Magic Pie III renewal = MP3 + VESC

[Sam.Vanratt]

Hi all
three weeks ago my MP3 stopped working (again) as there's no more throttle to get (while the recuperation braking still works). After searching for a replacement controller (and not finding any in the EU) I took today the time to determine what's not working. Of course I tried exchanging the throttle, batteries, unplugging brakes/PAS, to no avail. I measured the voltages on the cables and found that the +5V is not there anymore. Same feature happened on my second MP3 controller (which was exhanged by GM itself in 2013), the other two defectives had other failures.
So I disassembled my wheel (which is very uneasy thanks to the tight slices of my special designed fork) and worked my way up to the MP3 controller. When I last exchanged the controller in mid 2017 I found small amounts of water inside so I changed the seals of my MP3 then. When I opened it this time there was no more corrosion or any water inside despite the fact that it rained for the last weeks and the bike is always outside.
Last time I did the following:
a) the applied silicone to the cable on both sides so it should be more or less airtight
b) the applied very little layer of silicone to the wheel inside and afterwards when closing the controller enclosure
c) I applied assembly paste to the aluminium controller casing (my first exchange of the controller was quite traumatic as i'd not get it open as the paint was not dry while asseembled so it stuck), so there's no more friction and still tightness; the same paste was used for the Phillips screws. I used Weicons Anti-Seize btw.
d) I put bags with silicon salt tabs in the remaining area, so humidity (winter, rain, summer, ice/snow) get sucked up just in case.
e) for the controller to cool better I applied thermally conductive paste to the outer aluminium case so the disc brake helps cooling as well

Three years ago I have to exchange the three bearings (I used SKF ones instead) so with that mechanical preparation I'm very satisfied with GMs great MagicPie product..... if there wasn't the controller!!!

Maybe another one takes advantage of my experience. I'm riding 15.000km each year and have to leave my bike always outside, even for charging and I drive about 270days a year incl. storm, snow, sun, ..... So it's heavy duty. In the 5 years I accumulated about 70.000km so far, had to exchange my tires (Schwalbe Marathon plus touring) four times. The MP3 is worth the pain of the not so perfect controller.
Cheers
Sam

[Bikemad]

Hi Sam,

As the +5V feed is not there anymore, I suspect that the 5V regulator inside the controller has failed, but you may be able to supply a +5V supply externally via the red and black pedelec wires using a suitable DC/DC step down converter adjusted for a 5V output instead.

I would test it first with 3 x 1.5V batteries connected in series, as this should be close enough just to find out if it will work. 

Alan
 

[Sam.Vanratt]

Hi Alan,
I good to read you again (I was abstinent from the GM Forum, since my last controller died (again) nearly two years ago)
I thought about infusing as well, but why patchworking; I'm earning money by using my bike (not for a living, but driving to work instead of a car), so why not investing into it the right amount.
External controller is not what I intended to use when I build this bike (I reported a few times about it), so only the GM MP3 or the BionX P250 where to chosen from.
An external controller now (after four dead controllers) seems so much easier to check, exchange, maintenance. When I first used the fully programmable VESC it was a revelation in itself, so an alternative is now not as bad as when I started in 2011.
I opened a new thread for the BAC controller, as it seems a cheap and an acceptable controller.  I'll order two so I have a unit at spare. Currently no MP3 or BAC is available at the dealers in the EU, and I already contacted Gary to fetch it from him.... after three weeks with no eSupport and only 20kg additional weight I'm feeling really old/exhausted (and very sweaty....) after just 50km (=my single ride to work).
Cheers
Sam

P.S.: I used your pictures of the plugs and throttle tests to find the error; the GM documentation is still very poor for maintenance.

[Sam.Vanratt]

Hi all
I finished my conversion of my MP3 with int. Controller to an VESC external one.

First thing to do was getting the needed cables out. In this stage I exchanged the int. 1,5mm^2 cables to 4mm^2 (all high flex with thin nylon insulation) and used the old HALL connector to adapt a RJ45 cable to it. With the 3 extra wires I integrated a temp sensor (KTY81) and used the last one as shielding for the HALL information.
3*4mm^2 + 8*0,12mm^2 is quite an heavy duty to get into the small openings. Next time I'd choose 2,5mm^2. The cables are insulated with hotglue inside and outside
Wehn closing the inner hub I put some silicon salt pouches into the cavitation so moisture will not corrode everything.
The VESC should be mounted near the hub so the resistance and HALL signal is not deteriorating too much. I used 35cm cable and 25cm from the hub on my fork.
It took quite some time to figure out that the throttle was damaged as well (min. Signal was 2,5V, max 5.0V) and had to be replaced and the VESC is a bit different from signaling than the rest of ESCs. All signals needed to be converted to a 3,3V max. Pullup resistors are needed as analogue signals are wanted on the ADCs instead of digital capable ones.
The VESC works like a charm in FOC mode; the BC mode (BLDC labeled in the Tool) did not work with the wizard and I had to detect the Ri a few times as in 10 measurements I recevied ten wide spread values. I used the middle one which was 86mOhm; L=0,130mH, lambda=23,7mWb; with that and a 11A limit (at 28V) I will start tomorrow the live tests after being 75 days offline (and using a different bike).
My VESC is a SCRAM Board which has a heatsink (essential I think) attached and is more compact. It costed 140EUR which is OK for such a versatile FOC controller. With new brakes and throttle, new wires I paid about 30EUR more.
The Kelly controller I tried as well (did not find the MP3 right settings and I was in a hurry) was a KBS36051X (=BC) and the KLS4812S (FOC) one. The KBS took me too long figuring out the right HALL/phase settings but worked more or less out of the box. There seems to be no special advancement compared to the sure working BAC controller of GM. The KLS took me too long to get working at all, so it went into my storage and I resumed with the VESC.

Tomorrow I'll finish the conversion and my first trial will start.

I'll report back.

Cheers
Sam

[Sam.Vanratt]

The MP3 grew very quiet (min. 10dB less than before; now only a small buzz is to here) with the FOC mode and the overall torque is better than before.
The VESC is currently too slow to accelerate just like before, but that's a configuration issue (ramping). The linear regulation (throttle to RPM) like before is missing as I'm using "input is controlling the motor current" and not the RPM. I might tweak this after all. The possibility of an analogue brake function is a nice addon and behaves very smooth.

In short: it was worth investing into an external controller, and the VESC opens a lot of features (even when I'm using only the most basic ones). The KLS controller from Kelly is surely the same quality replacement as the VESC is one. The feature/price ratio of GMs BAC controller is far of (~40USD compared to 140USD for a Kelly) and is very adapted to the MP3.

Cheers
Sam