Imagine the apocalypse has struck, zombies are running wild, and civilization as we know it has ceased to exist– no phone service, no Internet, no electricity. Still, you must repair (or better yet, improve!) a metal tool (or better yet, a weapon!) but there are no welding machines available for use (nor an electrical grid to power them). There are however, plenty of abandoned cars left scattered about and since money is useless in a post-apocalyptic world, plenty of spare quarters that have no economic value. How will you make hard-core repairs to steel objects or construct new tools needed for survival? With three automobile batteries, battery cables (you’ll find them in the trunks of the abandoned cars), and quarters you can create a high amperage arc welder that will generate an arc of electricity between the metal work area and the welder electrode that is hot enough to melt steel.
The dangers of welding with car batteries
Before we begin, you should understand that welding with car batteries can be dangerous and should only be attempted in an emergency situation, and even then, the batteries should be covered to reduce injuries you could incur from hydrogen gases building up in the battery and exploding.
Also note that batteries wired in series increases the amperage provided by the batteries (a higher voltage is required to sustain the arc). If one battery produces 12 volts, two wired in series will produce 24 volts, three wired in series will produce 36 volts, and so on. Point is, lots of juice will be running through batteries wired in series.
And finally, remember there are also the normally expected welding dangers such as heat, sparks, eye damage from the ultraviolet light, and inhalation of dangerous gases and particulate matter.
Regardless, all welding dangers become inconsequential when you need a sharp metal weapon to stab zombies in the head.
How to create an arc welder using three automobile batteries
First, you will need three batteries. A single battery will not suffice. Three batteries will provide 36 volts of power – enough amperage to enable arc welding. The batteries must be wired in series (positive pole of one battery to negative pole of another battery) in order to produce the amperage needed to start and sustain the arc. To wire the batteries in series, set the batteries end-to-end and connect the positive end of one battery to the negative end of the next battery. For instance, connect the positive terminal of battery 1 to the negative terminal of battery 2, then connect the positive terminal of battery 2 to the negative terminal of battery 3, and so on.
The last free positive terminal will be connected to the metal object that we are working on. This becomes the “ground clamp”. Simply clamp one end of a pair of battery cables to the positive pole of the last battery and the other end of the battery cable to the piece of metal you are working on.
Next you must attach the electrode to the battery cable (don’t connect the battery cable to the battery yet). You can use a quarter as an electrode in a pinch but it is much easier to use a normal welding rod (easier to work with, produces better welds, and it’ll last longer). If you opt for a welding rod, you may need to use pliers to pry the teeth of the battery cable inward in order to make a slot to securely hold the welding rod in place. Make sure that the welding rod (or quarter) is secure in the clip and that there is as much surface contact, between the battery cable clamp and the electrode, as possible. Tying a rubber strap, such as a bicycle inner tube or other elastic material, tightly around the clamp may provide more pressure to hold the electrode firmly in place. Similarly, vice grip pliers or a similar locking tool can be used to hold the clamp tight around the electrode (but they do tend to get in the way).
Finally, to complete the connection, take the free end of the battery cable that is holding the electrode and attach it to the last remaining free battery post (which should be negative). Once connected, the welder is now “hot” so be careful what you touch with it and where you set it down.
At this point, you will likely want to cover the batteries with some sort of protective covering (jacket, welding blanket, sheets of plywood, etc.) to keep sparks from igniting the batteries and to offer at least a little bit of protection if the batteries were to explode. You’ll also want to make sure you are wearing welding gloves, a welding helmet, and non-flammable clothing – typical gear you would use with any welding job.
How to weld
Now that the welder is ready to go, we next must “strike an arc”. Hold the electrode holder (i.e. the battery clamp) in your dominate hand and sweep the electrode against the work so that it sparks and flares up. It make take a few tries but the objective is to stop the electrode about 1/8 inch away from the work so that the arc is maintained, melting the electrode and the metal beneath it. If the two metals accidentally touch, the circuit will be completed and no arc of electricity will be created or sustained. It may take some practice to get the electrode close enough to strike an arc but far enough away to not complete the circuit.
Once the arc is created, hover over the area where you want to start the weld to give the arc time to form a puddle of molten metal on the work. This will be your first “tack weld”. Do the same thing at the other end of the metal you are working and every six inches in between. The “tack welds” are needed to hold the metal work areas together while you run the continuous weld.
The glassy-looking substance on the resulting weld is “slag”. As the electrode is heated, the flux on the outside of the rod boils away, spewing out a shielding gas that pushes away air, purposely saving the hot welded metal from oxidation. You can strike the slag with a hammer to break it away and expose the weld underneath.
Potential problems and solutions
Since welding with automobile batteries is not as controlled an operation as using a real commercial welder, there are bound to be problems, some of which can be overcome with a bit of practice. For instance, it’s impossible to control the amperage using a car battery so if the welding rods are too thin, they will basically evaporate. The solution is to use a thicker rod or tie two rods together using baling wire.
Sometimes the electrode gets stuck to the work area. In this case the circuit is completed and no arc is thrown. The rod will heat up and likely catch on fire. Simply break the circuit by releasing the electrode from the clamp. Once the stuck rod cools, you can pop it off with pliers or a hammer.
If things seem to be working, strike an arc, then make a puddle of molten metal. Push the rod in a little to fill the melt pool, them move forward a little (half the diameter of the weld pool) and repeat. Imagine that you are making a red-hot stack of dimes that overlap each other. This will produce the “prettiest” and most effective weld.