The creator bought the latest AWithZ H2 handheld welder to build his own packs. In the box are two parts boxes: 2 spare welding pins + a Type-C charging cable; practice nickel-plated steel strip; a manual and a card (read carefully, mind the precautions). Safety reminder: welders and lithium batteries are both somewhat dangerous, wear goggles. The body is pen-sized, with a built-in lithium battery, Type-C charging and a color screen showing the parameters; two welding pins; a Type-C port and two buttons at the back (the select key combines several functions), model and power on the rear label. Principle: a momentary heavy current through the resistance heats the metal instantly so it fuses — unlike a soldering iron; the nickel-plated steel strip on 18650/21700 cells takes solder badly, and lithium cells hate heat. Long-press to power on; the color screen shows weld mode, trigger time, gear and preheat time; short-press to step through settings, the up key enters the menu; beginners should keep the factory defaults; gears 1–10 map to different thicknesses, and gear 8 is more than enough for the thin sheet in hand — it punches through. Demo: the two pins touch the sheet for an instant — a flash of sparks; wood underneath gets a burn mark and smoke; the weld is flat and takes no room, and pulling hard won’t separate it; then a demo on 4 × 18650, and if a weld is not solid enough, add a few more.