Slow, noisy brushed hub motor

[fizzit]

Hey guys,
I am helping a friend rebuild an electric scooter. He got it from someone for free, because apparently they were riding it one day and it just "stopped working". It sat for a long time and the lead batteries died, so we recently set to work replacing them with a large quantity of Turnigy LiPo. Today, we hooked up some of the batteries for a test run and were disappointed to see that the rear wheel was spinning very slowly and making a strange noise.

The scooter is an Evader scooter. Apparently they were made for a few years in Bellevue, WA. It has a 48V 1000W brushed hub motor and controller that I haven't been able to find any information about on the internet.

Here's a video of the noise that I'm talking about. The throttle is being held wide open, and we were measuring about 20A and 46V from the battery. On the motor output of the controller, however, there was only about 16V DC. We're not sure if this is because the controller is limiting the current, or because there is some problem with the controller.

[youtube]9p156ALXvmU[/youtube]

The motor spins freely when you turn it by hand, with little cogging, so it doesn't seem likely that it's a bad bearing.
Any tips or ideas would be appreciated. Thanks!

 

[ian.mich]

Likely a busted sensor and/or busted controller. I suggest getting an ebike tester, replacing the controller with a higher power model if possible, and upgrade as much wiring as you can.

 

[fizzit]

Actually, the motor is brushed. The controller seems to be doing okay, it PWMs the motor just fine, doesn't get warm or anything. We were thinking that one of the brushes might be busted, but I don't have much experience with hub motors or brushed motors, so I don't know what the symptoms are. The wiring looks pretty good to me - the battery and motor wires seem to be at least 10 AWG.

 

[amberwolf]

It could be a dry bearing, or one with dirt in it that has damaged the balls.

It could also be a commutator segment that has come loose inside the motor, so it sticks up and is hitting the brush each time. If so, eventually it will get quieter and quieter as it gouges out the brushes as it passes them, and builds up carbon like a ramp on the leading face of the comm segment--or it will pull the whole segment out completely and the motor will stop working.


It oculd also be a burned winding, so that when it passes that one no new field is created, and the other collapsing fields and momentum keep the motor rotating past that point. If this is the case, it's possible taht if you rotate it manually to each "cogging" point, mark that point so you can see which ones you've tested, then try starting the motor with the throttle, it will not start from the open winding position(s), but will from all the others.


Could be other things, but I'd check those first.

 

[e-beach]

I googled "Evader scooter replacement parts" and got this place. Maybe they know something. Could be worth a phone call to ask them what's up.

http://www.gekgo.com/evader-parts.html

BTW..Was the video shot in 3D?

 

[fizzit]

@amberwolf Thanks, those all definitely sound like possible problems. Except I'm not so sure about the bearing being bad. The motor turned very smoothly.

@e-beach That place (MC scooters) is actually where we got a replacement dashboard for the scooter. It seems that they just have a lot of parts, and don't know a lot about the actual workings of the scooter
The video was indeed shot in 3D. My phone has a 3D camera and screen, so I take a lot of 3D photos of my bike. Sadly there is almost no one for me to share them with!

 

[John in CR]

With the wheel off the ground try running the motor directly from batteries. Start with low voltage first. That should tell you whether there's a motor problem or if the controller is limiting it.

 

[e-beach]

Also, don't forget to test your throttle to make sure it is giving you a variable voltage. I don't know what color your wire would be, green or grey maybe, but if the motor runs smoothly after you test it like John in CR said, test your throttle. If the motor is ok, and the throttle is ok, and all your wiring is good, it is probably the controller.

my 2¢

 

[fizzit]

Thanks for the tips, John and e-beach. The owner told me that he had already hooked the motor up directly to the old lead batteries, and it did the same thing whether or not the controller was in-line. I think that he is going to buy a three jaw puller and try to get the hub apart to check it out, before he pays an electric motor shop to do it.
Unfortunately a replacement motor is around $350, so it would probably make more sense to replace it with something brushless if it's really dead.

 

[e-beach]

Thanks for the tips, John and e-beach. The owner told me that he had already hooked the motor up directly to the old lead batteries, and it did the same thing whether or not the controller was in-line. I think that he is going to buy a three jaw puller and try to get the hub apart to check it out, before he pays an electric motor shop to do it. Unfortunately a replacement motor is around $350, so it would probably make more sense to replace it with something brushless if it's really dead.

If the motor is making the noise when running on batteries only then you may have two problems. One in the motor itself and the other in that you only got 16v from the controller.

When you friend opens the motor have him do it carefully as the brushes are spring loaded and he will need to make sure nothing goes flying across the room and get lost.

Can you friend take some pictures of the operation and post them?