Welding on clean DC

[mikenash]

Bruce, you're welcome of course.  Cheers

[BruceM]

I got the trencher welding done, it's over at my neighbors for testing.  We need to add more "wings" to keep the diggings out of the trench.

I'd love to add another 6V for hotter rods, but it's not in my budget and it's serviceable now on 3/32-6013 rods.  Because this is a choked fixed voltage welder, no long arcing is possible, nor much whipping.  It's limiting, but it will do serviceable work.

As a side note,  I think direct battery welding might be better with a MIG setup, since that is by design a fixed voltage, and 23V would be well suited to 0.032" wire that is commonly used.  A smaller choke or none might suffice, also.

I made a rolling case for the two group 29 marine deep cycle batteries and my custom gapped toroidal choke/arc stabilizer.  I used standard welding connectors and made 12 foot, 2 awg cables, brass C clamp grounding connector.  I'm using fixed shade 9 glass in the welding hood, which is OK if I can weld in direct sun.  I've got a shade 6 lens to try for shaded work.

Floor space in my shop is getting tight so I wanted a small footprint.  The front and back are removable. Welding tools in the bin on top. I intended to fill in the sides but decided it was fine open; the batteries are accessible but well protected from an accidental short.  I'll give it a coat of gray Behr Ultra once the green Douglas Fir has dried. Pictures attached. 

I know you're thinking; why didn't I weld a steel rolling cabinet.  I'm cheap, and this was built with about $25 worth of wood.  I had the salvaged castors, and paid $8 for the other wheels.   Wood also makes me feel safer when connecting cables and such; a wrench touching the frame won't cause a melt down/explosion.

[mikenash]

That's the best-looking welding trolley I have ever seen 

[dieselspanner]

Nice trolley!

And an interesting thread, too

Cheers
Stef

[BruceM]

Thanks, Gort, MikeN, Steff.  Yes, it was like sloppy, fast and fun furniture work, using construction lumber, exposed screws. A far cry from fussy hardwood furniture/cabinet work.

MIG welders use a fixed voltage regulation, which is just what you get naturally from batteries. The shorted wire feed method to the puddle will cause some spikes in current, and I think it's interesting that fixed voltage proved to be the best regulation scheme for MIG, instead of the current regulation long used for stick welding.

If I ever mess with a direct battery powered MIG type setup, I'd prefer keeping the wire feed motor away from me, instead of the spool gun.  I'd have to shield and filter it as I expect the cheap ones are brushed DC motors, and I'd have to make a linear regulator for motor speed control.  Stepper motors might also be used for better speed control, and that means a microcontroller to shield and filter, and I could use the soft switched H-bridge PCB board from my low EMF inverter.

A battery powered MIG would be an interesting project and I suspect a far better welder, but for my limited use I think the utter simplicity of the 24V dual marine battery stick welder is OK, even though the fixed voltage regulation (with some current regulation aid from the choke) is quite limiting compared to the fixed (adjustable) current regulation most stick welders provide.

I did have an interesting development when checking out the active welding filter; the small one I bought for $11 was in fact still a radiating EMI source, with a microcontroller.  It was just a better design so I had initially missed it with the AM radio at a distance; it only could be picked up right next to the filter.  I feel MUCH better after welding using the passive glass filter.  No matter how bad my hearing gets, I won't be wearing a digital hearing aid!

[BruceM]

Got a 120VAC powered trickle charger finished today for the 24V welder batteries.  It's designed to be left plugged in, and whenever I turn on the inverter for laundry, it will charge at 1.5 amps max to 14.2V x2 (28.4V) and hold it there while the inverter is on.  I was motivated to do this when I found that I had a small toroidal transformer on hand that would do the job perfectly.  I didn't have a project box the right size, but I did have some light gauge galvanized sheet steel on hand, so I made the box. 

It's job is to keep the batteries in good shape when not in use.  I designed it to be low stray magnetic field, but I had to make it a small regulated DC linear supply (with bulk capacitors added later after initial testing) when I found that the large current loop at the batteries was causing too much stray field when fed "lumpy" DC.  9000 uF of 50V electrolytics was almost everything I had on hand, and that works fine. Screwed up my perf board layout but oh well.  An LM317T linear regulator I had on hand limits current to 1.5 amps, which is fine.  Even at these low currents, I had to add a fair amount of EMI suppression for the bridge diodes;  0.1 uF caps snubbing each diode, and common mode chokes on incoming AC and outgoing DC to knock down what's left.  The diode noise is stronger than normal because of my 5 step sine inverter with 43usec rise/fall times on each step. 

