Back to front page

Go to yahoogroup 80SCOOL email group

Enter the 80SCOOL picture gallery

A wealth of technical information

You've got the car - Now learn how to use it

80SCOOL group stuff for sale

80SCOOL Trips

What's 80SCOOL all about?

Emergency Welding
Using Automotive Batteries

Another Sunday morning with little else to do but tinker in "the shed" ;-)

General information:

Most DC welders work at around 40 volts, and a general purpose electrode of 3.25mm will need about 120 amps for good penetration of weld. 36 volts is available from three automotive batteries connected in series. The batteries we use in 4WDs are more than capable of supplying the amperage for an ample amount of time for a repair weld; after all, they supply winches at up to 400 amps, and starters on diesels at 300 plus!

There is no danger of electrical shock using automotive batteries in this manner; however, the batteries should be disconnected from the vehicle, and protected from welding sparks.

Case histories:

1) In the late seventies, three other Land Cruisers and mine traversed the Canning Stock Route in Western Australia. In those days the route was ill defined and there was no support in the way of fuel dumps, and water supplies were unreliable. We carried heavy loads of fuel and water (650 litres fuel and 60 litres water each) and supplies for 20 days.

The weight and rough conditions caused one vehicle to break a front wheel bearing spindle. We painstakingly filed the fracture to a vee for welding, welded it, filed it to refit the bearings, and it lasted 100 metres before breaking again. We then hack sawed off a piece from the inner axle and welded it through the spindle to make a solid unit. The vehicle no longer had 4WD, and required towing over some dunes, but it made it home.

2) In the early eighties I built six land yachts, and with some friends, circumnavigated Lake Frome (large dry salt lake in South Australia). One of our group was nicknamed "Disaster Dave". In thousands of square kilometres of lake, Dave was quite capable of having a head on with one of the other yachts; and he did, breaking his yacht's chassis in half. We were able to use battery welding to get him mobile again.

3) On two separate occasions while doing some cross country exploration in the Simpson Desert, we successfully welded broken main leaves in a Hilux and MQ Nissan. This was done with general purpose rods by filing the breaks to a vee, warming the spring in a fire to weld, and burying welded area in warm sand to slowly cool and stress relieve the weld.

4) The photo of Bal and Richard (bottom picture) shows them constructing a makeshift drive shaft from a piece of water pipe. This became necessary when the shaft banged on a rock and was twisted completely in two pieces.

This is all you need for battery welding. The light jumper leads joining the batteries are carried in my tool kit specifically for this purpose. The various size general purpose electrodes and glass from a welding mask are carried in the plastic electrode box, and held against movement by a rag stuffed in the box with them. The electrode is more easily held by a pair of vice grips than it is by the jumper lead clamps.

You will notice that the earth to the work is positive. This is the norm in DC welding.

One would normally keep the work as far as possible from the batteries, and cover the batteries with a ground sheet or blanket. This reduces the possibility of sparks from the weld igniting the hydrogen gas produced by the batteries.

Batteries do not need to be all the same size. If three batteries are not available, 24 volts can be used, but it will be difficult to hold an arc unless you are an very experienced welder. With 12 volts only, an acceptable weld is virtually impossible.


This shows one method of introducing resistance to the circuit to reduce amperage for small diameter electrodes. It is simply a piece of "good ole" No 8 fencing wire. It can be increased/decreased in length to change resistance, and held to battery post by vice grips or tight twisting. Be aware that this piece of wire will get very hot; perhaps to the point where it will droop and melt the plastic battery case(s). KEEP AN EYE ON IT!

Heavier wire, or smaller wire doubled up, can be used to join all the
batteries if no jumper leads are available.


In this case Bal was able to scrounge a welding mask. If no mask is available, tape your welding glass into a cut-out in a piece of cardboard. A mask and skin covering is necessary to prevent radiation burn (like sunburn) only if you are doing any appreciable amount of welding.

If the weld is going to be short (a few seconds only) simply hold the glass close to your eyes.

In high ambient light (bright sunlight) you will get away with using a couple of pairs of sun glasses on top of each other. DO NOT attempt to weld without proper welding glass in low ambient light conditions. In these conditions, heavily dilated eye pupils will allow intense welding light to damage eye retina.

