Magic Pie 4 won't react to thumb throttle

[Speedsterharry]

Hi All,

I was a happy MP4 user up to now, for around 1 year. My kit was used primarily for going to work. One day, I went to work without any worries and at the end of the day, I noticed that the MP4 wouldn't react to thumb throttle (strictly no reaction), although the battery had more than enough energy to move a bit (48V 10Ah LifePO4). I had to go back home on foot  and use the train that day (very frustrating time for me). The motor showed resistance when forced to rotate.

The few tests I've done until now: Battery works great as far as I know (plugged a 60W light bulb and the filament would glow). Charger would charge the battery if asked to. The brakes have variable resistance depending on lever position. The 3 LED gauge shows 3 lit LEDs. I don't know what else to do.

I stumbled upon a topic on endless sphere showing exactly the same symptoms, so I suspect this is a problem with the controller MOSFETs, although I didn't experience any loss of power during my 600 meter uphill trip (just before failure). The failure was so unexpected I thought someone vandalised my setup (could a MOSFET fail at rest, is this possible Even after some kind of effort ?).

I'm ready to change the MOSFETs myself, but first: Are the IRF3077 mosfet the best to have in the MP4 these days, for a sub 60V battery ? If there's anything better, I'm ready to try that instead.

If the MOSFETs are not guilty, what else to try ? Is there anywhere to buy a MP4 controller ? I read that this version of the MP was discontinued ....

Thanks in advance
Jerome

EDIT: I can still access the controller settings thru USB-cable and Windows XP machine, via the Vector software

[Bikemad]

Hi Jerome andto the forum.

If the wheel can be rotated relatively easily at a very slow speed, but becomes very difficult to turn at normal speeds (almost impossible to pedal normally) then it does sound like one or more of the MOSFETs will have failed in a closed circuit state.

To check this you will need to remove the controller and disconnect the three phase wires, and make sure the connectors cannot touch each other, and you should find that the wheel will spin more easily again if it was failed MOSFETs.

I haven't actually tried, but I imagine it could be difficult to gain access to the FETS, due to the way the controller's PCBs are completely sealed into the cast aluminium heatsink/controller housing.

If the MP4 controller is no longer available, the standard MP5 controller or Bluetooth upgrade kit can be used instead.
However, you may also need to change the connectors on the Hall sensors and phase wires if they are not the same.

Also, if you were using a BAC-601 Smart Display unit with the MP4, I don't know whether it will still work with the MP5 controller. 

Alan
 

[Speedsterharry]

 Hi Alan,

I'm glad this forum is still active, thanks Alan for your help !

I can indeed rotate the wheel very slowly, but not really pedal, including when going downhill.

I understand I can barely do anything from the outside of the wheel, and I'm ready to open the latter. Meanwhile, I ordered a set of 6 IR4030 Mosfets instead of the (apparently) usual 3077s. The allowed voltage is higher but the RDSon too (meaning more heat will be dissipated I fear :/ ).
What if I parallel the new IR4030s over the still-good 3077s, since they are pin-to-pin compatible, ie gate to Gate, Drain to Drain, Source to Source ? Is there a risk for the motor, the controller, the mosfets or me (I'm no electronician so bear with me) ?

I didn't know one could upgrade the controller to that of the MP5, glad to know that. I will try this if all else fails.

I have the BAC-601 display at home but removed it because I feel it's not useful enough (battery levels are for Li-Ion, I'm on Lifepo4) and there's no display for cumulative energy dissipated by the motor (which would be extremely useful to know the real battery capacity - too bad GM didn't think about this option !).

Thanks for those PRECIOUS infos, Alan, they will be put to good use. I'll report back here when I have something new from my side.

[Speedsterharry]

OK, I opened the motor wheel. The controller is accessible from the side opposite of the freewheel.
I had a hard time opening the flask on the controller side until I followed Alan's advice

However, the controller components are made completely closed to any replacement (a very sad thing). I tried cancelling my purchase of TO220 mosfets because there's very little hope I'll be able to install those in the MP4 controller (that and the Mosfet format is probably not TO220 anyway). Checked the official Golden Motor web site for a stand alone MP5 controller to buy.... nothing. Only available on GM Canada, damn it.

From now on, I don't know if I should order a new controller from GM Canada (which is going to take ages) or try something with my fried controller...

Meanwhile, I'll have to use the car to go to work 

Open to ideas   

[Speedsterharry]

Another view from the freewheel side. The trap was used to hide a few cables, and not the controller ...

