That would certainly filter lot more air than my filter fan.
I have a Shop-vac HEPA filter, wrapped in Activated Charcoal, that uses a 92mm x 36mm 7500 rpm capable 12v fan to pull air through.
I need to rewrap it with new AC, and place near the welder.
I wanted to try again, to weld 0.2mm copper, without Flooux. 
I returned tre more worn, wider tips into the welding pens and insured they were clean and the same size and shape
Gear 700, No preheating, triple pulse, 2MS interval between pulses.
Carefully positioned electrodes with equal pressure.
Result = stinky electrolyte geyser which laughed as it bypassed my newly tuned Hepa charcoal air filter.
Pretty sure it happened on third pulse.
Looks like the electrode tip melted some separator plastic and pulled it outside the cell. Good thing it was drained to 0.0623v
The other electrode did not stick at all.
So this is basically the same result as the last time I tried to weld 0.2 copper without flux.
I still have more power available.
Perhaps these Wintonic cells have super thin cans.
Perhaps That raised portion in the center of Anode/ negative/Can allow them to use thinner steel.
I guess I can try welding the cathode tab, but I am leaning against the viability of this welder to weld 0.2mm copper no nickel sandwich, no Flooux.
0.2mm copper alone is VERY hard to weld without flux if not impossible. 0.1 and 0.15 is easier.
I carefully filed the electrode that had can steel stuck to its tip, and made sure it was same size and shape as the other.
Flipped a cell over in holder and tried welding the + tab with the same settings. no Flooux
No preheating, triple pulse, 2ms interval
Two very even, weak welds lifted off very easily.
Tiny holes in copper, didnt bother with photo
Tried again with gear 750, 1ms interval, triple pulse.
Notice the steel colored ejecta on the weld on left. That is not a weird reflection, it is steel colored. could there still have been steel stuck on electrode? I was pretty sure I got it all, but perhaps there was some on the side.
It too lifted off pretty easily, but left the copper behind.
Yowch…
Could this have happened because the center of the bottom of the cell is raised so you didn’t have as much pressure on the copper as you thought?
I made sure to press really hard and conform the copper to the shape of the raised portion, then let off a bit and use normal pressure before the weld.
I think that raised portion design allows them to make the cell can thinner.
They were pulled from an old Aftermarket Dell laptop battery and the cans on the two worst performing ones, on tear down, were compressed the most.
2200 mah Wintonic Cells(6.6 amp cdr) 3 and 4 were in parallel in the middle of the end to end long 3s2p and their cans were crushed by the spot welder, in china sometime after 6-2017. I discharged them in a 3s1p holder powering a 12v fan and cells 3 and 4 hit 2.8v when cells 1 and 2 and 5 and 6 were still above 3.48v.
I am taking requests on what strips to test next, with and without flux, but would like to avoid using 99%+ power of the welder
I have 0.1, 0.15, 0.2mm copper.
I have 0.15mm pure nickel
I have 0.1 and 0.15 nickel plated steel.
I also have some marine grade 316? stainless steel, which is probably 0.4 mm thick.
I have 2 relatively unmolested Anodes and 3 relatively unmolested cathodes to test on. I am not going to try copper, no flux on the anodes of these cells anymore though.
Do you use a pipe cutter to open cells? I am kind of curious enough to open up the punctured cells and have a look and see what the digital calipers say
The marine Stainless I have is 0.5mm thick. Pretty stiff and strong. I know it is of little to no purpose in battery building
I used the gear 750, no preheating, triple pulses, 2ms interval to weld two not quite flat pieces together. There was a small gap on bottom weld Did not notice until I took this pic and put it on computer and zoomed in.
Still amazingly strong.
Amazingly, NO Sparks! The electrodes made almost no attempt to stick to the weld. This is the exact opposite of what I expected.
Underside:
Added a second weld, same gear and interval but 2 pulses instead of 3.
I figured why not weld it to a battery cathode +. I used NO flooux.
Ripping it off was not happening. Rolling it off took a lot of force, where it felt like I was going to pull the tab out of the battery, but once it started moving it came off easily.
I find it very interesting that this cell is one I had welded copper to before using Nelvick’s Flooux. The Flooux obviously tins the copper in immediate proximity to the weld, but it appeared to NOT tin the nickel of the cell itself.
