BionX Torque Sensor Help Needed

pdxperson

1 µW
Joined
May 19, 2019
Messages
2
Hi,

I have an older(circa 2012) what I think is an 350 PL-350 system. The battery has 350 HT L written on it.

The boost isn't working the way that it did originally. We used it heavily for the first 5 years with about 1k a year on it, but then it let it sit for the past year. The battery was pretty worn down so I just got it refurbished and have been trying to get the bike back up and running the way I remember it.

The problem is that it doesn't boost while riding. The thumb throttle still works great, but the pedal boost doesn't seem to kick in. I've tried playing around with the sensor signal (1234), sensor gain (007) and extra assistance (008). But nothing gets it back to where I remember it being.

I took the computer off and swapped it with another bike that rides that way I remember my bike riding and my computer on the other bike is fine. The other bike computer on my bike doesn't improve anything.

This is to say that I think it it's the strain gauge/torque sensor that is bad. I put it in diagnostics mode (3772) and stood on the pedal, but the reading didn't change from 004002. Sometimes when I get off of the pedal the first 2 digits jump around a bit, going up in the teens maybe? If I ride it around a little I can see that it sometimes gives boost right when starting pedaling hard and the numbers jump all around. I thought the first 2 numbers were boost and the last 2 were a reading of the gauge. I also don't see the strain gauge reading on the panel change, except sometimes when starting off, when it will go up for a few seconds and then drop off.

Is there anything else I can do short of disassembling the wheel and replacing the sensor? Did I misconfigure something? When you program the console do the settings live with the console? Or are they programmed into the hub? Should I look for a new rear wheel?
 
In BionX motors a common problem is the strain gauge sensor detaching from the axle. When this happens you'll either get no output signal, a very weak one, or a sporadic one. It very much looks like this is what happened here.

Unfortunately there's no easy fix. If you want to get it working again, there are ways to reattach the sensor, but this involves delacing the wheel, opening the motor, and working on small parts with some precision and care required.

It's easier to simply swap out the wheel with a functional one. You can occasionally find used ones on Ebay and such for acceptable money.
 
Thanks for the info. That failure mode seems to line up with what I am observing.

I'm a little concerned about buying a used one if this is a common occurrence. There doesn't seem to be a way to verify before buying.

I've seen some of the posts on splitting the case. It appears within my skill set to do. Can the strain gauge be reattached? If not, do you have a part number for a replacement?
 
The sensor is glued onto the axle, and both sensor and axle need to be perfectly flat before doing so. You'll need to buy a new sensor (peanuts), cut out the old sensor, clean and smooth the axle flat, solder the new sensor to the cable (taking care not to damage the sensitive leads), then carefully glue it onto the flat.

I'm sure someone on ES has documented it at some point. However I'm only aware of German documentations. You can try Google Translate to see if they make sense to you:

http://www.weiszhar.com/Home/Bionx_DMS.html

https://www.pedelecforum.de/forum/index.php?threads/sos-dehnmessstreifen-retten.23723/#post-334138

https://www.pedelecforum.de/forum/index.php?threads/versuche-defekten-dehnme%C3%9Fstreifen-zu-ersetzen.37663/
 
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