Shrink wrapping wire splices.

[JHZR2]

I'm installing a connector for a battery charger for my 135i. I do this on all my vehicles as it easily lets me maintain batteries when I don't use the cars much.

I had to lengthen the positive connector, so I am splicing in some high temperature, underwood certified wire, I forget the coding for it, but it's good stuff.

I'm using crimp butt splices, I have some that you heat up and it shrinks the plastic covering and melts some glue snide to help seal. I don't think there is solder inside though.

That worked beautifully, looked good. However, I wanted more coverage, and I thought that black shrink wrap would look more finished. I put the smallest stuff that would fit over my butt connector that I had already heated and shrunk. I heated it and it shrunk well except that it seemed a bit lose at the very end where the wire came out.

Then I put another layer overtop and shrunk it, same deal.

Am I over thinking this, or is there anyway to actually get a good tight connection of the shrink wrap to the wire? Is any gap typical? It was minuscule, but instill saw it. Was there another better way?

Thanks!

 

[ChrisW]

I don't think I feel as confident as carefully hand stretching 3M super 33+ electrical tape over a connection as with heat shrink, unless its the heat shrink that has the goopy stuff inside.

I sometimes notice a gap with regular heat shrink depending on how sharp I cut the piece [like a straight down motion with an exacto knife and not 'sawing' on it] or depending on what brand I use or the thickness of the tubing. The thinner walled stuff seems to conform better, and the right temp and amounnt/length of heat seems to vary how well the end shrinks down.

 

[FL_Rob]

I'm familiar with this problem.Some brands of heatshrink do this,others don't. IIRC 3M waterproof underwater rated stuff?,was one of the best.
For the lesser brands(but all we had to work with)at the time we would run a plain 8" ziptie down on the end while the shrinkwrap was still hot and the goo would then ooze out and seal well.

Once the excess tie was snipped clean it didn't look too bad.

 

[Saleen0679]

Your best bet is to find some adhesive lined tubing that has a 3:1 shrink ratio. It will shrink tighter than the 2:1 that you possibly have.

 

[scurvy]

Probably due to the shrink ratio of the stuff you're using as mentioned by Saleen0679.

I would not bother with heat shrink tubing on top of a crimp splice connector with hot melt glue inside of it. The connector has all the sealing capability you need; the addition of heat shrink tubing is for aesthetics only and doesn't seem to have worked out so well in that capacity anyway.

 

[JHZR2]

Well it still has better aesthetics, but that's the info I need. No idea what the ratio is for what I have. I was thinking of doing a hand wrap as I have some high-temp 3M tape. Since the crimp connector fully seals, I guess I won't worry about it, but now I know what I need for next time.

Thanks!

 

[jg1]

One method is on the last layer of heat shrink tubing place some silicone in both ends BEFORE you shrink it. Remove the excess after you shrink it - provides a good seal and looks good. If you really want to overkill use 3m black marine silicone.

take care.

 

[HerrStig]

Heatshrink only shrinks so far. You have to use the right size. I often rip the plastic off a butt splice, crimp it, and then solder it.

 

[another Todd]

Originally Posted By: HerrStig
Heatshrink only shrinks so far. You have to use the right size. I often rip the plastic off a butt splice, crimp it, and then solder it.


That's fine, but for a quality connection, the wire must also be supported away from the connection and at the wires insulation. The plastic sleve can be crimped to accomplish this. Aircraft crimps and crimpers will crimp the electrical connection and plastic sleeve at the same time making a good solid connection. If you crimp then solder you make a superior connection but then must support the connection with tape or shrink tubing, otherwise the wire flexes at the connection and can break (I realize the solder will run up the wire a bit making it stiff but support is still needed).

 

[Doog]

I just use marine grade shrink wrap connectors. They have the goo inside and never fail.

 

[Cujet]

In the aviation world, there are specific and appropriate ways to do this.

First, not all heat shrink is equal. The higher quality stuff is rated to a specification. It has a specific shrink, a specific required temperature and flexibility.

But the post above is correct. You probably want to create an "environmental splice". If so, purchase quality heat shrink with sealant inside.

Oh, and a properly designed, constructed, installed and sealed "environmental splice" is rarely soldered in aviation applications. And, they will provide a lifetime of troublefree service.

 

[cascivic]

Something I did on my jet ski that may help you is I would cut a small diameter piece that fit the wire pretty tight and then one that was more normal size that would fit the end then layer the, so the small one stuck out the end of the larger one and then heat and it gave me a nice tight fit at the end.