Author Topic: Welding on clean DC  (Read 1831 times)

BruceM

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Welding on clean DC
« on: May 25, 2019, 12:42:31 AM »
I bought a new group 29 "marine deep cycle" battery to give the clean DC, 24V welding thing a go. They are rated 385 cranking amps so a good match for 100+ amp welding current, and they are what I have in my 120V battery bank now.

I made a 600 uH choke from a gapped 1000watt laminated toroid core; 22 turns, 16 feet, of 6 strands of 12 awg. I gapped the core with a 10" abrasive chop saw blade in my table saw. I only lost 1/4" of blade on the job, but it took 4-500 gallon tanks of air to make the cut.  I filled the gap with steel filled epoxy. To save some $ on the trial, I used some heavy jumper cables for welding cables. 

The exciting news for me is that yes, I can do it. While regular welders have me running for the hills from EMI headache, this was doable for me.

Welding on 2-12V batteries does work, and as the article I found by a welding enthusiast stated, the choke makes it possible. When I bypass the choke, it's just not possible to maintain an arc and get the puddle going. Alas, I seem to be a bit lower voltage than I'd like- no such thing as long arcing with this setup!  7018 (3/32) rods were a bust, could not maintain an arc and liked to stick and melt the rod. 6013 (3/32) worked, best with positive on the electrode.  I'll have to set up some meters on volts and amps and get my neighbor to watch them while I do a practice bead.  I'm ordering some 1/8 rods- more current may have better arc length and stability.

I suspect the losses in the jumper cable are not helping, so I will pop for some fat and short welding cables.  I may also reduce the turns on the choke.  No need for that much inductance, but I goofed on calculations when shooting for 250-300uH.  Battery and all cables were cool immediately after a 6 inch test bead. 

I'm very rusty, my last stick welding was in 1974.  I think with some practice and some fine tuning of the setup, I can do my own welding again.

Yippee!

« Last Edit: May 25, 2019, 04:21:32 AM by BruceM »

mike90045

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Re: Welding on clean DC
« Reply #1 on: May 25, 2019, 05:34:58 AM »
Awesome  Glad it's working and you can weld.  Next, cast iron repair ?

BruceM

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Re: Welding on clean DC
« Reply #2 on: May 25, 2019, 07:29:33 AM »
Next is a small but tall plow blade attachment for a subsoiler/ripper I got for the Kubota tractor.  I have ideas about doing trenching for pipes and such by ripping a few passes on the sides and middle of the trench, then plowing it.  The ripper pulls easily with the Kubota L2250 and can go down the 18 inches needed, even with rocks. 

mikenash

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Re: Welding on clean DC
« Reply #3 on: May 25, 2019, 07:47:35 AM »
Hey Bruce

That all sounds good

Just a couple of thoughts on the 7018s - I guess they're your equivalent of the Low Hydrogen 16TCs I like to use?

Firstly, if the rods aren't fresh & dry, they will perform poorly - hard to strike an arc etc; and the weld may have poor characteristics

Secondly, unlike the General Purpose electrodes, the Low Hydrogen ones are inherently harder to strike an arc with and the technique required to maintain the arc is different - in general terms you need to push the electrode at the work rather than draw it away . . .

However, the Low Hydrogen electrode will give you a very good weld in a short-arc situation and it sounds as if that is what your set-up wants?

More importantly,  the Low Hydrogen electrode, imho, will make a better piece of equipment if you're looking at building something like a ripper blade - it will do a better job on good quality steels and it will never allow any slag inclusions.  If you do your welding "downhand" but with a slight uphill slope in your direction of travel - to facilitate the slag around the edge of the weld to settle away from your weld - you may be surprised at how well you can do a good join with a small electrode and relatively modest current and several runs

Electrode on positive

Just a thought or two

Glad to hear you are making progress


BruceM

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Re: Welding on clean DC
« Reply #4 on: May 25, 2019, 08:06:07 AM »
Thanks MikeNash,  Yes, similar to your 16TC's, I read about the good welding properties of the 7018's and was very disappointed to not be able to use them.  As my skills improve, maybe I'll figure them out. Right now, they stick on striking an arc, or the arc goes out immediately.  I have not made even the smallest puddle or bead.  So perhaps I should put them in my propane oven and heat them up for a few hours?






glort

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Re: Welding on clean DC
« Reply #5 on: May 25, 2019, 09:09:49 AM »

Bruce could you explain a bit more about the Choke. What is it's function and what is it's layout and where does it go in the circuit?

Have you tried welding off your solar panels?
I Imagine yours are set up at around the 120V mark  from what you have said previously and that should give you a decent arc.
I have been playing with the  greenhouse heating setup I have which is 2 strings of 5 panels in series for about 140V open circuit and those things will pull an arc 4CM long and hold it  till whatever including thick nails burn away.

