That is a lots of cable .....

[Lewis Balentine]

To solve my SP4 mounting problem I purchased a new (with bicycle attached). It was the cheapest thing (and possibly ugliest) on offer from Amazon. 

I worked out all the mechanical problems and now have the rear battery rack, front rack, front Smart Pie, throttle and LCD display mounted. ROuted the power cable up the fork, down the down tube, up the seat tube and to the rear rack with about 8 inches (20.3 cm) to spare. Then I go to hook up the control cable for the throttle ... it is so long that I can route it all the way to the ass end of the rear rack and back to the handle bars. Seriously, where do they expect one to stuff all that extra wire? I am thinking GM uses a "one size fits all" approach. I fully understand that a long cable is needed to go from the rear motor but a front hub does not need anywhere near this much wire. Not to mention some protective caps for the unused connectors.

It is pointless to produce excellent watertight connectors if the user has to cut them off to get rid of all the extra wire. Is there a colored code wiring diagram for the motor cable ?

[Hastings]

Yes a separate front wheel harness would be better. However  is  not so difficult  with some planing to cut soder and isolate. there will be an elongated  bulb on the cable so it comes down to what you are most comfortable with.

[Lewis Balentine]

Yes a separate front wheel harness would be better.

Golden Motors Canada lists two seperate part numbers for the 10 pin MP4/SP4 wiring harness:
MP4-10PIN-Front and MP4-10PIN-rear
They however do not indicate what the difference is (length?). I am ordering one. I will dissect it to document the pin outs and wire colors.

However  is  not so difficult  with some planning to cut solder and isolate. there will be an elongated  bulb on the cable so it comes down to what you are most comfortable with.

I have been thinking about exactly that.

First of all note that bike has only a rear hub coaster brake and strangely I am running out of space to mount things on the handle bars. If I install lights and/or a horn then they will be 12 volt not 36 volt devices. Thus I would like to repurpose the 2 button switch to be cruise control and front 'regen' brake. I am assuming both of the pushbuttons in the switch are momentary switches.

Secondly with the existing wiring harness design, if one needs to remove the front wheel to fix a flat then they must also remove (cut away) a great deal of the wiring harness as well. A properly designed harness should have a connection very close to the hub to rectify this problem.

See the two attached images (the color coding is arbitrary).  The first is what I think is running through that ugly blob closest to the motor. The second represents the new cable  splice. My concept is as follows:

1) Cut the main motor cable below the first big blob.
2) Separate the battery power wires for termination with wire nuts (until I find something better).
3) Splice in the 8 pin male to the remaining wires as noted in the second picture.
4) Cut the 8 pin female pigtail to an appropriate length.
5) Splice in the male pigtails for the display meter, throttle and two button switch as noted in the second picture.
6) Color code connectors: yellow=meter, green=throttle, blue= switch.

Actually 3 and 4 above should say 10 pin but there is NO documentation on GM's new MP4/SP4 harness.

Thoughts or comments ?

[Morgen 3Eman]

Just a word of warning from an old fart.  Around 80 % of all the electrical/electronic problems I solved were caused by some kind of electro-mechanical failure….bad solder joints, corrosion, etc.  Be very fussy about what connectors you use, and how you assemble them.

TTFN,
Dennis

[Lewis Balentine]

From one old fart to another:
Thanks for the advice. I plan on using the original connectors. New splices will be soldered and shrink wrapped. I ordered the spare harness to have something to work on rather than the one that I am running.

[e-lmer]

I might suggest Vaseline in the shrink wrap.  Two dissimilar metals and water, yanno.

[Aeberbach]

I have just spent near $100 on quality sealed electrical connectors to rewire the Magic Pie 4 harness. If you know it's going to bother you then this is about what you have to spend unless you have an uncle in element14 or something.

A much cheaper fix is to get a piece of electrical conduit and double the spare cable within it, then fasten the conduit to the underside of one of your frame tubes. It can't catch on anything, it won't rattle as much (or at all if you're clever with padding) and you don't have to look at it any more.

[Morgen 3Eman]

Vaseline will work, but IMO silicone grease is a much better choice.  It doesn't react with stuff like petroleum jelly will.

TTFN,
Dennis

[Lewis Balentine]

I have just spent near $100 on quality sealed electrical connectors to rewire the Magic Pie 4 harness. If you know it's going to bother you then this is about what you have to spend unless you have an uncle in element14 or something.

A much cheaper fix is to get a piece of electrical conduit and double the spare cable within it, then fasten the conduit to the underside of one of your frame tubes. It can't catch on anything, it won't rattle as much (or at all if you're clever with padding) and you don't have to look at it any more.