When I tore off the stainless, the layer of tinning from the Floux came off with the Stainless.
Maybe this ridiculousl stainless could go on top of 0.1 copper, and make a rigid battery, which could then keep the deck and enclosure from flexing 
I
so copper expands to roughly 15000x is volume when vaporized… and i think that is a part of why the no flux weld failed so spectacularly. when you are attempting to put more energy into the weld, the conductivity of the copper is keeping the current path on the surface between the two probes and super heating that spot. its not saturating through the copper to then also pass current through the skin of the cell heating both at the weld location. there is enough energy to vaporize a small amount of the copper and cause it to explode and splatter the liquified materials bypassing the weld point. i don’t think the weld will work at that energy unless you can shorten the pulse duration or swap polarity between pulses in a sort of square wave ac you might get from a good tig welder.
also i see a lot of oxidation or discoloration in the copper and weld point that makes me think its getting fowled. also the puddled stainless blobs on the stainless weld make me think too much energy id the wrong spots
can you try a shorter pulse at that power or turn it down slightly and still get it to stick at all? a slot in the copper i think would also go a long way towards making it easier to keep the weld energy directed where it needs to go
also stainless steel is one of the absolute worst metals for conductivity electrically as well as thermally, you could almost use it to insulate electrical components (not really its just bad) it also could become not stainless if you weld it in atmosphere and will fowl up pretty bad without shield gas in tig or arc welding. kinda impressed you got a good spot weld but also because its a poor conductor of heat you can probably get quite a hot spot weld and good connection.
the more i think on this the more i think that the flux is not just going to make it easier to weld but will also play a part in making the weld a good strong weld not just because of the tinning effect but because of how it is protecting the weld spot. have you welded through the flux (flux on both sides of copper)?
The 0.5mm stainless was more a tongue in cheek experiment, because I remembered where it was.
I agree that I used way more power than necessary welding it. Turning it down from triple to double pulse was not nearly enough.
Blowing a hole in the cell can with 0.2mm copper, no flux, has to be a combo of factors. The raised center ridge likely allows the can to be thinner, and even though I used a lot of pressure to conform the copper to the can before pressing the foot pedal, there could have still been a gap, and the air in the gap expanding could have lifted the probes in my hand on first or second pulse, and then the third pulse blew the hole into the can.
The other time I punctured the can there was no geyser. I had to look close and give a sniff to confirm
Welding 0.2mm copper on the cathode no flux worked fine. In my opinion even though the welds were good, the 0.2 copper peeled away from the welds too easily. Perhaps too much power, or I am too used to peeling 0.2mm+ worth of nickel plated steel sandwich.
I am still of the opinion that 0.2 copper by itself is just not strong enough.
My stacked 0.1 and 0.15 flux’d copper tear off felt more than 20% stronger than 0.2.
It is also possible my electrode tips are not rounded enough. I have been trying to hold them as vertical as possible, for consistency reasons, and the sharp edges could weaken the copper at edge of weld, making it tear from the weld, too easily.
I might be too frugal in filing the tips rounder too since a pair costs 10$, and that is like two JP30’s man…
The higher power levels oxidize and melt the tips and I’ ve been trying to insure they are clean, for consistency.
I did not try flux both below the copper and on top, sinking electrodes into the flux.
I never thought to try that. I imagine it would tin the electrodes, impairing subsequent welds.
Hmm, lots to think about.
The stainless steel being less conductive than nickel plated steel, is a technique that has been used by others to sandwich weld thicker copper.
I want to try 0.05, and 0.1 SS on top of 0.25mm Copper.
Nelvick says one of his clients is claiming to sucessfully weld 0.3copper with 0.1 stainless sandwich, with the smaller AwithZ 10kW model, and I have the 14.6kW.
I expected huge sparks and for the electrodes to stick to the 0.5mm stainless.
Neither occurred.
Nelvick said SS stuck strongly to the Glitters tips. Are the electrode tips a different alloy, or because Glitter doesnt have preheating or double pulse, or is one welding with 304 SS and the other SS being 316 the difference?
I am petty sure my 0.5mm stainless is 316. My dad had gotten if for his boat and that is supposedly the stainless grade better for marine environments.
