Two Magic Pie 5 motors has a same failure.

[Vanarebane]

Hello! I need advice!
Within a couple of weeks I have already broken 2 motors - the rear Magic Pie 5 and then the new front wheel Magic Pie 5.
They failed in the same way - I started driving and then after intensive braking the power disappeared and the motor no longer worked. After that, the wheel is difficult to push by hand.
I read from this forum that it refers to controller malfunction.
Recently my lithium ion battery BMS (20AH, 48V) was replaced because it left the battery too low and it didn't start charging. Can it somehow affect the engine controller, or are the motor settings wrong and braking will cause an overload?
Since the engine has no power, I can't see what settings I had. I created this table from memory, as I remember.
What can cause these failures and how can I avoid these things in the future? It's a bit too expensive to learn it in such a way.

[Bikemad]

Hi Vanarebane,

Unfortunately, I think your BMS may be causing the failure of the controllers. 

And I suspect that the 5A Maximum Continuous Charge Current setting is what's causing the problem.

Intensive braking will produce a lot more than 5A of current and I suspect that the BMS is suddenly disconnecting the battery from the controller while it is still under high current regen. This sudden disconnection can cause an instant voltage surge which can instantly exceed the safe working voltage for the controller's MOSFETs, causing one or more of them to fail.

Disabling the regen altogether may help to prevent further controllers from being damaged.

Alan
 

[Vanarebane]

Thank you very much Alan! 
So as I understand I must disable "Regen braking enable" option from Speedometer app after installing a new controller and thats it?
Should I also do something with battery BMS controller? Isn't it suitable for this battery, because before I had "Regen braking enable"

[Bikemad]

If you had Regen Braking enabled with a different BMS without experiencing problems, then it must be due to differences in the BMS, and the battery must be capable of accepting the regen current.

It might be possible to add a suitable 30A diode between the P- and B- terminals to allow regen current to reach the battery even if the new BMS is trying to prevent it:



I presume that the battery power would be re enabled as soon as the speed slowed down sufficiently to reduce the charging current passing through the BMS. But with a diode fitted, it is also possible that there may not be sufficient current returning through the BMS to actually trigger the BMS to cut out in the first place. 

Adding a suitable diode should allow regenerative braking to be used just as it was before. 

Alan
 

[Vanarebane]

Thanks again for the smart advice!

[Vanarebane]

I replaced the new controllers for both motors, switched off regenerative braking and got them to work. Thanks to Alan! 
Now for the future, which parameters the 48V battery should have for safe Magic Pie5 regenerative braking?

[Bikemad]

If your battery's BMS is unable to accept all the current from the regen, then regen should be left disabled.

I would not recommend gradually increasing the regen current to see what the battery's BMS can handle, because the controller is likely to fail when the amount of regen becomes too much causing the BMS to instantly disconnect the battery. 

I mainly use homemade LiPo battery packs (without any BMS) that can easily accept all of the regen current that the Magic Pie produces, and I therefore have my regen set to the maximum to provide greater stopping power under regen which significantly extends the life of the mechanical brake pads. 

Alan
 

[Tommycat]

I'm curious of the new BMS verses the old one...  Did you replace? Is it an exact replacement? Does it have an individual charging wire connection? (C-)
Do you have the specifications of the new BMS if different from the OEM one? Possible link...


Regards,
T.C.

[Vanarebane]

I'm curious of the new BMS verses the old one...  Did you replace? Is it an exact replacement? Does it have an individual charging wire connection? (C-)
Do you have the specifications of the new BMS if different from the OEM one? Possible link...


Regards,
T.C.

Unfortunately, I can't answer that, because I didn't change BMS myself and I don't have old one anymore.
I only know that old BMS was able to handle regenerative braking.

[Tommycat]

Who changed the Battery Management System?   

Thanks for the IOS update information BTW. Still a ways to go though eh?

[Vanarebane]

Who changed the Battery Management System?   

It was a local company that deals with the restoration of the batteries.

[Tommycat]

Would not this professional company be directly responsible for ruining two controllers by not properly matching the replacement battery management system? And leaving you stuck with out being able to safely use regen. I'd be a bit upset and certainly bring it to their attention.   

Unless of course if it's owned by your father in law...   

[Vanarebane]

I haven't much places to choose where to order such a job.
Repair of electric bike battery is not their main job and apparently they didn't know all options that this controller and MP5 motor have.
In fact, this BMS works, but it's too defensive over battery.
At least for now, I know what causes motor controller failure. In the future, I intend to buy a battery that will enable regenerative braking again.