I'd be interested to hear what the drawbacks with that may be with a view to buying a packet of rods and seeing what they will do on a good day.

24V off batteries is much more doable in the field though so would like to learn more about the choke and it's function and why it's needed over straight 24V from the batteries.

Also on welding cable,  The guy that works for my father took some power cable from a car that came in for his welder.  These kids hell bent on going deaf as a post before they are 30 Put some monster amplifiers in their cars and hook them up with cable you wouldn't find in a factory electrical system.
He put it on his largish welder and reckons he can run a large rod at full tilt and they don't even get warm. a Lot of it is like battery cable only comes in 5M lengths!
Of course some of these people are putting 250A alternators in their cars and more than one so the wiring has to be heavy.

If ever there is no welding shop nearby and you need some cable, check if there is a car audio centre around!   :o

BruceM

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Re: Welding on clean DC
« Reply #6 on: May 25, 2019, 03:49:57 PM »
The choke resists a change in current in a passive manner; no electronics needed as in the modern DC welder which electronically attempts to maintain a set current by adjusting voltage.  I have the choke in the ground lead right at the battery, but I will move it to the electrode lead for the final setup. Anywhere in the welding current path will work.

It helps stabilize the arc as follows: as the current of the arc is starting to be interrupted, the choke will increase the voltage and thus help keep the arc going.  Likewise, voltage and current will be reduced by the choke in case of starting an arc.

The modern DC welder is capable of doing this electronically, using high frequency PWM from an excessively high voltage.  This keeps things compact and lightweight, but generates massive high frequency EMI from the high current, high speed switching.  Just like a typical switch mode power supply, but at 10-100x the current.  Emission strength is related to current times frequency times current loop area.  The welding cables radiate this EMI, and the welder is very close.  Ignoring what this does to the welder, the electronic regulation of current is a technically marvelous; no massive, expensive 40 lb choke is needed.

If you have a voltage monitor on your DC welder, you will find that welding is taking place around 20 volts plus a bit at 100amps of current.  Current will increase dramatically as voltage is raised.  I think that solar panels have insufficient voltage regulation, so while a bunch of 24V panels in series might work with a choke, I think the voltage may be too wild; open circuit is 44V.  If your peak welding current is 125 amps this would still require 3000 watts of PV or better in parallel.  I don't have enough PV to try it.

Welding cable size is determined by your max welding current. Small units with 140A limit may use 4 awg., 250A typically use 2 awg., 300a use 1/0.  The point is to limit voltage drop in the cable and cable heating.  I've ordered some 2 AWG cable, and will have short, 12 foot cables since the batteries with choke are going to be wheeled and portable. 

Here's a link to the article which encouraged me to try a choke on a 2 battery setup:
https://weldingweb.com/showthread.php?8996-Welding-With-Car-Batteries-%96-2-ARC-STABILIZER

The one thing he didn't get right was his choke core; ferrites are never used for high current chokes as they saturate easily so that testing by LCR meter (testing with tiny current) will read way higher than the actual loaded inductance.  But since he related his methods and materials well, it was a most valuable and well presented piece of research. I have experience re-purposing toroidal transformer cores as DC chokes, since I used two in my inverter project (for keeping ripple off the 120VDC), and could compare them to a commercial E-I core choke made by Hammond.  Gapped laminated toroid cores have the advantage of being the most compact and lowest loss for high current, relatively high inductance DC chokes.  Still, not cheap or lightweight.

The choke, with 22 turns (16 feet) of 6 strands of 12awg is shown in the attached photo wit the 2 group 29 marine deep cycle batteries.  It's a 1000 watt transformer core, with a gap cut via abrasive blade, epoxy filled.  I think it would work as well with only 8 feet or 10 turns and would be less likely to saturate at higher currents.  Battery jumper cables were used for initial testing and will be replaced with proper welding cables and connectors next week.  I will be increasing all the battery connections to some old 1/0 wire I have, with lugs added. The welding cable with use the standard Dinse 10-25 connectors at the to be designed battery& choke rack/cart. 





« Last Edit: May 25, 2019, 04:42:40 PM by BruceM »

mikenash

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Re: Welding on clean DC
« Reply #7 on: May 25, 2019, 07:02:21 PM »
Hi Bruce

Sounds like progress

Modern inverter welders have made us lazy to an extent as they are so "smart" at holding an arc, whereas the old machines with no electronics weren't as user-friendly and you needed to master the art of striking and maintaining an arc

At work we have a good-quality BOC inverter welder to which I have attached heavy cables with good quality clamps.  We also have a little cheap shitter with thin cables and just a spring-clip earth clamp like a car jumper lead - it works almost as well as the good one, up to about 130A

I would say that it shouldn't as there must be lots of resistance in the cheap cables etc etc?  But I would guess that the electronics just "try harder" in its case perhaps?

