12 volt 'DC' welding - The good, the bad & the ugly (video)

Not at all Alby, it hardly knocked anything out of them. Did your mate have them set up for reversed polarity? Unfortunately we've welded using this method far too many times now and batteries are still going strong.

Cheers

Mick

I don't know the details Mick
He was just telling me of the problem after helping a stranded vehicle on the Canning and had to replace his batteries further into the trip

It may well just be coincidence but he is an electrician so would expect he had a reasonable idea of his batteries condition pre trip.

Good video though Mick

thanks for sharing

Maurice,

With the electrode on the positive terminal you are welding with reverse polarity. In a nutshell;

Straight Polarity (DC-) puts more heat into the work piece giving a deeper penetration, while Reverse Polarity (DC+) puts more heat into the electrode. Heating the rod gives less penetration and a broader puddle. You also need to remember that a DC current only flows in one direction where as AC alternates with 50% of a cycle spent each way.

When you use reverse polarity ( electrode + ) the electrons travel from negative to positive ( this means from the work to the electrode. This super heats the electrode and the rod material travels across the arc stream with a high velocity and digs into the metal causing deeper penetration. Two thirds of the heat is directed at the electrode and one third to the work.

When you use straight polarity ( electrode negative ) the electrons travel from the electrode to the work. Two thirds of the heat is directed to the work and one third to the electrode. Even though more heat is directed to the work the penetration is not a deep as with electrode positive.

Because it is so difficult to regulate the current using batteries and cables (oh for a lightweight rheostat) reverse polarity is often used for welding where more control of the weld pool is needed due to the increased risk of burn through (ie; thin materials or poorly fitted up joins).

Hope that makes sense.

Mick

Nice, really nice bit of equipment.
Very clever getting MIG technology so compact, the hand piece reel is brilliant.

Yes we've matured somewhat since those early days. We own one of these now and you ccan see a review on it HERE:

and here;Readywelder in use;

You can also see it in action in this video about half way through.

Because that's all we had.

While traversing through China just before the Olympics they were cleaning up tourist cities etc. I was down in Guilin and I witnessed workers using a cutoff wheel on some angle iron, no glasses , no Earmuffs and no shoes lol, then he handed it to the bloke with the MIG welder who then proceeded to use it, using a straw hat to shield his eyes from the flash. I guess that's all they had lol.... Its not ideal at all but sometimes you gotta use what you have to get by..

?? As you do. My portable "bucket" is a pair of the rectangle oxy goggles with a welding lens fitted. As well as a cut up welding jacket to go over the chrome dome. ??