Apparatus and method for estimating SOC of secondary battery including blended cathode material

1. An apparatus for estimating a state of charge (SOC) of a secondary battery, which includes a cathode having a blended cathode material containing a first cathode material and a second cathode material with different operating voltage ranges, an anode having an anode material, and a separator for separating the cathode from the anode, the apparatus comprising:

a sensor configured to measure a discharge inception voltage and a final discharge voltage when the secondary battery is discharged for a predetermined time; and

a control unit configured to estimate a SOC of the secondary battery corresponding to the measured discharge inception voltage and the measured final discharge voltage by using a predetermined relationship between the discharge inception voltage and the final discharge voltage and the SOC of the secondary battery,

wherein the discharge inception voltage is a key-on voltage measured right after the secondary battery in a no-load state comes to a key-on state, and

wherein the final discharge voltage is a key-on discharge voltage measured after the secondary battery in the key-on state performs key-on discharge for a predetermined time.

2. The apparatus for estimating a SOC of a secondary battery according to claim 1 ,

wherein the predetermined relationship is a look-up table which defines a relationship between the key-on voltage and the key-on discharge voltage and the SOC of the secondary battery.

3. The apparatus for estimating a SOC of a secondary battery according to claim 2 , further comprising a storage unit in which the look-up table is stored.

4. The apparatus for estimating a SOC of a secondary battery according to claim 1 ,

wherein the predetermined relationship is a look-up function using the key-on voltage and the key-on discharge voltage as input parameters and the SOC as an output parameter.

5. The apparatus for estimating a SOC of a secondary battery according to claim 4 , further comprising a storage unit in which the look-up function is stored.

6. The apparatus for estimating a SOC of a secondary battery according to claim 1 ,

wherein the relationship is predetermined by applying the same discharge condition as the key-on discharge.

7. The apparatus for estimating a SOC of a secondary battery according to claim 1 ,

wherein the key-on discharge is a constant current discharge.

8. The apparatus for estimating a SOC of a secondary battery according to claim 1 , further comprising a discharge unit selectively connected to the secondary battery,

wherein the control unit connects the discharge unit to the secondary battery in order to discharge the secondary battery for a predetermined time.

9. The apparatus for estimating a SOC of a secondary battery according to claim 1 ,

wherein the key-on discharge is automatically performed when the secondary battery comes to a key-on state.

10. The apparatus for estimating a SOC of a secondary battery according to claim 1 ,

wherein when the secondary battery is in a no-load state, the SOC falls within a SOC range which causes a voltage relaxation phenomenon by transferring operating ions between the first cathode material and the second cathode material.

11. The apparatus for estimating a SOC of a secondary battery according to claim 10 ,

wherein when the secondary battery is in a no-load state, the voltage of the secondary battery changes to follow a voltage relaxation profile originating from the voltage relaxation phenomenon.

12. The apparatus for estimating a SOC of a secondary battery according to claim 11 ,

wherein the key-on discharge voltage is a voltage selected from a voltage change pattern which appears while a voltage of the secondary battery is dropped and then returns to the voltage relaxation profile during the key-on discharge.

13. The apparatus for estimating a SOC of a secondary battery according to claim 12 , wherein the key-on discharge voltage is a voltage measured when the key-on discharge is completed, a voltage measured when a predetermined time passes after the key-on discharge starts, a voltage measured when a predetermined time passes after the key-on discharge is completed, a voltage measured when the voltage of the secondary battery returns to the voltage relaxation profile, a voltage measured when a minimum point is formed in a voltage change pattern of the secondary battery formed by the key-on discharge, or a voltage measured when the change of voltage per unit time is greatest in the voltage change pattern of the secondary battery formed by the key-on discharge.

14. The apparatus for estimating a SOC of a secondary battery according to claim 1 , further comprising a display unit for displaying the estimated SOC as a graphic interface,

wherein the control unit is configured to output the estimated SOC to the display unit.

15. The apparatus for estimating a SOC of a secondary battery according to claim 1 , further comprising a storage unit in which the estimated SOC is stored,

wherein the control unit is configured to store the estimated SOC in the storage unit.

16. The apparatus for estimating a SOC of a secondary battery according to claim 1 ,

wherein the control unit is configured to output the estimated SOC to the outside.

17. An apparatus for estimating a SOC of a secondary battery, which includes a cathode having a blended cathode material containing a first cathode material and a second cathode material with different operating voltage ranges, an anode having an anode material, and a separator for separating the cathode from the anode, the apparatus comprising:

a sensor configured to measure a discharge inception voltage and a final discharge voltage when the secondary battery is discharged for a predetermined time before the voltage of the secondary battery in a no-load state reaches an equilibrium state voltage; and

a control unit configured to estimate a SOC of the secondary battery corresponding to the measured discharge inception voltage and the measured final discharge voltage by using a predetermined relationship between the discharge inception voltage and the final discharge voltage and the SOC of the secondary battery.