I mention this because, maybe, in your case - absent electronics - the setup has to be pretty right?  If that's the case, then a couple of thoughts:

FWIW I wouldn't use the type of earth cable with a spring clamp like jumper leads - I like the ones that are like a small G clamp.  Ditto with the electrode holder - rather than the "sprung" ones, I like the ones where you turn the handle to open and close the orifice that the electrode goes into.  Equally, I would think the same would apply at both terminals of the battery and at the ends of your choke?

IMHO "big is good" when it comes to battery clamps of any kind and high-current DC loads - I'm sure you understand that; probably better than I do

I have made many sets of long, heavy jumper leads - in our work we'll often find something like a 6-cylinder John Deere engine driving a pump and which has a flat battery but which we can't get a vehicle nice & close to - so we need long leads.  Because we put down lots & lots of submersible pumps we tend to have off-cut lengths of the cables we use for them lying around and I use that.  I don't know what the MM2 of them is but 'd say the soft copper wire core would be 10mm in diameter?  I always buy the biggest, meanest clamps I can find off the NARVA catalogue at Repco - rated something like 400A - and big heavy copper lugs to attach them to the clamps.   The reason I mention this is, I wonder if scrap metal merchants would have lengths of something like that lying about?

I have often observed - coming across a motorist with a flat battery being "helped" somewhere by another motorist with a pair of gas-station jumper leads - that they just won't do the job; I guess the accumulated resistance in the thin cables and tinfoil clamps just overcomes the batteries ability to supply current.  As soon as I dig out the big cables from the ute - then things tend to turn over and start straight away

Your welder is an interesting project.  I'll watch with interest. 

And, yes, if the Low Hydrogen electrode comes out of the oven too hot to touch without using leather gloves - then it's arc is smooth and it "flows" lovely.  I don't know if the same is true of all electrodes, but I guess it is - I think maybe the coating is hygroscopic?

Good luck

BruceM

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Re: Welding on clean DC
« Reply #8 on: May 25, 2019, 10:40:43 PM »
Hey MikeN, Yes, I'm sure the modern welding machine will compensate for welding lead losses up to a point, to maintain the set amperage regardless of losses in fittings and cable.  I'm guessing that I should conserve voltage as well as I can within reason for <150 amp operation.  I'll try baking the 7018 rods and let you know how that works.

The batteries were not run down much at all from my practice welds, so I'm guessing the amperage must be fairly low.  I'll have to get some help to measure voltage and current.  No point in measuring now until I get the new cables and connectors. 

Can you show me a link for the type of ground clamp you like?


« Last Edit: May 25, 2019, 10:46:16 PM by BruceM »

glort

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Re: Welding on clean DC
« Reply #9 on: May 26, 2019, 12:35:20 AM »

Thanks For the Pic Bruce. Looks much simpler than I had in mind and was getting from the impression of reading the forum link you posted.
The core is a piece you were able  to Purchase and then just wrap your wire around right?
Looks about the size of the transformer in one of my old school solar inverters.

I don't believe I have ever used an inverter non electronic welder.  My Uncle taught me to weld on this thing he had which was a wooden Box with terminals  coming out of it. I think he said his father made it. It filled a Builders wheelbarrow which he carried it round in ( and needed to) and was ancient when I was young.
I only had a basic stick welder  after that before getting my MIG which I have had for many years since.

I didn't even realise about the inverter welders.  Interested to give one a go now and see the difference.
The one I had would stick the rods to start as it didn't seem to have the Grunt to strike the arc but then often had too much power once you got them going.

Sound like what you have made would be an improvement on what I was taught on and didn't know any different to!
Sticks have become so Cheap now I might buy one if I come across a deal.  I nearly bought a tiny one last year. They were selling them for $25 at a place closing down.  I had great reservations about their ability as a welder but I thought would have made a great battery charger for high current.
Didn't get one in the end as the Line to the cashier was about 30 Min and if there is one thing I hate it's lining up for anything. 

BruceM

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Re: Welding on clean DC
« Reply #10 on: May 26, 2019, 06:35:23 AM »
I'd much rather be able to use a wire fed "MIG" welder, but for now this will have to do.

