Watch Batterie : What is it?
| Watch batteries, also called button cells, propel the clockwork and other moving parts of a watch. They are round with a flat metallic face, which forms part of the positive terminal. They have a power capacity ranging from 1.5 to three volts. Most of them are installed at the back of a watch’s dial. They can also power other small devices, such as calculators, flashlights, PDAs, and some keyless remote controls.
Like other batteries, watch batteries contain a negative terminal called an anode, and a positive one called a cathode. Anode materials are usually zinc or lithium, while cathodes range from a number of alkali or organic chemicals. An electrolyte liquid, usually sodium hydroxide or potassium hydroxide, flows inside the cell to distribute current between the terminals.
Watch batteries are classified according to their chemical composition, using an alphanumeric coding system. The first letter indicates the type of cathode used, followed by a three- to four-digit code indicating their size and an R to indicate that they are round cells. The last letter represents the type of electrolyte used. |
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Kinds of Watch Batteries include the following: |
Mercury cells
- Mercury cells have a power capacity of about 1.36 volts.
- They have very consistent voltage and will last up to three years.
- They contain a powdered zinc anode, mercuric oxide and graphite cathode, and an electrolyte gel.
- Their mercury content is highly toxic, so they have been banned in many areas.
- They are protected by a nylon seal supported by a metal sleeve.
Silver oxide cells
- Silver oxide cells have an average capacity of 1.62 volts.
- They have the same construction as mercury cells, except that they use graphite and silver oxide for their cathode.
- They also have a constant voltage, but last only half as long as mercury cells.
- They are commonly used in series in small LED flashlights.
- They also include an interior membrane to separate the chemicals.
Lithium cells
- Lithium cells, also called coin cells, have a power capacity of three volts.
- They have a lithium anode and a manganese dioxide cathode. Lithium cells designed for other devices contain thionyl chloride, which have a capacity of 3.6 to 3.7 volts.
- They have a fairly consistent voltage, and have a shelf life of up to 10 years.
- They are ideal for low-drain devices, such as quartz watches.
- Their separator membranes are absorbent and contain a small amount of electrolyte.
Alkaline Cells
- Alkaline watch batteries are constructed like lithium cells, but with a voltage of 1.5 volts.
- They are the cheapest type of watch battery and are supplied with most new watches.
- They have a zinc anode and a magnesium dioxide cathode.
- They are also environmentally safe and ideal for low-drain and intermittent high-drain watches.
- They have an unbalanced voltage and last only half as long as silver oxide cells.
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Life span: Choose a watch battery that can last at least three years. If you have a low-drain watch, look for a battery with a low-drain capacity as well. Although high-drain batteries may also work, low-drain ones use up only the necessary power and will protect your watch from burning out. Use high-drain batteries only for watches with power-consuming features such as backlights, alarms, and timers.
Anti-leak casing: Choose a tightly sealed watch battery to prevent the chemicals from leaking out. Make sure the cell can will not dent or crack easily. Look for one with a thick nylon seal and metal sleeve.
Voltage consistency: Choose a watch battery with a consistent voltage. This will allow the cell to store more energy to be used in the watch. Look for one with an operating range – the difference between the highest and lowest voltages – from 0.2 to 0.5 volts. Silver oxide and mercury cells usually provide the most consistent voltage.
Safety information
Zinc-air cells are often used in place of other watch batteries. Although they are classified as button cells and have higher power capacity than the others, they are not meant to be used in watches. Their main use is in hearing aids. Zinc oxide cells must operate in specific environments to keep them from leaking, which can permanently damage the metal and electronic parts of your watch.
Dispose of cells only when they are fully discharged to make sure there are no reactive chemicals that can mix with the garbage. Silver oxide batteries are usually taken for recycling when you have them replaced at a shop. Lithium cells cannot be recycled.
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