Question About a Noisy Hub Motor

[Ch00paKabrA]

Hello, My project is finally done (I think) but there is one issue.

Upon start up, the hub motor is very noisy at part throttle but atfull throttle (after it gets to about 10 mph), it quiets down to near silence.

It is a mini hub motor, either Bafang or Tonxin (I am not really sure) 36V 250W.

When I wired the sensors, blue went to blue and yellow and green cross. With no load it was silent but with my fat arse on it, it makes a loud sound for the first few seconds of full throttle and a continuous sound at part throttle.

I only hooked up 2 of my fat packs 2.0ah each for the test ride.

Could it be that I need more AH or is it possibly the cheap ass china throttle, or maybe something else.

I would like to be able to ride it along side a friend who doesnt have an electric bike at slow speeds without waking up the neighbor hood.

Any suggestion or input will be welcomed.

Thank you.

 

[electr0n]

This could be an issue specific to the geared motors, maybe the clutch? I don't have any experience with the geared motors so I'll let someone else make suggestions in that area. Other than that you could check and make sure all your connections are secure. Having one of the wires loose on the hall can cause a rough noise and a bit of a jerky start that gets better as the wheel speeds up. It's unlikely to be the throttle or battery.

 

[dogman dan]

Few hubmotors are completely silent. Very often there is a grunting like sound produced when starting up, when the load is heaviest. In a gear motor, there may also be louder gear sounds at start up. It can vary a lot, even with identical motors. Some will grunt more than others. It shouldn't be loud enough to wake the neighborhood, but noticeable is normal.

As long as it's not super loud, or continuous at all loads, I wouldn't fret too much. That's assuming you don't have jerky running, or using more amps than normal when running no load. You could still have the wrong combo.

Check for bearing play also, if you have the right combo. occasionally a defect there lets motors rub inside if loose enough.

 

[John in CR]

Especially if you are large it's good to help small motors with some pedal assist on takeoffs. It relieves a lot of stress on the system, reduces motor noise, reduces heat, and improves range, because every start from a full stop begins at 0% efficiency. Plus our legs and bicycle gearing are best suited for short bursts of torque, so if you aren't going to pedal much, pedaling during takeoff is the best time.

Just to be sure the wiring is correct, check the no-load current, which will be low if it is correct. Another good indicator is quiet startup no load, but doing so advancing the throttle very slowly.

You mention "waking up the neighborhood", which definitely doesn't sound right. Even noisy hubmotors are pretty quiet.

John

 

[Ch00paKabrA]

Thanks, the wiring is definitely correct. I made a list of all possible combinations and this is the only one that ran nicely - most did not turn at all.

you hit the nail on the head when you described it as "grunting" that is exactly how it sounds. This issue is that unless the bike is at full throttle and "at speed" the grunting is continuous.

I think I will open it up and take a look inside to make sure everything is lubed up and working correctly. I was hoping that it was something very specific that was common but I guess not.

I will also try it with more batteries to see if that makes a difference.

It was really nice though at full throttle. Here at the Jersey shore, it is as flat as a pancake so I got excellent range - almost 2 miles per amphour with very little pedaling if any.

Last question.

I can get 36v 3ah batteries for about $120. I can also get 40v 4ah batteries for the same price. Can I run the 40 volt batteries on my 36 volt system without frying anything?

 

[dogman dan]

Should be able to run at least 50v fully charged through a 36v controller, if it has 50v capacitors inside. Many have 63v capacitors, making "48v" charged to 60v also possible.

So your "40v" battery is likely ok, I bet they charge to about 50v. "36v" generally charges to about 42-44v.

Sounds to me like your motor is grunting normally. It's the switching of the coils between the three phases you are hearing. At low rpms, it makes a grunting noise that goes away as the load diminishes and the switching increases in speed. At speed, on a steep enough hill, you will hear it then going faster.

Some motors are just noisy, and some grunt more with one battery than with another.