Power supply

Mobile phones generally obtain power from batteries, which can be recharged from a USB port, from portable batteries, from mains power or a cigarette lighter socket in a car using an adapter (often called battery charger or wall wart) or from a solar panel or a dynamo (that can also use a USB port to plug the phone).
On 17 February 2009, the GSM Association announced[10] that they had agreed on a standard charger for mobile phones. The standard connector to be adopted by 17 manufacturers including Nokia, Motorola and Samsung is to be the micro-USB connector (several media reports erroneously reported this as the mini-USB). The new chargers will be much more efficient than existing chargers. Having a standard charger for all phones, means that manufacturers will no longer have to supply a charger with every new phone.
Formerly, the most common form of mobile phone batteries were nickel metal-hydride, as they have a low size and weight. Lithium-Ion batteries are sometimes used, as they are lighter and do not have the voltage depression that nickel metal-hydride batteries do. Many mobile phone manufacturers have now switched to using lithium-Polymer batteries as opposed to the older Lithium-Ion, the main advantages of this being even lower weight and the possibility to make the battery a shape other than strict cuboid. Mobile phone manufacturers have been experimenting with alternative power sources, including solar cells.