Problems with 902 system

[Tbnrider]

I have 4 bikes equipped with the 36V  PRO 902 motors and speed controllers (ESC)
1.  Lately on one of the bikes each time I turn the power to the ESC, it gives me 2 beeps of the horn.  (It didn't do that before.) 
What is it trying to tell me?
2.  When I start to apply throttle, the motor hesitates and shudders a bit for a second and starts a bit roughly.  Then as more throttle is applied everything runs smoothly.  In case this might be a function of the speed controller, I switched ESC's but It did the same thing.  So I think the problem is in the motor.  It feels as as if the one-way clutch in the motor sticks and hesitates to activate for an instant.  But it seems to be intermittent and sometimes it starts off smoothly, especially if I apply throttle very slowly.
Has anyone else encountered this problem??  Is it likely to be the clutch, or some other problem?  If it is the clutch, are parts available to fix or replace it??

Roy 

[Bikemad]

According to page 18 of the eBike D.I.Y. User Manual 2 beeps indicate a hall sensor problem:

2. Motor hall-sensor malfunctions:
When the controller detects a motor hall-sensor failure, it will beep twice before
automatically entering into sensor-independent control mode. Twist/press the
throttle to run the motor and pedal your bike for a push start if the motor does not
operate. (This malfunction seldom happens in a state of sensor-independent
control status)

Start by checking all of your wires and connections coming out of the motor axle for signs of damage, and also check the individual connections for the Hall sensor connectors (both at the motor and the controller) to ensure none of the wires have come loose.

I must have checked the connections a hundred times and never noticed the plug from the wheel with five wires from it had one wire that had somehow slipped around to the outside of the plug.

If it is not a poor Hall sensor connection or a damaged Hall sensor wire outside of the motor, take a look at this post and this video for more details on testing the operation of the hall sensors.
Please note that the minimotors (902) need to be turned very slowly in a reverse direction when checking for variation of the hall sensors' signal voltage.

There's also some more useful information here.

If one (or more) of the Hall sensors are not working, you will have to dismantle the motor to access the Hall sensors.
Honeywell SS41 Hall sensors are commonly used as replacements, and I strongly recommend replacing all three while you have the motor apart.



Take a look at this post for more information on the components within the 902 motor.

The unidirectional clutch is very robust, but if it were to fail, it would either slip (and not allow the motor to drive the wheel) or it could possibly seize up completely (in this case, the motor would be constantly engaged and would behave similar to a direct drive hub motor, but with a fixed gear reduction)

Alan
 

[Tbnrider]

Thank you very much for the detailed explanation and good advice.
I wasn't even aware of the existence of that DIY manual.
I will have a good look at the Hall Effect wiring and sensors.

Roy

[Tbnrider]

I checked the external wiring and connectors carefully but couldn't find any faults

I ran the voltage test on the leads from the Hall Effect sensors and got the following results;
Black to Red.........4.81V
Black to Yellow......4.58V dropping to 0V
Black to Blue ........5V dropping to .01V
Black to Green.......5.1V constant, regardless of shaft position

I guess that means a short in the sensor or somewhere else inside  the hub.??

The question now is; if I continue to use the bike and just put up with the intermittent slight roughness at the start of throttle application until I can get some time to investigate further inside the hub and replace the sensor, WILL I BE DOING THE SYSTEM ANY HARM??

Roy

[Bikemad]

It is either the Green Hall sensor that has failed, or the Green Hall sensor signal wire may have touched against the red +5V supply wire if the motor windings have overheated and melted the insulation on the Hall Sensor wires. 

A break in the signal wire between the Green Hall sensor and the outer connector could also cause the +5V constant reading, as the Hall sensor actually pulls the voltage down to 0V. This might also explain why it is reading 0.29V higher than the red +5V supply.

Unfortunately, you will not know for sure until you open up the motor and take a look inside.

It should be OK running it in sensorless mode, but if you find that occasionally the motor will not start, you might have to turn the wheel backwards slightly to move the motor into a different position where it will hopefully be able to start again. 

Alan
 

[Tbnrider]

Thank you Alan for all your excellent information and advice.

Roy