Button cell

Button cell

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Encyclopedia
A watch battery or button cell is a small single cell battery
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...

 shaped as a squat cylinder
Cylinder (geometry)
A cylinder is one of the most basic curvilinear geometric shapes, the surface formed by the points at a fixed distance from a given line segment, the axis of the cylinder. The solid enclosed by this surface and by two planes perpendicular to the axis is also called a cylinder...

 typically 5 to 12 mm in diameter and 1 to 6 mm high—like a button on a garment, hence the name. Button cells are used to power small portable electronics devices such as wrist watches, pocket calculators, and hearing aid
Hearing aid
A hearing aid is an electroacoustic device which typically fits in or behind the wearer's ear, and is designed to amplify and modulate sound for the wearer. Earlier devices, known as "ear trumpets" or "ear horns", were passive funnel-like amplification cones designed to gather sound energy and...

s. Some cells larger than the dimensions above are also called button cells, but are less commonly used. Lithium cells
Lithium battery
Lithium batteries are disposable batteries that have lithium metal or lithium compounds as an anode. Depending on the design and chemical compounds used, lithium cells can produce voltages from 1.5 V to about 3.7 V, over twice the voltage of an ordinary zinc–carbon battery or alkaline battery...

 are generally similar but somewhat larger; they tend to be called either lithium cells or batteries or coin cells rather than button cells.

Devices using button cells are usually designed to use a cell giving a long service life, typically well over a year in continuous use in a wristwatch. Most button cells have low self-discharge and hold their charge for a long time if not used. Higher-power devices such as hearing aids, where high capacity is important and low self-discharge less so as the cell will usually be used up before it has time to discharge, may use zinc-air cells which have much higher capacity for a given size, but discharge over a few weeks even if not used.

Button cells are single cells, usually disposable primary cell
Primary cell
A primary cell is any kind of battery in which the electrochemical reaction is not reversible, rendering the cell non-rechargeable. A common example of a primary cell is the disposable battery. Unlike a secondary cell, the reaction cannot be reversed by running a current into the cell; the chemical...

s. Common anode
Anode
An anode is an electrode through which electric current flows into a polarized electrical device. Mnemonic: ACID ....

 materials are zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

 or lithium
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...

. Common cathode materials are manganese dioxide, silver oxide, carbon monofluoride
Carbon monofluoride
Carbon monofluoride , also called polycarbon monofluoride, polycarbon fluoride, poly, and graphite fluoride, is a material formed by high-temperature reaction of fluorine gas with graphite, charcoal, or pyrolytic carbon powder. Its CAS number is...

, cupric oxide or oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 from the air. Mercuric oxide
Mercury battery
A mercury battery 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...

 button cells were formerly common, but are no longer available due to the toxicity
Toxicity
Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...

 and environmental hazard of mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...

.

Cells have a metal can forming the bottom body, with a circular insulated top cap. The can is the positive and the top the negative terminal
Terminal (electronics)
A terminal is the point at which a conductor from an electrical component, device or network comes to an end and provides a point of connection to external circuits. A terminal may simply be the end of a wire or it may be fitted with a connector or fastener...

.

Cells of different chemical composition made in the same size are mechanically interchangeable. However, the composition can affect service life and voltage stability. Using the wrong cell may lead to short life or improper operation (for example, light meter
Light meter
A light meter is a device used to measure the amount of light. In photography, a light meter is often used to determine the proper exposure for a photograph...

ing on a camera
Camera
A camera is a device that records and stores images. These images may be still photographs or moving images such as videos or movies. The term camera comes from the camera obscura , an early mechanism for projecting images...

 requires a stable voltage, and silver cells are usually specified). Sometimes different cells of the same type and size and specified capacity in mAh are optimised for different loads by using different electrolytes, so that one may have longer service life than the other if supplying a relatively high current.

Properties of different types


Silver cells may have very stable output voltage until it suddenly drops very rapidly at end of life. This varies for individual types; one manufacturer (Energizer) offers 3 silver oxide cells of the same size, 357-303, 357-303H,and EPX76, with capacities ranging from 150 to 200 mAh, voltage characteristics ranging from gradually reducing to fairly constant, and some stated to be for continuous low drain with high pulse on demand, others for photo use.

Mercury batteries
Mercury battery
A mercury battery 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...

 also supply a stable voltage, but are now banned in many countries due to their toxicity and environmental impact.

Alkaline batteries
Alkaline battery
Alkaline batteries are a type of primary batteries dependent upon the reaction between zinc and manganese dioxide . A rechargeable alkaline battery allows reuse of specially designed cells....

 are made in the same button sizes as other types, but typically provide less capacity and less stable voltage (it drops gradually in use) than more costly silver oxide or lithium cells. They are often sold as cheap watch batteries to, and sometimes by, people who do not know the difference.

