just have to test in MissionPlanner motor test to identify the issue.
Maybe you just need to increase MOT_SPIN_ARM but that already looks high enough to me.

You should have:

ARMING_CHECK,1
BATT_FS_LOW_ACT,2

and check your battery failsafe values

3

Hi @xfacta !

Thanks for such a quick reply.

Indeed, MOT_SPIN_ARM is a bit lower than the values we were using before, but it’s been like one year since we started using this value and I never saw such a behavior.

We’ll keep an eye on it, of course, and I’ll keep this post updated.