Panasonic motor short circuit - Kalkhoff Agattu

[Oliver]

Hi there,

I am coming here because of issues with a Kalkhoff Agattu bike from 2012.
The bike was bought late 2012, pretty standard Agattu with a Panasonic motor.

Just after 2 years of use (end therefor the end of the warranty) I started to have issues with the bike. The battery did not work well anymore. I got the battery connections changed (about 150 euros..) and it worked again. About a year later I got a new issue, the motor gave up... Had to change it = 400 euros.
Got my bike back and tried it, the battery was dead... the shop did not test it so I went back and they gave me a new one.
Finally I could use my bike again, but now after 50 km the motor gave up again...

I kept the old one, so I opened it and here is what I found:
http://www.hostingpics.net/viewer.php?id=914300IMG1401.jpg
Looks like it has heated up a great deal... I suspect a short circuit? The red wire was all burnt and desoldered.

My question is: Had anyone had a similar problem before? I gave the bike back so it is checked but I suspect a similar issue on the motor (Same symptoms). I am now a bit frustrated with Panasonic motors!

I know now that Kalkhoff have discontinued the Panasonic motors and are using their own Impulse motor or Bosch. Maybe there is a reason why Panasonic went out and I am paying the price.

Hope somebody has some feedback on this.
Enjoy the weekend!
Oliver

 

[flecc]

Hi Oliver. I run a Panasonic unit support site and get to hear of most things that crop up, but this fault is a first so I've no idea what could have happened. I'm aware of the burnt battery contacts issue and there's a fix to prevent it on my site

In fact both series of the Panasonic crank units have been very reliable and continue to be so. In contrast the second version of the Impulse unit has been repeatedly failing so much that the makers have been forced to renew the two year warranty every time a motor is changed, and Bosch had several problems following their unit's introduction

The reasons the Panasonic unit was dropped were partly nationalism of the part of the German bike makers when the Bosch unit became available, partly that the Bosch unit was a more powerful 36 volt unit and partly that the prices of the Panasonic units were higher. Panasonic belatedly issued upgraded 36 volt units but too late to recover their former position in the European market.

Here's a link to my support website:

http://www.flecc.uk/p/panindex.html
.

 

[Oliver]

Hi Flecc, thanks for your answer and all the good info in it.
I found your website earlier and had a look at it but I did not find any info regarding my issue so I guessed it was not a common problem.

I am still not sure what happened but I will get some more info from the new motor that gave up and see if it is the same issue or another.

On your website you detail the different cables, but what are these red, black and white cables going to the motor? Are they Active, Neutral and Earth? When I tested with the multimeter I could not verify this.
Or are these linked to the 3 gears?
Do you by any chance know that?

Thanks for the help!

 

[flecc]

On your website you detail the different cables, but what are these red, black and white cables going to the motor? Are they Active, Neutral and Earth? When I tested with the multimeter I could not verify this.

They feed the three sets of phase coils, all doing the same job. It's the same sort of brushless motor that's used in most e-bike systems. Basically the controller feeds a high speed sequence of current pulses to each wire in turn, making the motor rotate.

Your motor has a magnetic rotor with North and South poles, surrounded by the coils in the stator which receive those current pulses. On another of my e-bike support sites I have an animation showing how that works. If you click on the right hand blue arrow of "Step Through Animation" below the motor diagram, it will change to red and the rotor stops spinning. Then each time you click the red arrow the motor will make one step, allowing you to track and understand how the sequence drives the rotor.

On the left of the motor diagram you'll see the controller's decoding citcuit diagram and above it the on-off steps of the current to each phase, showing the degrees of rotation, again in diagram form. The H1, H2, and H3 are the three colour wires and the pairs that light up are those connected by a current in each step. When only one H is lit, that's the current off between pulses.

Though it all looks a bit complicated at first, by following the colour coded steps you'll be able to understand how the system works. There's further in-depth explanation below the diagram. Here's the link to that animation:

http://www.flecc.uk/t/brushless_motor.html
.

 

[Oliver]

ah ha! This is great! I did not know how these motors worked. Nice to learn these things. Thanks!

Funny that one of these 3 completely overheated!

I will see what info I get back from the new motor. Had to give it to the shop beforeI can get it back and open it to make sure I do not infringe the warranty... I'll come back with more info once I open it.

 

[flecc]

ah ha! This is great! I did not know how these motors worked. Nice to learn these things. Thanks!

Funny that one of these 3 completely overheated!

I will see what info I get back from the new motor. Had to give it to the shop beforeI can get it back and open it to make sure I do not infringe the warranty... I'll come back with more info once I open it.

Thanks Oliver. It sounds like one of the stator coils short circuited internally. That could cause a sudden excess current flow, burning out the wire and probably also blowing the circuit board mosfets that feed the current.

It's quite a job pulling the rotor out of the stator of the motor due to the strength of the magnets, but there's advice on doing that on my web site page below. Even once the rotor is out you may not see much since the stator coils are fully encapsulated in black plastic, but there may be evidence of a burn on the plastic. Here's the page link:

http://www.flecc.uk/p/motorfreewheelrepair.html#bookmark2
.

 

[Oliver]

Yes! I took the rotor out of the stator when opening it. I was uncertain if the plastic was melted or not. I could see the stator coils in some places and other places there was still plastic. Looked melted to me but I was not sure.

Is it supposed to cover completely the stator coils? I can check if I have a picture of it.

 

[flecc]

Yes! I took the rotor out of the stator when opening it. I was uncertain if the plastic was melted or not. I could see the stator coils in some places and other places there was still plastic. Looked melted to me but I was not sure.

Is it supposed to cover completely the stator coils? I can check if I have a picture of it.

It's normal for there to be traces of the stator coils showing, you can see that at between 1 and 2 o'clock in the open motor illustration on that web page last shown above. I daresay the amount showing will vary since the stator parts are obviously very close to the surface.
.

 

[Oliver]

Hmmm ok thanks, I need to take a better look at it first. Anyway I will wait for info on the newer motor. Thanks for the help so far!

 

[Oliver]

I checked the motor, it is difficult to say if it looks like this from manufacturing or wearing or something else... it looks quite inconsistent.
https://postimg.org/image/owabxd3sr
https://postimg.org/image/6ur6zk9rv

Anyway I will get a new motor under the warranty, but I will try to see if I can get the motor back (not sure as they take it under warranty this time). If not I will ask the store to check what the issue is if they are ok opening it.
We will see what they say.

 

[flecc]

That looks quite normal Oliver, a litle more metal exposure than most but that surface layer of black plastic over the metal poles is always wafer thin and variable. I daresay the design doesn't include any plastic over them but there's inevitably some seepage in the mould and it can't affect performance.
.

 

[Oliver]

OK thanks a lot for your help. Hope I will get some feedback regarding the new motor that broke. I'll keep you posted if I do, could be interesting for somebody finding a similar issue.