SECONDARY BATTERY STATE DETECTION DEVICE AND SECONDARY BATTERY STATE DETECTION METHOD

Object: To accurately determine whether or not it is possible to start an engine while accurately detecting a degree of deterioration of a secondary battery. Solution: In a secondary battery state detecting device 1 detecting a state of a secondary battery mounted on a vehicle, a measurement unit (a voltage sensor (11), a current sensor (12), a CPU (10a)) measuring a value of an internal resistance of the secondary battery at an engine stop time; an estimation unit (CPU 10a) estimating a value of a diffusion resistance resulting from diffusion of an ion generated at an electrolytic solution of the secondary battery by supplying electric power to a starter motor at a starting time of the engine; and a calculation unit (CPU 10a) calculating a starting voltage being a voltage required for the starting of the engine from a resistance value obtained by adding the value of the diffusion resistance estimated by the estimation unit to the value of the internal resistance measured by the measurement unit, a starting current flowing when the engine is started, and a voltage before starting of the secondary battery are included.