is an electrochemical device for producing electricity by converting chemical energy. Disposable batteries, also called primary cells, are batteries which can only be discharged once. They're discarded until the chemical changes that induce the electrical current supply are complete. Rechargeable batteries
, or secondary cells, can be recharged after they have been drained. Typically, the batteries are charged after full or partial depletion by delivering energy to the batteries and reversing chemical processes within the batteries, by applying a voltage to the batteries, forcing current through the batteries, and, thus, restoring charge.
The main secondary battery which has been put into practice includes a lead acid battery
, a NiCd (nickel-cadmium) battery, a NiMH (nickel-metal hydride) battery
, a silver-zinc oxide battery, a lithium ion battery
, etc. The lead acid battery, in which lead dioxide is used as a positive active material, lead is used as a negative active material and dilute sulfuric acid is used as an electrolyte, has an operating voltage of 2 V. The lead acid battery has a good balance in quality, reliability and cost, and therefore is widely used for a motor vehicle, an electric vehicle, a UPS (uninterrutible power supply)
, etc. The NiCd battery, in which nickel oxyhydroxide is used as a positive active material, cadmium is used as a negative active material and potassium hydroxide aqueous solution is used as an electrolyte, has features of a small internal resistance, allowability of large current discharge, long cycle life, resistance to excessive charge/discharge, and wide range of using temperatur. In Ni-MH battery, nickel oxyhydroxide is used as a positive active material, a hydrogen storage alloy is used as a negative active material and potassium hydroxide aqueous solution is used as an electrolyte. The Ni-MH battery having a feature of a high energy density has been mainly put into practice for various consumer appliances. The silver oxide zinc battery has features of a high output and a high energy density, but a defect of high cost. Its larger scale type has been mainly used for space and deep-sea equipment, whereas its small scale type has been widely used for a watch or an electronic calculator. The lithium ion battery, which has features of a high operating voltage, high energy density and no memory effect, has been explosively used for consumer appliances. The consumer type AA or AAA sized nickel metal-hydride (NiMH) or nickel cadmium (NiCd) rechargeable batteries have widely been in use. Various electrical appliances, such as digital cameras
, video recorders
, AV equipment, notebook computers
, cellar phones
and toys, require high capacity and reliability AA or AAA sized rechargeable battery cells for operation. Battery chargers
have an input for power supply from the mains, a transformer to transform the current voltage to the right voltage, a rectifier to convert the alternating input current into full-wave direct current and an overcharge prevention circuit, so that when the battery gradually gets up to the charging voltage, the circuit for preventing overcharges allows current through. Overcharge of the battery can lead to complicated and undesirable side reactions, in particular as they pertain to the decomposition of electrolyte. The latter can lead to gas production, which in turn leads to increased battery internal impedance. Battery testers typically determine the condition of batteries, i.e., determine the internal resistance of a battery, by either a load test or a small-signal analysis of the battery. Many batteries are rated by a measure of CCA (cold cranking amps) according to an industry standard test procedure.