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Information About

Watch Battery




A watch battery or '''button cell''' is a small form-factor Battery designed for use in wrist watches, pocket calculators, hearing aids, and similar compact portable electronics products. Watch batteries are usually a single cell with nominal voltages between 1.5 and 3 V. Common Anode materials are Zinc or Lithium , common cathode materials are Manganese Dioxide , Silver Oxide , Carbon Monofluoride or Copper Oxide . The cylindrical surface of these types of batteries is part of the positive (+) terminal.


TYPE DESIGNATION

International Standard IEC 60086-3 defines an alphanumeric coding system for watch batteries.


Electrochemical system

The first letter identifies the electrochemical system used in the battery, which also implies a nominal voltage:

The "C"-type 3-V lithium cells are today the most commonly used type in Quartz Watch es, Calculator s, small PDA devices, and computer motherboard clocks.


Package size

Its package's size is identified by a three-to-four digit code, preceded by the letter "R" to indicate a round cell. The first 1–2 digits indicate the outer diameter of the battery (downwards-rounded millimeters), and the last two digits indicate the overall height (downwards-rounded 0.1 millimeters). Examples:
  • CR2032: 20.0 mm diameter, 3.2 mm height

  • SR516: 5.8 mm diameter, 1.6 mm height


ISO/IEC 83-3 lists the following diameter codes:
:4 = (4.8+0−0.15) mm
:5 = (5.8+0−0.15) mm
:6 = (6.8+0−0.15) mm
:7 = (7.9+0−0.15) mm
:9 = (9.5+0−0.15) mm
:10 = (10.0+0−0.20) mm
:11 = (11.6+0−0.20) mm
:12 = (12.5+0−0.25) mm
:16 = (16+0−0.25) mm
:20 = (20+0−0.25) mm
:23 = (23+0−0.50) mm
:24 = (24.5+0−0.50) mm

The following height codes are used with 16–24 mm diameter batteries:
:12 = (1.20+0−0.20) mm
:16 = (1.60+0−0.20) mm
:20 = (2.00+0−0.25) mm
:25 = (2.50+0−0.50) mm
:30 = (3.00+0−0.50) mm
:36 = (3.60+0−0.50) mm
:50 = (5.00+0−0.50) mm


Final letters

After the package code, the following additional letters may optionally appear in the type designation to
indicate the electrolyte used:


An appended letter "W" states that this battery complies with all the requirements of the IEC 86-3 standard.


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 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 APPLICATIONS



RECHARGEABLE VARIANTS

Regular watch batteries are not Rechargeable . Rechargeable button cells are commercially available, but are not commonly used due to their inferior capacity.


OTHER CHEMICAL COMPOSITIONS

  • Mercury Cells are now banned from sale in many countries.

  • Alkali Cells are sometimes found in low-end markets, but do only provide a fraction of the capacity of silver oxide or lithium based cells.

  • Zinc-air Cells utilize air in the chemical reaction (it is required to remove a plastic foil layer before usage).



LINKS



REFERENCES

  • IEC 60086-3: Primary batteries — Part 3: Watch batteries. International Electrotechnical Commission , Geneva, 1995. (also: BS EN 60086-3:1996)

  • http://www.sustainableproduction.org/downloads/MaineDEPButtonBatteryReportFinal12-17-04.pdf Mercury in miniature batteries



EXTERNAL LINKS