TSDZ2B intermittent assist cut-out

[ebike_builder]

Hi -- I have built my wife an e-mtb using the TSDZ2b mid-drive motor with 860c display and OSF software. It has developed a problem where the assist randomly cuts out (display stays on). Initially I thought it might be related to overheating since we have had very hot weather here. When the assist cuts out, powering off/on the display will bring the assist back. This used to happen only infrequently, but today (temps in the low 70s) it must have happened 15-20 times in an hour ride. Very frustrating. Note that there is no temperature sensor so although it kind of behaves like thermal throttling, that shouldn't occur w/o temp sensor. The only thing different about today's ride was that the battery only was charged to 40% to start the ride and gradually decreased to 30% by the end. It did seem as though the lower the remaining charge, the more frequent the assist cut-out. I felt the motor and it was just barely warm to the touch.

The battery is a Hailong 52v 13ah

Looking for troubleshooting ideas and possible causes of this behavior.

Thanks in advance,
--peter

 

[cultRider]

Before you go into the weeds ...
Check that the speed sensor has not rotated away from the magnet mounted on the spokes. It's been my experience that when this happens the assist will disappear, then reappear, then disappear, then reappear ... and on and on. Just rotating the pickup back into alignment with the magnet resolves the issue.

 

[ebike_builder]

Before you go into the weeds ...
Check that the speed sensor has not rotated away from the magnet mounted on the spokes. It's been my experience that when this happens the assist will disappear, then reappear, then disappear, then reappear ... and on and on. Just rotating the pickup back into alignment with the magnet resolves the issue.

@cultRider -- thank you so much for your simple suggestion! I just checked the speed sensor and found it noticeably misaligned by 40-50mm. Without your idea, I would have never thought to check that. Charging the battery now and will go for a long test ride. Will report back after.

 

[Zambam]

Experiment with different alignment between magnet and sensor. Too close is not good. I've found a slight offset (as in pic) gives a better signal.

 

[ebike_builder]

@cultRider -- thank you so much for your simple suggestion! I just checked the speed sensor and found it noticeably misaligned by 40-50mm. Without your idea, I would have never thought to check that. Charging the battery now and will go for a long test ride. Will report back after.

I am happy to report that realigning the speed sensor fixed the motor cut-out issue. Thanks again to @cultRider. BTW I aligned the magnet with the arrow (no offset needed).

 

[ebike_builder]

I am happy to report that realigning the speed sensor fixed the motor cut-out issue. Thanks again to @cultRider. BTW I aligned the magnet with the arrow (no offset needed).

Further update: my wife went on a 15mi ride and found the occasionally the power still went out (nowhere nearly as much as before though). She discovered that using the throttle would always work and then powering off/on would restore normal PAS. So at this point I am thinking there may be an intermittent problem with the torque sensor. I'm pretty sure that the throttle does not need the torque sensor to work.

Wondering what could make the torque sensor stop working, but always start back up after a power off/on. Any ideas? I suppose I could test by trying the magnet alignment suggested by @Zambam.

 

[Zambam]

The speed sensor on my TSDZ2 was not happy if the gap between it and the magnet was closer than 15 mm or so. Try experimenting with that also. Other things to check is the battery setup menu. Is everything set properly?

 

[ebike_builder]

The speed sensor on my TSDZ2 was not happy if the gap between it and the magnet was closer than 15 mm or so. Try experimenting with that also. Other things to check is the battery setup menu. Is everything set properly?

View attachment 359364

I checked the gap for the magnet -- it was approximately 10.2mm. Interestingly enough Tongsheng recommends making this gap 10mm.

I have the 860c display with OSF version V20.1C.4-2 installed. There is no "Battery Setup" menu, but instead here is the "Battery" settings page. My battery is a 52v 13ah Hailong

Note: I checked the speed sensor connection and noticed a very slim amount of yellow showing. After reseating it, there is no longer any yellow visible.

Headed out for another test ride. I will leave the 10.2mm gap to the magnet for now. BTW I have purchased a set of pedal extenders, but will only use the lefthand one to hopefully further prevent accidentally kicking the left chainstay with my heel. Picture attached also.

 

[ebike_builder]

Update: pedal extender was a big improvement in left side Q-factor. Test ride had a 1000ft climb (avg 7% grade). Made it to the top of the climb (only in assist level 1) with no drop-outs. Then turned off assist for ride down. About 1/2mi after turning assist back on, assist cut out. Checked speed sensor alignment -- fine. Powered off/on and assist was back for the remainder of the ride.

At this point I am starting to wonder if it is possible for a speed sensor to be faulty. Seems unlikely since it is such a simple device. Another thought: somehow (bumpy road perhaps) the rear wheel momentarily moves closer than the the 10mm spacing to the speed sensor. So I am thinking of increasing the gap (by rotating the speed sensor) to make it a few mm larger.

Does anyone think it is possible that something as simple as a speed sensor could be faulty?

 

[Zambam]

Have you tried increasing current to max for your motor?

 

[ebike_builder]

Have you tried increasing current to max for your motor?

No I haven't. I have the max set to 10a as suggested by the OSF guide (see screenshot)Do you think I should raise it? If so, that seems counter-intuitive since the cut-off always occurs at very modest power levels.