RECHARGEABLE BATTERY STATE ESTIMATION DEVICE

In response to demands for stably and precisely estimating states, a rechargeable battery state estimation device includes a current detecting unit which detects a charge-discharge current of the rechargeable battery as a detected current; a voltage detecting unit which detects a voltage between terminals of the rechargeable battery as a detected voltage; an OCV estimation method SOC estimation unit which calculates an OCV estimation method state of charge, based on the detected current and the detected voltage; a current integration method parameter estimation unit which estimates a current integration method parameter including a capacity retention rate, based on the detected current and the OCV estimation method state of charge; and a corrected SOC estimation unit which calculates an estimated state of charge, based on the detected current, the OCV estimation method state of charge, and the current integration method parameter.