As @Battery_Mooch stated a few times. This is terrible idea for self discharge. Please don’t do that again, it’s dangerous, it’s bad for environment.
Other than that, good progress with battery building.
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Is it just me or do those welds look toasty? I’ve had similar and was told they’re too crispy
nice input, thank you for that. I think I’ll never repeat this, I hope not to be in this situation ever again 
being scared of cells does not feel good
Too crispy and not good penetration. Too low current, for too long.
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wow @Darkie02 , so much information!
Watch the nickel corners if they get pushed in this could make a short the generally accepted way around this is to round your nickel corner
yeah, the first picture you reacted to is really the baaaad example that taught me to think twice and buy/do once. I’m not proud of this, but I’m happy that I saw that and edited the setup, stripped all this nasty nickel, and did it again.
rounding nickel would be cool, but so time-consuming, I was trying to put the corners more to the sides so that they are definitely over the fish paper ring.
Don’t weld in the center of the neg of the cell it’s were the main connections are welded on the other side it’s bad for them
yes, I was cautious about the negative centers, and I’m aware it is possible that sometimes I’m too close to them. I’m just trying to find a balance in the count of weld points.
3 strips of nickel is not enough for 100A on your series links.
It’s 0.2x10mm, I see it now I could give it more. all the other connections have 4 strips of nickel, here are 3. from what I’ve read this should be the borderline
Is this a burn mark?
yep, the only one, one electrode slipped right when the timer was up for the impulse. there was probably less pressure on it and some arc blew a small hole in the strip. the fish paper is not penetrated, nor the undelying plastic shrink or the cell damaged
You have all that potenchal restricted by this little cable that will get very warm.
fortunately, that is a picture from the past. the input cables were upgraded to 2AWG wires with proper battery clamps and pressed copper eye terminals.
800A bare minimum
1200A recommended minimum (this is what the KCaps deliver)
1400-1600 is a good place (this is what dule KCaps deliver)
I’m getting 1500A from the 65Ah 800A rated lead acid car battery. it seems the bottleneck now are the output leads to the electrodes
If your going to play around with the cables and battery’s I recommend you do a quick bit of maths
nice, I did not know about that image
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Would good penetration look like this?
From what I can tell these are more ‘dimpled’; and because of more pressure applied onto the electrodes/nickel with a shorter pulse width at a higher current, right?
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Update, this works great
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I push down hard when I’m welding, I don’t call the calibration on my lipos but it was something above 1400A. I typically run about 38-42J on a single layer of .2mm nickel. and thicker nickel seems to dimple more than the thinner stuff. The push also tells me if I’ve missed the mark on the positive terminal since it will flex a lot due to nothing under it. I keep the tips files to a neat ball point.
*that pack was before mooch taught me to avoid welding in the center of the negative terminal
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Does this apply to A123 cells as well, or is it the positive anode on those cells?
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Penetration isn’t really something you can look for. You gotta do some tests and see if you can rip the nickel off the cell. If it leaves the weld behind and tears the nickel, it’s great. If not, then that isn’t great.
You want the minimum energy/heat input while still achieving that strength.
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I have been thinking about making a dual tip grinder to touch up easily while welding, hopefully without putting them down.
Bad idea? doing them one at a time with sandpaper good enough?
iirc those are reversed poll compared to standard li-ion, so it maybe the positive. @Battery_Mooch would definitely know better than I would.
I use a small file that’s a pretty fine abrasive. Probably file them every ~120 welds?
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The “button” for the 26650, usually the positive terminal for a Li-ion cell, is the negative terminal for the A123 and Lithium Werks cells. I don’t know if the flatter positive terminal is spot-welded internally but I’m thinking it would be safer to assume so.
There’s nothing in the datasheets about connecting cells and I’ve never seen a cell teardown.
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I might be mistaken I just avoid the very center on both ends and do 6 welds in a circle
As a very general rule of thum I do 1 x 10mm by 0.2 per a cell of q30 in a p group. Depending on how you build your batery this needs to be re assessed
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What is the concern if you don’t mind me asking? I’ve been doing this for years and have never had a problem.
Although I usually fully discharge my lipos to 0 volts on a concrete pad outside, or something along those lines. Everything I’ve ready is that inert lipos are the safest way to dispose of them.
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According to the wise words of Mooch:
“Salt water discharging is incredibly slow and causes electrolysis destruction of the tabs, exposing the inside of the cells and creating toxic sludge water”
Wow I really can’t get this to work on my phone
**there we go
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I recommend you fined proper places to do research sutch as manufactures instructions or recycling businesses. Just because people say carrots help you see in the dark, eating crusts make you hair curly doesn’t make it true. Disharging lipos below there safe limit is dangerus and toxic.
Should I be covering the naked nickel on my pack if shrink wrap is going to be going over the whole pack?
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More insulation is (almost) always better 
That said, you know the use case for your battery better than we do. Sometimes its the best idea to wrap every single square inch of a battery in fish paper. Sometimes thats either not possible, or not necessary. It all depends.
Here’s a battery I am building for a customer right now:
Notice how the only fish paper are the rings on the positive terminal, the strips under the positive nickel fold, and the strips between the sides of the p-groups?
Normally I would wrap the entire p-group all the way around, but that is actually not possible on this pack, as the space in each enclosure segment is wide enough for 8 21700’s, one layer of fish paper, and literally nothing else. Adding one layer of kapton all the way around each group nearly made the battery not fit.
Though in addition to it not fitting, I also deemed a full fish paper wrap unnecessary, as with so little space in the enclosure and each section of the battery being total isolated by the enclosure, the chances os something conductive getting where it shouldnt are slim to none.
So it really all comes down to your application.
To answer your question simply,
A bit of kapton almost never hurts anything, and fish paper is even better 
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