Magic Pie II lost power

[Frogyt]

Hello all,

I bought a second hand Magic Pie about an year ago and have used it with no problem. About a week ago I changed the bearings, because they were worn. In order of that I had to solder off all the wires of the controller. I did it, changed the bearings and soldered back all the wires at the place they were before. I put the motor on the bike and noticed that the power was less.. Even the top speed (when the wheel is off the ground) was  with 4 km lower. I connected the motor to my PC and verified that all the settings were the way they were before...
Why did this happen? What can I do to have the same fantastic torque I had before?

Thanks everyone in advance!
PS: If you need any further explanations, please ask me.

[Ernie_13]

I was able to change bearings on my MP3 and MP2 without cutting off the cables. Anyway, it looks that problem must be in that soldering. I would check all the connections again and check or re-make soldering connections.

[Frogyt]

Hello,

I checked all the soldering connections and they all look good. I will remake them again and see what happens..
Also I noticed that the battery goes flat after less kilometers..

Thank you!

[Bikemad]

Hi andto the forum Frogyt.

Is the wheel lumpier to turn now compared to what it was like before? If so, you might have a similar problem to the one I experienced here:

I then carried on and refitted the stator back into the wheel. I decided to check that the motor was turning freely before fitting the wheel back on the bike. I placed a 10mm spanner on the axle flats and was disappointed to find that the shuddering was still there, meaning that the stator had to be removed again to find the cause.

I rechecked the resistance between all six of the MOSFETs and each of the phase wires and could not find a problem.

I decided that the only other thing that would cause the juddering would be a short between two of the windings. I measured the resistance between all three windings and discovered a very low resistance between the blue and yellow phase wires. Assuming that the problem was somewhere in the windings, I unsoldered the phase leads from the controller and rechecked their resistances. All three sets of windings had the same resistance with no sign of a short, so I turned my attention to the controller.
When I checked the resistance between the three phase wire contacts, I confirmed that the short was between the blue and yellow contacts on the circuit board and not the windings.
I looked very closely between the tracks on the circuit board, but could not see anything amiss. I then unsoldered the two thick battery wires and removed the three screws holding the controller onto the heatsink and turned it over to inspect the other side.
I then noticed that some solder had somehow run across the gap between the blue and yellow tracks, this was quickly removed with the soldering iron and everything was reassembled and rechecked.

It's possible that you may have a partial short circuit between the soldered connections so have a really good look with a magnifying glass to make sure that there is a clear gap between each of the phase wire soldered joints and any adjacent contact areas on the PCB (including the common ground track immediately below the three phase wire connections).

If solder has flowed across a gap between the tracks of the PCB and but has not made a good contact with the other track, it might still have a low enough resistance to cause the reduced motor performance and increased battery consumption.

Alan
 

[Frogyt]

Hi Alan and thank you for welcoming me to the forum!

I will use a magnifying glass and see what happens and let you know!
I hope I find the problem.

Regards
Nicolas