When the chemicals in the electric cell are used up, the electric cell stops producing electricity. The electric cell is then replaced with a new one. In case of rechargeable batteries (such as the type used in mobile phones, camera and inverters), they are used again and again. How?

Rechargeable batteries are those batteries which are reusable after they are discharged by recharging them.

The main principle of battery is that the chemicals inside the battery react and produce electricity, but once those chemical reacts completely there is no electricity left, then the battery is said to be a discharged battery.

But, there is a way to use discharged batteries again by reversing the reaction which produce electricity. That is, if we reverse the reaction which uses all the chemicals inside the battery and produce electricity, the chemical will again start generating electricity. This is the working of rechargeable battery.

The reaction which consume all the chemicals and produce electricity inside the cell is reversed and this is done by charging of the battery. That is how rechargeable batteries work.