I use steel wool or fine sand paper, while welding I rub the tips together to scrape off the oxides and pass the time between welds
One thing I’ve found really helps w consistent welds is to run a fan over the system. In particular, the xt90 and lipo (assuming that’s what ur running) as this goes a long way to keeping things cooler, especially once u get into the battery build. U can work faster and still get consistent work. Also, whenever I’m not working, I stick the electrodes right in front of the fan bc they get hot af when ur moving along.
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The leads from my lipo are the only things getting warm at the slow pace I was going.
If things are getting warmer I’m guessing I would see lower amperage higher weld times as resistance goes up? longer weld times being worse for the welds because heat gets more time to spread and is less concentrated. is my understanding correct?
I do have what I think is a “baby” lipo. it was the one on the kweld site for a while. Nano tech 5000mah. but everyone uses a bigger one.
I have 2 5000mah graphenes and will run them in parallel once my connector shows up. Right now, juat rotating them. They are def powerful batteries but they do get hot after a while. I imagine 2 in p will reduce that heat signficantly.
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Can I ask what the risks of solder.getting can too hot on the cells is? Can you blow the fucker up that way and start a fire? Damage the cell in other ways? Is it possible you could damage a cell by getting it too hot via soldering and not know by simply checking voltage?
Again, far from an expert but soldering anything on the negative aka ‘hot’ part of the cell (which is essentially the entire cell excepting the pos terminal) is very risky and can cause thermal runaway and possibly explosion. That being said, many people successfully solder liion cells every day. It is def risky tho. Soldering the pos terminal still carries risk but not as much. Anyone feel free to correct me but this is my understanding.
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Nope im pretty sure what Gabe was referring to was the possibility of a shoulder short. You are soldering on your positive terminal, but the shoulder of the can (and, as you said, the rest of the body) are negative. If a bead of solder sneaks off your nickel, onto the cell, and through the shrink wrap, them you will have big 
Diagram showing that the shoulder of the can is negative, and only a few mm from the positive terminal.
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Plus the chance of melting the shrink wrap and allowing a direct nickel-to-shoulder short unless there’s some fishpaper or other heat-resistant material under there.
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Yep, also this. (though from the picture it appears that he is using fishpaper rings under his nickel)
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exactly. thank you for saying it so much better.
Yeah, the shoulder always sketches me out, knowing that a dead short is less than 1mm away 
A little stray solder blob and POOF. Big POOF.
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Ah… Ok this is helpful. I had intended on covering pretty much every exposed area in fish to prevent anything from touching anything else to avoid shorts but now I more comprehensively understand the risk.
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How the hell do I size heatshrink for the outside of my pack. It’s going to be a 12s4p of 21700 cells molicel 42a. Should I hear shrink the whole thing at once or each parallel group?
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The trade name is Silastic. Generic name is silicone rubber.
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it feels hard though, not soft like silicone. has a matte chalky texture.
Then its most likely the “white chinese glue” as described here: https://electronics.stackexchange.com/questions/18525/what-kind-of-glue-should-i-use-for-pcb-mounted-components-to-avoid-vibrations
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What thickness strip should I use for a 12s5p 42a Flatpack like this for a decent 80a discharge?
I would use 0.2x25mm nickel for series in the middle of pack and 2x 14awg or thicker wires (or similarly capable braided copper) for other series connections.
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