Patent ID: 8400116

Claim:
An apparatus for controlling a battery, comprising: a capacitor for charging a voltage when the apparatus is on and discharging a voltage when the apparatus is off; a discharging circuit for discharging the voltage charged in the capacitor; a first switching unit for connecting or disconnecting the capacitor to/from a predetermined power source for the purpose of charging of the capacitor; a second switching unit for connecting or disconnecting the capacitor to/from the discharging unit; a voltage measuring unit for measuring a power-off charging voltage of the capacitor when the apparatus is off and a charging voltage of the capacitor when the apparatus is on; a controller for calculating a power-off duration time according to a difference between the power-off charging voltage or a full-charging voltage of the capacitor and the charging voltage; and a memory for storing the full-charging voltage and the power-off charging voltage, wherein the controller reads the full-charging voltage or the power-off charging voltage, stored in the memory, and then calculates a power-off duration time based on a difference between the read full-charging voltage or the read power-off charging voltage and the measured charging voltage.