Motor crystallite HT3525 braking

[unebonnaventure]

Hello,
My HT3525 (rear hub motor) has started braking while assisted pedaling.
Now it keeps braking and no more assistance. Braking remains with battery removed. Braking is is a succession of hard and soft points and not continuous, which is why I thing the motor is the cause.
Any ideas of the problem and associated fix ?
Thanks for your help, the bike is our only way to get kids to school ...

 

[captain387]

The motor resistance is most likely caused by shorted phase wires, try unplugging the controller and give the wheel a spin by hand if it spins, the controller most likely has a blown Mosfet, or you have a problem with your wiring to the controller.

If it doesn't spin with the controller unplugged, you are into further investigations into the motor but you can do some tests to check the phases

Here:
https://ebikes.ca/learn/troubleshooting.html

 

[unebonnaventure]

Thanks a lot captain !! There are just three cables between my motor and controller I'll try unplugging quickly !

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[unebonnaventure]

Blue, yellow, and green cable, if I unplug just the green, the brake stays, if I unplug any other, the wheel is free again

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[captain387]

No problem, well unfortunately it sounds like one of the mosfets is burnt out in the controller, OR, you have a short in the wires on the controller side. The link I had provided has instructions on checking out the controller mosfets.

2 options -

Option 1 - open the controller (after determining it is definitely the controller, checking the connectors and wiring and by doing the tests in the link) and see if there are any other burnt items.

If everything looks ok inside the controller, then you could try replacing the mosfets, (I've heard that all three should be replaced at the same time).

Option 2 - Buy a new controller, and you may want to check the wires as they go into the hub motor by removing the outside seal as there was an issue at one point where the wiring didn't really have enough space to go into the groove of the hub motor shaft and over time the seal (which has a steel spring) would cut through the wires shorting things out and it may have been intermittent.

 

[unebonnaventure]

There is indeed a short in the wire due to melt insulation of yellow and blue.
But still three questions :
1) When I separate the cables so that there is no more continuity between two cables, motor was blocking before getting back to normal spinning. Now it is spinning normally. Is this normal ?
2) what is the root cause of this damage ? Too little section of copper in the cable ?? It seems strange as it was made by V-fiets for Amsterdam Air
3) when I measure continuity at the unconnected hub motor, it is continuous between all three phases, is this normal ?

Thanks a lot for your help, looks like we'll be able to use the bike again tomorrow !

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[captain387]

Glad you were able to find the issue.

1) When you disconnected the cables and made sure there was no short at that location there was still resistance? and then it started spinning again?
That seems strange, was the motor partially seized due to frozen water in the hub? or could there be a bad bearing?

2)Looks like an issue with the connector, not the wiring. The connector resistance increased due to,,,,? poor fitment/corrosion/bad crimping, combination of all three?? I use soldered bullet 5.5 mm connectors (Over kill for my set-up and I'm sure yours as well so you could go for smaller ones) for my entire system and I have not had an issue. With that being said I'm not commuting 40 miles a day through ice and snow like some members so they may have different experiences.

3)There should be continuity between the phases (not dead short) because you are sending power into a phase but in order for the current to flow it needs to be connected back to the controller through a different phase. Since all three are the same that is a good sign. One additional check would be to see if there is continuity between each phase wire and the axel of the hub motor to make sure it is not shorted out there.

All the best.

 

[unebonnaventure]

Thanks a lot !!

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[captain387]

No problem at all