I thought of the conduit idea as well. Two problems with that. One is the aesthetics of course but the other is that it does nothing to correct the problem of having to remove the harness to remove the front wheel. In my opinion (bearing in mind said opinion is worthless) that is nothing short of piss poor engineering on GM's part. It is like having to remove an V8 engine to change to change the spark plugs (oops ... that was a different GM).

Yep, I saw your post about those connectors and looked 'em up. That is why I plan on splicing the cables instead.
I am a 'fair weather' rider so water protection is secondary. Having said that, the bike paths in Houston, Texas can best be described as 'open sewers with white lines'. Thus some concern is fully justified.

The only connectors that I will need are for the power cable. I would rather have a pair of wire-nuts hanging off the the front fork than deal with removing the wire harness  to remove the wheel. I am thinking Anderson SB30 or SB45 connectors might work for the power connections. I think GM may have gotten the ones on the battery a tad large (perhaps they were concerned about someone hot-plugging the battery and vindictive litigious lawyers).

Another interesting thing about your previous post: I had to build up an XP laptop to try reprogramming the SP4 while mounted on the bike. No joy whatsoever. So I removed the wheel and hauled it upstairs so I could use my VM Windoze 7 Image. That works perfectly (perfectly is a bit of exaggeration). Long term project might be to decipher the GM com protocols via an RS232 sniffer. I plan on having an extra 10 pin cable for programming. That cable will also be used as a 'break out' for test points when needed.

Did you document the color coding and pinouts for your MP4 10 pin cable?
What are those extra 2 pins used for ?

I also plan on integrating a volt meter into the back end of the battery pack: http://www.ebay.com/itm/271801572043
I ordered the red version so that I could call it a 'tail light'. 


Reference Anderson Connectors: http://www.powerwerx.com/anderson-powerpoles/powerpole-sets/45-amp-red-black-anderson-powerpole-sets.html

[Aeberbach]

I haven't yet chopped my cable (box of connectors arrived only yesterday) but looks like Bikemad has cleared it up - it is roughly the same as the MP III only with the moldings in a different place.

Anderson are well known from RC plane days, I think they would be a good choice if you only ride in fair weather.

It would be awesome to get a spec for the MP4 - I would really like to add a bluetooth module to my USB cable permanently, I could run the USB wire up and house a Bluetooth LE controller under the seat. Then I could write an iPhone app for it to handle programming and to use the mobile as speedo, battery gauge etc. I'd open source it too. iOS development is my full-time job. How about that GM, release your serial spec, get an app developed free.

[Lewis Balentine]

I spoke with Gary of GM Canada today. He said that the difference between the front and rear cables is the length (he thinks that I may have received a rear cable with my SP4). Be careful of cutting the motor cable. He has reason to believe that there may be something in the first bulge other than wiring (perhaps a small circuit board). I still plan on pursuing this but I will plan on peeling away the potting on that piece very carefully. Some possibilities are  5 Volt DC regulator, RS232 voltage converter, directional diodes, current shunt, ... ? Come to think of it a current shunt makes a lot of sense considering the display can give current usage readings.

Personally I would rather see an Android application but any application other than Windoze is a start in the right direction. My guess is that if GM was going to release the com specs then they would have already done so. So reverse engineering may be the only option in that regard.

[Hastings]

just a word on anderson power poles :have you seen the weather protected versions ?http://www.andersonpower.com/products/spec-pak-connectors.html

[Lewis Balentine]

Before I start trying to dissect the new cable I figured that I needed to come up with a pin number diagram.
I made drawings (obviously not to scale) for both the old and new connectors.
For anyone who might want use, abuse or enhance them for their own purposes the attached zip file has the original DWG, PNG and PDF files.

Note: Revised 23 April 2015, Includes both male and female connectors

[Bikemad]

Lewis, the diagram I posted (which has now been corrected  ) was for the connector on the end of the throttle unit wire not the connector on the control harness.

Here is the corrected diagram (throttle signal and battery -ve were accidentally swapped) as viewed from the connector pin (sockets) side:



I have just finished checking the continuity of the harness wires and have therefore updated your drawing accordingly:



You might also have noticed that I have added the third pin on the brake connectors, as the harness is now supplying a +5V feed to the connector. Unfortunately, the brake levers that came with it do not use the +5V feed, but I assume it's there in readiness for brake levers to be fitted with hall sensors instead of mechanical switches.

Does this mean that variable regen might be available soon?



Alan

P.S. I have just added a PDF copy of this diagram as an attachment which is much clearer to read.
 

[Hastings]

You also need a feed voltage for hydraulic brake switch . At least if you are using Hall sensors.This brake type has been lacking in GMs products a long time.