18. An apparatus for estimating a SOC of a secondary battery, comprising:

a sensor configured to measure a discharge inception voltage and a final discharge voltage of the secondary battery when the secondary battery is discharged for a predetermined time before the voltage of the secondary battery in a no-load state reaches an equilibrium state voltage; and

a control unit configured to estimate a SOC of the secondary battery corresponding to the measured discharge inception voltage and the measured final discharge voltage by using a predetermined relationship between the discharge inception voltage and the final discharge voltage and the SOC of the secondary battery.

19. A method for estimating a SOC of a secondary battery, which includes a cathode having a blended cathode material containing a first cathode material and a second cathode material with different operating voltage ranges, an anode having an anode material, and a separator for separating the cathode from the anode, the method comprising:

measuring a discharge inception voltage and a final discharge voltage when the secondary battery is discharged for a predetermined time; and

estimating a SOC of the secondary battery corresponding to the measured discharge inception voltage and the measured final discharge voltage by using a predetermined relationship between the discharge inception voltage and the final discharge voltage and the SOC of the secondary battery,

wherein the relationship is predetermined by applying a discharge condition when the secondary battery is discharged for a predetermined time.

20. The method for estimating a SOC of a secondary battery according to claim 19 ,

wherein the discharge inception voltage is a key-on voltage measured right after the secondary battery in a no-load state comes to a key-on state, and

wherein the final discharge voltage is a key-on discharge voltage measured after the secondary battery in the key-on state performs key-on discharge for a predetermined time.

21. The method for estimating a SOC of a secondary battery according to claim 20 ,

wherein in the step of estimating a SOC, the SOC of the secondary battery is estimated using a look-up table in which a relationship between the key-on voltage and the key-on discharge voltage of the secondary battery and the SOC is predetermined.

22. The method for estimating a SOC of a secondary battery according to claim 20 ,

wherein in the step of estimating a SOC, the SOC of the secondary battery is estimated using a look-up function which uses the key-on voltage and the key-on discharge voltage as input parameters and the SOC as an output parameter.

23. The method for estimating a SOC of a secondary battery according to claim 20 , further comprising:

connecting the secondary battery to a discharge unit for the key-on discharge.

24. The method for estimating a SOC of a secondary battery according to claim 20 ,

wherein the key-on discharge is automatically performed when the secondary battery comes to a key-on state.

25. The method for estimating a SOC of a secondary battery according to claim 20 , further comprising:

the voltage of the secondary battery following a voltage relaxation profile, when the secondary battery is in a no-load state.

26. The method for estimating a SOC of a secondary battery according to claim 25 ,

wherein the key-on discharge voltage is measured in a time region while a voltage of the secondary battery is dropped and then returns to the voltage relaxation profile during the key-on discharge.

27. The method for estimating a SOC of a secondary battery according to claim 26 , wherein the key-on discharge voltage is a voltage measured when the key-on discharge is completed, a voltage measured when a predetermined time passes after the key-on discharge starts, a voltage measured when a predetermined time passes after the key-on discharge is completed, a voltage measured when the voltage of the secondary battery returns to the voltage relaxation profile, a voltage measured when a minimum point is formed in a voltage change pattern of the secondary battery formed by the key-on discharge, or a voltage measured when the change of voltage per unit time is greatest in the voltage change pattern of the secondary battery formed by the key-on discharge.

28. The method for estimating a SOC of a secondary battery according to claim 19 , further comprising:

displaying the estimated SOC as a graphic interface.

29. The method for estimating a SOC of a secondary battery according to claim 19 , further comprising:

storing the estimated SOC.

30. The method for estimating a SOC of a secondary battery according to claim 19 , further comprising:

outputting the estimated SOC to the outside.

31. A method for estimating a SOC of a secondary battery, which includes a cathode having a blended cathode material containing a first cathode material and a second cathode material with different operating voltage ranges, an anode having an anode material, and a separator for separating the cathode from the anode, the method comprising:

measuring a discharge inception voltage and a final discharge voltage when the secondary battery is discharged for a predetermined time before the voltage of the secondary battery in a no-load state reaches an equilibrium state voltage; and

estimating a SOC of the secondary battery corresponding to the measured discharge inception voltage and the measured final discharge voltage by using a predetermined relationship between the discharge inception voltage and the final discharge voltage and the SOC of the secondary battery.

32. A method for estimating a SOC of a secondary battery, comprising:

measuring a discharge inception voltage and a final discharge voltage when the secondary battery is discharged for a predetermined time before the voltage of the secondary battery in a no-load state reaches an equilibrium state voltage; and

estimating a SOC of the secondary battery corresponding to the measured discharge inception voltage and the measured final discharge voltage by using a predetermined relationship between the discharge inception voltage and the final discharge voltage and the SOC of the secondary battery.