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What about soldering wire to nickel strips? Could one safely connect together, via soldered wire, groups of nickel-welded batteries?
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I do that
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d00d
you can do anything you wish to do…
ok… yes… I’ll admit it. I’ve soldered on 18650 cells and I’m alive…
some of us have made mistakes… yes… some of us know how to mitigate such mistakes…
what my dear friend @b264 is attempting to express… is:
there are trade-offs and risks in every endevour… educate yourself as to which risks you’re willing to take… and then learn how to mitigate that risk…
and then you end up with common knowledge…
no one can predict the size of the village of idiots… some of us just tend to heard them so they won’t hurt themselves or others…
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I used a 18650 module of yours and stretched it 45% in the x & z planes in cura, So I am unsure as to its actual constraints. Sorry for not having the answer. I would like to use your file, (And thank you so much for the offer) but I don’t think I have the filament to print off 14 more modules 
…Like really, I’m running really low
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and to all would like to quote a guy who were in designing battery for Zero motorcycles and is knowledgeable to say the least:
If the penetration is making a perfect weld, then the inside surface of the steel of the can in wetted contact with the organic electrolyte reached >1200degC. This does mean you contaminated your electrolyte with byproducts of electrolyte thermal decomposition at best, and at worst thermal damage that mechanically impacts the separator end overlap, which will cause non-uniformity in active material use (premature aging and impedance climb, gassing etc).
Just my $0.02, but there is a reason you don’t see spot welds on cylindrical cells outside of Alibaba/ebay and home garage tinkerers.
Some projects are fine if say, 1 in 250 spot welds to the bottom of cans causes some noticeable damage. Some projects have say, 2000 welds per assembly, and no tolerance for tearing it apart to replace the expected 8 damaged cells out of the 2000 weld assembly.
Weldless packs don’t have to damage the cell to be assembled. Done right they can have lower contact resistance than bussing you would be capable of spot welding through at home, and they can reduce surface current density from a wider contact area for improved thermal performance. That said, almost everyone’s weld-less packs is neither good or done well, but that’s a design problem not an intrinsic to the process problem.
http://m.jes.ecsdl.org/content/165/16/A4051.full
The reason this CT scan imaging is nice, is because it shows you not only the separator overhang area, and how it’s just a mm or so from where it begins it’s job separating anode and cathode foils from contact. That plastic both has a delicate microscopic pore structure it needs to maintain to transport ions while insulating, and it melts around 130-190degC. How much of that little edge overhang do you feel comfortable melting back from the coated foil?
Because these images are of an event that evolved gases, you can see that gas bubble displacing the electrolyte that was wetted against the bottom of the can.
This electrolyte wetting that back wall is thermally sensitive, and undergos a small scall gassing at 70 degC and a macro scale decomposition at 150-250degC depending on carbonate chain lengths and stabilizers. Don’t have to believe me, it’s been throughly researched for over a decade.
Now you’ve put reactive decomposition species into your pure cell environment to contaminate reactivate surfaces with materials that aren’t storing energy for you, and are an ionic impediment (impacts cell impedance).
If you’re making little packs where it doesn’t meaningfully matter your decay rate is higher, or fallout rate in mfg is higher, or cell to cell performance is more inconsistent, then hey, it’s the cheapest game in town to make something work. If it’s an application where quality matters, you find ultrasonic bonds and controled depth laser welds, or hybrid processes.
More welds on the bottom = more thermal damage
In practice for me, thermodynamics has been painfully reliable and merciless irregardless of my opinions. For this reason I’m happy to agree to disagree with you that it’s good practice to raise places on the floor of the can to >1200degC.
Everyone’s knee-jerk reaction is to hate on a weld-less design, and point out the shortcommings of the thousands of awful little battery holders in your TV remote controller or toy. This doesn’t mean it has to suck, it would be a huge advantage to DIY EV builders to have something that can be assembled and reconfigured without needing specialty equipment. If we encourage and support efforts like that they will be more likely to happen and mature into something good for the community.
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Also for everyone soldering to bare cells, which is not reccomended, i would suggest to use the same flux used for soldering on aluminum, that stuff makes solder flow on plastic haha
But the fumes are quite nasty
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Yes and do not solder on cells. But if you do, keep a piece of aluminum handy and the moment you remove the iron, press onto the hot part to suck the heat out as fast as possible before it travels too far into the cell. But do this in such a way that you don’t short anything out. And only keep the iron (set to the highest setting) on there for like 2 seconds maximum. And be a pro solderer before you start.
Don’t solder to cells though, farm out welding to someone else if you need to. Solder to the welded nickel. It’s better.
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Are you saying spot welding is bad as well?
I dont know but i tend to trust people who work in that industry on a deeper level.
I think spotwelding is ok for diy but soldering is out of the question.
This partly was the reason i got into working on weldless system.
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Sounds like he’s saying both spotwelding and soldering are bad.
Well, rip my soldered battery pack.
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FULLTEXT01.pdf (1.2 MB)
this is claiming that there is neglectable damage to cells. The weld heat is generated between the nickel and the plate of the battery, the contact point may reach 1200 between the two metals, but I wonder how much of it spreads out…
Of course my dumbass tried it. Did a 50J pulse to nickel on top of a razor blade while I was holding it on my finger. It was definitely hot as hell idk 1200c though… kinda feel like accidentally touching the hot end on a printer extruder… 5/10 may try it again.
Edit: Did it again without the nickel. 0/10 will not try again.
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These are looking more and more appealing for my planned A123 12s1p pack. Did you buy or print these?
Printed. Took about a week at 2 modules Produced a day
Do you guys think there will ever be a high conductivity adhesive? It would be nice you could glue a battery together
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Did you use an open source print design or did you custom design it?
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I saw a post about taping a battery together with conductive copper tape.
Obviously not a great idea, but the possibilities in the future 
.
For OP, what kinda current are you trying to pull out of pack, how far you trying to go?
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¡Spray on shoes!
You talking about a thick spray on metal type o deal? That would be so bad for your health and a mess to apply/clean, not to mention it would probably be brittle once dry and have a low melting temp. I didn’t mean to go that far into it, lol, those are just prob some reasons it hasn’t ‘hit the scene yet.
Tape would be kinda cool tho. Like the adhesive is solder based sorta, you peel off the lining from the adhesive and like… it evaporates in the air shortly after except where it contacts metal to leave the copper base of the tape joined in a flush higher-contact patch on the battery’s terminals. That would be sick.
I took the existing 18650 modules design, and scaled it 45% in the x & z planes on my 3-d printers print bed to change the diameter of the cell from 18mm to roughly 26mm to accommodate the larger 26650 cells. Everything else scaled around it, and while the holes on the modules are slightly stretched, it’s no big deal as they aren’t load bearing and aren’t being used as thread. As you can see in the pic I had posted, they work just fine.
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