Welding with batteries

Howdy Hairy,

Michael (Mossvale) provided this bit of advice on Rods to me a while back. Haven't had an opportunity to put them to the test as yet (thankfully).

"Excellent rods to use for hard to weld metals and dissimilar steels is a CIG Weld All rods. You can buy a handy man pack with 10 and 12 gauge rods in the pack. They are excellent to weld stainless and spring steel also hardened steels like gears etc. They are very easy to use and are easy to strike an arc and continue a clean bead with little experience. They add material to the part welded and have the ability to "build" the rod material easily compared to standard rods. They are available from most engineering supplies for about $35 for a pack of about 20 rods of the two sizes mentioned above..Worth carrying a pack."

Gday Mick,
Weldall's are great rods and well worth carying. They do have a fairly brittle flux so its adviseable to wrap them individually to stop them chipping. Also WIA 12p are a great GP rod with excellent down hand properties so its worth throwing in a few 12p's in different sizes too. Low Hydrogen are handy by most jobs where you would need them can be done with Weldalls.

Cheers

Pop! Another thing to try is to use the positive as the earth and use the negative with the rod. This tend to add material easier to the job and less splatter on AC welders, it could have the same effect on DC as well . Worht a try.. Great to see it works ok with 2 batteries with a lot of years on them... regards Michael

Yeah you're right, tried both polarities and neg to rod seems o work best

Cheers
Pop

I believe negative to the electrode is standard for dc welding.
I do know that electron flow is from the negative (cathode) to the positive (anode) so I guess this must also apply to molecule movement through the plasma of the arc.

Pop,

you are correct on all assumptions. It does use a flux core wire. It also has facility to connect gas if you wish to carry a small bottle. Will work on a single battery but we've found 2 to be the best scenario. We've been very happy with the results and kit has provided good penetration on all our jobs so far. For the lighter jobs using thinner materials, it's a damn site easier to use and control than stick on 12V. We've welded up Rims, brackets, Scotties Trailer (the biggest job) and it has done a great job. On heavy steel, where you can get away without a lot of finesse, I'd go back to stick and throw in a third battery (if needed).

Cheers Mick

Mick,

Yeah cheers mate, I have a stick welder that I use for the heavier welding and a MIG for the thinner stuff as you do. I guess a gas shield would make a better looking job but the gasless works ok for me, I might have a look at one of those Easy welders. A bloke can never have too many toys...er I mean tools.

Safe travels

Pop

Note to self...Readywelder, readywelder, readywelder not Easywelder dumbo

Hi Eric, Inductance will have no effect with dc welding current. Inductance only has effect in an alternating circuit. Fundamental of electrical physics I'm afraid.

Apart from reducing the supply voltage, you can only limit the dc current with circuit resistance.

Rickety rickety rats, I was thinking about wrapping the lead around a bit of pipe and giving it a shot....oh we'll

Cheers
Pop

In ac mains supplied welders, inductive chokes or heavy (usually cast iron) resistance is used to regulate the welding current. This also provides a characteristic of a slightly higher voltage to assist in arc initiation, with the voltage falling somewhat after the arc is established.

With mains supplied dc welders, any regulating inductors are located in the ac part of the circuit before rectification to dc takes place. There may also be some induction in the dc output to provide a degree of smoothing of the rectified current. This would be of no benefit in battery welding as the dc from the battery is already smooth, it has no ripple.

With rotary motor-driven dc welders, the welding current is provided from the driven generator and welding current control is achieved by the characteristic and controls of the generator.

Allan, I think you are correct about the polarity with dc welding. It works well on thin materials with ac also. I regularly used an old "bullet" DC welder in the seventies as an apprentice. Noisy thing from memory with a load on it. Michael

Hi Allan,

I have used both of the type of welders you have described without understanding any of the electrical engineering involved.

Now I am only very vaguely in touch with what is happening in either of the following examples so be gentle please.

As far as I can remember an electro magnet uses DC current to generate a magnetic field. I would imagine some current would be used/required in the generating of this field so would this have any effect in reducing or using up some of the amperage available??

The other example I had in mind is the old fashioned ignition coil where the collapsing of a field induced a much higher voltage in the secondary windings. And the longer I typed that the less sure I became how that might help in reducing the amperage in the primary windings. Just thinking that every time work was done power was consumed and some losses incurred.