I plan on using a commercial switching battery charger for regular recharging after welder use.  I ordered one for $35 that will charge 24V at 10 amps.  If that checks out OK,  I'll add some EMI suppression and call it good.

[mikenash]

Life would be so much more do-able if I understood how to think through all that stuff . . . But I just don't

Good onya Bruce

[BruceM]

I still use switchers for my computer and projector gear, just have a great effort and expense in filtering.  -120dBm from 10K to 2GHz facility filter (military surplus) for the home 120VDC and 12V power, plus 7 stage LC filters at the computer and pedestal for the projector power.

That toroid stays cool, could do more but it's fine for the trickle charger.  It's pretty small and is only 60VA.  We all get spoiled by the tiny sizes of switching power supplies. 

For rapid charging, I'd want 15 amps at 35V secondary,  so a 500-800 watt transformer core.  At that power level,  critical filtering by inductor (another gapped toroidal choke about 5-10 millifarads ) is needed before the capacitors; rectifying and then dumping it directly to capacitors is often done (cheap) but it's rude and lousy PF.  So it's a full days work unwinding and rewinding a core, and another days work for a gapped choke.  I have a linear regulator design for 10A I could modify for double the capacity (second linear Mosfet, current sensing resistors and op amp to current match the first), so another hand built, custom board.
Then substantial heat sinking and a vented case and building it all.

For $35 I can get a 10A, 24V switching charger that is programmable delivered to my door...  I just won't be in the shop when it's charging.  The trickle charger I do want to be able to be in the shop. 

[BruceM]

My jealousy for MIG welding (a better match for 24V battery power since it's a fixed voltage process) is over.  Ends up the most useful shorting method of just feeding the wire into the puddle causes about 100-150 cycles of current surge per second.  That would be a massive AC exposure that makes continuous DC stick arc welding look good (for me).

I got the shade 8 lens and it works fine in shade or sun, so I don't have to re-engineer an auto darkening helmet. 

I'm still hoping to find a good deal on a 6V battery to add to my 2- 12V batteries to see if that gives me more capability.  I may end up hacking a 12V battery down to 3 cells.

[BruceM]

Yep, cutting and plastic welding the case would be a mess, and toxic for me, so I'm holding out for a 6V battery.  We're smoked in again last night and this AM from wildfires so my health and enthusiasm is ebbing. 

I'm fast charging each 12V battery separately, with two inexpensive commercial 15/3 amp smart chargers. Great product functionally, but hideous EMI emissions; they completely obliterate the entire AM radio band. Very limited options for 24V chargers, and big bucks.  One of the 12V marine batteries is 3 years old, the other new, so fast charging separately is better anyway.  Maintenance charging at 1.5A or less is presently at 24V. If I added 6V to have a 24/30V option, I just add another 15/3 amp charger, which also does 6V, but would revise the maintenance charger, probably to 3 separate 1.5A chargers as well.

My neighbor finally got his welded projector shielding enclosure back yestetrday.  MIG welded 1/8" thick steel, 24x30x24", with a waveguide for light, honeycomb vents, deep lapped 3/16 access lid in the rear.  Built to my sketches, doesn't look bad though an amateur welding job. Someone didn't get the basic welding class/chapter on gapping and filling joints from the outside of the box and instead it's lapped joints with welding inside and out. Twice the work, not as good for shielding due to discontinuity of shield thickness. Oh well.

I've noticed that the price of EMI shielding products like honeycomb vents and fingerstock or conductive fabric over foam gaskets have doubled in the last 20 years.  And lead times have gotten longer, with virtually no one stocking anything.  I had to order the honeycomb vents from Holland to get anything in less than 3 months.  It seems not too many hobbyists or anyone else are doing serious EMC work.

I ordered an oxy-acetylene cutting/welding rig last week. Got it yesterday, tanks in a couple days.  While sold as Neiko made and Victor-type, it's neither; no flashback arrestors in the handle or otherwise. (I ordered them immediately.)  I'm going to try my hand at gas welding and brazing, which is zero EMF exposure, but primarily, I have always wanted a cutting torch.  I have the fantasy that with a neutral or oxidizing flame, the acetylene won't do me in, used outdoors. I should be able to turn off the acetylene for cutting once started if it does.  A respirator is an option, and I also have a fresh air supplied helmet (with remote blower) if needed.

