Pls help identify this motor/how many magnets?

Twistgripper

100 mW
Joined
Sep 20, 2019
Messages
35
A rather uncommon chinese fat ebike came into my hands.

It has a 750 or 1000w rated motor (not sure which) and a S900 display. When in throttle "on" mode, the display shows "8" in the error field - the manual says hall error - check hall sensor. It wont display speed either. It pulls strong and will take off from a dead stop.

I don't know if the S900 was programmed correctly, so i wanted to try that first rather than pulling the rear wheel and opening the motor (I'd need to buy a gear puller too first i guess).

Problem is, I need to program in the number of motor magnets into the s900 display.

Is there a way to determine the # of magnets without pulling the motor apart?

attached are some pics of the motor. The manufacturer of the bike (Sobowo on alibaba) shows bikes with several different motors so I have no way of knowing what this is. There is a number etched on the motor: ZC61010310 - maybe someone knows a bit about these?

Side question: how do i find out the real power of this motor without doing a dyno test?
 

Attachments

  • IMG_20200618_004327 (Medium).jpg
    IMG_20200618_004327 (Medium).jpg
    86.5 KB · Views: 6,250
  • IMG_20200618_004247 (Medium).jpg
    IMG_20200618_004247 (Medium).jpg
    89.3 KB · Views: 6,251
  • IMG_20200618_004406 (Medium).jpg
    IMG_20200618_004406 (Medium).jpg
    83.9 KB · Views: 6,251
  • IMG_20200608_173540 (Medium).jpg
    IMG_20200608_173540 (Medium).jpg
    62.9 KB · Views: 6,251
  • IMG_20200618_004358 (Medium).jpg
    IMG_20200618_004358 (Medium).jpg
    42.3 KB · Views: 6,250
  • IMG_20200618_004335 (Medium).jpg
    IMG_20200618_004335 (Medium).jpg
    34.8 KB · Views: 6,250
Twistgripper said:
Is there a way to determine the # of magnets without pulling the motor apart?
This should work:
https://endless-sphere.com/forums/viewtopic.php?f=2&t=102547&p=1499942&hilit=how+many+poles#p1499942
 
As far as power, it's a little murky. These brushless motors are popular for several reasons, and one reason is that they are tolerant of a wide range of voltages...while being aware that the higher voltages provide a higher RPM. 48V, 52V 60V and 72V seem to be fairly common.

The biggest limiting factor seems to be how much heat is generated, and how much heat can the motor tolerate. I'd advise adding a temp sensor and keeping the stator at 140F for long life, though most hubmotors have gotten much hotter than that and survived.

A major heat generator is how many amps you are using. The controller settings can limit the max amps for safety. Also...if you have long up hills, then even a modest amount of amps can overheat the controller and hubmotor.

If you live on flat land, like a beach community, you can use a higher max-amp setting for better acceleration. This is because you will only be accelerating for a few moments, and all the components have a chance to cool off during the cruise-phase.

If you want to find the power limits of this motor, the best addition is ferro fluid, which helps to transfer stator heat to the aluminum side plates.
 
Motor power is normally related to its weight. Copper weight of course, but overall motor weight is a good indicator of stator size and fill.
 
amberwolf said:
Twistgripper said:
Is there a way to determine the # of magnets without pulling the motor apart?
This should work:
https://endless-sphere.com/forums/viewtopic.php?f=2&t=102547&p=1499942&hilit=how+many+poles#p1499942

"rotating the motor once and counting the pulses out of either a phase or hall signal wire."

if that's what you are referring to - not sure how to measure this with my meter...its not a sophisticated model so trying to count pulses could be difficult...
 
spinningmagnets said:
If you want to find the power limits of this motor, the best addition is ferro fluid, which helps to transfer stator heat to the aluminum side plates.

That sounds like fun, but i'm not really wanting to push the limits, more was just wondering what the general rating originally was to give me a ballpark idea what it is capable of. based on size, and the fact it pulled me up to 40-45kph on throttle only on a heavy fat bike I think its reasonable to assume it is "750-1000w" for all that means...
 
The diameter and width of the stator is the most often used method to determine the power range of a hubmotor. The common direct-drive hubmotor has a 205mm diameter stator with a 28mm width, and they are generally rated for 1,000W peaks.

These typically have 0.50mm thick stator laminations, and they put out a certain amount of waste-heat. If your hubmotor has the upgraded thinner laminations, it can take more amps, because the eddy-current waste-heat from the laminations will be lower.
 
You could count the pulses with this
https://em3ev.com/shop/ebike-tester/

Or hook up your dmm to a hall sensor and count the spikes.

maybe one of these can show you how to hook it up a dmm to a hall sensor without opening up the motor to count the spikes/pulses.
https://www.ebikes.ca/learn/troubleshooting.html
 
Twistgripper said:
if that's what you are referring to - not sure how to measure this with my meter...its not a sophisticated model so trying to count pulses could be difficult...
Literally just count the number of times, in one wheel rotation (turned by hand), that the meter changes from 0v to 5v, if measuring a hall signal. Start with the valve stem completely at the bottom, straght up, and then stop when it is back at teh same position again.
 
It's almost surely a 46 magnet motor, which has become the standard for that diameter direct drive hubmotor made in China.
 
I just discovered an easy way to count the magnets.

1. Disconnect the battery so there is no possibility of blowing your controller.
2. Short out two phases of the motor. (If you short all three this will not work)
3. Turn the wheel slowly and you will feel it cogging. Just count the times you feel it cogging for one rotation.
4. REMOVE THE SHORT BEFORE TESTING AGAIN!!!!!

I have a Voilamart 1500W motor with a serial number very similar to the OP's and I counted 46 "cogs" this way so it sounds like 46 is correct
 
Back
Top