NOVELTY - The detecting method involves calculating a remaining capacity variation rate based on a difference between first and second determined capacities. A capacity variation value of a battery (1) e.g. lithium ion rechargeable battery, lithium polymer battery is calculated based on integrated value of charging and discharging currents of the battery to be discharged from first to second no-load timing. A fully-charged capacity of the battery is calculated based on the remaining capacity variation rate and the capacity variation value by a predetermined formula.    USE - Method for detecting full-charged capacity of battery e.g. lithium ion rechargeable battery, lithium polymer battery for e.g. mobile device.    ADVANTAGE - Reduces the error in capacity measurement of battery since a capacity variation value is a set as predetermined value. Calculates a fully-charged capacity of battery based on remaining capacity variation rate and capacity variation value using a predetermined formula, so as to accurately detect and correct fully-charged battery capacity or deterioration degree of the battery, without bringing the battery into fully-charged or fully-discharged state.    DETAILED DESCRIPTION - The predetermined formula to calculate the fully-charged battery capacity is Ahf = sigma Ah divide by ( sigma S divide by 100) where Ahf is the fully-charged capacity of the battery, sigma Ah is the capacity variation value of the battery; and sigma S is the remaining capacity variation rate based on the difference between the first and second determined remaining capacities. The first and second remaining capacities are determined based on first and second no-load voltages, respectively.    DESCRIPTION OF DRAWING(S) - The drawing is a circuit diagram of the battery pack used in the full-charged battery capacity detection method.    Battery (1)    Current detector (2)    Voltage detector (3)    Capacity calculator (5)    Remaining capacity detector (6)    Full capacity detector (7)    Remaining capacity corrector (8)