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

Submitted: Monday, Sep 28, 2015 at 13:34
ThreadID: 130437 Views:2896 Replies:6 FollowUps:8
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It's only taken me 7 years but I finally got around to stitching a few video clips together of our adventure on the Sandy Blight way back in 2008. Having developed a crack in the frame of the trailer, we had nothing for it but to effect repairs with a bit of 12 volt or 'DC' welding.

This was the first time we had attempted this so you'll note that as novices, we had a few issues particularly around regulating the amperage to the rod. We alleviated this to a large extent by adding a couple of jumper leads between the batteries to increase resistance.

While not pretty, the results were effective and got us over 800km where we were able to weld with better equipment (just to be sure).

Advice; Always make sure you pack a sense of humour - you need it in these circumstances!

Drama's on the Sandy Blight






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trip would doubtless be attended with much hardship.''
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Reply By: AlbyNSW - Monday, Sep 28, 2015 at 14:20

Monday, Sep 28, 2015 at 14:20
Mick did you find that it effected your batteries at all?

A mate did some bush welding and said his batteries prematurely failed not too long after, not sure if it was related to the welding or not.
AnswerID: 590823

Follow Up By: Mick O - Monday, Sep 28, 2015 at 15:57

Monday, Sep 28, 2015 at 15:57
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
''We knew from the experience of well-known travelers that the
trip would doubtless be attended with much hardship.''
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Follow Up By: AlbyNSW - Monday, Sep 28, 2015 at 16:31

Monday, Sep 28, 2015 at 16:31
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

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Reply By: maurice b - Monday, Sep 28, 2015 at 16:20

Monday, Sep 28, 2015 at 16:20
Good afternoon Mick .I have always used the electrode handpiece on the positive terminal ,never thought about the reverse . Do you know why this makes a difference.
AnswerID: 590825

Follow Up By: Mick O - Monday, Sep 28, 2015 at 17:29

Monday, Sep 28, 2015 at 17:29
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

''We knew from the experience of well-known travelers that the
trip would doubtless be attended with much hardship.''
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Reply By: Allan B (Member, SunCoast) - Monday, Sep 28, 2015 at 18:02

Monday, Sep 28, 2015 at 18:02
Mick,

Good welding practice is to attach the 'earth' lead close to the point of weld and in your video i can see that the 'earth return' is connected close to the weld site. However, if you are trying to reduce the weld current there is a case for attaching the 'earth' lead to a location on the structure a further distance away. In the case of your chassis weld, the 'earth' lead could be attached some distance away on the chassis to employ the electrical resistance of the steel chassis. Of course always observing that the current path will not be passing through a 'fragile' zone.

I carry appropriate battery welding equipment but have been lucky to have not yet needed it.

In the 'Good Old Days' car batteries had exposed links between the cells permitting voltage selection in 2 volt increments. I used to employ this feature to drive a 6 volt spotlight at 8 or even 10 volts to gain a brighter light. As the battery discharged we would even move up to the 12 volt connection. Push it too far though and you blew the filament!
Cheers
Allan

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AnswerID: 590831

Reply By: Member - John (Vic) - Tuesday, Sep 29, 2015 at 00:01

Tuesday, Sep 29, 2015 at 00:01
Now that's a younger "thinner" Mick I see. :)

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Reply By: Peter_n_Margaret - Tuesday, Sep 29, 2015 at 02:41

Tuesday, Sep 29, 2015 at 02:41
I carry one of these in the OKA.
http://readywelder.com/
200A of MIG welding capability from a 5kg package using 2 x 12V batteries.
Will weld steel, stainless and aluminium.
Fantastic bit of kit.

Cheers,
Peter
OKA196 Motorhome
AnswerID: 590837

Follow Up By: Les - PK Ranger - Tuesday, Sep 29, 2015 at 07:53

Tuesday, Sep 29, 2015 at 07:53
Nice, really nice bit of equipment.
Very clever getting MIG technology so compact, the hand piece reel is brilliant.
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Follow Up By: Mick O - Tuesday, Sep 29, 2015 at 16:08

Tuesday, Sep 29, 2015 at 16:08
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.


''We knew from the experience of well-known travelers that the
trip would doubtless be attended with much hardship.''
Richard Maurice - 1903

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Reply By: Stu & "Bob" - Tuesday, Sep 29, 2015 at 16:55

Tuesday, Sep 29, 2015 at 16:55
One needs to ask, why are oxy welding goggles being used to arc weld?
AnswerID: 590858

Follow Up By: Mick O - Tuesday, Sep 29, 2015 at 17:11

Tuesday, Sep 29, 2015 at 17:11
Because that's all we had.
''We knew from the experience of well-known travelers that the
trip would doubtless be attended with much hardship.''
Richard Maurice - 1903

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Follow Up By: Swaggie - Wednesday, Sep 30, 2015 at 06:48

Wednesday, Sep 30, 2015 at 06:48
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..
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FollowupID: 858965

Follow Up By: Gaz@Midge Point. - Wednesday, Sep 30, 2015 at 19:31

Wednesday, Sep 30, 2015 at 19:31
?? 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. ??
Mmmmmmmm, now where do we go next?

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