CHARGEABLE BATTERY STATE DETECTION DEVICE AND CHARGEABLE BATTERY STATE DETECTION METHOD

Regardless of an influence of a dark current, an open circuit voltage can be accurately estimated. A chargeable battery state detection apparatus configured to detect a state of a chargeable battery, the apparatus including: one or a plurality of processors; and one or a plurality of memories communicatively connected to the one or the plurality of processors, wherein the one or the plurality of processors read out a group of instructions stored in the one or the plurality of memories, and execute: a detection process for and detecting a voltage and a current of the chargeable battery based on signals output from a voltage measurement unit 11 and a current measurement unit 12; a storage process for storing a plurality of voltage values detected at different times by the detection process after charge and discharge of the chargeable battery is stopped; a fitting process for fitting, with respect to the plurality of voltage values stored by the storage process, by adjusting coefficients of a predetermined function; a calculation process for calculating an open circuit voltage based on the function, the coefficients of the function being adjusted by the fitting process; and a discard process for discarding at least a part of the plurality of voltage values stored by the storage process when a detected current value or a voltage value fluctuates by a predetermined threshold value or greater.