emergency welding with batteries

2 battries are enough for most welding jobs but a third will make bigger jobs a lot easier. So you need two vehicles and leave a start battery in one of them.

I have used two battries to weld up a broken engine mount on a vehicle while on the CSR.

Join the battries with a jumper lead (300 Amp) I then use the electrode and earth lead off my home welder, as you say earth to earth and positive to the welding rod, which are for me Satincraft 12. Set the job up with clamps or some form of holding device, and away you go.

2 Batteries in series - 24 Volts

Series means you connect the positive of one battery to the negative of the other together. Then the two remaining terminals are used to weld from.

It really doesnt matter if its the red or black cable that is connected to the "job" as far as I know - but to make it simple - clamp the black (negative) cable to the job. There is no earth cable as such with 12 volt systems - just negative and positive.

I don't really know what sized rods to use - I'd imagine standard 2mm rods would be fine but I've never actaully put theory into practice.

It always makes wonder if it will stuff the 2 batteries you use. Theres alot of current being pulled. Don't think I'd attempt it if I was by myself - the suspension might be fixed - but now I cant start the bugger coz my batteries have melted!

-Myfourby

check out:

http://www.lcool.org/technical/80_series/bat_weld/battery_welding.html

- good pics of setup and demo's.

In series means connecting +ve on battery A to -ve on battery B. Then 'earth' (black) is negative on battery A, live (red) is +ve on battery B. The voltage will be higher Vtotal = Va + Vb = 24 V (assuming you have 12 V batteries), but the current capacity will be the same as a single battery (but will last longer).

Parallel means +ve A to +ve B AND -ve A to -ve B. Batteries in parallel will give you higher current capacity for same voltage (12V).

I think Jeff covered everything else.

The CCA rating of a battery tells you what current it can supply for 30 seconds to turn over the engine when it's at 0 deg F ( I think that's around -18 deg Celcius, which it probably never will be). eg a 600 CCA battery will continuously supply 600A for 30 seconds.

How long you can use the battery for welding also depends on the Amp-hour rating of your batteries. Say it's 50 Amphours, that means (in an ideal world) you can draw 50A for 1 hour, or 1 amp for 50 hours, before the battery voltage drops to 10.5V, which is when it's deemed to be 'flat'. So in theory you can draw 600A (the CCA rating) for 5 minutes, but it's not an ideal world and heat and other power draining processes get in the way, so you get less time to do your stuff.

If you are welding then you'll actually only draw current (around say 150A max) for a few minutes total for most jobs on your car - that's actual 'weld' time rather than all the set up and muck about time. I wouldn't like to guess how long you've got, but if the job takes longer than 5 minutes actual welding time then you've probably got a bigger problem on your hands than you can fix in the bush.

Jeff, I must agree with David/Dave, only use this system in extreme emergencys as the max time you will be able to weld is a couple of minutes and also the batteries do suffer. If you are looking for a substitute for emergency welding, second hand chevy alternator (120)amp converted by my local Auto Elec to supply the amps. I have fitted this system to my vehicle and have been using it for a few years now. Any good Auto Elec will know this procedure. There is also a web site that explains this setup somewhere, but cant remember the adress.

Hope it helps

Mik

I too have had to weld vehicles and trailers up in the bush about half a dozen times. As has been said two fully charged batteries will usually give more than enough power to weld most things up and still start the vehicle after.
The biggest job I've done was to rebuild an engine mount, radiator support cradle and reattach the drawbar on a box trailer that should have been left in suburbia.
We came across the vehicle involved (a 40 series troopy with trailer) by himself on a little used track a long way from regular routes and spent most of the day getting him mobile again. Used his two batteries, welded everything up and the two together still fired the old 2H into life when we had finished. I carry a selection of rods, satincraft 13's, cast rods and hydrogen rods for welding leaf springs. When welding leaves they must be preheated in a fire and cooled in the fire as it goes out which stops them cracking. I've also done a few alloy repairs using those rods that the bloke demonstrates on coke cans at the shows, they work well and I've repaired power steering pipes, thermostat housings and alternator brackets with great success.

Jeff , most things have been coved here , but one thing i will say , make sure you have a good earth ( black lead clamped to job ) , dosn,t matter how good your batteries are , if you havent got a good earth , you won,t get a good weld and you will find it hard to get an ark started .