The creator buys 100 × 18650 cells at ¥2.5 each (2000mAh, 5C discharge), tests the internal resistance of every one (3 read high and are rejected), picks 90, puts a fish-paper ring on each positive end, loads them into holders and builds five 3S6P packs. When spot welding, a copper strip is laid under the nickel strip to raise current capacity; each group is wrapped in fish paper, gets its balance lead and main + / − brought out (thicker wire for current), gets its own BMS, then is wrapped in fish paper again and bound with fiber tape. The storage box (with carry handle) gets a battery fuel gauge top-left and a voltmeter top-right, a front cutout for the 90W charging module, one cooling fan on each side (one intake, one exhaust), an aviation connector with waterproof cap on the back as the charge port, and a 22W wireless charging module; the five packs sit in the bottom of the box, the output leads are twisted into one bundle (one thick, three thin), tinned with a flame and covered in heat-shrink. Charging goes through a constant-voltage / constant-current buck-boost module, DC input up to 30V (a solar panel under 30V can be connected), output set to about 12.7V with a multimeter; two thermostat switches, one stuck to the buck-boost module heatsink and one to the inverter housing, control the fans; the thick leads get crimped terminals reinforced with molten solder to the 1kW inverter, and two 220V sockets are paralleled onto the inverter output. A ‘dangerous operation, do not imitate’ warning stays on screen for the whole video.