Many mobile or portable devices are supplied with electrical energy by batteries. These include flashlights, children's toys, radios, radio microphones, radio mice, weather stations, medical devices, measuring instruments, kitchen scales and many more. So-called primary cells = non-rechargeable batteries can only be used once, i.e. until they are exhausted. But it is a waste to dispose them! Because with a little bit of electronics, you can use old batteries.