Zinc-air batteries
Zinc-air battery
Zinc–air batteries , and zinc–air fuel cells, are electro-chemical batteries powered by oxidizing zinc with oxygen from the air. These batteries have high energy densities and are relatively inexpensive to produce...

 use air as the depolarizer
Depolarizer
A depolarizer or depolariser, in electrochemistry, according to an IUPAC definition, is a synonym of electroactive substance, i.e., a substance which changes its oxidation state, or partakes in a formation or breaking of chemical bonds, in a charge-transfer step of an electrochemical reaction.In...

 and have much higher capacity than other types (they use air from the atmosphere which does not need to be supplied in the battery). A seal is removed before use to allow air to enter the cell; the cell will then self-discharge in a few weeks even if not used up.

For comparison, a cell of diameter 11.6 mm and height 5.4 mm from one reputable manufacturer has the following properties. In many cases there are several batteries of the same chemistry and size with different capacities and properties; figures listed are merely indicative.
  • Silver: capacity 200 mAh
    MAH
    The National Security Service was the governmental intelligence organization of Turkey between 1926 and 1965, when it was replaced by the National Intelligence Organization ....

     to an end-point of 0.9 V, internal resistance
    Internal resistance
    A practical electrical power source which is a linear electric circuit may, according to Thévenin's theorem, be represented as an ideal voltage source in series with an impedance. This resistance is termed the internal resistance of the source. When the power source delivers current, the measured...

     5–15 ohms, weight 2.3 g
  • Alkaline (manganese dioxide): 150 mAh (0.9), 3-9 ohms, 2.4 g
  • Mercury 200mAh, 2.6 g
  • Zinc-air 620 mAh, 1.9 g


Examining datasheets for a manufacturer's range may find a high-capacity alkaline cell with a capacity as high as one of the lower-capacity silver types; or a particular silver cell with twice the capacity of some particular alkaline cell. If the powered equipment requiring a relatively high voltage (e.g., 1.3V) to operate correctly, a silver cell with a flat discharge characteristic will give much longer service than an alkaline cell—even if it has the same specified capacity in mAh to an end-point of 0.9V. If some device seems to "eat up" batteries after the original supplied by the manufacturer is replaced, it may be useful to check the device's requirements and the replacement battery's characteristics. For digital callipers, in particular, some are specified to require at least 1.25V to operate, others 1.38V.

Datasheet
Datasheet
thumb|A floppy disk controller datasheet.A datasheet, data sheet, or spec sheet is a document summarizing the performance and other technical characteristics of a product, machine, component , material, a subsystem or software in sufficient detail to be used by a design engineer to integrate the...

s for some cheaper cells, particularly alkaline, are not available, so it is not possible to say whether capacities are about the same as for documented types. Discussions on web forums suggest that they can be very poor.

In some ways the size is the most important property of a button cell: cells of different chemistry are to a considerable extent interchangeable. In practice only cells of fairly similar voltages are made in any given size; there is no "CR1154" 3V lithium battery mechanically interchangeable with a 1.5V silver or alkaline size 1154 cell. Use of a battery of significantly higher voltage than equipment is designed for can cause permanent damage, but use of a cell of the right voltage but unsuitable characteristics can only lead to short battery life or failure to operate equipment.

Type designation


International standard
International standard
International standards are standards developed by international standards organizations. International standards are available for consideration and use, worldwide...

 IEC
International Electrotechnical Commission
The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...

 60086-3 defines an alphanumeric coding system for "Watch batteries". Manufacturers often have their own naming system; for example, the cell called LR1154 by IEC standard is named AG13, LR44, 357, A76, and other names by different manufacturers. The IEC standard and some others encode the case size so that the numeric part of the code is uniquely determined by the case size; other codes do not encode size directly.

Examples of batteries conforming to the IEC standard are CR2032, SR516, and LR1154, where the letters and numbers indicate the following characteristics.

Electrochemical system


The first letter identifies the chemical composition of the battery, which also implies a nominal voltage:
Letter
code
Common
name
Positive
electrode
ElectrolyteNegative
electrode
Nominal
voltage
End-point
voltage
L Alkaline Manganese dioxide Alkali Zinc 1.5 1.0
S Silver Silver oxide Alkali Zinc 1.55 1.2
P Zinc-air Oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

Alkali Zinc 1.4 1.2
C Lithium Manganese dioxide Organic Lithium 3 2.0
B Carbon monofluoride
Carbon monofluoride
Carbon monofluoride , also called polycarbon monofluoride, polycarbon fluoride, poly, and graphite fluoride, is a material formed by high-temperature reaction of fluorine gas with graphite, charcoal, or pyrolytic carbon powder. Its CAS number is...

