The brushed finished?
Perhaps. Now we have to decide if it makes any difference in weld characteristics/settings as that finish is on both sides of the SS? 
Afraid if I sit down in front of welder right now I will get stuck there, and there be fiberglass and epoxy needing to fondle each other in the garage.
The process of making rolls of copper, I wonder if it is already work hardened, or not.
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The unidirectional brushed finish on the 304 SS, or tool marks/ striations, catch a fingernail scraped across them in one direction, more than they do scraping it in the other. Also the other side of the SS there is a different looking finish, and I have not been paying attention to which side is up or down on all welds previously.
So I am going to ignore it, and come back to it as a potential variable to explore when no other solutions make sense, depending on what arises As I continue.
I decided to go with 0.1mm copper on top of the cell, 0.15mm copper on top of that, and 0.1mm stainless on that.
Flux between cell and 0.1m only
Gear 370
0.10ms preheat
Double pulse
2MS interval between pulses
Once again, grabbing all three layers in both sets of thumb and forefingerss and pulling straight up, no wiggling or rocking, with all I have reveals the above photo. The 3 strips are deforming around the welds.
Busting out the needle nose is required and some slight wiggling and rocking is required to start tearing the bottom layer of copper, and then the stainless pops off and then the copper continues tearing, getting easier and easier to tear.
The flux tinned the area between the spot welds and in a even circumference around them.
The welds are not going anywhere, but the SS is not welded as firmly as I would like to the copper layers below.
But I have No idea if this even matters.
Iād bump up the power a bit if trying this weld again.
The probes are not feeling like they sink as much when the capacitors fire, as they do when using nickel plated steel.
The 2 layers of copper are throwing another variable into the mix, but I think if one uses 0.25mm copper under 0.1mm stainless it would be stronger than stacked.
Onto dual 0.15mm stacked under 0.1 SS
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Dual layers 0.15mm copper under 0.1mm Stainless
Gear 550
0.10ms preheating
double pulse
2ms interval
Once again there is no way to remove this from the cell with bare fingers, doubled on each other grasping strips and prying knuckles. upwards. The Plyers are required to start tearing it and even then some wiggling and rocking is required to start the copper tearing from the weld
both layers of copper are firmly welded to the cell , and the weld on the left has a bit of stainless stuck to it, but the weld on the right has a mere Dot.
The exact forces I exerts with the plyers and how they grab the 3 layers, play a huge part in how this appears. I am trying to be consistent, but there are variables at play here.
I am wondering at the point in continuing to stack copper.
Stacking SS on top of one layer of copper is no big deal, but setting 3 layers, on Flux, on the cell can so the strips are not laying atop previous welds, then getting the magnet on top to hold them, then the electrodes positioned, pressed evenly and firmly then moving foot to pedal, is a bit of a process.
Gear 550 and 0.3mmcopper, 0.1mm stainless is definitely in the range.
I went to gear 590 for the final weld on this cell, and used more of an impatient rolling motion to remove the layers, and my wrist and shoulder made funny noises, and this picture looks like it did not weld as firmly as gear 550, but in my opinion it was stronger and both welds more even.
I over saturated many a q tip with rubbing alcohol thus diluting the overapplied flux, which has migrated under the heatshrink and up the can wall. I am going to place the cell in the hot garage for a while and then peel off the heatshrink and see if corrosion has started.
I will pull out the Samsung 50E with the lowest voltage and clean off the previous weld remnants before doing more testing.
But I stil question the validity of stacking copper to simulate 0.25 or 0.3, or 0.35, or 0.4.
I am pretty sure this machine has enough juice to weld 0.4mm copper under 0.1mm Stainless, and instead of incremental stages, just going for 0.4mm and gear 800 to start with.
Maybe flux between layers, see if the SS will bond strongly with the copper, as strong as the copper bonds to the cell can anyway.
The flux is a bit like Antiseize. Its messy and gets everywhere if one is not vigilant about keeping tools and fingers clean.
i am obviously using way too much of it as well.
How little one can get away with can be explored later.
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Ok, I tried dual stacked 0.2mm under 0.1mm stainless and gear 800
No chance
Tried again at gear 900, bumped up preheating to 0.15ms, and triple pulse. At first I thought it was a good weld, and it took a fair amount of force to lift off, but then abruptly let go and left only the slightest smidges of copper on the cell.
