Introduction: Spool Gun Handheld Wirefeed Welder Powered by Car Batteries

Picture of 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

Step 1: Gun Shopping

Picture of Gun Shopping

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.

Step 2: Power Supply

Picture of Power Supply

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.

Step 3: Flux Core Wire

Picture of Flux Core Wire

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.

Step 4: "Reverse Polarity" ???

Picture of "Reverse Polarity" ???

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.

Step 5: Wirefeed Speed

Picture of Wirefeed Speed

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.

Step 6: Always HOT!!

Picture of Always HOT!!

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.

Step 7: Bamboo Insulated Tip

Picture of Bamboo Insulated Tip

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.

Step 8: Replacement Parts

Picture of Replacement Parts

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 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 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"

Step 9: Spoolgun Video

Picture of Spoolgun 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 more metal. Notice that my first weld is terrible because I forgot to do that. The next welds get a lot better.

Step 10: Ramps!

Picture of Ramps!

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


zacker (author)2016-12-01

can this be made to run off of 110v house current? it would be great to just plug it in and use it without haveing to store car batteries and keep them charged.

JamesF201 (author)zacker2017-05-20

I figured this was a good idea and decided to modify my horrible freight welder to stick got the rod stuck lights go off fan dies <thinks> oh i popped my breaker <end of thought> wasnt the issue still dont know what is but essentially that is what a horrible freight welder is a transformer with two outputs that you can weld with (you can make one but oh is that sketchy) a mig wont have the problem because the wire never gets stuck (short circuits) for long periods of time so no consistent building up of heat / just know AC will never run right for flux cored welding it needs DCEN (direct current electrode negative)changing polarity 60 times a second (60 herts AC what the US uses) is like trying to weld with a sparkler your kids play with on the 4th of july it work but terrible weld quality id say just find a hf welder and modify it with a brige rectifirer like i should have done people do it all the time and see good results just dont cheap out with the bridge and capacitor and you will be good

zacker (author)JamesF2012017-05-22

lol... yeah i took out my little HF Stick welder to mess with it some more. I did get a "Better" weld... Meaning that the two pieces I welded together actually stayed together when I beat on it with a but the weld looked horrible. And when I say horrible, I mean HORRIBLE lol I do like the little wire feed HF welder but man... I'd much rather have a proper Mig with the gas set up and all that.. I really need to have a 220v line run out to the garage so I could get a proper welder set up!

JamesF201 (author)zacker2017-06-07

i did the instruct-able with my taken apart hf wire feed welder with an optima blue top and a walmart car batery and i was able to blow holes through stuff id like to know if theres a way to limit the voltage going to the gun

JohnG71 (author)2015-08-10

BradH13 (author)2015-07-15

Real nice! I'm thinking of doing this for my off road rig, like Bender Ridriguez. I'm going to use a gun that's gas compatible so that I can run hard wire for steel and also use the gas bottle for running pnuematic tools and airing up tires.

Bender Rodriguez (author)2015-05-13

You know, I was thinking this could probably be run on a pair of 24V electric bike batteries in parallel as a backpack welder setup. That would be amazing for off road repair and whatnot.

Emperor Towhid (author)2014-10-30

Very nice thank you very much. (author)2011-03-14

I don't get why people think that all these currents are so different. Our school shop has Lincoln stick welders that run DC with the work clamp positive or negative, and they have AC. I guess for this kind of welder a positive tip is different but not for "all" of them.
By the way, great video.

bigbodysmallbrain (author)jj.inc2012-01-12

does your school shop have mig welders? if so then you should know that polarity maters using flux core(DCEP) versus solid wire(DCEN). that don't mater much on arc welders the polarity on those is dependent on where you want the heat to go(though if your welds have the DC ability don't use AC).

You're supposed to use DCEN with FCAW and DCEP with Mig. The type of welding current does matter on stick depending on the electrode you are using. Some electrodes do not work well with different currents. For example, 6010 should be run on DCEP, whereas 6011 can be run on DCEP and AC current.

I'm not saying you can't get it to run, but it will perform poorly.
I know this is old, but people can still find this and take away the wrong information.

ZacWolf (author)2013-07-16

Hey, I used your Instructable as a basis for building a portable welder. I created an Instructable for my project, and would be honored if you'd comment on it!

