A buddy of ours is a professional welder now retired and every once in a while in the conversation is what do you do when you are out on a job and you brake something but you don’t have a welder. Can you put something together with a few car or truck batteries and maybe weld a part good enough to get it back to the shop.
A lot of people do this and maybe its common in third world countries like west texas but its not really a great thing to do if you like your batteries and your equipment.
However in a real emergency yes it is possible to do some really rough welding by hooking up a couple car batteries and letting it fly.
YouRepair and its management really recommend against trying this but for the sake of discussion lets get to it.
If you know anything about welding you know that normally you use shielded gas or a flux of some type that creates a shield for your weld while you are welding. If you don’t shield the weld from oxygen you end up with a weak, brittle weld that won’t last.
Considering if this is an emergency situation you might not have access to a welding rod that is flux coated. If you try to weld with something else like a metal coat hanger your results are going to be just that much worse.
Amperage of the batteries is going to be very important. If you have larger batteries from a truck with higher cranking amps you are going to get a better result. Because you probably won’t be able to weld with one battery you will probably need to use 2 to 3 batteries to get a good arc going. Again this depends on the size of the battery. You have the choice to wire the batteries together in series or in parallel. To increase the strength you want to wire the batteries in series. This is where the negative of one battery is connected to the positive of the next battery and then you connect your arc welding leads to the remaining terminals on the two batteries. This doubles the output. If you wire them in parallel where the negative goes to the negative and positive to positive and then connect your welding leads to the end battery all you do is increase your welding time but not the output.
What Parts Do You Need?
For best results you want at least 2 gauge cable with heavy shielding. You also want to get some lead terminals to use for your cables. Finally you want to get a ground clamp and if possible an electrode holder to hold your welding rod.
More than likely if you are in this situation you will be using jumper cables to attach the batteries and clamp and weld your work but if you are you need to be really careful to not electrocute yourself and also that the wires don’t overheat.
Again the best situation is to use a thin arc welding electrode stick to do the welding because it has flux on it. If you end up using some steel rod or a coat hanger you want to get it as clean as you can by sanding the outside and you want to keep the diameter thin in the 1/8th to 1/4 inch thickness. Cut your rods to about a foot so you have good conductivity.
Make sure you are not looking directly at the weld when you are welding. Wear sunglasses if you have them and thats the best you have but even then you can not look near the weld when you are welding or you will damage your eyes. You need to wear an arc welding shield if you expect to watch what you are doing. So pretty much you need a solid shield between you and the work and also wear sunglasses to protect the best you can. DO NOT LOOK AT THE ARC WHILE YOU WELD. it can not be said enough. It will just be a matter of welding small spot welds unfortunately unless you have an arc welder’s shield.
Final Note
Can you weld with batteries? Yes you can. You can weld metal as thick as 1/2 inch thick under the right situation but there are problems.
First you have to completely shield your eyes from the work meaning its going to be near impossible unless you have a face shield.
Second you need the proper wire and connectors and really should have a stick welder electrode holder.
Third the welds won’t be controllable. You will burn through thin metal and not have enough penetration on thicker metals.
So the situation is that some people that live in remote areas will set up welders by putting together all of the right parts and taking precautions by using good shielded wires, proper ground clamps and electrode holders and even using a face shield.
In this situation you can perform some pretty decent welds. If you were building a remote home you could weld a steel flange or something else. Repair a piece of equipment. And you can do it with a little preplanning and basic things you will probably have.
On the other hand it is just as reasonable to buy a generator that also lets you weld. Or buy a small arc welder to use along with a portable generator. You are going to have much more control over your work and better welds in the end.
But if the end of the world comes and you need to weld something then you can weld pretty good with a few automotive batteries.
BE SAFE.. its not a good thing to try this. Get yourself a $150 arc welder and a $300 gas generator and you can weld all day in safety.