Lithium button batteries and coin batteries, CR1625, are used to power small portable electronic devices such as wristwatches, pocket calculators, artificial cardiac pacemakers, implantable cardiac defibrillators, car key entry transmitters and hearing aids. coin-shaped, they are usually 5-25 mm in diameter and 1-6 mm in height. Lithium sizes can be identified by their reference numbers. The first two digits refer to the diameter of the battery in mm and the second two digits give the height or thickness of the battery in tenths of mm. So, for example, a CR2032 is a lithium button with a diameter of 20 mm and a thickness of 3.2 mm. The CR2430 is a lithium battery, 24 mm in diameter and 3.0 mm thick. Lithium button batteries and coin batteries are prefixed with BR or CR and primarily provide 3 volts.