An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery (or "voltaic pile") in 1800 by Alessandro Volta, batteries have become a common power source for many household and industrial applications. According to a 2005 estimate, the worldwide battery industry generates US$48 billion in sales each year, with 6% annual growth.
quoted from Wikipedia
think of how many things in your house are now battery powered, or can be, flashlights are the first thing I am sure you think of. flash lights were just some of the first things we had use for batteries, there are now cameras, cars, tvs, radios, clocks, portable fans.
Batteries have made a lot of our life portable. and usable in any weather. Remember that next time you are driving around, talking on your cellphone, they are all powered by batteries.