Patent ID: 7893652

Claim:
A battery control apparatus comprising: a determination unit configured to determine whether a secondary battery generates a polarization voltage in response to resuming power supply from the secondary battery to a load; and a state-of-charge estimating unit configured to estimate a present state of charge indicating a state of charge of the secondary battery immediately after resuming power supply, in response to the determination unit determining that the secondary battery generates no polarization voltage, wherein the state-of-charge estimating unit calculates the present state of charge by measuring a battery voltage Vo measured before resuming power supply, a peak discharge current Is representing a maximum current value appearing within a predetermined short period of time after resuming power supply, and a lowest battery voltage Vs corresponding to the peak discharge current Is, and by referring to an SOC estimating map illustrating a relationship between a peak battery voltage drop ΔVs and the peak discharge current Is, wherein the peak battery voltage drop ΔVs represents a difference between the battery voltage Vo and the lowest battery voltage Vs, and wherein the state-of-charge estimating unit sets an initial value based on the estimated present state of charge and estimates a state of charge of the secondary battery based on the initial value as a value effective immediately after resuming power supply.