How does energy change from one form to another?
When you connect a battery to a charger an electric current flows through it. In the process the electric energy changes into chemical energy. Then you can use the battery.
Batteries are used for sooooo many things. Like on submarines to supply oxygen or the start a car or even to listen to music. Now with that in mind imagine what would the world be like without batteries. and we are lucky that some are recharable. Think about changing batteries in your ipod everytime you use it. Now think about that one.