[Speedsterharry]

A view from the controller. The screws and most components are covered with a transparent silicon thing, probably to prevent moisture damaging components or copper tracks. I couldn't inspect the mosfets since I found the screws are freely rotating 

[Asterix]

aren't the mosfets on the opposite side of the controlers board of the last picture?

[Speedsterharry]

@asterix: probably so, but like I said in my post, I can't unscrew the board from the heatsink, so couldn't access the mosfets. I think I need to drill the screws from the outside if I want to go further.
The IR4030s order couldn't be cancelled, unfortunately for me ....

Also, I tried disconnecting the phase wires and one of them had the quick disconnect "parting" the wire. Seeing that, I started the soldering iron and prepared a new round quick disconnect, which I planned to solder to the wire for better mechanical stability. I held great hope that this could be the root of my problem ... but no actually :/

[Asterix]

did you unscrew the big green blue and yellow wires and test them for continuity?
if you remove the battery and slowly move the wheel, is there power produced at motor power supply?

[Speedsterharry]

@asterix: I'm unsure where I should test for continuity (between which points exactly ?). As for your other suggestion (hadn't think about it, good idea), the motor wheel is still not reinstalled on the bike because I changed my mind: I ordered the MP5 controller on Golden Motor Canada and will resume repair when I get the part. Thanks !

[Asterix]

there are 3 big wires: green , blue yellow. Those wires are maintained through black screws that can be seen at your picture of the controler.
I do not know exactly what should be measured (I haven't open my Magic Pie, but your post is at least interesting for this purpose, thanks for sharing that info), but I could imagine that those 3 wires are connected to the copper wires of the wheel border (near to the magnets). If those wires are big, it means that big current is supposed to flow through them, so this means that their resistance must be low. So you should measure a low resistance between green and blue, but also blue and yellow. May be if you do not measure a low resistance, it means that a wire is broken somewhere. So this could help traking where to search about broken wires.

[Speedsterharry]

I'm about to get the new MP5 controller from GM Canada, probably tomorrow (having something delivered by UPS is such a pain though - you cannot really choose the rendez-vous date/time). Also, the customs tax will be around 40 EUR. I have no other choice though....

On the troubleshooting front, the wheel definitely exhibits a resistive behaviour (switching between smooth and resistive), so I presume some mosfets are really dead. But since I cannot access them, why bother  I contacted the seller of my MP kit, and he said GM could do a part exchange for the controller. Will take ages though, but better than nothing.

I have another problem when trying to fit the wheel in the bike frame: the axle is now out of shape after my various attempts at opening the flasks. What are my options on this issue ? Thanks

@asterix: I will make the measurements when the controller is out from the wheel again and report back.

[Speedsterharry]

Small update:

I got the thread of my axle rectified by a professionnal (because it got damage when I used the hammer to open the flasks). I tried replacing the controller, however the new controller isn't directly compatible with the new MP5: the new connector needs 4.8 mm quick disconnects instead of hollow, round disconnects than get screwed on the controller. Plus, and this is more annoying, the hall sensors connector is not the same between the MP4 and MP5 (see picture)

I changed the phase wires to quick disconnects, assuming the colors were the same with the new controller and let the hall sensors connector loose inside the wheel (I think the GM controllers work sensorless if the hall sensors are shot). When the system is under voltage and I push the thumb throttle, the wheel produces a slight hum but no movement occurs. I tried giving a little nudge to the wheel but still no movement....  (the wheel rotates with difficulty, even without controller and battery attached, I hope I didn't damage the mechanics of the wheel)

EDIT: Tried another time to remove the dead MP4 controller from housing to access MOSFET for testing/replacing purpose but no luck. I managed to removed the screws that I thought were maintaining the PCB to the housing but it's not enough. Damn it, I *hate* when companies make such decisions 

I measured the resistance between all phase wires: about 30k whatever the colors. Strange ...

[Asterix]

( (the wheel rotates with difficulty, even without controller and battery attached, I hope I didn't damage the mechanics of the wheel)

does the wheel also rotate with difficulty if it is not screwed on the bike?

I measured the resistance between all phase wires: about 30k whatever the colors. Strange ...

30KOhms ? Is it stable value and identical value if you change the colors of the wires? Are you sure of your measurement instrument?
Normally those wires go directly to the big copper wires, so how is this possible to put some amperes inside 30k ?
I would first try to follow those color wires and make a measurement with a needle on the copper wires (afterwards you can always put some glue on it).

[Asterix]

one other measurement to be done: the resistance between each color wire and the wheel itself (mass). I suppose it should be infinite (wires isolated from mass).

What happens if you rotate the wheel slowly without any battery: is there some voltage produced at power supply wires black and red?