HiramAbiff (author)2012-09-30

I think I saw a post here about using a couple of microwave power supplies. My question is, could this be done with a couple of pc power supplies (I imagine in series to get the voltage up closer to 24 volts -ish)? As these are switching supplies, I am nit sure this would work out. If it did, I am thinking that the 40 +/- amps one could get from a pc ps (or two in series) would be plenty for aluminum. Of course, since there are a lot of these things around for almost free at surplus, maybe use 4, a set in series and each set in parallel to up the current if needed. Am I on the right track, or would the switching ps or any other aspect of a pc ps make this a bad selection for a spool welder ps?
Thanks in advance.


Adam Manick (author)HiramAbiff2013-04-29

In theory it would work. I was planning on building something very similar to that (I'll post an Intractable if I do). The problem is that flux cored and mig welding both work best on DC; the microwave transformers obviously have an AC output. Now, some cheaper flux core units do use AC, but this produces welds with allot of spatter. The only way to do it properly would be to rectify the output, and the diodes can get pricy. Another obstacle, is that mig welders do have to be adjusted more so than others; a stick welder for example. So, it would be best to also have a way to adjust the current.

L3indy1965 (author)2012-12-29

Might you describe the wire hook up, can't make it out from the picture?

mikemmcmeans (author)2008-11-09

the bamboo is amazing apply this to a soldering iron, using the small tubes of solder stead of a spool

nevermind, i have dibs on this instructable

Spokehedz (author)mikemmcmeans2008-12-01

They make those already, and they absolutely STINK ON ICE. The problem is that unlike welding, soldering requires the wicking process to actually get into the joints of the part/wire. Welding is just blobbing new material to melt the other two metals together. Plus, you don't want to constantly be feeding solder into a joint. You want to heat the joint (touch the iron to the part) and then touch the solder to the other side of the joint (NOT THE IRON) and let it flow into the joint.

Derin (author)Spokehedz2008-12-12

So that was why my solder joints were terrible...I was touching them to the iron to melt it. I am a bit lazy. :)

ear0wax (author)Derin2009-03-01

That actually harder to do than soldering properly. Dont worry ever one does that at first.

Spokehedz (author)ear0wax2009-03-02

Well, I think that it's how most people who teach people how to solder... They teach cleaning the iron first--which is blobbing a bunch of solder onto the end, and wiping it off on a sponge... and that sticks in your head on how soldering works. I blob the solder onto the iron, and then it sticks to the part. This is flawed for a couple of reasons. 1) The solder never sticks, as the part is COLD and the solder is HOT. 2) The joint that is made is always a 'cold' joint because the flux boiled off on the tip. 3) People love watching solder melt for some reason--and this gets them thinking that you need a LOT of solder when you actually need very little. What I do, I teach people how to tin wires first--a skill that I see as being the most important one in Soldering. How I do this is I clamp the wire into a handy-holder and then tell them this: 1) heat up the wire for a second. 2) touch the solder to the wire, and watch it wick. 3) move the iron up and off the end of the wire. Taa-daah! And then i move onto though-hole components. Same principal, only with a component leg rather than a wire. The students pick up instantly on what they should do. Then I move onto SMD which is only marginally trickier. Replace "wire" with "component" and the steps are the same. Once that is all out of the way, then we learn cleaning. Wipe it off on the sponge/stick it into the copper cleaner. There. Now they have all the skills they need for soldering, and IMO in the proper order of importance. Sure, a clean iron is a happy iron--but if you don't constantly blob a bunch of solder on there, and let the flux burn off, then your iron wont get dirty in the first place. Proactive thinking, rather than Reactive thinking.

snowluck2345 (author)Spokehedz2011-07-17

I always leave a blob of solder on my soldering iron and I use that when soldering, but just to get better heat conduction between the iron and wires. Then I apply solder to the wire.

lukeyj15 (author)mikemmcmeans2009-04-05

what about using thick solder instead of flux

frontpage (author)2010-01-25

hi there ok question how hard wold it be to make the battery power variable so rather than having to vary distance you just vary vary the voltage something like a foot pedal for a sewing machine but beefier ? would this work and how hard to do ? or some sort of dial ? ? ? ? sorry far from expert hoping this adds to this and so want to try this .. alot cheaper than $500 for a bigger used 120v mig welder too lol ..

