The battery is a chemical current source, in which electric current is generated by chemical reactions in the battery.
Thus, the principle of operation of the battery is a little different from ordinary batteries. Battery capacity is the quantity of electricity which can give a new or fully charged battery.
Battery capacity is measured in ampere-hours or milliampere-hours. So, if the capacity of the battery is 2000ma-HR (milliampere-hours), which means that the battery can give current of 2 thousand milliamps for 1 hour or 200 mA for 10 hours.
To determine the capacity, the battery should first be fully charged, then discharging a given current and to track the time the battery is fully discharged. Then you need to calculate the product of current times the time that battery is dead, the obtained value will be the capacityu of the battery.
Similarly, a measured capacity of the battery. The meaning of the measurement of the battery capacity or battery is that you can find out the time during which the battery or battery completely discharged. The battery will require a recharge and the battery will come to full unfitness.