All that probably sounds pretty naive so please consider.

Cheers
Pop

Michael, I do remember the "Bullet" welders you referred to. About 900mm long, 200mm diameter and probably painted grey?
Maybe a Lincoln and looking like this?

Pop, Actually, a steady dc current through an ideal coil uses no power to create the magnetic field. I know it sounds impossible but it is true. Where the power is consumed is that the coil will not be ideal, it will contain resistance of the copper wires and that will cause the losses that consume electrical power. This resistance accounts for some current limitation.

It is not the same for a coil passing alternating current. The ever changing (alternating) current produces a changing magnetic field which in turn causes a reverse EMF (voltage) to be created in the coil which opposes the original current and so limits the current flow.

With dc applied to a coil, at the instant of initial application the current is rising from zero to some steady value. During this short time the field strength is changing so the reverse EMF effect described above takes place briefly until the current reaches a maximum steady value.

The circumstance of an ignition coil is similar but in reverse. A steady maximum current and magnetic field is firstly established in the coil. when the points open and the current flow is interrupted, the magnetic field collapses and in so doing becomes a rapidly changing field which again induces the reverse EMF referred to above in the coil secondary winding. The results is a brief high voltage discharge. The condenser in the primary circuit serves to shunt, or short circuit, the primary winding at the moment of point opening and assist with rapid collapse of the magnetic field.

Fascinating stuff electricity, eh?

Makes sense to me Pop.....Sound is your best judge

Pop, "negatively affected by temperature rise".

That is of course because the photovoltaic cell is energised by light (photons actually) whilst the sun's rays also contain the lower (infrared) frequencies that cause heat. But as you say, "Amazing".

I'm still contemplating a good current control method. It gives me something to think about when I am not steering the Troopy down a track!

Allan,

Surely I wouldn't be the first bloke to think about fitting some sort of infrared filter over the panel to allow the useful photons through and blocking the heat generating infrared or is this not possible?? I know prisms break white light into a visible spectrum because of the different wavelengths for different "colours' and I guess infrared is just a "colour' that is not visible to the naked eye.
As you are probably thinking by now "this bloke has way too much time on his hands" (;-)).

With the welding part I was wondering, if the only way to decrease amps is to increase resistance, how would a length of say 25mm x 3mm flat bar about 2m long and bent into a tight zig zag for storage go as the resistor?

Cheers
Pop
PS Yeah I was one of those annoying kids that took alarm clocks apart just to see what made them tick (no pun intended)

Yes Pop, The flat steel bar could be OK as a series resistor. The electrode cable could be clamped to any point along it to "tap" the required resistance. 25mm x 3mm x 1 or 2m sounds about right to me.

This bar resistance would be very similar to the cast iron resistors incorporated into welders of long ago before adjustable core induction chokes were developed.

ps. I was delving into cast-off electrical appliances from the age of five. Still doing it!

Eric,

So this happens with a DC current as well as AC? I can see how that would happen with AC because of the polarity switching but I was under the impression that DC being a "smooth" current flow this may not occur.
I am not questioning what you say, I am just trying to get my head around what is going on.

Cheers
Pop

Pop.
I will try to explain in more detail.
When you start the weld by touching the electrode on the job the voltage at that instant drops to near zero but the current rises to say 200 amps, this causes the end of the electrode to melt and a small blob of metal about 1 mm in diameter drips of the end of the electrode onto the job. When this happens the connection is broken and the current drops to zero, the voltage rises to more than the 24 volt supply. The reason the voltage rises higher is because of the magnetic field around the leads that was created by the high current collapses and in doing so induces a voltage in the leads that adds to the battery voltage. This high voltage ignites the arc and causes another small piece of metal to move onto the job. This happens at about 1 million times a second. When you add extra inductance,or a choke into the lead the build up of the magnetic field is much greater so the voltage of the arc is greater, when the field collapses, this gives you a more stable arc. Because this happens so fast the effect is the same if the supply is dc or ac changing polarity at 50 timesecond. Eric

You won me on the "usefullness" of a Readywelder. Just got to convince the minister of war and finance that one of these is far more use than the new carpets she wants...lol.

Cheers
Pop