Help: e-Bike making noise with throttle

[ABTsportsline]

Hello everyone,

I'm stumped as to the issue with my e-bike conversion. When I give it either near full-throttle or any throttle under load, it makes a loud resonant frequency-type hum across the entire bike chassis. I've reached out to the kit manufacturer and after some back-and-forth with descriptions of the issues, they think the problem is with my bike. Whatever it is, I can't figure it out so I come to you.

I have an e-bike kit with a rear-wheel 350w gear-drive, controller, and LCD screen. I'm using a healthy 48v Ping LiFePO4 that reads > 53v during my testing. The kit only has about 25 miles on it and was installed on a brand new bicycle I purchased in August of 2013. The setup worked fine last summer, but I later moved (and then a cold & wet winter) has seen the bike shelved for the last several months. In the meantime, the battery has been kept indoors and checked/maintained every month.

This problem started after I pulled the bike out for the first time in 3 months. A rare nice day gave me the opportunity to go for a ride again, but the trip was short-lived. After a minute of riding, the kit completely cut out. When I got home I unplugged everything & re-attached all connections. The system came back to life, but made a loud noise. If I give partial throttle with no load (i.e. with the rear wheel elevated in the garage as in the video), the wheel turns fine. If i give more than ~65% throttle I get a loud hum. If I give any amount of throttle under load (i.e. when I'm riding the bike), it makes the loud noise. I've unplugged everything and re-attached, double-checking all connections.

I have made a video of the bike & noise: http://youtu.be/VOimXqEG8b8

Nothing has been added or modified on the bike since it's last use, and nothing is visibly changed from what I can tell. Nothing appears obviously loose. I've scanned all bolts nuts around the bike but nothing seems to be loose or shaking. Unfortunately my technical & troubleshooting background is not robust enough to go beyond here.

What should I try next? Thanks!

 

[Tench]

That sounds like the gears in the motor to me, it could just be that they need lubricating?

 

[amberwolf]

The two things I've heard before that sound like that are misalignment of bearings or gears in various kinds of motors--something rubbing that shouldn't. Sometimes it's not misalignment, but just lack of lubricant.

If the brake shoes on the wheel are rubbing because of wheel wobble/rim untrueness, it could also make certain noises at certain speeds.

However, you state that it makes that sound under *any* load, which implies it's in the motor itself.


If you want to eliminate the bike from the equation, take the motor off the bike, clamp it's axle flats in the jaws of a vise that's securely bolted to a worktable or other fixed surface, hold the wheel lightly with gloved hands to provide a teeny bit of load and give it slight throttle.

If it requires mroe than just "any" load to cause the problem, or higher speeds, I recommend putting it in two vises one on each end of the axle so you don't have to worry about it flying across the room after it wiggles loose.


EDIT: Oh, and I've also heard something similar from sensored motors/controllers when it's the wrong combo or a hall is either not working or has a connection problem somewhere.

 

[d8veh]

When you had the connection fault and gave it full throttle, you can damage the controller (FETs) like that, which is probably what's happened. One of the FETs is probably breaking down under load, which causes the sound and vibration that you've got. These type of problems feel and sound mechanical, but their cause is normally electrical.

 

[SamRich]

Hi I watched your video (which BTW is great way to troubleshoot problem!) and I think I had the similar issue recently....It would make that noise when close to full throttle, but also at very low speed under load when riding but once I got going fast enough everything was fine. My "solution" was to use a different controller (even if it was rated for a lower voltage and amperage than the original) and the problem was gone. I'll probably have to buy another controller with the right voltage rating. I still don't understood what was wrong but it must have been with the controller...but not 100% sure.
Good luck

 

[ABTsportsline]

Thank you everyone, I appreciate the replies.

The motor and controller are part of an overall kit from e-bikekit.com, it wasn't something I pieced together. I wouldn't be against upgrading the controller if that's what it took to fix the issue but customization would be venturing beyond my knowledge level (I'm still new to this stuff and it's the reason I went with a kit.)

The kit manufacturer tells me the culprit is likely something else on the bike. But I gave it a test ride without turning on the assist system and the bike did not make the noise. It only makes the noise when I use the assist. That's why I was thinking what you guys were suggesting. But I guess I'm misunderstanding what's wrong.

I think I will seek a local bike shop to figure this out. This has been a frustrating experience.

 

[lotrwiz]

I had like, exactly the same problem, look through my threads to see the description and video, the problem turned out to be a blown controller due to water getting in.