Telephones operated with dc power often supplied by rechargeable batteries. A wide range of batteries is supplied for these purposes, as now telephones become common household article. Nickel cadmium battery are charging batteries and often used for telephones and cordless telephone applications. Nickel metal hydride battery are rechargeable often used for higher capacity and for longer talk time. These batteries are often used for wireless pocket telephones, cordless telephones etc. They are provide with longer service life cycle. They are rate by the number of charge or discharge cycles they are subjected to. A normal ni-cd battery expected 500-800 discharge cycle, and after that they should be replaced. Rechargeable sealed lead acid battery are often used for telephones. They come in wide configurations with variations in voltage and capacity.
