Repairing a Philips shaver with a new battery so it lasts another 10 years. After years of use it died a few minutes after charging; now with a higher-capacity cell it runs twice as long as new

Swapping a flashlight battery with a handheld mini Li-ion spot welder. The handheld mini welder is easy to carry and works for re-celling power banks, players and other small gadgets. Solder a Li-ion cell with an iron and the heat raises the pressure inside and can ruin the cell — only a spot welder will do