<p>A mercury battery (also called mercuric oxide battery, or mercury cell) is a non-rechargeable electrochemical battery, a primary cell. Due to the content of mercury, and the resulting environmental concerns, the sale of mercury batteries is banned in many countries. Both ANSI and IEC have withdrawn standards for mercury batteries. Mercury batteries were made in button types for watches, hearing aids, and calculators, and in larger forms for other applications.
The mercury oxide-zinc battery system was known more than 100 years ago but did not become widely used until 1942, when Samuel Ruben developed a balanced mercury cell which was useful for military applications such as metal detectors, munitions, and walkie-talkies. The battery system had the advantages of long shelf life (to 10 years) and steady voltage output. After the Second World War the battery system was widely applied for small electronic devices such as cardiac pacemakers and hearing aids. Mercury oxide batteries were made in a range of sizes from miniature button cells used for hearing aids and electric wrist watches, cylindrical types used for portable electronic apparatus, rectangular batteries used for transistor</p>