Spool Gun Handheld Wirefeed Welder Powered by Car Batteries

Here's my new wire-feed (MIG) welder.
All of it.
They sell these things as accessories for commercial MIG units, but they can also work great on 24 volts from two car batteries.
I have it loaded with .030" flux-core welding wire.
It cost me less than $100 on ebay.
The "Ready Welder" is a similar commercial product.
WARNING: The tip is electrically on all the time!

Cheap Welding for Punks compares this gizmo to other homebrew welding methods.

In the following video, notice that I'm controlling power with the distance to the work. Close in melts in more, further away increases the wire resistance. That decreases current and the weld is cooler and builds up metal in a taller puddle. Notice that my first weld is terrible because I forgot to do that. The next two welds get a lot better. These are two random batteries that have been sitting out in the yard for at least a month. I don't know how well charged they are.

Thanks to Star for videography and other good works.



Want more homebrew welders?
Try an AC stick welder from microwave oven transformers,
DC stick welding with car batteries,
Solar powered golf cart welder

Spoolguns are sold as accessories for MIG welders for welding aluminum. The aluminum wire tends to jam up in a conventional wirefeed welder. So people get these spoolguns. They also get them for confined spaces and to work longer distances from the powersupply unit.

I bought this spoolgun on Ebay for under $100. There's no brand name on it and no provision for shielding gas. It's well made and works great for flux-core wire. I don't see any like it at the moment, but there are a number of Miller and other major brand spoolguns for sale. Do "show completed listings" to see how much they've been going for.

Wirefeed welding on steel uses a DC constant-voltage power supply.
Lucky for us, that's exactly what a car battery is.
The range you want is between 18 volts and 36 Volts. I prefer 24 Volts for most of my welding.

Here's my power supply. It's two car batteries. They say "deep cycle" on them, but I don't think they really are. You don't need deep cycle batteries for this purpose anyway. Or even very good ones.

To get 18 volts, use three 6 volt golfcart batteries or a 12 volt battery and a 6 volt one in series.
To get 36 volts, use three 12 volt batteries in series, your whole golfcart worth of 6 volt batteries, etc. etc. You get the idea.

I bought this 2lb spool of flux-core wire for $7 from Harbor Freight. Looks like they're asking $20 for it now.
Here's a cheaper source of welding wire. $5/lb is a decent price.
Every welding supply shop and most hardware stores will carry something like it.

I get the .030" thick stuff. You need to get tips to match your wire, $3.50 for a pack of 5.

Online welding forums debate the merits of different vendor's wire and prices.
All agree on one thing. Don't let it get rusty.

If you've got a big spool you can reload the little ones like this.

Wirefeed welding steel is done with DC "reverse-polarity".
"Reverse Polarity" in welding parlance means the same as "Electrode Positive".
That means you connect the ground cable from the "-" battery terminal to the workpiece. The gun is connected to the "+" battery terminal.

The confusing name for this polarity happened for historical reasons.
For most welding (stick, the standard) the electrode is negative. That's called "Straight Polarity". They do it that way so most of the heat will go into the weld instead of the electrode.
The electrons have an easy time jumping out of the electrode, but when they jump into the workpiece they have to mill around and get acquainted and find their way around a bit. That makes more heat than just jumping off an electrode.

The gun has two wires coming out of it. One is thick and one is thin. The thin one powers the wire feeder. Inside the handle of the gun there's a DC brush motor with a gear reduction turning a pair of pinch rollers that push the wire forward.

The speed of a DC brush motor is proportional to the voltage. That works out well for this gun, since the higher the welding voltage, the faster it spews out wire.
This particular wirefeeder seems to feed at just the right speed for whatever welding voltage I'm using.

If you want a different speed, try hooking the thin wire to different voltages in your battery bank. To get a continuously variable speed, use a variable DC powersupply for it. A small one will do.
Or butcher a battery powered electric drill for its speed controller.
Replace the trigger potentiometer with a rotary one of similar resistance.

Welding books have tables for voltage and wirefeed speed for welding different materials.
To measure the speed of your wirefeed, press the trigger for one second and measure the length of wire that comes out.

Once you've hooked the welder up to the batteries, it's HOT!!
The trigger only controls the wire feed. The tip is wired direct to the battery.

I started out welding with the tip bare, but I accidentally brushed it against the work and pitted the gun. They make insulated "cups" to cover the tip, but I don't have one. So I proceeded to the next step.

Star was cutting up some bamboo and handed me a chunk.
I drilled a hole in the node and it works perfectly. It's a press fit.
The tip gets charred, but it's lasted through a few dozen welds. I guess it's like the hardwood re-entry tiles on the Russian space vehicles.
If it smokes after welding I dip it in water to put it out.
Welding is a lot more carefree now. I still have to worry about shorting the wire accidentally, but not about damaging the gun.

Eventually my tip got goobered up with spatter until it looked kind of like this diagram. You're not supposed to be able to weld dissimilar metals without flux, but that stuff was ON THERE.

I figured it was time to get some spares.
I got some spare tips to match the wire, $3.50 for a pack of 5. And a couple of cups for $3.80 each. They looked about right and I got lucky. They fit my gun perfectly. Probably it's "TWECO" compatible. That's the gun everyone uses. Does anyone have facts on this?

I sprayed some welding anti-spatter spray on the tip to keep it clean. The machinists didn't know what was in it so I looked it up. Ours might be phosgene-based, but apparently veggie lecithin works great.
Get some at your nearest healthfood store, or get a spraycan of "PAM" antistick cooking spray at the grocer's.

There are a lot of good welding forums, here are excerpts from a post by "chipmaker" 04-19-2005, 08:41 PM
"...If your looking for a good anti spatter spray get some spray PAM, the same stuff the wife uses in the kitchen to keep stuff from sticking in her pans. It works fine, and is dirt cheap, and if you get the buttered flavored stuff it smells great when welding.

I have run stainless steel safety wire i mine to weld up stainless and it works fine.........no need to buy expensive stainless MIG wire, unless your doing spec work and lots of it. Aluminum wire is iffy in a lot of these smaller mig units, and usually requires a special teflon liner and a different feed roller to work right, but I have pushed aluminum wire through mine as long as the hose / cable was in a pretty straight line using the standard liner and feed roller. A spool gun works best with aluminum wire, so don;t get disturbed if you try it on aluminum and its ot as easy as steel and you get jams etc.......alum wire on a smaller MIG is like that.......it can be done, but not as easy as a larger unit handles it with a spool gun. ...

Some good wire that is well suited to home and farm use is AWS class ER70S-6. Dirt, rust and paint is a big problem with MIG, as MIG likes relatively clean materials, and this ER70S-6 wire handles materials that are not real clean better than any other class of wire. Lots of companies make it, so just look for wire meeting meeting AWS spec ER70S-6"

Notice that I'm controlling power with the distance to the work. Close in melts in more, further away increases the wire resistance. That decreases current and the weld is cooler and builds up more metal. Notice that my first weld is terrible because I forgot to do that. The next welds get a lot better.

Here are the finished ramps.
They used to have plywood boards bolted to them.
Now they've got strong crossbars instead and a railing at the end to keep from driving off the end.

Want more homebrew welders?
Try an AC stick welder from microwave oven transformers,
DC stick welding with car batteries,
Solar powered golf cart welder