Patent ID: 7898263

Claim:
An onboard battery management device for managing the deterioration level of an onboard battery during engine operation, the device comprising: sensors for measuring terminal voltage and terminal current of an onboard battery; a computation processor for calculating and determining internal resistance on the basis of said measured value and determining the deterioration level of a battery; and a display unit of the battery state provided in a viewable location from the driver's seat, wherein the internal resistance is determined based on an AC voltage component and an AC electric current component that are calculated by performing differential processing and subtractive processing on the voltage value and electric current value of the onboard battery during engine operation measured by sampling several times per second to several thousand times per second without the application of an AC signal from a sensor terminal during engine operation; and the internal resistance is converter to static resistance value using a conversation formula established in advance based on data, wherein the static resistance value is battery resistance value prior to engine start up; and calculating cold cranking amperage from the static resistance value, and the deterioration level of the battery is determined based on the cold cranking amperage.