What controller to use with a modified bionx motor?

munlagoon

1 µW
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May 5, 2021
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Hi everyone,

I've recently got my hands on a decent ebike with a bionx motor. The thing was a great bargain because the LCD screen is missing so you can't actually use the motor. I'd like to keep the bicycle as it is, wire an external controller to the bionx motor and use the existing battery to start with. I'm not after an increase in power, just salvaging the bike and using it as is. I'm more interested in long term durability and ease of maintenance. Although I enjoy DIYing, so I'm happy to try doing things myself.

Now I've seen that modifying these bionx motors to work with external controllers is a popular thing to do. Also seems easier than trying to hunt down a working bionx screen, and I'll get the bonus of being able to use whatever battery I want in the future.

I've read through the forums her a bit, and checked out the nicely done video from grin tech https://youtube.com/watch?v=Wc8OJtFRUng
I've currently gotten the motor out of the wheel, and next step will be pulling it apart and checking out what's on the inside.

I wanted to ask what's a good controller to use? I've got another ebike which I built from a leafbike 500w geared hub kit, which comes with a KT controller I believe. Would this be a good choice for a controller? I guess the bare minimum is a controller with has the brake cutoff inputs and Hall sensor inputs. Having some wires for connecting the lights and being able to turn them on from the ebike controls is nice too.

What about the battery, will this also need taking apart and removing the proprietary bionx parts?

I've attached some pictures of the motor for reference.

Thanks for any tips!
 

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There is the possibility to run the motor with the original (very good, especially at regen) BionX controller via the 'BMT'.
https://github.com/stancecoke/BionX_Minimal_Translator

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BMT PCBs are available at the German forum:
https://www.pedelecforum.de/forum/index.php?threads/bmt-bionx-motor-mit-no-name-akku-und-kunteng-display-betreiben.79599/post-1493208

index.php


The original battery will not work without proper CAN bus communications.

regards
stancecoke
 
Also note that some bionx systems use an 11S battery instead of the usual 10S or 13S.
The motor is pressed together so it's not easy to disassemble.
First you will need to unspoke it before you can open it.
Another thing you have with those bionx systems is that the battery is not having any balance wires. They just charge the battery and hope the cells stay balanced.
Some of the batteries are a real pita to open. The cells are glued to the battery case real hard
The motors seem to be real robust and the system was state of the art some years ago as it had a torque measuring sensor embedded in the motor.
 
Thanks for your answers!

stancecoke: Thank you for the link to the thread on pedelec, will need to go through what is discussed there in more detail. You say the original controller is good, espcially at regen breaking. Are there other ways in which in it would be better than a standard KT controller?

obcd, stancecoke: What would you recommend to do for the battery? Ideally, I would take it apart, test the cells 1-by-1, replace dead ones, install a proper BMS with balancing, and assemble the entire thing. I'd need to get or build a spot welder, get some proper nickel strips, and do some more reading/research on battery building in general, and bionx battery refurb specifically. I've never done battery work, but I'd be happy to try my hand at it. From what I've read, you do need to take your time, be careful, and understand what you're doing. Otherwise, you can set things on fire.
What do you think, go the DIY route or is there an off the shelf battery replacement I can get?
 
munlagoon said:
it would be better than a standard KT controller?
The Kunteng Controller has really poor hardware componets. It can't do real FOC. I have a 6FET Kunteng (with open source firmware) in combination with a BionX IGH3 on one of my bikes. It works, but has vibrations at a small speed range from 12 - 14 kph.
So not really satisfying...
The original controller works worlds better and you don't have to open the motor housing. If you want to use an external controller, I recommend a Lishui FOC-Controller like this:
https://www.aliexpress.com/item/1005002711701202.html

munlagoon said:
What would you recommend to do for the battery?
Just try to sell the original BionX battery and buy a new "no name" battery like this one.
It is not worth the tinkering with replacing cells and attaching a new BMS...
Used BionX batteries are rare and expensive...

regards
stancecoke
 
Thanks for the tips.
Indeed, if the battery sells for as much as the ebay link you sent, then getting a new one will avoid me rebuilding the current bionx one.

I have some questions left about the general setup though.
- From looking through the BMT github it seems it's also possible to run lights from the battery, is that correct?
- What about setting different motor assist levels and a speed limit?
- Finally, is there also an odometer in this setup?

I may need to go ahead and order the blue pill board as well as the other parts :)
Regen breaking would be awesome, don't have it on my current ebike.
 
munlagoon said:
From looking through the BMT github it seems it's also possible to run lights from the battery, is that correct?
you can switch the lights with the Kunteng display, but I don't remember, if we have we have implemented a switched pin on the BMT PCB for enabling an DC/DC converter for the light supply.

munlagoon said:
What about setting different motor assist levels and a speed limit?
Levels can be set by the Kunteng Display of course, changing the speed limit is not implemented so far.

munlagoon said:
Finally, is there also an odometer in this setup?
the odometer is a integral part of the Kunteng Display.

regards
stancecoke
 
Thanks for the answers!
Quite an impressive project I have to say. I'm sure many BionX owners are happy that you made effort of sharing it with the community.
Ah, I forgot to ask about break cutoffs, does the motor stop when you apply the brake? Or does this not matter with the torque sensor?

What do you mean by the BMT PCB? Is it the one shown under the blue pill board in this picture: https://www.pedelecforum.de/forum/index.php?attachments/1606056574976-png.353572/
What's on this board? Is it basically the 12V and 5V step downs + the CAN controller put into one board for a neater package? What are the parts you recommend getting then?

Thanks
 
munlagoon said:
Ah, I forgot to ask about break cutoffs, does the motor stop when you apply the brake?

The brake lever activates regen.

munlagoon said:
What do you mean by the BMT PCB?
Yes, the green PCB. You can get it from @reinosmart at the german forum. I guess, he has some in spare.
The necessary parts are listed in the BOM at reichelt.de.
I've just added this infos at the github wiki.

Of course, you can put all single components on a perfboard also....

regards
stancecoke

Pinout BMT.JPG
 
Hello stancecoke,

is your solution working with the original CANBus display provided by BionX?
If not, is there any reason why you didn't make it compatible?

thank you
 
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