A rechargeable alkaline battery, also known as alkaline rechargeable or rechargeable alkaline manganese (RAM), is a type of alkaline battery that is capable of recharging for repeated use. The formats include AAA, AA, C, D, and snap-on 9-volt batteries. Rechargeable alkaline batteries are manufactured fully charged and have the ability to hold their charge for years, longer than NiCd and NiMH batteries, which self-discharge. Rechargeable alkaline batteries can have a high recharging efficiency and have less environmental impact than disposable cells. History The first generation rechargeable alkaline batteries were introduced by Union Carbide and Mallory in the early 1970s. 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". Their first product to be licensed out and sold commercially was to Rayovac under the trademark "Renewal". The next year, "Pure Energy" batteries were released by Pure Energy. After the Renewals were reformulated to be mercury-free in 1995, subsequent licensed RAM alkalines were mercury-free and included ALCAVA, AccuCell, Grandcell and EnviroCell. Subsequent patent and advancements in technology have been introduced. Construction of rechargeable cells Rechargeable alkaline cells are constructed very similarly to disposable alkaline cells. A cathode paste is pressed into a steel can that forms the positive terminal of the battery. The negative electrode consists of zinc powder suspended in a gel, with a steel nail contact that runs to the base of the cell to form the negative terminal. Features of the rechargeable alkaline that differ from a disposable alkaline cell include: The presence of barium sulfate or other additives in the cathode mix, which improve cycling and increase capacity by preventing the formation of insoluble manganese compounds. The cathode also has a catalyst to recombine any hydrogen that forms; hydrogen is produced as the fine zinc grains created during recharge are corroded by the electrolyte. Zinc oxide is added to the cathode mix to reduce generation of hydrogen gas; the zinc oxide dissociates on charge to form oxygen. The separator between anode and cathode is formulated to be particularly resistant to growth of zinc grains, which could penetrate and short-circuit the cell. The cells are manufactured in the charged state, ready to use. Charge behavior Although these batteries can be used in any device that supports a standard size (AA, AAA, C, D,