#Power bank

I was always too scared to touch spot welding — afraid something would blow up. The day my U3 Pro arrived I practiced on scrap nickel strip all afternoon, and today I did it for real. Six salvaged cells, sorted by internal resistance. Tested it with a flashlight after welding: in 38 minutes it charged my phone full twice. Grinning like I'd found money on the street. My wife says I'm acting like a kid. Yep.

Can I get you to make me a custom one?

The heart of it is a power-bank boost module with a digital charge readout and fast-charge protocol support (about ¥10), paired with 8 × 18650 (¥2–3 each). Test the cells’ internal resistance, stick fish paper on the positive ends, load them into a single-row holder and wire everything in parallel (the module is a boost type, so it only needs 3.7–4.2V); 8 × 2000mAh = 16000mAh. Wrap in fish paper, spot-weld, insulate the positive and negative ends again with fish paper, measure 3.6–3.7V, solder leads onto the positive and negative pads and wrap the joints with filament tape. Two wires go to the module; press the switch and it shows the charge level. The case is hand-cut from PVC sheet (a 3D printer would look nicer), openings cut with a home-made fret saw and a small electric saw, glued with strong adhesive, with cut-outs for the display, the USB / Type-C ports and a small button. The Type-C port does input and output; with a powerful enough charger it goes into fast charge (green lightning icon), the USB port also fast-charges, and it will keep a phone going for two or three days.

The creator (a designer-toy channel) wanted a C4 explosive-pack power bank with a timer look. Materials: a dead power bank (for its charge/discharge board), 18650 cells, a few circuit boards as decoration, a glue gun, wire, kraft paper. Along the way he unboxes the AWithZ portable welder: about the size of a 10000mAh power bank, doubles as a power bank itself, comes with a welding pen (very thick copper tip), nickel strip, manual, charging cable and sandpaper; in settings he switches to Chinese, turns on the welding sound, sets auto trigger 0.5s / 1.0s; power at eight-point-something throws too many sparks and punches through the cell, too little won’t hold, so mid-range around 4.3 is right. Kraft paper is misted with a little water to soften it, then rolled into cell tubes; several groups of cells go in parallel (red is positive — remember parallel, not series), get stuffed into the paper tube and fixed with hot glue, the charge/discharge panel and decorative boards are glued on, and the wires are spot-welded instead of soldered (no preheat, welds wherever you touch, with vibration feedback); powered up it shows 34% charge; a coiled cable and black tape finish the weathered look. Warning: don’t take it into crowds or onto public transport.