From South Africa:

I read of welding with car batteries on the 80's LCOOL site about six months ago and forgot about it until this past Dec. I am writing this in case anyone find themselves in a situation where this can be used.... Hope it will not happen but then sometime it does...

On our way from Vioolsdrif to the Richtersveld in South Africa we used the road through Helsekloof pass and Eksteenfontein. Yes, the road was badly corrugated but at about 80km/h it feels OK in the Cruiser. I towed a Venter Bush Baby trailer with standard leaf springs and without aftermarket shocks.

We were 3 cars in the convoy: Cruiser, Range Rover and Hilux 2.8 TD. The road started taking its toll. The RR's back doors opened every now and again and the familiar call over the radio that the RR is stopping to close the doors came trough every so often. The Hilux had an after market extra petrol tank and about 40km from Kuboes the pick-up pipe inside the petrol tank broke off. Result was that we had to change the petrol pipes running to the engine around so that it uses the "return-to-tank" as its pick-up. Don't know if it work the same on the Cruisers but it is something to keep in mind.

About 20 km south of Kuboes I saw my trailer jumping violently. Stopped to asses what was going on. The axle moved and the wheel was touching the back of the mud guards causing it to jump each time the tyre touches the mud guards. The leaf spring bracket broke where it attaches to the trailer body. We pulled the axle in line and secured everything with some wire. Whilst we were doing it a Local came past and we were taken to his Uncle in Kuboes for a welding job. Welded, fixed and least we thought.

We entered the Richtersveld at Sendelingsdrif at about 20:00 and was routed to Potjiespram for camping. The next morning we returned to reception at Sendelingsdrif, completed the paperwork and proceeded to Richtersberg camp site. The trailer was checked every so often and everything was OK. At Richtersberg we did a recon of the campsites and whilst reversing with the trailer the leaf spring bracket broke again. For those who have not been there - Richtersberg is about 3 hours drive from the closest infrastructure through quite hospitable terrain. Towing a trailer fixed with some wire was a last option. We did the beer thing and thought..... I mentioned that I have read about welding with car batteries but was met with a healthy dose of scepticism. One of the guys with us welds for a living  and he offered his talents if we could get the welder going...BUT... We did not have any welding rods.

That is where Koos comes into the picture. Koos is a local herdsman and stays at Richtersberg. He had a battery problem which we sorted buy jumpering his Hilux and borrowing a spare battery to him for a day. We explained the situation and he offered to get some welding rods on his scheduled visit to Kuboes the next day. So said, so done.. Koos arrived the next evening with some welding rods... but the only ones he could find is 3mm. This normally required around 140A if you use an ordinary welder. The welder-man was worried......

The next morning we took out my 2 105AH Deltec's and a 55AH Raylight. Now we have the batteries but it was clear that the jumper cables would not suffice as welding leads because they are way to thin. As luck would have it I installed some welding cable for my additional battery in the luggage compartment.

I took out the earth strap and used it for the welding earth lead. I had an off-cut of the welding cable in my toolbox which we used as the positive. We connected the 3 batteries in series giving us about 36 Volts - amps unknown. To limit the welding current we used a piece of "Bloudraad" (thick bluish wire) between the terminals as resistors.

We took a battery terminal clamp to secure the end of the positive lead to the welding rod and used a vice grip for the welding handle.

TEST - It works fine but it was burning holes in the metal so we removed one of the batteries and only used the 2 Deltecs in series to provide less amps. One could have probably lengthen the resistor wire to limit the Amps as well but in any case ......

Our pro-welder did not have a welding helmet but closed his eyes whilst welding. It worked fine.

30 mins later the job was done.

We left the park after the trailer was fixed. The weld held through the rest of the trip (down to Hermanus (on the  SA west coast dirt roads), Jeffrey's Bay and back to Pretoria).

Learning points:

  1. I have now made up a set of jumpers with welding cable
  2. I will always carry welding rods (2mm, 2.5mm, 3mm) and a loose smoked welding glass insert.
  3. Make sure that the connecting wire between the batteries makes good contact with the battery's poles. My one did not and took away half of one of the poles. I used a vice grip after this to secure it properly to the poles.
  4. Always remember what you read......

Hope this will help somebody in future.

Best Regards

Anton Matthee

Pretoria, South Africa