I was using a Wintonic Anode I had not yet welded to previously. It was one of the punctured cans that Iād had filled with some e6000 a few days ago.
I did not want to go Dremel off the 4 tiny remnants of previous welds on a 50E. My dremel is behaving poorly. it cant hold a steady speed.
I think 0.4mm copper under 0.1mm SS is perhaps just within reach of this welder with gear 999 and triple pulse and maybe 1ms interval, or maybe 5ms interval. Iāve not played with the interval much. or preheating for that matter.
I can say that I see no purpose in welding anything thinner than 0.2mm copper and 0.1mm stainless steel sandwich
The experiments with 0.5mm stainless was interesting in that the amount of force required to remove the sandwich was just next level, and the copper below seemed flattened to the cell can with lots of obvious direct contact.
Instead of 0.5mm stainless, perhaps 0.25mm would be a way to weld 0.2mm or thicker copper fat and flat, without having to greatly increase the welder power. Iād like to keep the welder power well below its maximum.
I think I want to order 0.20mm stainless, 0.3mm copper and consider that as the overkill maximum I need not use, but would be nice to know that I could weld with 75% or less of welder power.
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Absolutely fantastic work!!! If you need more flux, metals or cells lets me know. I will be sending more tips for you since I know they will worn out.
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If you have some 0.3mm copper scraps, Iād love to compare results to stacked 0.15mm, and solid 0.25mm instead of stacked 0.15 and 0.1.
Maybe that joint in the stack increases resistance and helps welds better?
Maybe any trapped oxides in between layers inhibit the weld?
I still have one untouched set of electrode tips and one with only light use, and the heaviest used ones still have half their taper left, but welds over gear 800 really hammers them.
I thought 0.05mm stainless would perhaps have a place in maximizing copper thickness, and then that 0.5mm 400 series stanless went and blew my mind.
Welding with flux and without stainless sandwich is certainly possible, but the tear off strength is far superior with 0.1mm stainless, and it requires less power, and there is more thermal mass and perhaps less welding heat enters the cell.
I didnāt fully explore the raw dog pure copper no flux no sandwich potential, but Al and Chris will soon have the ability with more powerful welding machines, and way more battery building experience than myself.
I think trying different thicknesses of SS such as 0.05, 0.15, and 0.2 should be explored. The 0.5mm stainless just seemed to flatten the copper to the cell, and the force required to remove it was insane, with just one pair of weld dots.
The 400 series is more stiff and rigid than 304, so maybe exploring different grades of SS would be beneficial too.
This 14.6kW P20B welder seemed to dabble with its limits with 0.4mm copper, but I didnāt try 0.35mm, or dial up 100% power, but 0.4mm copper is how many degrees of overkill?
I still need to transfer my soldering station indoors, and I want to modify my air filtration/ fume extraction methods, and my desk chair seems to be a prostate torture device.
Could be a while before I weld again.
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I have 0.3mm copper and 0.15mm nickel on the way.
Iāll probably order some 0.2 nickel as well for science.
I am hesitant to even bother with stainless, as Iām concerned that it will dull cutting tools too quickly. I like to round the corners, i used to use the corner chomper tool and that worked a treat, but it was messy to empty/clean.
This time around iāve ordered this benchtop bad boy, hopefully it is reasonably quick, easy, neat and long lasting.
I admire the lengths you are going to with your testing @SternWake but iām much more likely to get my machine dialled in for the way I like to work and go with that. I donāt really have a lot of time for shenanigans.
That saidā¦. Iām sure there will be at least SOME shenanigans 
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@glyphiks have you tried with this tool?? Amazon.com
I have good success with it but not as durable as that bench.
You could consider the cheapest 30W rycus laser that is about $1500 only and can cut 0.5 copper instead to put $200 in a bench cutter. I mean you just invest in the best welder you can get. Only for that I am mentioning this. The laser will solve MANY other problems. The ben only work for 1 purpose.