jchambers (author)frontpage2011-05-22

you could just buy a cheap mig on ebay, and feed it with fluxcore rather than buying a gas canister.

onlyeh (author)2011-01-19

Nice mobile get you out of trouble idea. You can do the same with a set of jumper leads and some welding rods.
Beware that it is a dangerous practice as the batteries give of a very flammable gas when worked hard and the sparks canmake them explode spraying you and everything with Acid and not to mention the fire burns, so good ventilation is needed and some cover on them to keep sparks away.

pseudoki (author)2010-10-21

very nice instructable, any chance you could weld aluminum with this setup?

abadfart (author)2010-02-05

very cool I'm going to make a transformer to output 24 v  so i have a small rig to keep in my apartment

twenglish1 (author)2009-10-12

where can i find one of those spool guns, fairly cheap, and could i hook the spool gun up to a stick welder? will it work like that?

ravingking (author)twenglish12010-01-19

i was thinking exactly the same . my welder is 48v 200a and i reckon thats to much. any help would be great

twenglish1 (author)ravingking2010-01-19

mig welding is done around 20 - 30 volts right? and the use a constant voltage power supply, instead of the constant current stick welders use, the voltage on my stick welder is too high anyway, i measured it, it is like 80 volts open circuit voltage that is

MrRodrigez (author)2009-10-01

sweet i think i might try this for practice in welding class

Sun Gear (author)2009-02-26

can u use 2 microwave transformers (with 10-guage wires for the secondary coil) instead of 2 car batteries.

bylerfamily (author)Sun Gear2009-07-19


dodgedartgt (author)2009-07-03

Tim, I enjoyed reading through your welding tutorials, thnx. This one in particular has intrigued me. As for the tip always being "hot", I think there is an easy way to resolve that issue. At the junkyard, grab a starter relay (I think the Ford style double post would be ideal) and use the roller feed power to energize the tip when the trigger is pulled. Just an idea I thought I'd share. Mike Bynum

John Kiniston (author)2008-10-21

This is really cool.

Lor (author)John Kiniston2009-06-29

love the hat!

Sandisk1duo (author)2008-10-31

i wouldn't park my car on those ramps...

cowgomoo (author)Sandisk1duo2008-10-31

yah the welds didnt look very nice... but who knows... im not very experienced in welding.

cowgomoo (author)cowgomoo2008-10-31

oh its cuz its chicago brand haha

Lor (author)cowgomoo2009-05-03

I think they look great. And if you're concerned about cosmetics, you could always put a finish on them. This project is great. I've been looking for this. I'm not a welder, and I don't want to spend a lot of money on the equipment when I'm not going to do it all the time. But I need it for a project. Thanks so much. You've saved me!

Derin (author)Lor2009-06-29
Quoting TimAnderson:
A wise lady once told me:"A project isn&apos;t finished until there&apos;s a finish on it.Get it?"
Lor (author)Derin2009-06-29

very punny!

cberes (author)2009-01-26

How long of a bead were you able to put down before the batteries gave out? How often did you have to recharge your batteries?

mschefter (author)2009-01-15

Cool Instructable! I will diffidently have to make something like this. Would be perfect for quick and dirty fixes on the off road trail!

LinuxH4x0r (author)2008-10-21

Not bad! I personally prefer stick (SMAW)

Derin (author)LinuxH4x0r2008-10-23

i prefer the simplest stick welding (AC with no controls)

LinuxH4x0r (author)Derin2008-10-23

Then you can't control the amps and your welds turn out either too hot or too cold making them weak

Derin (author)LinuxH4x0r2008-10-24

i remember we welded a broken trailer hitch with it,and it still lasted for being used twice a day for a year or two The load is one man,steel trailer and about 12 50 kg bags

Esmagamus (author)Derin2008-10-30

And I remember a welder that welded the ends of a reinforcement on a device that is used to haul fishing nets back into the boat. The stress on the reinforcement broke the supporting beam and the whole thing fell on a fisherman and killed him instantly.

About This Instructable




Bio: Tim Anderson is the author of the "Heirloom Technology" column in Make Magazine. He is co-founder of, manufacturers of "3D Printer" output ... More »
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