Have you ever wanted to get into welding, but don’t know how? Then go and buy a cheap 100$ welder instead of reading this post. It’s safer, in fact cheaper and you will probably make better welds after a month or two than using this method.

Why would you want to weld with car batteries?

That being said I have a feeling that some people might be in the same boat as I am and for some reason can’t get a regular welder. Maybe your basement or garage doesn’t have (the necessary) power, or your landlord would hook you up to DC current if you tried welding at home – or like me you use your truck as a workbench so that you can drive wherever you want to work and craft and build and be creative.

How To Weld With Car Batteries (and why it's awesome) 1

Why not have your own little workshop near your favorite lake?

In this post I’ll give you a report on what you need and how to weld with car batteries, from a practical standpoint and with actual experience because I do this at least once a weekend.

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This is me making scrap art with my hacky battery welder.

I researched (mobile) welding for months before purchasing the gear explained in the next step and I have come to the conclusion that welding with two car batteries is actually the cheapest and best option if you have to weld off the grid. There are two other options: A welding generator (cheapest one in Germany at 600€) or an actual battery powered welder like the Li-Ion welders made by Fronius, Lorch or Würth. I link those just in case you have the over 3,000€ to spend that it costs to get a professional one, not that I wouldn’t if I could.

A generator welder has the severe disadvantage of being noisy, I for one just can not concentrate while an engine is running next to me and I hate how wasteful it is to idle it when I only need it every couple of minutes.

So in a lot of ways welding with car batteries is actually the best option – for me – and now that I have used this setup for a couple of months I can recommend it to at least some people.

This is also a really nice option if you do off-roading, which I don’t but it seems to be one of the primary motivations for why people do this kind of thing. You can simply slap a handful of electrodes in a container and buy a cheap welding glass just in case someone breaks something. The rest you have with you considering you have at least two cars, or you take a second set of jumper cables and have a truck that has two batteries like many do these days.

What you need to weld with car batteries

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It’ll be pricey at first, but good things seldom come cheap.

One of the nice things about car battery welding is that it’s super simple from a technological standpoint and you might just have most of the needed gear at home. So here’s what you’ll need:

  • An understanding of how welding works and why it works. Go watch some YouTube videos on welding for beginners and start this build only after you understand the basics. It’s important, you’re playing with potentially lethal electricity that can blind you and emit dangerous fumes, get a basic idea of what you’re getting yourself into.
    • Don’t let yourself be discouraged, with a bit of common sense welding is fun and I wish I had gotten into it sooner. It’s incredible how many options suddenly open up and you’ll wonder why you never tried this before.
  • Two 12v car batteries, ideally new, good ones and of the same capacity. This is not a hard requirement, it just makes it easier to know when to charge your bank. 3 batteries is also an option, I just found that 2 work just fine and in fact are a little too much current for thin metal sometimes.
  • One set of jumper cables, get the sturdy kind as the price difference is negligible. If you get thin cables they will heat up and you might or might not run into issues. I started with the thick ones from the beginning so I can’t comment on whether thinner ones work or not, but we’re talking about 20 bucks in total here so do it right.
  • Either a second set of jumper cables or a battery connector. I bought a connector but if I were to do it all over again I would buy a second set of jumper cables.
  • A pack of electrodes, I found that 2.5mm thick works best. They run a little hot, but they start consistently and the welds hold just fine. I do not feel comfortable suggesting exact brands or the strength in inches, but they are the third-smallest size here if you need a ballpark. You can get little packs of ten to experiment though for roughly five bucks, then you’ll know what works best for you.
  • Welding gloves, a welding mask and ideally a sturdy jacket.
    • Spend the money on an auto-darkening mask. Mine cost 70 bucks at the hardware store and you can get a good one for about fifty bucks. Fifty bucks is how much I wasted on a shield (hold it in one hand, only have one free, see nothing of your electrode until it sparks) and a flip-up hood (same problem, but at least you have both hands free). I just couldn’t work with those two, the auto-darkening mask is what you’ll want to get.

In total I spent

  • 220€ on two (good, new) 12v car batteries
  • 85€ on protective gear (70 mask, 15 gloves), not counting the money I wasted on two bad masks
  • 50€ on the jumper cables and battery connector
  • ~20€ on a massive pack of electrodes that will last a looooong time. It’s so big the woman at the register struggled to lift it which was a little funny, that little pack doesn’t look as if it weighs ten percent of what it actually does.
  • 25€ for a battery charger. This is an item you can easily get used, people buy them once to recharge their dead batteries and then never need it again all the time.

So that puts me dead at 400€ and I could have probably saved some money on the battery front. The cheapest (new) car batteries at my hardware store were forty bucks each, but I knew I wanted something decently sized so that I do not have to worry about charging them so much. Each time I charge the batteries I have to carry them up to my third floor apartment (no power sockets in the basement remember?) and it is no fun.

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Those things are HEAVY. Luckily I only need to recharge them every couple of weeks so I feel like the extra bucks were worth it.

How to build the car battery welder

When you have all parts together the actual build is super simple. All you have to do is connect them in series which means you connect the negative of one battery to the positive of the second.

It does not matter which battery connects to which, you end up with one positive and one negative „open“ connection in the end.

The only thing that matters is that you connect your jumper cables to the work piece and electrode in the right way. Stick welding with electrodes works best when you connect the negative (black / – ) to your electrode and the positive (red / + ) to the work piece.

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I use the red cable to connect the positive of the second battery to the workpiece. This way I always know which color is which.

Depending on your jumper leads you might have to bend the copper parts of the black / negative a bit with a Leatherman or something just so that they can properly hold the electrode.

Then you put on your mask, stick an electrode in there and do a test weld.

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This was the very first test I did with two rusty, muddy pieces of steel from magnetfishing and yes, it looks horrible. It does however hold so well that you can’t pry it apart even with a hammer.

If you go back to the picture above you will see a weld I did a little later while making scrap art wind chimes, that too holds just fine and the weld looks much better in my opinion.

The quirks

Since this is certainly an improvised way of welding there are some quirks, only a few though. The one I noticed most was that it sometimes gets hard to start a rod, but I think that is a universal problem. I solve that by breaking off a tiny bit of the flux with my glove, just push the rod against your gloved finger and turn it once and then you can start welding. I’ve seen some people scrape the rod, but that might not always work when the pieces are just pressed against each other and not tack-welded together yet.

Another thing I noticed is that if you get your rod stuck you should open your black clamp immediately and get it off. If you don’t the rod will overheat and melt, which is not the end of the world as the rod serves as a circuit breaker and all that happens is that you can trash that electrode.

The good

If you do this one or two times you’ll come to realize that it’s actually a pretty easy thing to do and if you do it ten times the welds will turn out quite okay for hobby purposes. I make all my scrap art this way and welded a little holder to my truck where I hang my hearing protection headphones and that thing is rock solid.

I have by now easily made that money back just in scrap art sales and there have been a couple things I tacked together for friends in exchange for gas money and some beer as well. Of course nothing of that is structural welding on life-threatening parts but for things like fences, tool repairs and such there is really no reason not to do it this way.

I hope you enjoyed this post and the pictures! In case you want to see more of the welder in action let me show you this trailer I built for flea market selling, near the end I do a bit of welding on a part:

I'd love to hear your comments!