2017 August 17     Tech     Electronics - How To


In "How To Solder Heavy Wires and Cables", we looked at some detailed information on the subject.

Well, I had a couple short pieces of heavy cable, and I decided to solder lugs to them.  I figured I'd do a quick summary-type article with better photos.

Safety Warnings:    Soldering can be dangerous.  Solder may contain lead, which is toxic.  Soldering also involves rosin fumes, which can harm your lungs.  Please read the Disclaimer.

In This Article

Buying Cables

Cut The Insulation

Clamp the Cable

Soldering the Connector


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Buying Cables

For arc welding, #1/0 cable is overkill for most uses.  But it will run any amperage you'll ever need for stick welding. (Make sure you get the right lugs for it, too.  )

500 feet of #1/0 at 300 amps will drop less than 3 volts. 

Actually, though, 2 gauge would be plenty for most arc welding.  (2 gauge copper lugs here.) 

Power equals E times I.  A welder at 30 to 80 volts can use thinner cable than a 12-volt starter.  But even there, #1/0 welding cable is usually an upgrade;  many cars use smaller cable for that.  (Disclaimer again;  I can't know if anything described here will be correct for your specific use.) 

Whatever terminal lugs you get, make sure the hole in the tab is big enough for what you're going to attach them to.  The lugs for 1/0 cables can have a hole size of up to 1/2".


Cut the Insulation

Cut back the insulation so there will be at least about 1 1/2" of bare copper.  That leaves space so the heat won't melt the insulation.

Try to avoid twisting the individual strands.  I forgot about this on one of the cables, and it was more difficult to get all the strands into the terminal lug.  As it is, you may already have to snip a few strands that don't go in.

Make sure to put the piece of heatshrink tubing down over the cable before you solder anything.  So, cut a section of that a couple-three inches long, then put that over the cable.  Keep it far back from where you'll be heating. 

Don't put the heat shrink tubing anywhere near the bare metal until it has cooled down.  Otherwise it will shrink onto the cable where you don't want it to.


Clamp the Cable

Use a bench vise.  Even a low-cost one works great for this.  Use a piece of leather (etc) to keep the vise jaws from marring the insulation. 

Clamp the cable a few inches back from the bare copper end. 

Make sure the copper lug seats fully onto the cable end.  Now apply some rosin paste flux or liquid rosin to the bare copper wires.  Generic rosin paste can work OK, but it may lack activators and won't tin the copper as easily.

It's probably a good idea to use a metal container, such as an small foil pan, to catch solder drips.

Get your solder ready;  it should be rosin-core (preferably) and somewhere between 0.06 and 0.125 diameter.  (Here's one of the best.) Non rosin-core works OK if you use a lot of paste flux, but rosin-core seems to flow better.


Solder the Cable

You must wear a respirator for this.  I also recommend a fan to keep the air moving.  Don't try to solder without adequate ventilation!!  Rosin fumes can harm your lungs.

Look where the copper lug meets the copper wire strands.  There's kind of a ledge or a seam.  This is where you'll heat, mostly, with a propane torch.  First the heat will melt the rosin down into the strands.  You may want to add more rosin at that point.  Get ready with the solder. Periodically drag the end of the solder along the seam;  once the copper is hot enough, it should start running down into the wire strands and underneath the connector.

At first you might not think it's working, but if you fluxed everything correctly and heat correctly, it will.  It could take a lot of solder to wick down into the strands and under the terminal lug.  There has to be enough to make a good bond.

Let everything cool. Then slide the heat shrink tubing down over the cable until it covers the bare wires (and the solder).  It should overlap the terminal lug somewhat.  Next, heat it gently until it heat-shrinks onto the cable snugly.  Then the cable is ready.



This was the quick version of "how to solder heavy wires and cables".

For a more in-depth look (including a "How Not To" example), take a look at the original article.

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