About button cell:
The button cell, also known as coin cell, enabled compact design in portable devices of the 1980s and similar button cell.
Higher voltages were achieved by stacking the cells into a tube. Cordless telephones, medical devices and security wands at airports used these batteries.
Although small and inexpensive to build, the stacked button cell fell out of favor and gave way to more conventional battery formats.
A drawback of the button cell is swelling if charged too rapidly. Button cells have no safety vent and can only be charged at a 10- to 16-hour charge; however, newer designs claim rapid charge capability.
Most button cells in use today are non-rechargeable and are found in medical implants, watches, hearing aids, car keys and memory backup.
Cross section of a lithium-ion button cell.
For Note : battery voltage and mAh refer to separate energy characteristics.
mAh (milli-ampere hour) measures battery capacity. In other words – how much current a battery will discharge over a one hour period. Higher mAh ratings correspond to how long a current can be drawn, rather than how fast it can be drawn. The mAh abbreviation is also written as Ah or Ampere-hour. (1 Ah = 1,000 mAh). Overall capacity is influenced by factors like temperature and speed of discharge. A 40 mAh battery can discharge 40 milliamps for one hour, 20 milliamps for two hours, and so on.
Voltage is a measurement of electrical potential, with all batteries being rated in volts DC (direct current). Voltage is determined by electrochemical reactions that occur in the battery, which vary according to battery type.