Occasionally there are some ebay sellers offering bare cores, but not recently.  Any of the custom toroid transformer co's will sell you a core for an inflated price. I had the 1000W transformer left over from my inverter project. It's an Antekinc.com product, my favorite supplier.  The secondary wire was 12 awg so I unwound that and reused it for the choke. I cut off the smaller bifilar primary winding.  It took almost three hours to unwrap the mylar strip overwrap (which I saved and will eventually put on the choke) and unwind the core, saving the wire on "stick" type bobbins used for manual toroid winding and about an hour to gap and epoxy it.  It's  faster if you just cut off the covering mylar tape and all the windings. 

Wrapping with 6 strand 12 awg is no fun; if I was starting from scratch, more strands of 18 awg might be a better way to go. 

I started work on the new plow attachment for the ripper. Plenty of cutting, grinding, drilling and such left to go.  I'll get my new welding cables and fittings on Wednesday afternoon, so welding elementary school will continue then.
« Last Edit: May 26, 2019, 06:40:52 AM by BruceM »

mikenash

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Re: Welding on clean DC
« Reply #11 on: May 26, 2019, 10:01:14 AM »
Bruce, how do you regulate the current - turn the welder "up" or "down"?  Or do you just have to stop/start to control the heat build-up?

BruceM

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Re: Welding on clean DC
« Reply #12 on: May 26, 2019, 03:15:03 PM »
That's the downside, MikeNash, there's no current adjust, though some sort of resistance could be used to reduce current; I found one reference to using length of rebars as a resistor.

The inverter-DC welder method of high frequency switching to regulate current is very technically convenient.  In comparison, if I was to have 3-12V batteries (36V) , and regulate linearly in a fashion similar to my current PV regulator which presently uses 7 500V mosfets, linearly driven in parallel with an op amp for current matching control of each one,  it might have to dissipate 150 amps at 10 volts or 1500 watts of heat. I'd have to study data sheets but it might need 14 mosfet/op amps or more. Doable but certainly a fan will be needed and a heck of big aluminum heatsink.  Not very practical, thus the inverter approach of high speed switching.

Other battery welding enthusiasts have used smaller lead acid battery voltages, so that they could adjust power in 2 volt (individual cells) or 6 volt taps.  So more like the typical MIG welder in that voltage is regulated instead of current.  I might be better off with a MIG setup on batteries; using solid wire and inert gas saves me the burning flux chemical exposure and does a better job than the flux core.  This I have not seen articles on battery driven MIG but I guess I should look. 

Edit- It's hard to have an original idea these days.  Readywelder.com  has a MIG welder that uses 18, 24, 30 or 36V battery power for portable cordless welding. 18 volt is used for thin metals.  I would not want the motor wire feed drive in my hand but this is an interesting interesting idea.  With inert gas and easily switched batteries a hacked MIG machine could be pretty useful.
« Last Edit: May 26, 2019, 03:30:50 PM by BruceM »

glort

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Re: Welding on clean DC
« Reply #13 on: May 26, 2019, 08:19:03 PM »

I was thinking about a battery powered MIG when you said you rather have a wire fed MIG.

All you would need to do would be change the stick setup for a MIG Torch and feed. The wire can be down to .6mm so should weld at low amps.  You can buy wire feed mechanisms all over the net as replacement/ spare parts along with torches or, You could get a Spool gun and all you'd have to hookup would be 24V for the wire feed and your Power source. If you wanted to use solid wire and gas, provision is already there as well.

Feed mechanisms and Torches can be had very cheap on Fleabay.  Save the problem of sticking/ damp rods and knocking the flux off.

Doesn't ANY welding throw out stacks of EMI?  The early Morse code sets used a spark gap to generate a Radio / broadband EMI pulse so I would assume welding with loads of amps and striking a much bigger arc would do the same thing?

This does not affect you Bruce?


BruceM

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Re: Welding on clean DC
« Reply #14 on: May 26, 2019, 10:00:48 PM »
Sparks are a broad spectrum radio emitter.  That was my interest in DC welding, in that if you achieve a steady arc with DC you don't have the starting and stopping and all the spark emitted radio emissions.  Thus my interest in the passive arc stabilizer method, and staring with a clean DC source.

That said, yes, using the battery welder feels just like a trip to the grocery store, I get wired, some tachycardia, a headache and can't sleep.  How much is the burning flux I can't say. Not so bad that I won't use it when I need to, but I wouldn't want to use it every day.

I did see cheap wire feed mechanisms and MIG torch replacements on Ebay.  What I didn't find was the gas connection and regulator.  It would be well worth the complexity increase for me to use the CO2/argon mix gas instead of the stinky burning flux.

If only I could find a gas capable MIG welder with a ruined inverter on the cheap.  I couldn't find one on ebay or Craigslist.  A thousand go into waste bins every day, I expect.

Hey MikeNash-  I ordered a $20 solid brass C-clamp type welding ground clamp. That seems like a decent way to go for me.