Batteries are the primary power source for any wireless electronics, be it a TV remote, MP3 player, or digital camera. Can you imagine the situation without these small essentials? We have to rely on wired power source only. AAA battery is a common size of cell battery used in low-drain portable household devices, and that is standardized at 44.5mm (1.75in) in length and 10.5mm (0.41in) in diameter. Choose Alkaline type for devices such as clocks, while for high-drain devices like a digital camera, go with lithium batteries.