METHOD OF ESTIMATING BATTERY LIFE, BATTERY LIFE ESTIMATION DEVICE, ELECTRIC VEHICLE, AND ELECTRIC POWER SUPPLY APPARATUS
A method of estimating a battery life includes: for a secondary battery having a degradation rate R when X days have elapsed after initial charge of the secondary battery, calculating a degradation estimation value (X+Y) days after the initial charge from degradation master data, the degradation master data being identified with use of conditions of temperature T provided for the calculation and a battery state S provided for the calculation; and deriving number of elapsed days Xcorr giving the degradation rate R based on the identified degradation master data, and calculating the degradation estimation value (Xcorr+Y) days after the initial charge from the identified degradation master data.
1 . A method of estimating a battery life, the method comprising:
identifying a degradation master data by using conditions of temperature T and a battery state S,
deriving number of elapsed days Xcorr corresponding to a degradation rate R based on the degradation master data,
calculating a degradation estimation value (Xcorr+Y) days after the initial charge based on the degradation master data,
wherein the conditions during Y days are configured of n-number of conditions Z1, Z2, . . . , Zn where 1≦n, and
making transition from first degradation master data identified by the condition Zn−1 to second degradation master data identified by the condition Zn, so as that a final degradation rate in the first degradation master data is equal to a start degradation rate in the second degradation master data.
2 . The method according to claim 1 , wherein the battery includes a cathode active material having an olivine structure.
3 . The method according to claim 1 , wherein the secondary battery is a lithium ion battery including LiFePO 4 as a cathode active material and graphite as an anode active material.
4 . The method according to claim 2 , wherein the cathode active material having the olivine structure is one of LiFePO 4 or LiMn x Fe 1-x PO 4 , wherein x varies between 0 and 1.
5 . The method according to claim 1 , wherein, as the degradation estimation value, the first degradation master data and the second degradation master data are calculated based on a product of a value calculated from a temperature of an outer wall of the battery, a value calculated from number of days that have elapsed after the initial charge of the battery, and a value calculated from a state of charge (SOC) of the battery in a first condition or a second condition respectively.
6 . The method according to claim 5 , wherein
the value calculated from the temperature of the outer wall of the battery is calculated based on absolute temperature (“T”),
the value calculated from the number of days that have elapsed after the initial charge of the battery is calculated based on the number of days that have elapsed after the initial charge of the battery and power (“B”), and
the value calculated from the state of charge (SOC) of the battery is calculated based on the state of charge (SOC), the absolute temperature (“T”) and a value representative of a dependence of degradation on time (“C”).
7 . The method according to claim 6 , wherein the power (“B”) varies between 0.3 and 0.7.
8 . The method according to claim 6 , wherein the value representative of the dependence of degradation on time (“C”) varies between 0.1 and 1.5.
9 . The method according to claim 1 , wherein the “X” days include one or more days selected from a life range of the battery.
10 . The method according to claim 5 , wherein the first degradation master data is determined based on the first condition of temperature and a state of charge (SOC) of the battery existing at Xth day of the “X” days.
11 . The method according to claim 1 , wherein the “Xcorr” days refer to one or more days between the “X” days and “Y” days for which the degradation rate “R” remains constant.
12 . The method according to claim 6 , wherein the second degradation master data is determined based on the second condition of temperature and a state of charge of the battery (SOC) existing for the “Xcorr” days.