Opening: when a tricky job leaves him sweating and stuck, out comes the ‘ultimate weapon’. Job one, an Aige Bluetooth speaker — light won’t come on, won’t charge, something dead inside; after the fix the light is on and it enters Bluetooth mode, ¥30. Job two, a Tineco floor washer with a charging fault, bad contact, ‘Tineco machines are just no good, make do’; the (Fluke) multimeter can’t tell good from bad and can’t find the fault, a sip of tea dregs to calm down. Then the ultimate weapon, the ‘Yao Ni Ming 3000’ (spot welder): control board fine, panel fine, the battery isn’t supplying enough — one cell already dead, replace them all. Genuine Samsung cells, IR tested one by one at 9.6/9.7/9.8/9.8; to tell genuine Samsung, check the QR code on the bottom of the cell (e.g. 981945). Spot-weld the pack, very OK. Back on the charging dock: reads 28W, the machine is 26V 1A i.e. 26W, reaching 27W means it’s charging at full power; 5 minutes on charge, test run fine, charge was 49 and is now 53; smart switching and the ‘return to dock’ prompt work as normal. 439 comments: charges more than fellow creator ‘Jiadian Huatuo’; many ask for a build guide and the principle of the ‘Yao Ni Ming 3000’; Fluke multimeters aren’t cheap; someone lists the repairman’s tools — Fluke multimeter, IR meter, coulomb counter, Li-ion spot welder; which welder is it and how much.