Introduction: Soldering Clean Wire Splices

Here's a quick tip about properly splicing cables. This is handy for changing the connector on your solar panel, or simply making any two-wire cable longer.

This may seem like a basic skill, but I know that by the time I learned this technique, I wished someone had told me earlier.

You will need:

Step 1: Cut & Prepare

Picture of Cut & Prepare

Start out by cutting your wires and stripping off the outer layer of insulation. Slide a big piece of heat shrink tubing onto one side of the wire, which we'll use at the end to seal everything up.

Strip and tin the inner wires, and apply smaller bits of heat shrink to one side.

Step 2: Arrange Asymmetrically & Solder

Picture of Arrange Asymmetrically & Solder

The trick here is to get the pair of connections to be the same length, but offset the solder joints. This has the benefit of not bulking up the cable with stacked connections, and also keeps the connections away from each other, minimizing risk for short circuits.

For the cleanest end result, cut the wires asymmetrically as shown. Don't forget the heat shrink tubing before tinning and soldering the wires together. If they don't turn out exactly the same, you can reheat the longer one to adjust. Match red to red and black to black (or white to black as in my case), then heat up the heatshrink tubing to insulate the solder joints.

Step 3: Seal It Up!

Picture of Seal It Up!

Repeat to insulate the entire junction with the larger piece of heatshrink tubing, and you can hardly tell there was any wire surgery!

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WolfgangW10 (author)2017-10-31

Schrumpfschlauch mit dem Feuerzeug schrumpfen ist nicht die richtige Lösung. Richtig ist dies mit einem Heißluftfön.

Mudcat15 (author)2017-10-24

I don't have a hot air gun, so I fold a layer of aluminum foil over top and bottom of the heat shrink tubing before using a small flame. No soot, and seems to work better.

jtancrede (author)Mudcat152017-10-26

Immerse the shrink tubing in the flame (the blue or invisible portion). No soot.

wizardclassics (author)2017-10-24

When connecting two wires, you should make a mechanically sound connection before soldering (eg by hooking both wires around each other), laying the two wires side by side increases the possibility of a dry joint. Another possibility is to make a coil of tinned copper wire which can be slid over the two wires (laying parallel) before soldering the whole assembly.

jtancrede (author)wizardclassics2017-10-26

I agree. Properly splice the wires prior to soldering.

gm280 (author)2017-10-22

Nice job. What you created is called a "Lap" joint and it is used for the very reasons you stated, to not make a huge bulge in the wire by staggering the joints. I use that technique all the time and when done correctly, the wire length doesn't look bulky and lumpy. Nice project.

jtancrede (author)gm2802017-10-26

She should have used a splice to connect the wires for strength and electrical contact. She'd fail any class in soldering using that technique.

ivak245 (author)gm2802017-10-24

Good instructions. A mechanical bond is good to incorporate into this (I have used this in thousands of soldered connections ) like twisting together. When the wires are being soldered only leave the iron on the joint long enough for the joint to form , or the solder will "wick" up the flexible conductors and you end up with a solid piece of conductor either end of the joint, which will limit it's flexibility.

gm280 (author)ivak2452017-10-24

There are ways to stop solder from wicking up under insulation. They make a special tool called a anti-wick tweezers. They come in different gauges depending on the wire size you have. And you simply clip them on the ends of the insulation and solder away. The tweezers stops any solder from wicking up under the insulation. They also have heat sink clamps that do the very same thing. Check them out. It solves the wicking solder problems.

COMPUTIAC (author)2017-10-25

In your list of things you will need, you did not say what type of

solder to get or if any flux is needed.

jtancrede (author)COMPUTIAC2017-10-26

60/40 rosin core solder.

jtancrede (author)2017-10-26

Ooh. You shouldn't solder wires without making a proper splice. It provides good electrical contact and strength to the connection. I do like the offset idea however.

vishnumaiea (author)2017-10-25

Oh! I'm in love with those photographs. Real eye candies! RIP connector BTW.

