Hub motor short?

[hekdude]

I have a 20" amped bikes wheel on my recumbent tadpole. Tonight, going down a hill (at about 30mph) all of a sudden the motor started to shutter violently. It seems like the some of phase wires are shorted. Could this have happened. I had the battery disconnected so that the motor wouldn't drag as an e-brake. Now there is definite braking action in the wheel. I have disconnected the motor from the controller, and still get the braking action. Fortunately, someone offered to help out and give me a ride as I was walking by their house. (and where I live, everyone has a pickup truck

I haven't had a chance to do any testing on the motor, but does my diagnosis make sense?

Thanks for the collective wisdom

 

[DAND214]

Disconnected from the contrller and still cogging?

Then I would say you have a short in the phase wires.
try putting two together and see if it gets worse or the same. Move the wires arond in the axle and see if it changes.

What motor are you running? That info always helps.

Dan

 

[amberwolf]

If the motor is disconnected completely from everything else and still feels like the brakes are engaged, then either something mechanical is causing extreme friction (like a washer between the dropouts and the motor casing is rubbing on both), or a phase wire is shorting to another phase wire.

That could be inside the motor, on the windings, but is unlikely unless it's been ridden hard enough to get really hot, or there is something already wrong with the windings physically so that insulation was scraped off, causing a short after perhaps a severe enough bump.

More likley it is in the external wiring, most commonly right at the exit from the axle whre there are often sharp edges.


As an aside: If the battery was disconnected while you were going down the hill, but the controller was still connected to the motor, then it is possible that the voltage generated from the motor exceeded what the FETs coudl take, and some of them failed. The battery would probably have mitigated that from happening, by pulling down the voltage as current was forced thru it charging it (assuming it doesnt' have a BMS that prevents that, and/or could handle it).

So even after fixing whatever is wrong with the motor now, it's possible the problem will appear to return after reconnecting the controller.

 

[dogman dan]

the starting point is definitely checking the wiring you can see, for any kind of short, or nick that could be shorting in the phase wires. Typically it's the ol spun out axle twisted the wires, but tires can rub a wire too.

Climbing a big hill gets that motor hot, and descending makes more heat if you didn't stop to cool a really hot motor. I'm suspecting you melted something in there, likely the insulation inside the axle liquified, and you have a short there. Hopefully it did not blow the controller, but it might have. pop the wheel open and pull the bad wire further into the hub, and cut away the bad part. Or start over, replacing all of it.

 

[hekdude]

I was running an ampedbike 20" direct drive rear motor.

 

[JEB]

I purchaced a hub motor that was claimed to not be up to snuff as far as power, but rolling drag, I ran it with another motor (as generator) to check the output per phase all the outputs were the same, but one had a connection (short) to ground, never took it apart to see if I could check it out.

 

[Boestin]

After 5 years another update in thuis thread

Yesterday my motor was suddenly getting really hot while riding not so extreme, it got to about 170 degrees Celsius. That's when I stopped..
When the motor was relatively cool, 80 degrees, I noticed a drag. I made it home while riding at max 20 kilometers per hour, really slow. But the temperature was ticking 110 degrees.

I disconnected everything from the motor and there was still drag. There has to be a short somewhere in the motor.

At home I opened up my crystalyte HS 4080 ( with upgraded wires), but I could NOT see any shorts.
Could it be that the windings are shorted?
What should I do?

Thanks!!

 

[Ykick]

After 5 years another update in thuis thread

Yesterday my motor was suddenly getting really hot while riding not so extreme, it got to about 170 degrees Celsius. That's when I stopped..
When the motor was relatively cool, 80 degrees, I noticed a drag. I made it home while riding at max 20 kilometers per hour, really slow. But the temperature was ticking 110 degrees.

I disconnected everything from the motor and there was still drag. There has to be a short somewhere in the motor.

At home I opened up my crystalyte HS 4080 ( with upgraded wires), but I could NOT see any shorts.
Could it be that the windings are shorted?
What should I do?

Thanks!!

It sounds like you've eliminated the controller and if you're 100% certain the axle wiring isn't shorted someplace then yes, windings are probably toast. If so, probably need a new motor or that one rewound.

EDIT - make sure a magnet hasn't come loose?

 

[Boestin]

Hi ykick,

Well there was a magnet a bit shifted, but not completely loose. Hm.. I'm going to cut all the phase wires and see if it's still draggy.
Thanks

 

[Boestin]

I made some photos of the loose magnets. It could be the issue.
IF this is the issue, why is the motor heating up in a matter of a minute?

 

[fechter]

It looks like the stator is rubbing on the magnets.