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I don't know where I first heard about this, but a few months ago it was brought to my attention when browsing through a South African off-road website.Welding McGiver style using 12 volt car batteries. Numerous other off-road sites can be found with descriptions of it as well.
Well, I just had to try it. And even before trying it myself, I volunteered to demo how its done at the VanIsle Rally on June 11. Me and my big mouth. So, over the past week, between long hours of work, I've collected and prepared the equipment, and this evening I did the testing. I'm really excited about the results. This is a great emergency repair tool and I plan on carrying the kit with me on long trips from now on.
List of equipment:
2 12 volt starter batteries, fully charged. Not Deep Cycle.
4 Lead Battery Clamps
20-30 feet of heavy cable, either from a good quality jumper cable set, or used welding cable, which can be found easily at a flea market, auto jumble, or my shed...
2 Clamps, one end can be a standard jumper cable clamp, but the other end you are best to purchase an actual electrode holding clamp, about $16 or find a used one.
Welding Mask or goggles, full hood not required, as this is only for short term emergency use.
Welding Rods, 2.5 mm general purpose, or "dirty metal", farm use rods will work fine. I used #6011 rods.
Gloves
Fire Extinguisher
Resistor Wire, a foot or two of 8 to 10 guage galvanized fence wire will do fine.
I started out by gathering this all together. In the shop at our place, there were numerous old discarded welding cables from the previous owner, so I used 2 15 foot lengths, and a couple of used ends that were laying around. Also, I was able to find an old hood. I had to go out and buy the welding rods - $10.95 for about 25 of them, a new piece of dark glass for the hood, and I found about a foot of 8 gauge wire, which the hardware store threw in for free.
I assembled 3 well charged batteries on the driveway, about 20 feet from the house in case of explosion or fire. Two of these came right out of my Land Rover, and one was recovered from a vehicle that had went to the wrecking yard recently. [As an aside, never store an unused battery on the ground or concrete. It will have the life drawn right out of it, never to recover. This has something to do with the conductive qualities of battery acid, and the fact that there is a light grime layer of acid adhered to the case of most batteries. This acts as a short to ground and will draw the charge right out. Don't ask me how I know this. Always put a battery to be stored on a piece of wood, instead.] The three batteries were each 625 cold cranking amps. So by linking them together in series -- positive to negative -- the maximum potential amperage would be 1875 amps. Wow, that's pretty heavy duty welding, since 120 to 150 amps is more typical of what's needed for day to day AC welding. I figured I'd have something a bit more like a plasma cutter than a welder.
One of the sites suggested putting a resistor into the curcuit, which reduces the amperage, but, of course creates heat. Remember, you'll be using this for emergencies so you want everything to be really simple. I used 8 gauge galvanized fence wire for this purpose, putting a small U on the end and then attaching a battery clamp on each end. This goes between two of the batteries and you should be very careful that no part of the wire itself touches or comes close to the plastic battery cases, as it can get quite hot.
Trial number 1, 3 batteries. I clamped a 2" by 6" piece of 12 guage flat iron into the ground clamp and figured I'd try to create a bead on its surface just to get the feel for it. Well, in seconds I was digging holes -- I had a cutter on my hands. It cut through 2 inches like butter. Checked the clamps on the batteries, nothing even warm. Checked the resistor wire, it was warm, but could still be touched with bare hands.
Trial number 2, remove 1 battery, keep resistor wire in the circuit. Again I tried to create a bead. This time, it was successful and I was able to run an inch of weld quite easily across the metal surface. The most noticeable difference between regular welding and this was the lack of power behind the current -- lots of zap, but everything seemed to be happening in slow motion. The circlular motion of creating the bead also had to be slowed down. I can still touch the resistor, not too warm.
Trial number 3, still with 2 batteries and the resistor in place. This time I planned on welding together two pieces of 1" square tube, 1/8" wall. I think this would be typical of the work it would take to re-attach a broken spring hanger or other trail carnage. I stopped a couple of times for a few seconds to check the resistor wire. It got hot, but not untouchable. 4 inches of welding later, I have a fairly flat bead, but with deep penetration. There seems to be a fair bit of spatter, compared to the mig welding I normally do, but this may just be a characteristic of this particular rod.
Trial number 4. This time I changed the resitor wire back to a normal thick battery cable. Even with two batteries rather than 3 I had a cutter again. Actually it was quite controllable, so in my kit I'm keeping both the resistor wire and the standard cable.
A few things to note:
--Always make sure all your connections are well tightened on the batteries before you start. Loose connections can result in arcing at the battery terminals, not only causing danger of fire or explosion, but the current going through is very high and the heat generated will melt the head off a battery terminal in no time. As long as all terminals are tight, there is no heat created at the batteries.
--Work about an inch or two at a time and let everything cool off before continuing. Each inch takes about 15-20 seconds which is similar in draw to cranking your starter.
--Always use starter batteries and not deep cycle batteries. The deep cycle ones are not made to take deep amperage draws like that needed for welding.
A small canvas sack to throw your cables in and you have a portable emergency welding kit. Don't forget to use gloves and keep a fire extinguisher close by!
