US Patent 7118817 Coin cell protection against reverse insertion in cell holder

A method and associated apparatus for preventing applying a reverse polarity voltage to an electronic circuit from a coin cell used to power such circuit by providing a first insulating wafer over the top conductive surface of a coin cell and a second insulating wafer over the bottom conductive surface of the cell. The first wafer has a central opening and the second wafer is designed to cover the portion of the bottom conductive surface corresponding to the opening of the first wafer so that when the two wafers of the protection system are placed over the coin cell with the first wafer and the insulating area positioned on the top and bottom conductive surfaces respectively, the insulating area extends fully under the first opening.