and there we have it… our first resource for the battery builder wiki…
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Don’t calculate with actually pulling 45A from a P42A. That’s a max rating that greatly reduces cycle life and heats up the cell quickly. Not recommended without temp control. Mooch rates it at 30A continuous and 40A with temp control.
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For high power 1p or 2p I usually end up soldering copper to the cells. 
it’s not that bad! Standard procedure in some circles.
But imo doublewide (25mm) nickel folded over, and one copper series connection per cell, 14awg or bigger, will be sufficient. With one wire per cell, the nickel will carry big current only over very very short distances, and with doublewide foldover, there will be a lot of nickel in that single layer.
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Oh I forgot to say, with one copper wire per cell, no piece of nickel should see more than 1 cell’s worth of current. @kook
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Yup, that’s pretty solid. Looks like you had to rip the tab off with some pliers, so that’ll hold up just fine. What thickness nickel is that?
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0.15mm.
A good amount of force was needed to rip it off.
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you might find you need to turn it up to 25J or more as the welder/battery heats up. It punches hard when it’s cold but after 10-15 welds you’ll have to compensate for temperature a bit.
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Good thing to know about.
Fun Fact. My mom asked me, what in Merlin’s underpants I am doing with the batteries. Is it dangerous with alkaline cells?
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Alkaline batteries can indeed explode, but it is very unlikely. They have a venting mechanism that releases any excess gas. You’re more likely blowing up a lithium ion cell while welding, I think.
Leason Learned today - dont wear a metal watch band while battery buildind touched nickel tabs spot welded my watch buckle cant remove and burns 12S6P.
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no watches, bracelets, rings while welding
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also, tape/insulate everything you are not working on
(ouch)
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pretty flowers!
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Lol yeah looks more like flowers than pentagrams
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Really good explanation. Good diagram for him. This needs to go into a repository.
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Why would they double?
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Umm…5 cells at 10 amps per cell over 2 tabs…25 amps per tab. That’s definitely right
Also, need some help. I just made a 10s1p 40T and brought it up to full charge last night. It keeps loosing 0.5V over a couple hours.
Prior to welding I checked each cell to be 3.45V and the charger puts out 42.2V so I let it sit to come to full charge then pulled the charger out because I was leaving my apartment. Left the battery at 42.2V and came back to it at 41.7V so I guessed it was just balancing? The entire pack was still cold. Last night I brought it back up to 42.2V then let it sit unplugged over night…it’s back to 42.7V
Is it bad that it’s just dissipating power like that? I’m not worried about loosing that much charge because it’s just 2% of my range but I want to make sure it’s safe for it to do that