There are many button cell batteries on the market; however, "button cell battery" is actually a misnomer. A button "battery" is actually a single electrochemical cell, whereas a battery refers to two or more cells working in unison. The main applications of "button cell batteries" are in cameras, watches and a range of other electronic devices. The nominal voltage of this type of battery is 3 volts.
Diameter
The diameter in millimeters is indicated in the first two numerals of the cell's name. The CR 1216 and the CR 1220 are 12.5 mm in diameter. The CR 1616 and the CR 1620 are both 16 mm in diameter. Three popular button cells are 20 mm in diameter: the CR 2016, the CR 2025 and the CR 2032. Two button cells that are 24.5 mm in diameter are the CR 2430 and the CR 2450.
Height
A well-known battery manufacturer refers to the thickness of a button cell as its "height." The height in millimeters is indicated in the last two numerals of the cell's name. The CR 1216 has a height of 1.6 mm. The CR 1220 has a height of 2 mm. The CR 1616 is 1.6 mm in height. The CR 1620 is 2 mm high. The CR 2016 is 1.6 mm in height. At the other end of the scale, The CR 2450 is 5 mm in height.
Milliampere-Hours
Each button cell has a capacity, normally given in mAh, or milliampere-hours. The CR 1216, for example, has a capacity of 27 mAh, in normal use. This means that during its lifetime, it should theoretically deliver the equivalent of 27 milliamps per hour. The CR 1216 has a typical capacity of 35 mAh. The CR 1616 has a typical capacity of 55 mAh, while the relevant figure for the CR 1620 is 70 mAh. At the other end of the scale, the CR 2450 has a typical capacity of 560 mAh.
Other Specifications
All the button cells mentioned are lithium cells. In other words, they contain lithium manganese dioxide and an organic electrolyte which work together to create the power source.
The CR 1216 weighs just under a gram, at 0.7 grams. The physically larger CR 2450 weighs significantly more at 6.2 grams, with other button cells having weights somewhere between the two. A "+" sign on one face of the cell indicates the positive side, while a "-" sign indicates the negative side.
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