Energizer AA size 2500mAh rechargeable cell

A rechargeable battery (also known as a storage battery or secondary cell) is technically a group of two or more secondary cells, such as a laptop battery containing six individual cells. However, they are often used to refer to a single cell, such as a NiMH AA battery. These batteries can be restored to full charge by the application of electrical energy, such as through a battery charger. In other words, they are batteries in which the electrochemical reaction that releases energy is readily rechargeable. Rechargeable batteries come in many different sizes using different chemicals. Commonly used secondary cell ("rechargeable battery") chemistries are lead acid, nickel cadmium (NiCd), nickel metal hydride (NiMH), lithium ion (Li-ion), and lithium ion polymer (Li-ion polymer).

Rechargeable batteries can offer economic and environmental benefits compared to disposable batteries. Some rechargeable battery types are available in the same sizes as disposable types (eg. AA, AAA, CR123A). While the rechargeable cells have a higher initial cost, rechargeable batteries can be recharged many times. Proper selection of a rechargeable battery system can reduce toxic materials sent to landfills compared to an equivalent series of disposable batteries. For example, battery manufacturers of NiMH rechargeable batteries claim a service life of 100-1000 charge cycles for their batteries.

Usage and applications

Rechargeable batteries currently are used for applications such as automobile starters, portable consumer devices, light vehicles (such as motorized wheelchairs, golf carts, electric bicycles, and electric forklifts), tools, and uninterruptible power supplies. Emerging applications in hybrid electric vehicles and electric vehicles are driving the technology to improve cost, reduce weight, and increase lifetime.

Unlike non-rechargeable batteries (primary cells), rechargeable batteries had to be charged before use. The need to charge rechargeable batteries before use deterred potential buyers who needed to use the batteries immediately. However, new low self discharge batteries allow users to purchase rechargeable battery that already hold about 70% of the rated capacity, allowing consumers to use the batteries immediately and recharge later.

Grid energy storage applications use industrial rechargeable batteries for load leveling, where they store electric energy for use during peak load periods, and for renewable energy uses, such as storing power generated from photovoltaic arrays during the day to be used at night. By charging batteries during periods of low demand and returning energy to the grid during periods of high electrical demand, load-leveling helps eliminate the need for expensive peaking power plants and helps amortize the cost of generators over more hours of operation.