Here where I purchased my laser. I can contact you with Jack Liu to ask for discount. Manufacturers Metal 20w 50w 100w Fiber Laser Marking Jewelry Engraving Machine - Buy Fiber Laser Marking Machine 20w Fiber Laser Marking Machine fiber Laser Marking Machine 100w Product on Alibaba.com
I agree the job that @SternWake is doing is amazing. I stop here in this group 10 times a day or more.
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I say Let there be shenanigans, and let them fly.
I did notice how difficult it was to cut the 0.5mm 400 series stainless with my tin snips, and that they feel a bit gritty now. But 0.1mm 304 SS cuts like butter.
Iāll definitely round my corners when I build a pack, but I think I am done with pure nickel and nickel plated steel.
The stainless sandwich welds better with significantly less power, and that has to mean less heat entering cells, and less cumulative stress on the welder, and the tips, and something about stainless steel has always just reverberated in my soul.
Perhaps my battles with rust, and the frustration of knowing I will lose the war but have to fight the battle anyway.
Iāve no plans to build battery packs for others, so the production time is money mindset does not factor into my personal equation at this point, and all the above testing is kind of fun, and I like macro photography as well.
Scroll and zoom on a big display, and see little details that Iād miss with a magnifying glass. My little point and shoot 2007 era Canon A640 with my 1100 lumen 4k light right next to the lens, no flash, and aperture as small as possible, and 1/120th of a second seems to work the best, so far. I can get a better depth of field than I can with my DSLR with its magnifying filters attached. A dedicated macro lens is not in the budget.
The flux is kind of a necessary evil. I think with more power one can weld 0.2+mm copper without it, but that consistency will suffer and the welder tips will require more regular tuning, eating up some of the time saved by not applying it.
I think the syringe the flux comes in is a clumsy way to apply way too much of it, and it is impossible to not apply too much using it.
I think pulling it with a small 8mm wide squeegee for + and 18mm for -, from a pile then applying to the cell would be far more precise and efficient in terms of time, effort and the amount of flux wasted.
The 0.2mm scraps from the laser cutter off cuts Nelvick sent, and the videos of the laser cutter in action, just seem so satisfyingly precise. It makes me want to learn CAD, just to send him files to cut copper so I donāt need to spend time with tin snips and a dremel and have the end result look so much more professional .
Can it cut stainless too?
I want to make Anode copper tabs with round holes to avoid the 6mm center of the Tabless cells, but drilling would be a mess and a hole punch deform the copper too much.
Welding across the slots will also reduce the welder power required, but slightly reduce the potential surface area of copper in direct contact with cathode.
I have some untinned copper braid ordered I want to experiment with.
I have ideas for the elimination of solder for series connections. No idea if they will work.
So shenanigans will be necessary.
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This thread is incredible. Really good R&D work here.
Forgive me if this has been answered elsewhere:
Has an A-B test of a pack made with the same shape and thickness conductors? One with nickel one with copper?
All the work done in this thread has value but Iād need to see how much better it is to justify the extra steps compared to welding nickel.
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I believe @Battery_Mooch and @Pecos have plans to perform precision tests.
I am not sure of the breadth nor depth, but will gladly contribute to the process of getting samples into Moochās hands.
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Iād really like a test of a full esk8 pack, with actual riding. Two Minnie logs I can compare ideally.
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Calculating the resistance difference assuming one pack made with 0.2 copper, one with 0.2 nickel all other factors being equal, even though they rarely are, shouldnāt be too difficult.
The 10.x kW 139$ AwithZ uf20b should be able to weld 0.2 copper.
One of Nelvickās clients says he can weld 0.3mm copper under 0.1 stainless with it, and I believe it. I was able to using 60% of the 14.6kW of my P20B.
Using flux.
Nelvick, you should consider offering smaller syringes of the flux, rather than a 100gram tube. Sample size 10 gram convincer packages which fit in an unpadded envelope, and cost a stamp or two to mail. USPS.
Maybe flat squeeze tubes like the little dielectric grease packages that come with spark plug lead kits.
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Goddammit Nelvick, you are bad news for my bank balance
Will the laser cut nickel as well?
That cropadile corner chomper is the one i was talking about, its excellent at what it does, but cleaning the shards out of it is annoying
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Dudeā¦ I can cut 2mm of copper. I cut a coin that is 1.5mm in seconds. Check this epoxy sheets.
