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A nickel–metal hydride battery (NiMH or Ni–MH) is a type of rechargeable battery. The chemical reaction at the positive electrode is similar to that of the nickel–cadmium cell (NiCd), with both using nickel oxide hydroxide (NiOOH). However, the negative electrodes use a hydrogen-absorbing alloy instead of cadmium.
A battery charger, recharger, or simply charger, [1] [2] is a device that stores energy in an electric battery by running current through it. The charging protocol—how much voltage and current, for how long and what to do when charging is complete—depends on the size and type of the battery being charged.
The first generation rechargeable alkaline batteries were introduced by Union Carbide and Mallory in the early 1970s. [3] [5] Several patents were introduced after Union Carbide's product discontinuation and eventually, in 1986, Battery Technologies Inc of Canada was founded to commercially develop a 2nd generation product based on those patents, under the trademark "RAM".
An AAA battery is a single cell that measures 10.5 mm (0.41 in) in diameter and 44.5 mm (1.75 in) in length, including the positive terminal button, which is a minimum 0.8 mm (0.031 in). The positive terminal has a maximum diameter of 3.8 mm (0.15 in); the flat negative terminal has a minimum diameter of 4.3 mm (0.17 in). [ 2 ]
Under certain conditions, some battery chemistries are at risk of thermal runaway, leading to cell rupture or combustion.As thermal runaway is determined not only by cell chemistry but also cell size, cell design and charge, only the worst-case values are reflected here.
Rapid chargers can typically charge cells in two to five hours, depending on the model, with the fastest taking as little as fifteen minutes. Fast chargers must have multiple ways of detecting when a cell reaches full charge (change in terminal voltage, temperature, etc.) to stop charging before harmful overcharging or overheating occurs.
A Li-ion 1.5V AA-size battery, sold by the Chinese company Kentli as "Kentli PH5" since 2014 and with similar batteries later available from other suppliers is a AA-sized battery housing containing a rechargeable 3.7 V Li-ion cell with an internal buck converter at the positive terminal to reduce the output voltage to 1.5 V. [19] The Kentli ...
Ni–Cd cells are available in the same sizes as alkaline batteries, from AAA through D, as well as several multi-cell sizes, including the equivalent of a 9-volt battery. A fully charged single Ni–Cd cell, under no load, carries a potential difference of between 1.25 and 1.35 volts, which stays relatively constant as the battery is discharged.