Magic Pie 4 Loud noise and strong vibration during acceleration

[lgergo]

Hi!
I have been riding my MP4 bike for about 7 years, and now it started to give very loud noise and vibration.
The problem is not always exists. It comes periodically. When it comes, the only thing that helps is stopping with my bike and start again.
I made a video about it: 
https://drive.google.com/file/d/1BTPrX8vnTq_WWapGMexZXTJD1I21egre/view?usp=sharing
Things that I have done so far:
I opened the controller and checked the 3 hall IC working, disconnected and cleaned the phase wire connectors.
But he problem is still exists. It doesn't help if I switch off/on the battery during the ride!
I can't decide if it is electical or mechanical problem. But I think it must be electrical.
Could you help what can cause this problem? What can I try?

[Bikemad]

Hi andto the forum.

I've not come across that noise before but I also think it is more likely to be an electrical problem than a mechanical one.

If the noise/vibration doesn't occur with a freshly charged battery, it could be the battery's BMS rapidly switching the power On and Off caused by a weak cell (or a group of weak paralleled cells) as the cell voltage drops under load.
As soon as the BMS cuts the voltage, the voltage of the weak cell instantly rises allowing the BMS to supply power again, and I suspect this may be happening at the same frequency as the noise/vibration.

Temporarily connecting a wire between the B- and P- of the BMS should confirm if my suspicions are correct. If the fault disappears, then the fault is either a weak cell/cell group or a faulty BMS.
If the battery is also 7 years old, I think a weak cell/cell group is probably the most likely cause.

However, if the fault still remains with the BMS bypassed, it could be a controller fault, something on the electrical system interfering with the operation of the controller, or perhaps it is a mechanical fault.

I've seen pictures of a cracked stator on an MPII with an external controller but I've not seen this failure on a MP4 and I'm not even sure if it would cause the same noise/vibration, but it might be worth taking a cover off and having a look inside if you can't locate an electrical fault.

Please let us know what the outcome is.

Alan
 

[lgergo]

Hello Alan,

First of all, thank you for your suggestions. Now I think (I hope) I have found the problem!
It was independent of the battery level. Last year I switched to a downtube type battery with built in BMS, so I couldn't test it.
I dismounted the controller again and saw something that I had not noticed before.
At this time, one of the phase stud bolt was loose, and when I unscrewed it from the silicone moulding it was very corroded. See the photos attached.
After cleaning the corrosion I replaced the bolt with a new one then I went for a test round and now it seems good. I hope this was the cause. It will turn out when I go for a longer trip.