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Cutting nickel
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This is moving beyond the scope of this threadā¦ i will meet you in pms
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Liar Liar
I took the lowest voltage Samsung 50E, and took it to the dremel with stone wheel, well, to the can anyway. I did not want to get conductive dust under the +, or take the precautions so that it could not. I guess there is a chance this cell becomes part of a pack again, and I donāt want to ruin it if I donāt have to.
A bit of a reminder how welds are done in some other other applications. Nelvick, Do you know what these cells came out of?
Note that this is not the cell I dremeled and welded to, as shown below.
This is 0.2mm copper on cell, under 0.15mm copper, under 0.1mm Stainless steel. Triple stack.
Gear 900,
Double pulse
2ms interval between pulses
0.15ms preheating.
I messed up, and forgot to use the magnet to help align and immobilize the triplestack, then got the electrode too close to the edge of the stainless. There was the most sparks yet of any of my Stainless welds, But not really all that many. My old welder with 0,1 Nickel plated steel atop 0.1mm copper shot more sparks by far, every weld.
The damage to the heatshrink was not there previously.
Once again, bending the 3 strips straight up, clamping with both handās thumb and forefinger atop one over the other, with all my strength, and lifting, this triple stack was not coming off, and even some minor rocking wiggling and a circular motion was denied. I had to bust out the needlenose plyers, and start rolling it off, and then the 0.15mm copper separated from the 0.20mm below it. The stainless stayed bonded to the 0.15 on the left weld, and to the right weakly, immediately adjacent to the spot.
Notice the larger bits of āgritā in this photo, and what appears to be copper stuck to the can itself in between the welds.
I wish the stack didnt slip, from a proper looking weld perspective, but that flux tinning and bonding the two layers of copper on the sides is interesting.
Overall, I think this stacking of copper is reducing the tear off strength of the weld, but it is still taking a significant amount of force to roll the welds off. The weld on the right, there is a lack of dot tearing off, but the second layer of copper is stuck outside with weld circle, likely as the flux wicked between the two layers when the stack slipped.
Do they sell 0.35mm copper? because I am pretty confident I can weld it at 90% of the power of this welder, and perhaps lessā¦
One other observation, look how roughly textured the nickel plating on this Samsung 50E is.
I suspect the rougher the cellās Nickel plated surface, the more resistance, the hotter the weld
I think I want to repeat this stack weld, and go down to gear 850 but add a third pulse.
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Ok, this one is interesting.
Gear 850
Triple pulse
0.15ms preheating
02ms interval
0.2mm copper on cell
0.15mm copper on top of 0.2 copper layer
0.1mm stainless on top of both.
triple stack.
Flux between 0.2mm copper and cell can
Flux between copper layers
I was trying to be frugal with the amount of flux, and spreading it wide and flat and evenly, with the 0.15mm piece.
This photo nicely shows the 3 different material thicknesses.
Iād pulled all three straight up again with pinched thumb and forefinger, and once again there was no removing them without plyers.
When I lifted them, I heard and felt the crunchy noise one hears when one allows solder to wick too deeply up silicone jacketed wire meant to stay flexible.
I then grabbed the stainless steel with fingers and tried to rip that layer off by itself. Not happening, had to use Pliers and copper stayed put.
I then tried to pull off the middle layer of 0.15mm copper, but it tore at the edge of the plyers.
I then grabbed the 0.2mm bottom layer and pulled straight up, with plyers and they slipped. I regrabbed it and rolled until it started to tear.
Look at the horizontal cracks in the tinning. Iāve not seen this on any other fluxād weld
After ripping the two stuck layers of copper off, I tried to separate them, grabbing the 0.15mm with side cut plyers, but not intending to cut the copper, but it tore at the cut line.
I tried again and the 0.2mm copper just ripped. This is the fluxās tinning holding the copper together, not the weld points.
After a triple pulse at gear 850, the 15 amp 9 volt power supplyās fan runs for significantly longer than a gear 900 double pulse, not just a third longer.
I think it is safe to say if you weld two pieces of copper together with this flux between, they are both welded, and soldered together.
i think it would behoove one to insure both pieces were as flat as possible with as much flux squeezed out as is possible.
This stack was welded strongly to the cell, but the copper dots left behind on the cell are lesser diameter than the previous weld.
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