[BruceM]

Thanks, but I've taken apart a unit with "no batteries" and found...a battery.  It's charged by the tiny PV panels which are also used for arc sensing.  Battery in itself is no problem to me at all.  The problem for me is a live, unshielded microcontroller with connected wires right next to my head.  The processor can be in deep sleep mode, with uA draw much of the time.  No critical reason for it really (it could all be done in analog), but more nifty features, cheap, using it.  The LCD darkness when on can be controlled PWM, as 3V has it fully dark.  Likewise, the adjustable time delay before going clear is easy via microcontroller. 

I'm satisfied with my fixed glass shade 8 lens for now. 

Let us know how you like your new welder once you've had a chance to check it out!

[BruceM]

The emissions from the little unshielded microcontroller is tiny, on the order of a solar calculator but alas, it's right next to my head, with it's frayed wiring from MS.  I do use a calculator and digital volt meters, but not for long and at arms length as they do bother me and make me increasingly confused. So I use an analog VOM except where I must have more precise measurement.  We forget that before LCD displays, the world was analog and we got along just fine. 

As for shielding- the see through LCD itself is connected, and there is no ground available, so it's not very practical to shield.  Easier to just remove their tiny electronics board and use the PV panel(s) and drive the LCD with some analog circuitry.  I may do it someday, but for now the shade 8 glass works fine.  Per MikeN's suggestion, I also have used a 250 watt flood lamp for seeing the deeply in a shadow work better; that helps.

[BruceM]

I had to replace the Optima yellow top in my car; 6 yrs old and seems to have an open cell.

I thought it was prime for some welding experiments.  I opened some of the top with a carbide burr, and soldered a copper tab to the center lead connector to make a center tap at 6V.  Then cut a slit in the lid I removed for the copper tab and duct taped the lid back on.  One 6V side had the bad cell (open under the slightest load but looks fine on volt meter) , as expected, but the other side is in great shape still.

Welding on 30V was an entirely different experience; long arcing is easy, but it's TOO HOT, easy to over penetrate, more spatter/spray. I need to see how it goes on 1/8" rods on 1/4 steel, and practice more with 7018 now that I can long arc and move the electrode around. I did try some 6011 and at 30V it's too hot for 3/32 6011; it eats up the rod fast and I can hardly keep up lest I burn through.  On 24V 6011 just won't stay lit. I can see now why arc welders have adjustable current regulation...dialing it in for any rod and material sure would make things easier.

I may open up the Optima again and solder copper tabs at 2V and 4V (26V and 28V total) to give them a whirl. 
 

[BruceM]

I read about the Optima debacle. Johnson Controls owns them now, so they will get on the problem, I hope.  I had to buy a battery in town immediately after getting a jump start; otherwise I would have bought one of the other AGM batteries, as I have before.  The advantage of the MB 300D is you can motor down the road with OV at your battery...nothing else working but engine and transmission and of course the vacuum door locks.

I soldered in copper tabs in my defunct Optima at 2v and 4V, avoiding the bad open cell.  See photos.  With just 2V added, I can use 3/32 and 1/8 6013 rods nicely, with a more steady arc.  3/32 7018 also works nicely.  Enough better that now I need to find a 2V, 100 AH cell.  If anyone knows of a source for such a small 2V cell please let me know.  I found them on Alibaba but I don't want 100.

My losses are pretty low in wiring and cables; I used 1/0 welding cable for the interconnects and my 12 foot welding cables are #2.  I guess I should record voltage at the electrodes while welding to see...  Oh, for just 2 more volts.

[BruceM]

I did some tests while welding, using a camera in video mode on a tripod looking at meters.

At the batteries, voltage swings from 27.1 to 25.6 (-1.5V) with a 110 amp welding current. The only way to fix that is with AGM batteries or Lithium, no thanks on the price of either. All my battery interconnects are 1/0 with soldered connectors.  No chance of improvement there either.

Measured at the electrode, the choke, welding cables and connectors are losing another 1.5V.  Loaded welding voltage at 110A is 25.6V measured at the electrode to ground clamp on a 3/32 rod, about 150 on 1/8 rod.  I've previously measured the choke loss at 0.4V.  The welding cables are #2 and only 12  feet long.

I don't see any low hanging fruit for cutting losses further. I could gain only 0.7 volts by rewinding the choke and going to 1/0 welding cables...not enough.

There's so much better welding characteristics with that 1 extra 2V cell that I'm going to try and find one or make one.  The Optima cells are too small capacity from age.