Life estimation apparatus for lithium ion secondary cell

A life estimation apparatus that estimates a remaining life of a lithium ion secondary cell, the apparatus comprising:

• a first acquisition unit that acquires a cumulative number of cycles or a cumulative capacity from a time when use of the lithium ion secondary cell is started;
• a second acquisition unit that acquires open circuit voltage, a voltage rise width after discharge is stopped, or a voltage rise rate per certain time after discharge is stopped at a certain depth of discharge of the lithium ion secondary cell;
• a first calculation unit that calculates an amount of change of the open circuit voltage, an amount of change of the voltage rise width, or an amount of change of the voltage rise rate during a certain period;
• and a second calculation unit that calculates a remaining capacity, which is a capacity with which the lithium ion secondary cell is capable of being charged or which the lithium ion secondary cell is capable of discharging, based on Equation 1 having an exponent n1 of 0.9 to 1.1 and Equation 2 having an exponent n2 of 0.4 to 0.6, wherein the second calculation unit calculates the remaining capacity using Equation 1 if the amount of change of the open circuit voltage, the amount of change of the voltage rise width, or the amount of change of the voltage rise rate has a positive value and calculates the remaining capacity using Equation 2 if the amount of change of the open circuit voltage, the amount of change of the voltage rise width, or the amount of change of the voltage rise rate has a negative value:
• Remaining capacity=Capacity 1−α×(Cumulative number of cycles or Cumulative capacity)n1 Equation 1
• Remaining capacity=Capacity 2−β×(Cumulative number of cycles or Cumulative capacity)n2 Equation 2
• where α and β are different constants, Capacity 1 is an initial capacity of the lithium ion secondary cell or the remaining capacity calculated according to Equation 2, and Capacity 2 is the initial capacity or the remaining capacity calculated according to Equation 1.