Splicing an 8 conductor motor wire: how to make an elegant slender splice?

[zacksc]

The wire going from my controller (Baserunner) to my motor (Bafang G3x), is a 9 conductor wire ending in a Z9 molded Higo connector. Due to the very close proximity of the Baserunner to the motor in my set-up I have a lot of excess wire length and, even though I like the Higo connectors, I think I will need to cut and splice. The cable is about 7 mm diameter overall, and contains 3 phase wires (18 AWG?) and 5 Hall sensor wires which are smaller. I am pretty new to this and would love to learn how to do a splice that does not bulge much. Any advice is most welcome. I know there are a lot of blogs and posts around that discuss splicing, but I haven't seen anything that focusses on keeping the splice diameter close to the diameter of the original wire, in this case for a total of 8 wires. Is it practical to try to stagger the individual splices or something? Does ordinary heatshrink provide adequate insulation for the phase wires, which presumably would be pressed together inside a larger heatshrink.
A big concern for me is not to have a large unsightly bulge. Is it realistic to think that I can keep the overall diameter to say 8 mm, starting with an 7 mm diameter 9 conductor wire? I don't have much experience and I am very appreciative of expert advice from experienced people. (Also, if you are near Santa Cruz and interested in a gig, that is another possibility.)

 

[amberwolf]

The best way to keep a small diameter to the resulting section is to stagger the splices, so that none of the heatshrink or splice points of any wire overlaps any other wire. But this leaves a very long total opened section.

One plus is that even if you mess up the heatshrink over the exposed conductors, or even leave it off entirely (not recommended), the conductors can't short to each other because they are all separated by insulated areas.

Another plus is that you can actually end up with a thinner splice section than the original, if the jacket on the cable was thick and you remvoe it and heatshrink it instead. Though for cable toughness I recommend just splitting the jacket open lengthwise, doing the splices, and stuffing the wires back in, with at least one layer of heatshrink over the entire cut section plus an inch or two beyond. (filling the entire splice area with dielectric grease will also leave no space for water intrusion, if that is a concern, though it is very messy during the heatshrink process as it is squeezed out by the shrinking plastic).

When you actually do the splices, there are many ways to connect the conductors. My favorite when going for a skinny result is to not twist up the conductors after stripping insulation, but leave them slightly "frayed", then butt them together, interleaving the two sets of conductors, then "rolling" them so they are "tornado twisted". Then take a long strand of wire (like out of the phase wire lengths you're removing), and wrap that tightly around the exposed conductor area. THen solder, then slide the heatshrink over the exposed conductor, then shrink it. Then move on to the next one. THe basic idea of this process can be seen over here:
https://endless-sphere.com/forums/viewtopic.php?f=2&t=86600#p1463762

 

[Voltron]

They make high performance heat shrink also, I use it on boat wiring. High temp glue lined, 3 to 1 shrink ratio.

 

[John in CR]

I typically go the route AW said with the staggered cut and splice points, but rarely end up with something I'd call elegant. To me the way to get it truly elegant and exactly the right length is to cut the harness at the appropriate point(s) and redo the connector(s) at the end.

 

[John in CR]

They make high performance heat shrink also, I use it on boat wiring. High temp glue lined, 3 to 1 shrink ratio.
51Ou2mga04L.jpg

Thanks for pointing that stuff out, since I didn't know it existed. That's a must buy for me, and will actually save me time and money with less double shrinking and no need for long runs of shrink tube.

 

[Voltron]

It's pretty satisfying watching the glue getting squeezed out the ends during heating.
Works good for two smaller wires joining a single bigger wire, you can make a little space between the small ones and squish the heatshink while it's cooling and it gets a pretty good seal. Helps to start the heating in the middle so the glue flows towards both ends.

 

[Voltron]

They make high performance heat shrink also, I use it on boat wiring. High temp glue lined, 3 to 1 shrink ratio.
51Ou2mga04L.jpg

Thanks for pointing that stuff out, since I didn't know it existed. That's a must buy for me, and will actually save me time and money with less double shrinking and no need for long runs of shrink tube.

One note though... It's incredibly hard to get off later!

 

[John in CR]

They make high performance heat shrink also, I use it on boat wiring. High temp glue lined, 3 to 1 shrink ratio.
51Ou2mga04L.jpg

Thanks for pointing that stuff out, since I didn't know it existed. That's a must buy for me, and will actually save me time and money with less double shrinking and no need for long runs of shrink tube.

One note though... It's incredibly hard to get off later!

The more it acts like wire insulation the better. I can't remember ever needing to remove shrink except a few cases where the sliding shrink made it harder for my stripper to work properly.