partially dead brushed hub motor, why?

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aaronski
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partially dead brushed hub motor, why?

Hi,

I'm experiencing an odd issue with my no-name brushed hub motor ebike. I was running it full throttle up hill and after about 2 minutes I noticed that in a single rotation of the wheel I was only getting power for about 20% of the rotation. When riding it will surge power on and off as the wheel rotates. What could be causing this partial failure? I'm mostly just trying to understand the problem, I've already decided this is not nearly enough power for me, but that's a separate posting ;-)

Ken68
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Re: partially dead brushed hub motor, why?

It could be a few things;

- check the wiring connections to the motor and make sure all wiring connections are properly connected
- disassemble your motor and check and clean the brushes and the commutator
- some of the windings on the rotor may have failed, replace the rotor if it is damaged
- some of the magnets may have been overheated and lost some of their magnetism, this would make the motor lose power on that side of the motor, replace the magnets if possible or replace the motor

Good luck in troubleshooting your E-Bike, I hope this helps you.

Thanks,
Ken Finch

aaronski
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Re: partially dead brushed hub motor, why?

Thanks Ken, I'll check just as you suggested. The way it failed makes me think winding or commutator/brushes. The power was uneven, I let it cool off and it totally tanked on me. I'll disassemble tomorrow and take a closer look. Comparing my motor to the pictures on the forum really shows that mine is el-cheapo. Live, learn and upgrade I guess.

Ken68
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Re: partially dead brushed hub motor, why?

You are welcome and good luck.

Thanks,
Ken Finch

aaronski
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Re: partially dead brushed hub motor, why?

Hi Ken,

Thanks for your advice, all fixed. It looks like the brush(actually a carbon rod) on the positive side is half the length of the negative side and not coming into contact with the commutator. I stretched the spring that pushes it up so it would have full contact as a temp fix. Is there someplace to get replacement brushes for a no name motor? Also, is it normal for the motor to smell horribly like burnt plastic, look like crap and have bits of solder floating around everywhere in it, or do i have a crap motor? This was all well and good for learning, but I'm thinking a BMC geared hub motor is in my future.

Thanks!
Aaronski

Ken68
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Re: partially dead brushed hub motor, why?

Do not get mad at me, but no it should not have a burnt smell or have solder all over it. That is a definite sign the motor has been severely overheated and really on it's last legs. Even if you replace the brushes the motor still will not run properly and will not last too long at all. My suggestion is toss it and buy a nice brushless controller and a nice brushless motor. Brushless motors do not have any brushes at all. The only moving part inside the motor is the sealed bearings on each side of the motor case supporting the rotor, and those bearings usually last the lifetime of the motor with no maintenance required, just use the motor and that is it. Plus brushless motors are a lot more efficient then brushed motors which means you get more range out of your batteries.

Thanks,
Ken Finch

Ken68
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Last seen: 6 years 3 months ago
Joined: Tuesday, August 5, 2008 - 12:37
Points: 138
Re: partially dead brushed hub motor, why?

Do not get mad at me, but no it should not have a burnt smell or have solder all over it. That is a definite sign the motor has been severely overheated and really on it's last legs. Even if you replace the brushes the motor will not run properly and will not last too long at all. My suggestion is toss it and by a nice brushless controller and a nice brushless motor. Brushless motors do not have any brushes at all. The only moving part inside the motor is the sealed bearings on each side of the motor case supporting the rotor, and those bearings usually last the lifetime of the motor with no maintenance required, just use the motor and that is it. Plus brushless motors are a lot more efficient then brushed motors which means you get more range out of your batteries.

Thanks,
Ken Finch

mf70
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Re: partially dead brushed hub motor, why?

That's a heavily overloaded motor. Before you put effort into fixing it, read:

http://visforvoltage.org/forum/6623-looking-replacement-brushes.

Brush motor technology isn't ~bad~, but there are real limits to their power, and real steps to be followed in rebuilding them.

aaronski
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Re: partially dead brushed hub motor, why?

Whole kit has been replaced by a 600w BMC kit and 48v Lifepo. Much much better. I'm trying to adapt the brushed kit for my wife's bike which only goes 10 miles a year. ;-)

james joule
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Re: partially dead brushed hub motor, why?

Hi do you want to sell the burned out motor , cheers james

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