Watch battery manufacturers offer several types and sizes of batteries. Some batteries are referred to as watch batteries even though they are used for other purposes, such as hearing aids, because they resemble watch batteries. Some varieties of watch batteries have been developed because batteries containing mercury have been banned due to environmental concerns.
Different watches require different batteries.
Definition
According to Rob Berkavicius, who has been servicing Accutron watches for more than 30 years, the main thing that makes a battery a watch battery is its construction. Watch batteries are made to adhere to strict parameters that minimize the possibility of leakage inside a watch. The energy an appliance gets from a battery, or cell, depends on the type of chemistry inside the cell, the amount of that chemistry and the ambient temperature surrounding the appliance. In addition, different types of watch batteries serve particular applications. For example, some watches requires low current for a long time, while others need reliably constant voltage.
Mercury Batteries
Berkavicius says mercury was the main type of cell for watches for more than half a century. They were extremely good at delivering a constant voltage; in fact, some watches were designed to use a mercury cell. However, mercury is considered a deadly poison, and environmental concerns have caused this type of cell to be banned in most countries.
Silver Oxide Batteries
Silver oxide cells have a higher energy than mercury cells and are rated at 1.62 volts. They have a similar design as well, with a constant voltage throughout their lifetimes. Further, they do not have harmful chemicals. They are better than mercury batteries overall, although they have about half the useful shelf life. These cells are used mainly in watches.
Lithium Batteries
Usually referred to as "coin cells" because they resemble coins, lithium batteries used in watches contain lithium-manganese dioxide and are rated at 3.0 volts. There is another type of lithium cell containing lithium-thionyl chloride that has a higher voltage but normally is not used in watches requiring constant energy. For example, a quartz watch that requires intermittent energy is suitable for this type of lithium cell.
Alkaline Batteries
Alkaline cells are the least expensive battery on the market, with zinc-alkaline chemistry and a rating of 1.5 volts. Its voltage is not very constant, and it has a relatively short shelf life. Free watches and toy watches usually contain this type of battery. It is environmentally safe.
Zinc Air Batteries
These are not watch batteries at all, but are mentioned here because they are often found on racks with watch batteries. They are not at all suited for watches because they must be vented to the outside of the battery to work. A good use for these is in hearing aids. The potential for water to be formed and ejected from the cell makes this battery type unsuitable for use in watches.
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