Advice wanted: melted motor connector: next step?

[Twistgripper]

Basically, pulling the motor apart is a fair bit of work, hoping those with a lot more experience can tell me most likely if just connector or likely also problem inside motor.

Bike setup: Bafang G06 500w geared rear hub motor, Grinfineon 20A controller, Cycle Analyst v3.1, 24 pole PAS, 36v battery pack - all from a Grin tech fat bike kit.

Symptoms: weak motor, pulsing. I did factory reset on Cycle analyst - no change. tested pas sensor - working properly.
When i went to do some testing on the motor I found one of the pins/wires had melted (see pics).



I separated the pin and did the motor cog test - shorting all 3 combinations of the phase wires made motor more difficult to spin. resistance on all 3 combos of phase wires was initially infinite on one set, but then all 3 tested .2-.3 ohms so maybe a short there still?

Tested controller by connecting a brand new motor i had on hand and it works but i cant do a full load test/ride as the motor is on a different bike and I cant swap them (not a fat bike).

Based on your experience, it is likely there is internal motor damage? or likely just replace the connector and test again?

This is for a customer's unit (I sell and service ebikes but still learning) so i dont want to rack up billable hours opening the motor if its unlikely damaged.

(side note: any tools out there for load testing a controller without actually installing it on a bike?)

 

[e-beach]

Shorts get hot at the point of a short. Then the heat spreads down the wires. I would also check the female side of the connector for lose wiring. If your customer melted it at the connector it is most likely that the customer was hammering the throttle and the under-valued connector couldn't handle it. Even at 20A. As for the .2 .3 readings, my guess is that is just an artifact from an under-priced DMM. If you are going to replace the male part of the connector, also replace the female part.

 

[Twistgripper]

Thank you for quick response. I suspected thats how shorts work re: at the ends of wires). good call on the other connector will check female end too.

Bike has no throttle, just PAS levels only...maybe climbing long hill? Grin says these connectors are good for 30a..
re: ohms. yes i do have a rather cheap dmm lol.

luckily the only connector i can find is a Z910 extension cord - so i can cut it in the middle and get both a male and female connector out of it..

so, to clarify, you think it is LIKELY that the motor itself is ok?

 

[fechter]

The motor is probably OK.

If one of the hall sensor wires melted and made contact with a phase wire, you could blow a hall sensor. Otherwise, shorting the phase wires won't likely hurt the motor. The controller would be more likely to fail.

Resistance phase to phase is very low normally, so your readings are in the ballpark. You don't want an open phase wire or any connection to the case. If it spins freely with the phase wires disconnected, it indicates no shorts.

 

[Twistgripper]

Its a well matched system AFAIK, and its only 2-3 yrs old. could loose connections cause this? i'm a bit stumped as to the original cause. A lot of the wiring was not well secured...

 

[fechter]

Yes, if a connection gets loose or corroded, it can develop a high resistance and burn up very quickly.

 

[markz]

I personally do not like those connectors the OP has, to easy to bend and break.

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I had to change batteries today and my controller side XT90 solder job broke.
Seems to happen once every year or two.
Its always the exact same fix to get me home.
I always carry around electrical tape, so I stripped the wire, and wrapped it around the bit of wire strands still on the connector and made sure no loose strands were about, and taped it up.
Worked a charm

I tell ya, that Chinese wire is some mystery. I got silicone from the king, so hopefully it will fit through the plastic mesh of the controller. This evenings project is changing out the controller battery wires and hopefully I have a new fresh XT90 male somewhere in my pile :thumb:

Fun Times
:thumb:

 

[docw009]

Bafang now ships their 750W G06 fat tire motors with a bigger connector. Is that the Z90? The 9 pin model you show there should handle a sustained 500W, but I guess it did not. If the old motor spins no load on a different controller, it's probably fine.

If the extension is long enough, I'd splice the controller side of the Z90 inside the controller. It's less work, being able to wrap the thick wires together, I also like using solder forms to splice the phase wires. I take them out of crimp connectors.