BLDC hub motor troubleshooting guide

I haven’t posted for quite a while, and have been quite busy lately. The exams came, as usual I screwed them and life began again. But as the musical gods said,

It was dark all around
There was frost in the ground
When the tigers broke free

The problems were there to stay. My Singapore intern got cancelled, owing to the recently fractured ankle of the professor I was dealing with. Manchester United screwed up its Champions League spot and as time went on, AGV’s BLDC hub motor got haywire.

bldchub

So the last three days were spent running around the area (Read Kolaghat, Keshiary, Kolkata and Kharagpur) in order to get it back up and running. Although I was mildly successful, I learnt lot of tricks of the trade, and am writing this to share this with you.

This article deals with the generic BLDC hub motors which are usually made in China and are meant to be fitted on electronic bikes. I am listing down various things that I learnt from the experience, not in any specific order.

Removing the glue between the wheel and winding assembly

Use Alcohol or any alcohol based solvent to remove the glue between the wheel frame and the shaft winding assembly. The glue is pretty hard and it is pretty tough to separate the two without removing the two first. The two entities are held by strong magnets as well as the glue, and a combination of the two is virtually inseparable. Use a hard toothbrush or something similar to rub the junction with alcohol and the glue would slowly start to come apart. I used Dettol 😛

Caution. The magnets are pretty damn strong

Once the glue is completely removed, it takes a lot of strong strikes on a hard ground to make the assembly “pop out”. Also while putting it back in place, ensure that no delicate item, including your fingers are not in the way. It can be a pretty bad time for your indices that way.

Checking the motor driver

Short only the stator wires one by one, and try to apply an analog voltage using the throttle or some other source. A correct motor driver is indicated by the motor going completely in braking position.

Checking the hall effect sensors.

bike_hall

Take the probes of your multimeter in short test mode. A correct hall effect sensor wire should not be shorted to either ground or 5V wire. A value in the range of 500 to 2000 should be displayed on the screen with probes between the wire and ground.

Replacing a broken sensor

Carefully tap the top of the sensor with a screwdriver and a hammer. It should pop out with a few good strikes. Carefully desolder the sensor using a desolder wick or a desolder pump. Don’t forget to note the polarities and the direction, and carefully solder a replacement one back in place. It can be a tough task if the sensors are on a PCB, try to get an expert do it.

 

 

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