Best soldering practices when joining wires

Thread Starter

Lumenosity

Joined Mar 1, 2017
612
I am going to connect a fuse holder to a wire.
The wires are all 12GA stranded, copper automotive Primary wire

I prefer to connect the fuse holder 'in-line" such that the wire always maintains a straight path like a continuous tube rather than soldering at 90 degree or greater angles.

"Normally", I strip back about 5/8 inch of the plastic sheath on both wires, slide shrink wrap onto the wire, then tightly wrap the exposed wires around each other, then solder...like this

And lastly, move the shrink wrap into position over the soldered joint and heat it.
Is there a better way?
 

cmartinez

Joined Jan 17, 2007
7,393
I am going to connect a fuse holder to a wire.
The wires are all 12GA stranded, copper automotive Primary wire

I prefer to connect the fuse holder 'in-line" such that the wire always maintains a straight path like a continuous tube rather than soldering at 90 degree or greater angles.

"Normally", I strip back about 5/8 inch of the plastic sheath on both wires, slide shrink wrap onto the wire, then tightly wrap the exposed wires around each other, then solder...like this

And lastly, move the shrink wrap into position over the soldered joint and heat it.
Is there a better way?
There definitely is a better way. What I've done for years, and has never failed me, is first tin both wires, and then solder them together completely in parallel. Just make sure that solder has uniformly joined them through their length... this method is far easier to perform and maximizes electrical contact between both wires. I've also never seen it mechanically fail.

And yes, shrink wrap around the joint is always a must ... never ever use electrical tape...
 

MrSoftware

Joined Oct 29, 2013
2,015
You can follow the NASA suggestions and expect reasonable results I think:

https://workmanship.nasa.gov/lib/insp/2 books/links/sections/407 Splices.html

Side note: what has worked well for me on our saltwater boats is to use heat shrink filled with electrolytic grease. After soldering, slip the heat shrink over the joint leaving lots of room on both sides. Fill the entire tube with electrolytic grease then heat shrink it, some grease will squirt out the ends. I've had great luck with this for joints that are frequently submerged in salt water for extended periods. It's also important to use tinned wire.
 

mcgyvr

Joined Oct 15, 2009
5,394
I always just make a J hook with the end of each wire and hook them together as it gives "some" mechanical strength too..
Holds them together easier that way IMO..

Something like twisting creates too much of a potential for breaking/weakening strands..
 

cmartinez

Joined Jan 17, 2007
7,393
I still prefer the mechanical strength and connection achieved using the twisted method, never yet failed me.;)
Max.
The problem with twisting is that it increases the joint's volume, and it can also create unnecessary stresses in the cable, which can later make it prone to fatigue. Plus ... it looks ugly ... but that's only my opinion. If someone with a 40-plus years of experience behind him tells me that twisting works for him, then I'm not gonna argue the point any further ... I've only barely completed my first 30 years of working in this field, after all ... :p:D
 

MaxHeadRoom

Joined Jul 18, 2013
23,594
I would add that this applies to stranded cables only, which can often be twisted tightly that the dia does not exceed the insulation dia, so when heat shrunk, the OA Dia is practically no larger than the original. ;)
Max.
 

MrChips

Joined Oct 2, 2009
24,141
Different strokes for different folks.

Sometimes when you just have to keep the diameter the same, here is another solution.
Remove half the number of stranded wires on each end. Slide the two ends together in parallel and solder. Apply heat shrink.

Remember to insert the heat shrink tubing before splicing. How many times have you forgotten to do this!:mad:
 

MrSoftware

Joined Oct 29, 2013
2,015
I don't think I've ever seen a soldered joint come apart inside the joint unless it was put through a lot of bending. Most failures I've seen are on either end of the joint where the wire is prone to bending sharply such as if the joint isn't in the middle of a strait run.
 

Reloadron

Joined Jan 15, 2015
6,058
Years ago I had a nice sound system installed in my wife's Jeep Grand Cherokee. There was a large 500 watt amplifier. They used a really slick inline fuse holder directly off the battery with a pair of copper lugs and #6 wire. There are lug combinations designed for coming right off the battery.

Since I doubt using the cigarette lighter type plug / socket you will ever draw over 10 Amps I would just twist and solder as depicted in your initial post. Run some heat shrink over it as a few layers and be done.

Remember to insert the heat shrink tubing before splicing. How many times have you forgotten to do this!:mad:
WE will not even discuss that. <FACEPALM/> :)

Ron
 
Last edited:

JMW

Joined Nov 21, 2011
137
There definitely is a better way. What I've done for years, and has never failed me, is first tin both wires, and then solder them together completely in parallel. Just make sure that solder has uniformly joined them through their length... this method is far easier to perform and maximizes electrical contact between both wires. I've also never seen it mechanically fail.

And yes, shrink wrap around the joint is always a must ... never ever use electrical tape...
That sir, is the definition of a "cold solder joint". While it "works" and I too use it frequently it is not an proper splice.
 

