Down and dirty diy 18650 spot welder?

I’ve got 48 cells coming and overwhelmed with info about pack-making. I’ve gotten pretty good at soldering but the challenge of going fast enough soldering batteries I’m intimidated by.

I’ve seen a couple diy spot welders using microwaves or here:

Any of you soldered a pack and can tell me what u know? Also how much current would go through each wire if it’s 40 amps total and 4 paralleled strings of 12s? I’m guessing 10 amps through each paralleled set of 12 and adding up to 50 volts through the series connection. Don’t know what wires or preferably spot welded tabs to go with.
Any of u done a pack or made a welder…or want to rent me one even maybe.

@barajabali might be able to help you.

The JP Spot Welder on ES looks pretty good. Here’s the link: https://endless-sphere.com/forums/viewtopic.php?f=31&t=68865&sid=da9b29126c004ea9a0109819ab4e2113

someone on here had a spot welder from some Caps and a foot switch. looked good.