Q85 fault?

[Geebee]

The motor cuts out intermittently, no repeatable cause, starts working again after a random amount of time, nothing seems to help getting it going again it just decides to work.
The motor behaves the same when used with all electronics, wiring and battery replaced.
Soldering in hub looks good, any ideas?

 

[shemozzle999]

Hi Geebee,

If you have eliminated all the other electric parts as being OK and now suspect the motor to be the fault then I can only think of two things that will make it stop completely:

1. A faulty speed/ temperature sensor if fitted.

2. The power supply to the hall sensors has been cut so no motor commutating signals.

Both could point to a damaged motor cable or a dry joint on the junction pcb.

If you remove the motor core and mount back in the forks as show in the video attached then you can monitor the voltages on the junction pcb.

 

[Geebee]

Cheers Shemozzle999,
no temp sensor, I just re soldered the hall board but no bad joints visible.
Wiring to the halls is a possibility but everything test ok, the fault is very intermittent so hard to catch if not in use, playing with the wiring doesn't cause the cut out or make it restart.
I will try it locally since resoldering, the biggest problem is that I can't safely ride a bike that can lose assist as I cant pedal much

If it reoccurs I will try replacing the hall wiring after that a motor swap maybe in order.

 

[shemozzle999]

If it cuts out again check to see if you lose the lcd/led display indication.

Much like a petrol engine just needs fuel,air and a spark the electric motor needs uninterrupted power from the battery but also the 5v generated by the controller for the throttle, pas and display to switch the motor on and off.

 

[Geebee]

The leds stay on when it dies, and I am fairly certain I had the issue running sensorless now I have thought about it.
I used to repair electronics for a living so locating issues is not usually a problem but this one is bugging me, if my memory of it playing up sensorless is correct it has to be a fault in the motor wiring or coils.
Cheers
Geebee

 

[shemozzle999]

The battery level leds are powered indirectly from the battery supply the motor power level leds are powered from the 5v, you need to see if the latter are still operating when the motor fails to confirm that the 5v is still operable.

The motor coils are wired in delta format and can only fail by burning out or having a break in the windings. If that was the case the motor would be permanently dead or run rough. I have had a motor winding that has been badly wound where the insulation has worn through and the copper winding come in contact with the armature (check for a short between any phase wire and the motor body) but its effect was to cause the appearance of cogging under load.

 

[Geebee]

The battery level leds are powered indirectly from the battery supply the motor power level leds are powered from the 5v, you need to see if the latter are still operating when the motor fails to confirm that the 5v is still operable.

I have recently run the motor with a complete different setup from the motor connector back to the batteries with the same intermittent fault, I have also removed the connector and soldered the motor wires to eliminate the connector as well.

The motor coils are wired in delta format and can only fail by burning out or having a break in the windings. If that was the case the motor would be permanently dead or run rough. I have had a motor winding that has been badly wound where the insulation has worn through and the copper winding come in contact with the armature (check for a short between any phase wire and the motor body) but its effect was to cause the appearance of cogging under load.

Initially it did chug a bit before dying now it just dies as if the motor was turned off and comes back to life the same way.

 

[shemozzle999]

Chugging suggests a failed hall device in hall sensored motor or a blown controller fet in a non hall driven motor. It is possible that when the bike comes to rest that the wheel is positioned in the non operable position. this can be checked by manually rotating the wheel or the whole bike backwards (if it has a freewheel clutch) to see if it engages motor forward drive again.

Recheck the connector wiring you did to make sure that the phase and hall signal wires have not been jumbled up as this would also cause chugging.