Help! How to use a 48V battery on 43V M600? Would a TVD diode work?

[big4x4]

Over the last few months, I have purchased parts for 2 m600 builds since I sold my bafang ultra bikes. Had the frames, components, motor sitting but just got the 48V batteries in so started putting everything together. I finally had everything buttoned up and turned it on just to get an Error 07 on both bikes. Should have checked the motors they clearly say 43V I know I don't have to charge the batteries fully and it can still work, but that is not ideal for the batteries and system performance.

I did purchase the right motors but the seller on alibaba won't respond back since it had been months so I am kind of stuck and definitely don't want to drop more money into new motors.

On my bafang ultra, I did modify the main wiring harness with a TVS diode so I could run higher voltage without any issues (15S battery) and that worked with no problems. I decided to try my luck on the M600 but even with the proper diode inline on P+ from the display, it is still getting error 07.

I am decently proficient with soldering and electronics so I am willing to try to get these guys working. If someone helps me get these working, I'll send you a $50 amazon giftcard lol

 

[larsb]

I don’t know the m600 system but i’d say no, it won’t work. I guess error 07 is an overvoltage error and to drop the voltage (by any means) is not a good idea since it will burn off power you could use.

What should work is to update the firmware:
https://endless-sphere.com/forums/viewtopic.php?t=100777&start=400

I din’t read the entire thread but if you use the 48v firmware then system should be matched again.

 

[big4x4]

A diode will consume less than 5W so the loss is negligible. The problem is finding the correct place to put it.

Flashing the system might work but doing the diode is only a few cents

 

[Chalo]

A diode will consume less than 5W so the loss is negligible. The problem is finding the correct place to put it.

Flashing the system might work but doing the diode is only a few cents

You're barking up the wrong tree. You can't regulate voltage that way. If you don't believe me, try it and see. Post video.

You could use a giant buck converter, but that's a pretty lame and inefficient solution.

 

[big4x4]

A diode will consume less than 5W so the loss is negligible. The problem is finding the correct place to put it.

Flashing the system might work but doing the diode is only a few cents

You're barking up the wrong tree. You can't regulate voltage that way. If you don't believe me, try it and see. Post video.

You could use a giant buck converter, but that's a pretty lame and inefficient solution.

Gotcha. I'm curious though, why does the TVS diode on the ultra motor work just fine?

 

[Chalo]

A diode will consume less than 5W so the loss is negligible. The problem is finding the correct place to put it.

You're barking up the wrong tree. You can't regulate voltage that way. If you don't believe me, try it and see. Post video.

Gotcha. I'm curious though, why does the TVS diode on the ultra motor work just fine?

It doesn't. Probably the Ultra motor doesn't care what voltage you send it. A diode can only lower voltage by the amount of its Vf, which for most diodes is in the 0.5V to 1.1V range. The catch is that any given current, the diode must dissipate Vf *I watts. If the TVS diode is dumping 5V at 30A, that's 150 watts of heat that have to go somewhere.

 

[SUPERJC]

A diode will consume less than 5W so the loss is negligible. The problem is finding the correct place to put it.

You're barking up the wrong tree. You can't regulate voltage that way. If you don't believe me, try it and see. Post video.

Gotcha. I'm curious though, why does the TVS diode on the ultra motor work just fine?

It doesn't. Probably the Ultra motor doesn't care what voltage you send it. A diode can only lower voltage by the amount of its Vf, which for most diodes is in the 0.5V to 1.1V range. The catch is that any given current, the diode must dissipate Vf *I watts. If the TVS diode is dumping 5V at 30A, that's 150 watts of heat that have to go somewhere.

Diode for BBSxx (0x07 High voltage protection)
On my bafang BBSxx I have been using this principle for several years
The zener diode must be in series in the P+ wire of the return from the display to the controller
The return current P+ to the controller is very low (about 50mA)
The measurement is mistaken because it is made on this P+ auxiliary input instead of the power wires
different voltage Zener Diode:
https://www.mouser.fr/c/?q=BZX85C

I'm not sure you can do that on the M600 because the schematic is different

 

[Chalo]

So you're spoofing the controller into reading a lower voltage, and not dumping input power to the controller? I guess I don't understand what's going on.