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Bafang ultra 620 Canbus motor and battery repair.

Mike_vdv

New here
Joined
Dec 27, 2025
Messages
4
Location
Ontario
Cutting to the chase, 2 questions.
1) Where can I get a Battery BMS compatible with Canbus Bafang M620 motor + battery. I believe it communicates with the motor over can bus.
I'm running the motor at 48V 1000W. BMS Is outputting incorrect/reduced voltage, when measured cell voltage shows no issues.
I want to replace the BMS in the battery There are many BMS systems available but none (that I could find) seem to have the comm wires.
Feel free to educate me if this is not needed and why.
Here's a pic of what's in my battery currently if you recognize this I need a few

IMG_4465.jpeg

2) after replacing torque sensor and control board on a broken M620 Canbus motor. I'm struggling with the BESST tool.
I can't compete the calibration step. In generally I struggle with the BESST tool communicating reliably to the motor.
tips tricks or known problems?


Greetings and introductions.
Hi, new to this forum, hope to be a valued contributor, but right now I need a bit of help. Used the search couldn't come up with any similar posts. but read enough to know this is a valuable form where people really know their stuff.

A bit about me.
Long time Mountain bike racer.
Bike mechanic.
Licensed Automotive engineer and technician.
Builder/tinkerer love to fix stuff.
Live in Ontario Canada.

A bit about my bike.
I bought a light carbon LCE18 equipped with a 17.5aH battery and Bafang 620 motor.
IMG_0497.jpeg

I started this as an "electronics project" to learn a bit more about batteries and motors as this will be useful for my role professionally.
Little has been done in the way of "electronics project" I just plugged it in and everything worked. Rode it and started giggling....that feeling doesn't go away.
I chose this bike because it is a long travel full suspension fatbike.

The selection criteria was as follows.
Fat bikes are dumb because they are slow and terrible to pedal.
Full suspension fatbikes are then even slower.
E bikes are evil because they are cheating ;o)
Figured these in combination should offset one another to make something awesome. I was right.

I love it, it's an absolute weapon. I've ridden it for three years and beat the ever living crap out of it.
Frame it built like a baseball bat and I've basically used it as such. Awesome in winter in fat mode and I'll run it with 29 x 3.0 the extra tire volume has saved some rims in summer.

However, having some issues keeping motors and battery packs alive.
I've broken some stuff and now it's project time. I'm 2 motors and 3 batteries in at this point believe they are salvageable but need some help salvaging these.

Any questions on the bike, shoot, I have over 25 years riding high end bikes and travel all over to ride you will get honest, educated and experienced answers.

Any people in the southern Ontario who are experts with Bafang, point me to them.
 
I do not know about M620 CANBus but it looks like M600/500/560/510 motors (which is CANbus too) do not use CAN communication with battery BMS (or can ignore it). You just connect the battery power cables to the motor and that's it (the motor controller measures the battery voltage and determines the battery charge level). Try to connect the battery to the motor and do not connect other cable to the battery and see if it works and if it works you can probably use any BMS.
 
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Thanks I'll give it a go with those wires disconnected.
To do that I need to get a functioning motor.
In order to do that I need BESST tool working
I think the BESST tool is stuck in TEST mode after a recent software update It will no longer communicate.....
BESST software gives the following instructions.

IMG_4511.jpeg

After following instructions and entering serial number, I cannot get update completed.
I emailed address shown. If others have firmware for BESST tool I could try it would be appreciated.

#electronicsprojects ;o)
 
Bafang sent me firmware file based on serial number provided.
BESST tool is working correctly now.

If anyone else has the problem of BESST tool stuck in TEST mode (as shown) it can be corrected.
It should be in "RUN" mode and show can bus communication when working properly.

After firmware file update it allows communication with known good controller, battery and HMI .
IMG_4515.jpeg
 
The version I got from bafang was BESST.UC 3.0.3_BSF33.05
I have replaced a control board (visible damage due to my assembly error)
and torque sensor for this motor

After attempting to calibrate (the motor turned)
I got the message Error code 08 Fault with motor Hall sensor inside.
any known issues with this?

on an m620 Canbus where is the hall sensor?
Stator?
 
I believe CANbus version does not use hall sensor. UART versions do not use it too. They use rotary encoder instead. It is mounted on the bottom PCB of the controller and it senses the magnet mounted on the end of the rotor shaft.

Can you please post the pictures of the battery to motor controller connector on the battery side? Is it 4 positions connector with 2 wires (yellow and green) by chance?

1768887646080.jpeg
 
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