DIY Battery Pack Guidance needed

[glyphiks]

pretty much perfect welds straight outta the box with the right power source

Kweld spot welder

Having run into problems with Boss welder (link) I was stumped on how to carry on building my battery packs for my ATBs. It’s still my go-to soldering iron, there is much to love even though I would like to bring back it’s welding capability. I suspect FET damage but there are no errors or visible signs, apart from weak welds even with high settings. It wasn’t always this way, I was very happy and able to weld nickel on top of copper even with a 3s 3Ah 65c Graphene which is ever so slightly s…