Organic Lithium 3 2.0
G Copper oxide
Copper oxide
Copper oxide is a compound from the two elements copper and oxygen.Copper oxide may refer to:*Copper oxide , a red powder;*Copper oxide , a black powder...

Organic Lithium 1.5 1.2
M,N(withdrawn) Mercury Mercuric oxide Alkaline Zinc 1.35/1.40 1.1


For types with stable voltage falling precipitously at end-of-life (cliff-top voltage-versus-time graph), the end-voltage is the value at the "cliff-edge", after which it drops extremely rapidly. For types which lose voltage gradually (slope graph, no cliff-edge) the end-point is the voltage beyond which it is deemed that equipment will not work properly, typically 1.0 or 0.9V.

Common names are conventional rather than uniquely descriptive; for example, a cell called a "silver [oxide] cell" rather than "alkaline" actually has an alkaline electrolyte.

"L", "S", and "C" type cells are today the most commonly-used types in quartz watches, calculator
Calculator
An electronic calculator is a small, portable, usually inexpensive electronic device used to perform the basic operations of arithmetic. Modern calculators are more portable than most computers, though most PDAs are comparable in size to handheld calculators.The first solid-state electronic...

s, small PDA
Personal digital assistant
A personal digital assistant , also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet...

 devices, computer clocks, and blinky lights
Blinky (Novelty)
Blinkies are small electronic devices that make very bright light using LEDs and small batteries. They are often sold by vendors at night-time events that have fireworks displays such as Independence Day, Canada Day, or Guy Fawkes Night...

. Miniature zinc-air batteries
Zinc-air battery
Zinc–air batteries , and zinc–air fuel cells, are electro-chemical batteries powered by oxidizing zinc with oxygen from the air. These batteries have high energy densities and are relatively inexpensive to produce...

 type "P" are used in hearing aid
Hearing aid
A hearing aid is an electroacoustic device which typically fits in or behind the wearer's ear, and is designed to amplify and modulate sound for the wearer. Earlier devices, known as "ear trumpets" or "ear horns", were passive funnel-like amplification cones designed to gather sound energy and...

s and medical instruments.

Package size



Package size of button batteries using standard names is indicated by a two-digit code representing a standard case size, or a three- or four-digit code representing the cell diameter and height. The first one or two digits encode the outer diameter of the battery in whole millimeters, rounded down; exact diameters are specified by the standard, and there is no ambiguity, e.g., any cell with an initial "9" is 9.5 mm in diameter, no other value between 9.0 and 9.9 is used. The last two digits are the overall height in tenths of a millimeter.
Diameter codes (1st 1 or 2 digits)
Number
code
Nominal
diameter (mm)
Tolerance
4 4.8 ±0.15 mm
5 5.8 ±0.15 mm
6 6.8 ±0.15 mm
7 7.9 ±0.15 mm
9 9.5 ±0.15 mm
10 10.0 ±0.20 mm
11 11.6 ±0.20 mm
12 12.5 ±0.25 mm
16 16 ±0.25 mm
20 20 ±0.25 mm
23 23 ±0.50 mm
24 24.5 ±0.50mm


Examples:
  • CR2032: lithium, 20 mm diameter, 3.2 mm height
  • SR516: silver, 5.8 mm diameter, 1.6 mm height
  • LR1154/SR1154: alkaline/silver, 11.6 mm diameter, 5.4 mm height. The two-digit codes LR44/SR44 are often used for this size

Letter suffix


After the package code, the following additional letters may optionally appear in the type designation to indicate the electrolyte used:
  • P: potassium hydroxide
    Potassium hydroxide
    Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

     electrolyte
  • S: sodium hydroxide electrolyte
  • no letter: organic electrolyte

Also:
  • W; the battery complies with all the requirements of the international IEC 60086-3 standard for watch batteries.


Other package markings


Apart from the type code described in the preceding section, watch batteries should also be marked with
  • the name or trademark of the manufacturer or supplier;
  • the polarity (+);
  • the date of manufacturing.


The manufacturing date can be abbreviated to the last digit of the year, followed by a digit or letter indicating the month, where O, Y, and Z are used for October, November and December, respectively (e.g., 01 = January 1990 or January 2000, 9Y = November 1999).

Common manufacturer code


A code used by some manufacturers is AG (alkaline) or SG (silver) followed by a number, where 1 equates to standard 621, 2 to 726, 3 to 736, 4 to 626, 5 to 754, 6 to 920 or 921, 7 to 926 or 927, 8 to 1120 or 1121, 9 to 936, 10 to 1130 or 1131, 11 to 721, 12 to 1142, and 13 to 1154. To those familiar with the chemical symbol
Chemical symbol
A chemical symbol is a 1- or 2-letter internationally agreed code for a chemical element, usually derived from the name of the element, often in Latin. Only the first letter is capitalised...

 for silver, "Ag", this may suggest incorrectly that AG cells are silver.

