No power assist (G330.350)

[Bli99!]

Hi folks (sorry for the spelling)

On my 4-5 trip on my bike, suddenly the power assist stopped. No errors in the display (DPC-18)
I have one time earlier had the error 21 (speed sensor) after a twig bumped the sensor out off position.
so in my error log I have one error 21.
Walk assist is ok
Speed sensor on back wheel ok


After some time surfing the forums after similar symptoms, but can’t find any similarity’s.

I have tried to test the sensors.
- discontent the speed sensor on the rear wheel
- if I ride the bike I am not getting the error
- if I activate the walk assist I get the error 21.
- disconnect the 2 connectors under the controller box for the torque/speed sensor inn the crank.
- no error if I ride the bike or use the walk assist.

how can I test if I have a faulty controller or the torque/speed sensor in the crank.
can’t find any wiring diagram for he controller or crank sensors
I have the tools and some knowledge to test the controllers.
But like to have the wiring diagram on hand so I don’t burn something.


Yes I have warranty, but the shop is a long way and have no workshop.
If I can narrow the problem to one thing, it’s easier for me to contact my seller or bye change it myself.

 

[Dewey]

Here's the manual http://www.cr-service.se/E-FLY/Bafang/Max Drive System User Manual.pdf Note the motor appears to be known by 3 names: M400, Max, and G33.350
Error 21 is a speed sensor issue, page 32 shows the speed sensor assembly.
I have a BBS01 and on that design one time the speed sensor cable wrapped around the kickstand and I tore it out of the controller. I was able to continue to ride it for a couple months before I replaced the controller, during that time while the display would quickly shut off it would stay on long enough for me to change PAS level. Your motor also uses a torque sensor, so it may need continuous input from both the torque and speed sensors. If your bike is still under warranty, the selling shop or bike brand should be able to supply you with a code to download and use the Bafang BESST remote diagnostic tool so you can plug in your bike to a computer and have the problem assessed by a technician at Bafang's EU customer service center in Wijchen, Netherlands, http://www.bafang-e.com/en/oem-area/service/after-sales-support/, they can mail you the speed sensor or controller or whatever parts you need.

 

[eyvind123]

Bli99!, did you ever find out what the problem was? You see, I have a similar problem.
If anyone else has any input, please feel free to speak out! Any help would be much appreciated.
I bought a bike knowing it wouldn't turn on. I checked the display using an external power source and it worked. Then I bought a new controller and the display now works. Speed sensor works, and walk assist works. I also tested the torque sensor using the programming tool with continous torque readouts and confirmed the values were changing(but the idle value was 7XXmV, is this correct?).
So, were to go on from here? There are three connectors between the controller and the motor. One round, large plug that I'm guessing is power? Two smaller ones which I assume is torque sensor and temperature, am I right? Does anyone have an idea of what is wrong?

 

[willpage]

I had this problem start 2 days ago.

Riding along the flat the assist dropped out. I stopped and turned the bike off and on again, removed and replaced the battery, eventually got it going. However at the end of my ride there's a hill and while it managed to provide full boost up there, it felt like sort of surging.

Next morning nothing. Zero assist, but walk mode works. I don't have throttle but I expect it would work too. Speed sensor works, brake sensors normal, no reason it should not be assisting and there is no error code or wrench icon.

Anyway, found this YouTube vid:

It's only 2 weeks old, and someone commented asking how to diagnose. The channel admin has replied saying if you have no assist but the ratchet is good then 99% it's the torque sensor.

On that basis I ordered one from the same people who make the video, just over US$100.

If I had the problem just 2 weeks ago I would not have found this video so the timing is good. There isn't a lot of service info for these motors online.

I'll report back if it solves the issue.

 

[eyvind123]

I ended up buying a new motor and it worked, for a while.. I have now a new motor, new controller and a new display. It worked fine and I put the bike outdoor where the other bikes are. One day I was going to use it and it did not work, same issue as before(only walk assist works). Now I have no clue to what this could be. I guess I will have to change the wiring to the display and maybe change the speed sensor(but the display shows a speed). After this, the only thing left is the battery, but since it is only connected with the power leads it should be OK.

 

[willpage]

The part finally arrived from China and I fitted it today. Taking apart the motor it became clear what the cause of the problem is.

The rust is from the steel springs on the ratchet, but it's obvious water has got in.

I ride this bike to work every day rain or shine, a little over an hour round trip. I've concluded this motor is not really suitable for this type of use and maybe I should use my road bike in the rain and the ebike only while dry from now until I sell it and get something more water resistant.

This might explain your problem too eyvind123.

Anyway, new sensor fitted and everything is working as expected.

 

[willpage]

I thought I should tear down the old torque sensor to see how it works and if there's any chance of finding out exactly how it failed.

Looks like it's mostly electronic. There's a circuit board in potting compound on the outside, connected to an aluminium ring, with nothing going through the casing.

Inside on the shaft there's a steel strip with chevron patterns engraved on it.

I expect the aluminum ring on the outside contains a hall effect sensor and the change in the magnetic field as the steel inner strip distorts or changes its position relative to the casing when torque force is applied is picked up by that.

On mine the chevrons are dirty with old grease but I'm not convinced that's the issue.

Next I'll tear down the outer casing further...

 

[cencen]

Hi Willpage, I am a new member from Holland. I have the same torque sensor problem with Bafang M400. I plan to tear down the sensor and try to repair the sensor electronics. You mentioned that you will tear down the outer casing. Could you do that? I would like to know about your experiences.
Best Regards
Cencen

 

[willpage]

There's no way you can service the torque sensor. I didn't post any photos because the electronics is just a tiny IC surrounded in potting compound. It was impossible to get in without destroying it.

 

[cencen]

I was slightly hopeful about it but now its all clear. Thanks anyway for your reply, really appreciated. I will order a new one from China and with curiosity tear down the faulty one and see how it looks like.