Button batteries are used in hearing aids, digital thermometers, insulin pumps, portable medical monitors, hospital pagers, watches, toys and calculators.
Silver oxide and alkaline manganese button cells provide a nominal 1.5 volts per cell -- zinc air button cells provide a nominal 1.4 volts per cell.
Zinc air button cells are used primarily in hearings aids. Oxygen, which reacts with the zinc electrode, is obtained from air that enters the cell from one or more holes. Because of need for continuous supply of air, zinc air batteries cannot be used in tightly sealed products. Because zinc air cells are used in hearing aids, this chemistry is the most
prevalent type of button cell. Because of the number of zinc air batteries sold and the level of mercury in these cells, zinc air button cells contain over 70% of the mercury used in button cells.
Alkaline manganese and silver oxide button cells may be used in tightly sealed products. Common applications include watches, toys and calculators.
Lithium coin cells are similar in appearance to coins and provide a nominal 3 volts per cell. Lithium coin cells cannot be interchanged with other button cells because of their different size and different voltage. Lithium coin cells contain no mercury.
Mercuric oxide button cells use mercuric oxide as an electrode. This results in these cells containing 30-40% mercury by weight. These cells were used primarily in hearing aids. The battery industry phased out these cells between 1991-1995. Federal law enacted in 1996 bans the sale of these cells.
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