Took note and ordered some .25 by 25mm sheet plus som of the tined or plated copper from @DIY500AMP.COM with some flux and tips with the welder
Might look at some silicone bronze rod to make some more durable probe ends if they are wearing so fast. Might be helpful but im not gonna try it until after i get some use on the thing.
Gonna build something fun then use it way under capacity first and get some vibration on it. Have a 12s2p that only needs 80a but ive got space to over build the pack and try to max out the cells. I’ll build it like it’s gonna need 160a just to figure it all out. Gonna be interesting
I wouldn’t say the tips are wearing excessively fast, but I have no basis for comparison. My old cbeapo welders had a fraction of the power, around 1/10th, and I wound up making 8awg probes with copper tubing compressed in a hydraulic crimper then shaped.
Unfortunately I didn’t think to clean the inside of the copper tube on the weld end. and the ferfect cold weld never seemed to happen, and I could always see a line when shaping the tips.
I just measured the tips.
New is 2.99mm diameter, and 29.97mm long.
My used tips are 27.7 and 28.67mm long.
The shorter one is likely the one which punctured cans and had steel welded to the tip, which proved very resistant to the file provided.
I just received a roll of 304 stainless steel. I will be sending few cuts for @SternWake and @Pecos today for testing too. Let me know the size of your strip. I can cut in the laser.
A single row continuous section with slit holes every 21mm like this center roll would be useful i think:
Simple 2p straps like this may be easier to fill the sheet and would be useful for adding the ss sheet as reinforcements though my preference is to have the simple slit vs a the open fork like this drawing
Surely you all know about these
I think the risks of blowing a hole trying to do the sandwich are too high and it’s not as assured as welding these
I was wrong about the 0.5mm Stainless steel I have and welded.
My Dad bought it 50+ years ago, to attach a TV antenna to the chimney.
He said it was a 400 grade, but is not sure which.
I found a magnet and it is strongly magnetic., where 316 and 304 SS alloys are not.
I am looking forward to trying the SS Nelvick sourced atop 0.2, and 0.25 copper.
I want copper touching my cells.
Period.
I need to make the template. But I can cut small strips like 10mm x 150mm just to testing. I may have a good feeling. I will be testing this today as well.
The very existence of these assemblies is proof that copper can be welded to Steel and Nickel consistently and effectively. The availability of 15 and more kilowatt welders at affordable prices makes building them yourself reasonable if the process can be figured out and streamlined. Doing it collaboratively on the forums helps spread the costs of trial and error out and introduces new fresh ideas.
Kinda the whole point of this forum ¯_(ツ)_/¯ it’s not all about that boty prize pool 
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Blowing holes in cells is just a nice little bonus. Not really the goal here so much as literally the purpose of this thread to sus out how to avoid.
Let us cook, im sure (though i have no direct experience) those work really well. Not sure if the nickel connection would withstand 125a but it’s possible with the cooling offered by the giant copper bus that it’s a non issue, until you look at voltage drop at high amps and volts. Could quickly add up to more than .3% and start being a bottleneck when all added together. Removing the bottleneck is not necessary in every purpose you can make a battery for but that’s not where direct copper makes sense anyway.
And fixing it by using thicker nickel seems like the same problem - needing more beef in your welder so why not remove an additional connection point and higher resistance point all together due to the welders now exceeding the threshold needed to weld pure copper when they can weld .4 nickel
This is also what it’s about for me.
It’s the best possible scenario.
As well as direct copper to cell action, especially with the flux, the welds look a lot beefier than traditional nickel welds.
So before we would claim that each weld spot with nickel could carry about 5a, i would assume that a fatter weld with a better conductor would have better ampacity per spot.
I would love to see/do some kind of testing around that
I still disagree here and believe the entire surface area will conduct current and the welds are effectively fasteners so a flat connection is more critical than many weld points but I digress 
I was thinking if each spot weld on 0.2mm pure nickel is good for 5 amps, then we should see hot that nickel weld gets after X amount of time at 5 amps, or 10 amps for a pair of welds.
Then perform same test with 0.2mm copper
or maybee have two strips welded to a single cell, one 0.2 pure nickel, one equal length width of 0.2 Copper.
Have a 10 amp load on each strip 20 amp on the whole cell. See what the thermal camera shows. See how much current chooses the copper vs the nickel with a clamp meter over the strip.
Probably have to paint everything flat black for an IR camera/thermometer to get a good reading
