METHOD FOR DETERMINING BATTERY STATE AND BATTERY STATE DETERMINATION DEVICE

A method for determining a negative electrode capacity of a rechargeable battery is performed by a measurement device that includes a voltage detector that detects a voltage value of the rechargeable battery, a current detector that detects a current value of the rechargeable battery, and a state of charge detector that detects a state of charge of the rechargeable battery. The method includes calculating an absolute value of a voltage slope indicating a voltage change amount with respect to a discharge amount when the state of charge of the rechargeable battery is less than 40%, comparing the absolute value of the voltage slope with a preset lower limit, and determining that the negative electrode capacity of the rechargeable battery has decreased when the absolute value of the voltage slope is less than or equal to the lower limit.