Waste Of Space (author)2017-10-24

It would also be necessary to use a multimetre to check that he earth side is connected to the earth side and that the positive is connected to the positive side. You cannot just rely on the colours of the cable to make the joint correctly polarised.

DaviDBCoe (author)2017-10-24

I've been doing the exact same thing for 20 years. Right down to the three (3) pieces of heat shrink tubing, pre-soldering and staggering the splices (for compactness and as a fail-safe against a short circuit).

It is wonderful to find that I am not alone with such ideas. And most excellent to know that this technique is, indeed, not as crazy as my co-workers have said in the past. I ignored them (mostly), but unsolicited criticism is something I really dislike.

rjkorn (author)2017-10-24

Great tips....

The staggering makes a nice smooth splice. Sometimes on larger cables I use some electrical tape under the heatshrink to really make it look seamless.

On garden wiring I coat the splice in RTV then slide the heatshrink over that and shrink it as the RTV is just starting to cure to make it waterproof...

Ditto on the RTV.

Just don't use "GE Silicone 1" or any other silicone that smells like vinegar.

The acetic acid (vinegar smell) fumes emitted during curing will eat/corrode your wire badly.

It should say on the back of the tube acetoxy aka acid cure or alkoxy aka alcohol cure.

+1 The acetic acid (vinegar) stuff will chew up electronics.

mariosk8s (author)2017-10-24

I love the simplicity of this method.

LTHAtlanta (author)2017-10-24

Excellent approach, very nicely presented. I’ve used it for years with one “old school” variation. We were taught back in the vacuum tube build-it-yourself kit days to make a good mechanical connection before soldering. After tinning, you can make a small hook at the end of each wire, connect, crimp and then solder. Makes a somewhat more reliable connection because the joint is less likely to accidentally flex while cooling thereby avoiding the dreaded Cold Solder Joint.

PaulS28 (author)2017-10-24

The key to any splice is the mechanical connection. Solid wire should be twisted together prior to soldering. For stranded wire, I like to spread the small wires slightly on each end and then slide them together so that the small wires slide past each other. Squeeze with fingers or pliers as appropriate to get everything close and then heat the connection until the solder flows through all the strands.

rjkorn (author)PaulS282017-10-24

Sounds like you favor the western union or linesman splice like I do.....

ElegantAndrogyne (author)2017-10-24

Nice and simple, so much better than insulating with electrical tape (which I do only when I really have no other option). I do it a little bit different:

1. wrap the wires together before
soldering (unless the joint is temporary). It gives the joint extra strength and less resistance (important for higher currents, anything
over 10A or so),

2. usually use an additional layer of heatshrink tube
for mains connections (230V here), and the outer insulation is also two
layers for a smoother look and extra durability,

3. shrinking the tubes is
best done with a hot air gun: quicker, smoother and less risk of burning the tube by overheating.

rjkorn (author)ElegantAndrogyne2017-10-24

Sounds like you favor the old western union or linesman splice. same here......

hummyi (author)2017-10-23

If you left more wire attached to the two"cutting plugs" remained ( just a bit more ) u can reuse them! Why not :-)

fstedie (author)hummyi2017-10-24

I agree with this one. Always leave enough wire on the connector to possibly reuse it.

rifflehitch (author)2017-10-24

There's another reason for staggering the connections and that is it significantly reduces the chance of one wire shorting another, especially in the case of an electrical cable. The heat-shrink certainly helps reduce that possibility while he staggered joints make it even better.

Kafukai (author)2017-10-22

This is great technique :)
I'm using almost the same, but I am using before the heatshrink sleeve a wire crimp connector - to make it stronger. As long as the soldering is strong, both techniques are the same :)

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Bio: Becky Stern is a content creator at Instructables. She has authored hundreds of tutorials about everything from wearable electronics to knitting. Before joining Instructables, Becky ... More »
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