Can anyone help re Suzhou Bafang 250 watt humming but not turning the wheel?

[rooel]

I recently had a 250 watt Suzhou Bafang which was in good working order rebuilt into a new rim. Now with everything reconnected when I work the throttle the motor makes a loud humming noise but does not drive the wheel. There is also a much quieter whirring noise inside the hub as though the motor was turning but not driving.

The motor is the Hall effect type: three thick wires, and five thin wires connected to the controller. I have checked all the connections and they seem to be in order, exactly as they were prior to the rebuild, and the same working controller is in use.

The thin wires which enter the motor spindle seem to be intact and probably have not been tugged out of place during the wheel rebuild.

Any suggestions as to what is wrong?

 

[shemozzle999]

I think it is running backwards, activating the freewheel - you need to re-check the phase and hall wires.

What controller and motor version is it?

 

[Deleted member 4366]

Assuming that the colours of your phase wires and halls match, reverse any pair of phase wires and the same to the corresponding pair of hall wires.

Say you reverse green and yellow wires: green will connect with yellow and yellow with green. This means you have to remove two pins from the hall connector and re-insert them. You need a very small screwdriver or darning needle to release the barb to pull the pin out.

All this also assumes that your controller doesn't have a reverse switch.

 

[rooel]

Thanks for your advice. The controller is a Santroll 24 volt date of manufacture 03 2008 Model number WZKD2415KA-QAQ and 022-58218688. All I can say about the motor (as it has lost its label) is that it is a Suzhou Bafang 250 watt 24 volt, brushless with the three thick phase wires and the 5 thin ones. This combination was working fine before the motor wheel had to be sent off for a rebuild, and I have reconnected everything (using the existing connectors which were all intact) in the same way as before, which would make me a bit doubtful about adopting d8veh's suggestion that I reverse some of the wires, but I may try that if all else fails.

 

[Deleted member 4366]

Some controllers have automatic phase sequence identification. I had one start sending the motor backwards before for no apparent reason. There's three possible causes of your problem:
1 Motor running backwards
2 Gears stripped
3 Clutch stuck

2 is unlikely because it can't happen by itself.
3 is possible because it wasn't used for a while, but it requires the motor to be disassembled to fix it, which isn't too hard if you have a side-plate retained by screws.

You should eliminate 1 first, and if it still whirrs with the phase wires reversed, then it's 3. No harm will come from doing that procedure: It only reverses the motor direction.

 

[rooel]

Thanks to the advice about switching round some wires I seem to have solved the problem. I first switched the greens and yellows (phase and Hall) with little effect except that the wheel, while still humming roughly, turned very slowly in reverse. I then had a closer look at the connectors and noted that the Hall wires from the motor had the green connecting to the blue to the controller, and the blue from the motor connecting to the green from the controller. Switching these around had little effect until I remembered that the blue and green phase wires should also be switched. Now I have normal operation again with full fairly quiet power in a forward direction. There is something of a mystery here however. Before the rebuild the motor was working well with the connectors in their original factory supplied configuration. All I did was disconnect to send the motor off to the wheel builder, and then reconnect - I shall be doing some trial runs before taking this bike on holiday!

 

[rooel]

I should add that having lifted the front of the bike and put the motor on full throttle, I find it does seem to be running rather faster than usual, and the phase cables at the controller end are becoming very hot.

 

[rooel]

I have checked the wheel speed and sound against my other ebike which has the very same configuration and the motor wheel turns very much more slowly, therefore still something wrong with the one with the motor wheel rebuild, but at least I now know the motor works.

 

[Deleted member 4366]

I think you have what's known as a false positive. Something is still wrong with your phase/hall connections.

There's 36 combinations. Three will give correct forward motion; three will give reverse motion. Out of those, one might work better than the others; however, one of the wrong combinations can give smooth forward motion , but with massive current, which can be bad for both controller and motor. Sometimes a wrong combination can spin the wheel at 90 mph. These false positives are easier to spot with a wattmeter or ammeter, but hot phase wires is a clear symptom.

You need to have another look at those wires.

 

[rooel]

Thanks, I have disconnected and put all connections back to the original configuration so that the wheel does not turn but the motor makes a loud somewhat rough humming noise. I wonder if in fact the hall connectors have suffered some damage at the motor end.

 

[shemozzle999]

Thanks, I have disconnected and put all connections back to the original configuration so that the wheel does not turn but the motor makes a loud somewhat rough humming noise. I wonder if in fact the hall connectors have suffered some damage at the motor end.

You can check to see if the hall sensors wiring lines are working while in situ, they should switch from 5v to 0v when the rotor magnets pass over them.

Using a multimeter set on the correct dc voltage range insert the negative lead of the meter into the negative wire lead of the hall connector and the positive lead of the meter into one of the hall wire leads of the hall connector.

Switch on the cycle supply and get someone to very slowly rotate the wheel by hand (do not use the throttle) and see if the voltage switches on the meter, repeat the test for the other two hall lines.

If the voltage remains at 5v or 0v it indicates a fault, either in the wiring harness or a duff hall device.

 

[rooel]

Many thanks to shemozzle999 and d8veh for all their advice. However, having discovered that hall sensor motors and controllers have been superseded with more reliable designs (no mosfets), with replacements well nigh impossible to find, I have decided to revert my Dahon Speed TR to human power only. The next question to be answered will be how well my leg muscles can themselves revert to non-assisted pedalling. If they fail I may start saving for a Wisper 806Classic, which seems to have a Dahon or Dahon clone frame, the only folder design I would want.

 

[Deleted member 4366]

Idon't believe that there's anything wrong with your motor, the hall sensors or your controller. It's a simple connection issue. Try pulling the plug on the hall sensors to see if it'll run sensorless. Many controllers do. If it runs backwards like that, you just have to swap any two of the three.

It's not difficult to go through all 36 combinations, but you need to write them down first to make sure that you don't forget where you are.

You can remove all the pins from the motor side hall connector and plug them directly into the other half as long as you make sure that they're making good contact and don't touch each other. This speeds up testing a lot. Choose the smoothest forward normal speed combination.