Common applications

  • Electric wristwatches
    Watch
    A watch is a small timepiece, typically worn either on the wrist or attached on a chain and carried in a pocket, with wristwatches being the most common type of watch used today. They evolved in the 17th century from spring powered clocks, which appeared in the 15th century. The first watches were...

    , both digital and analogue.
  • Calculator
    Calculator
    An electronic calculator is a small, portable, usually inexpensive electronic device used to perform the basic operations of arithmetic. Modern calculators are more portable than most computers, though most PDAs are comparable in size to handheld calculators.The first solid-state electronic...

    s.
  • Hearing aids.
  • Some remote control
    Remote control
    A remote control is a component of an electronics device, most commonly a television set, used for operating the television device wirelessly from a short line-of-sight distance.The remote control is usually contracted to remote...

    s, especially for keyless entry.
  • Backup power for personal computer
    Personal computer
    A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...

     real time clocks and BIOS configuration data
    Nonvolatile BIOS memory
    Nonvolatile BIOS memory refers to a small memory on PC motherboards that is used to store BIOS settings. It was traditionally called CMOS RAM because it used a low-power Complementary metal-oxide-semiconductor SRAM powered by a small battery when system power was off...

    .
  • Small PDA
    Personal digital assistant
    A personal digital assistant , also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet...

     devices.
  • Various electronic toys (like tamagotchi
    Tamagotchi
    The is a handheld digital pet, created in Japan by Akihiro Yokoi of WiZ and Aki Maita of Bandai. It was first sold by Bandai in 1996 in Japan. As of 2010, over 76 million Tamagotchis have been sold world-wide...

    , Pokémon Pikachu
    Pokémon Pikachu
    Pokémon Pikachu, also known as in Japan, is a series of portable Pokémon digital pets featuring the famous yellow electric Pokémon, Pikachu. This product was intended as an exercise toy and mentioned by Guinness World Records as the most popular exercise toy of its time...

     or a Pokéwalker and other various Virtual Pet devices.)
  • Laser pointer
    Laser pointer
    A laser pointer or laser pen is a small portable device with a power source and a laser emitting a very narrow coherent low-powered beam of visible light, intended to be used to highlight something of interest by illuminating it with a small bright spot of colored light...

    s.
  • Small LED
    LEd
    LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....

     flashlight
    Flashlight
    A flashlight is a hand-held electric-powered light source. Usually the light source is a small incandescent lightbulb or light-emitting diode...

    s.
  • Battery-operated children's books.
  • Glucometers.
  • Security token
    Security token
    A security token may be a physical device that an authorized user of computer services is given to ease authentication...

    s.
  • Cyclocomputer
    Cyclocomputer
    A cyclocomputer or cyclometer is a device mounted on a bicycle that calculates and displays trip information, similar to the instruments in the dashboard of a car. The computer with display, or head unit, usually is attached to the handlebar for easy viewing.-History:In 1895 Curtis Hussey Veeder...

    s.
  • Red dot sight
    Red dot sight
    A red dot sight is a common classification for a type of non-magnifying reflector sight for firearms that gives the user an aimpoint in the form of an illuminated red dot...

    s and electronic spotting scope
    Spotting scope
    A spotting scope is a small portable telescope with added optics to present an erect image, optimized for the observation of terrestrial objects...

    s.
  • Manual cameras with light meters.
  • LED throwies.
  • Various video game cartridges or memory cards where battery-powered RAM is used to store data.
  • PCMCIA static RAM memory cards.
  • Solar/Electric Candles.
  • LED Bicycle head and/or tail lighting

Rechargeable variants


Most button cell batteries are not rechargeable
Rechargeable battery
A rechargeable battery or storage battery is a group of one or more electrochemical cells. They are known as secondary cells because their electrochemical reactions are electrically reversible. Rechargeable batteries come in many different shapes and sizes, ranging anything from a button cell to...

 due to the inferior capacity and/or high self-discharge rate of rechargeable batteries. There are a few rechargeable button cell batteries, such as lithium-ion rechargeable batteries intended to replace CR-series lithium manganese dioxide batteries in devices with relatively high current consumption or some devices with solar panels which can be used to keep the battery charged under certain circumstances.

Rechargeable NiCd
Nickel-cadmium battery
The nickel–cadmium battery ' is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes....

 button cells were often components of the backup battery of older IBM PC compatible
IBM PC compatible
IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Such computers used to be referred to as PC clones, or IBM clones since they almost exactly duplicated all the significant features of the PC architecture, facilitated by various manufacturers' ability to...

s as well as Amiga
Amiga
The Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities...

computers.

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