The solar-lamp project needs lithium packs welded; a soldering iron is slow on lithium cells and a safety risk, so he bought an AWithZ U3 welder, the Li-ion version with 11000mAh (on-screen specs: 0.1mm copper, 0.35mm nickel-plated, 0.35mm steel, 0.2mm pure nickel) — not expensive, good enough is good enough; if you have more use cases, buy a more professional model. Looks: palm-sized; welding-pen socket top-left; 2-inch colour screen in the middle; two buttons on the right (adjust key, power / option toggle key); USB and C ports on top — the official notes say besides charging it can emergency-charge a phone, but inefficiently; manual weld key on the right (touch to trigger in manual mode). Long-press to power on into the main menu: battery and temperature in the centre, 6 sub-menus toggled by tapping, short-press the adjust key to change values; settings menu top-right (language, pulse interval, sound etc.), defaults are fine — the only thing to set is the gear: 80 fine gears from 1.0 to 9.0, matched to the material, neither too high nor too low. The pens use thick copper wire — low resistance, low loss, no heating; detachable alumina-copper welding pins are safe and durable; the handle has a manual weld key; the pens are 40 cm long with a front-facing opening to maximise usable length; line up with the socket and push in. Set the parameters before use: auto mode, 0.5s trigger, 2 pulses, gear starting at 3; test on a dead CR2032 coin cell with the material supplied by the manufacturer: hold one pen still, press the other down close by, the machine welds automatically with a ‘beep’; check the weld by prying with pliers to see how solid it is, and if the weld is weak, raise the gear until it’s perfect. Verdict: highly recommended for DIY battery or small-appliance welding. Comments: what price, where to buy, how to remove a welded joint without damage (creator: ¥100-odd; needle-nose pliers will get it off but leave marks); ‘I have this one too, ¥200-odd’.