Motor Noise Normal?

[xXNuggettXx]

Hello All,
I'm a new eBiker that just "finished" my first build this , week (goodness knows it'll never be truly finished"). My specs are: 9C 2807 rear hub, Lyen 12 FET controller limited to 40A, 12s2p Zippy LiPo pack. All high current carrying cables are 12 AWG with 45A Anderson connectors. Now, it runs like a charm with no rider. It is quiet and fast. However, with a rider the motor makes a high pitched noise at about 10-12 MPH when under hard acceleration. If I left off the throttle or pedal assist the noise goes away. I'm wondering if this is normal for a 9C under heavy load (I'm a relatively big guy, 200+lbs). Any answers would be appreciated.

 

[Icewrench]

9c motors will resonate at different speeds with different controllers.
Mine will humm /buzz @ 17 or 18 mph.

 

[beast775]

my 9c 2806 had a high pitch around 12 mph and it would almost go away if i pedalled or reduced throttle.pretty normal for 9cs.

 

[dogman dan]

Yeah, load up a 9c motor with 2000 watts or more, and they start making a nice ZZZZZT sound under load. Gets quite loud with 24s at 40 amps. Stall one with any level of watts, and they start making grumbly sounds.

 

[xXNuggettXx]

Thanks for the quick replys. I'm glad that it is a normal occurence. I had thought about it being resonance but the noise goes away when crusing at that speed or when pedaling. I hadn't considered resonance of the electrical noise so that could be a definite possibility. I'm a little disappointed though. I was hoping to be a stealth ninja!

 

[dogman dan]

200 watts is pretty stealth. 2000 and up generaly gets noticed one way or another.

 

[wesnewell]

Are you sure it's the motor and not the controller. My GM kit used to whine at top speed. After I removed the controller, shunt modded it for 42A and reinstalled it, the noise was gone.

 

[amberwolf]

Also see here:
http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=21826

 

[ZOMGVTEK]

My GM makes a odd sound right around 1/2 of top speed. That noise used to be there on 48V, and it was at basically half the speed it is now on 100V. It used to be very quiet on 48V, without holes, and the stock 20A current limit. On higher currents, higher voltages, and big holes in the motor, it can be loud under heavy loads.

 

[Eclu Lardbut]

My Conhis 750W makes a noise like an old tramcar at 19mph, but it vanishes at 20. Solution - stay above 20

 

[docnjoj]

Our 9C's make a bit of sizzle but no where near the noise of my old geared Bafang. I consider this a fairly quiet motor but not as quiet as my old C/L brushed motors! I understand the C/L brushless are even quieter.
otherDoc

 

[icecube57]

I had resonance moans and groans with that motor being stock. The drilled covers made it worse. The resonance is normal with those motor. It was really bad on the low end but was quiet on the high end.