JMW

Joined Nov 21, 2011
137
I am going to connect a fuse holder to a wire.
The wires are all 12GA stranded, copper automotive Primary wire

I prefer to connect the fuse holder 'in-line" such that the wire always maintains a straight path like a continuous tube rather than soldering at 90 degree or greater angles.

"Normally", I strip back about 5/8 inch of the plastic sheath on both wires, slide shrink wrap onto the wire, then tightly wrap the exposed wires around each other, then solder...like this

And lastly, move the shrink wrap into position over the soldered joint and heat it.
Is there a better way?
A "Western Union" splice is preferred, and is similar to yours. It may not be physically possible with 12 ga stranded. Yours is more than adequate. Solder is only used to prevent corrosion, it is not there to provide strength. You must be careful the solder does not "wick" past the insulation. This will be the future failure point if the cable is subject to flexing as in repairing door locks or power windows.
 

sdowney717

Joined Jul 18, 2012
705
I have also spread the strands apart and forced the wire ends into each other till each end reaches the insulation of the other wire, then twisted them using my fingers keeping the splice inline. That very thoroughly intermingles the copper strands. Then soldered them. If the soldered joint is rough, I use a vice grip plier to squeeze it down so it wont snag the heat shrink tubing and make it straight and smoother.

I have used sometimes various things to coat the wires joint with before heat shrinking, such as silicone gasket maker or rubber cement.

Do you know the ABYC (boat related group) says solder can not be the only means of attachment, they say don't solder, use crimp connectors. Their reasoning is the joint could overheat due to high resistance and fall apart, at least for terminals. Inline splicing is not going to experience that.
 

cmartinez

Joined Jan 17, 2007
7,393
That sir, is the definition of a "cold solder joint". While it "works" and I too use it frequently it is not an proper splice.
I half agree with you.... normally, I don't work with cables thicker than 18 ga. As a matter of fact, 90% of my work is done with cables 22 ga and below. For cables that thin, I'd say that the "cold solder joint" (as you've just called it) is the best approach. I would never dare to use it on cables 16 ga and up. I don't even feel comfortable using it on 18 ga cables. And also, it is never a good practice to use a joint of any kind where a cable will be subject to flexing or vibration, no matter its thickness.
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
612
Different strokes for different folks.

Sometimes when you just have to keep the diameter the same, here is another solution.
Remove half the number of stranded wires on each end. Slide the two ends together in parallel and solder. Apply heat shrink.

Remember to insert the heat shrink tubing before splicing. How many times have you forgotten to do this!:mad:
Haha!
I've never had this happen to me (Riiiiiiiiiight)
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
612
Years ago I had a nice sound system installed in my wife's Jeep Grand Cherokee. There was a large 500 watt amplifier. They used a really slick inline fuse holder directly off the battery with a pair of copper lugs and #6 wire. There are lug combinations designed for coming right off the battery.
Since I doubt using the cigarette lighter type plug / socket you will ever draw over 10 Amps I would just twist and solder as depicted in your initial post. Run some heat shrink over it as a few layers and be done.
WE will not even discuss that. <FACEPALM/> :)
Ron
lol.
I have a RoadPro Food heater that draws 15A and an Igloo 26Qt mobile fridge that draws 6A.
I'm using a custom power panel I'm installing just to be certain it never overloads.
So I ran a 12GA power cable directly to the battery (and installed a 20A fuse right AT the battery). Of course, there is no need to run a Negative cable to the battery, I just ground it nearby the panel inside the vehicle.

If only I had a quarter for every time I made the most beautiful solder joint....THEN realized I left the shrink out <double FP>
Somehow the solder joint AFTERWARDS was never as purdy :)
 

dendad

Joined Feb 20, 2016
3,906
I like the Dual Wall heat shrink tubing. It has a thin layer of hot melt glue inside and makes a good strong cover over the joint. And I have (mostly) twisted the wires together.
As for leaving things off, I could mention about 30 years ago, at the Shepparton Radio Australia transmitter site, a 100 wire (or pair, I can't now remember) cable I terminated onto a plug for some equipment and saw the cover on the bench. Definitely a coffee moment!!!!!!
 

JMW

Joined Nov 21, 2011
137
I have also spread the strands apart and forced the wire ends into each other till each end reaches the insulation of the other wire, then twisted them using my fingers keeping the splice inline. That very thoroughly intermingles the copper strands. Then soldered them. If the soldered joint is rough, I use a vice grip plier to squeeze it down so it wont snag the heat shrink tubing and make it straight and smoother.

I have used sometimes various things to coat the wires joint with before heat shrinking, such as silicone gasket maker or rubber cement.

Do you know the ABYC (boat related group) says solder can not be the only means of attachment, they say don't solder, use crimp connectors. Their reasoning is the joint could overheat due to high resistance and fall apart, at least for terminals. Inline splicing is not going to experience that.
Crimp connectors are gas tight, necessary in engine room spaces, solder..........not so much
 
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