Apparatus for estimating depth of discharge (DOD) of secondary battery

• US 9,678,165 B2
• Filed: 12/04/2013
• Issued: 06/13/2017
• Est. Priority Date: 12/04/2012
• Status: Active Grant

• Current Assignee: LG Energy Solution Limited (LG Corporation)
• Original Assignee: LG Chem Limited (LG Corporation)
• Inventors: Joe, Won-Tae, Cha, Sun-Young
• Primary Examiner(s): WILLIAMS, ARUN C
• Application Number:
  US14/424,622
• Publication Number:
  US 20150226809A1
• Time in Patent Office: 1,287 Days
• Field of Search: 324426
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H01M 4/131 Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• CPC Class Codes: H01M 4/364 as mixtures
• CPC Class Codes: H01M 4/505 of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
• CPC Class Codes: H01M 4/525 of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• CPC Class Codes: H01M 4/5825 Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Disclosed is an apparatus and method for estimating a parameter of a secondary battery. The apparatus includes a sensor unit configured to repeatedly measure a voltage of a secondary battery including a blended cathode material containing at least first and second cathode materials at time intervals when the secondary battery is in an operation state or in an idle state, and a control unit configured to receive the repeatedly measured plurality of voltages from the sensor unit, identify an inflection point in a voltage change profile corresponding to the plurality of voltages, and estimate a depth of discharge (DOD) of the secondary battery by using a voltage measured after the inflection point is identified as a reference voltage.

Claims

1. An apparatus for estimating a depth of discharging (DOD) of a secondary battery, comprising:

a sensor unit configured to repeatedly measure a voltage of a secondary battery including a blended cathode material containing at least first and second cathode materials at time intervals when the secondary battery is in an operation state or in an idle state; and

a control unit configured to;

receive the repeatedly measured plurality of voltages from the sensor unit,

identify an inflection point indicative of changing of a cathode material reacting with working ions in a voltage change over time profile corresponding to the plurality of voltages,

measure a voltage a predetermined time after the inflection point, and

estimate a DOD of the secondary battery by using the voltage measured after the inflection point is identified as a reference voltage.

2. The apparatus for estimating a DOD of a secondary battery according to claim 1, wherein the control unit is configured to estimate the DOD by using a voltage measured after a predetermined time since the inflection point is identified as a reference voltage.

3. The apparatus for estimating a DOD of a secondary battery according to claim 1, wherein the control unit is configured to estimate the DOD by using a lookup table or a lookup function which defines a correlation between the reference voltage and the DOD in advance.

4. The apparatus for estimating a DOD of a secondary battery according to claim 1, wherein the control unit is configured to identify the inflection point when a voltage change rate (dV/dt) with respect to time is at the maximum in the voltage change profile.

5. The apparatus for estimating a DOD of a secondary battery according to claim 1, wherein the secondary battery has an open-circuit voltage profile including at least one inflection point or a discharge resistance profile including a convex pattern.

6. The apparatus for estimating a DOD of a secondary battery according to claim 1, further comprising:

a storage unit configured to store the estimated DOD;

a display unit configured to display the estimated DOD;

or

a communication interface configured to transmit the estimated DOD to the outside.

7. An electric-powered device, which comprises the apparatus for estimating a DOD of a secondary battery as defined in the claim 1.

8. An apparatus for estimating a DOD of a secondary battery, comprising:

a sensor unit configured to repeatedly measure a voltage of a secondary battery including a blended cathode material containing at least first and second cathode materials at time intervals when the secondary battery is in an operation state or in an idle state; and

a control unit configured to

receive the repeatedly measured plurality of voltages from the sensor unit, identify an inflection point indicative of changing of a cathode material reacting with working ions in a voltage change over time profile corresponding to the plurality of voltages,

estimate a reference voltage, which is to be used for estimating a DOD of the secondary battery, by means of extrapolation from a plurality of voltages measured at predetermined times after the inflection point is identified, and

estimate the DOD by using the reference voltage.

9. The apparatus for estimating a DOD of a secondary battery according to claim 8, wherein the control unit is configured to determine an approximation function for approximating a voltage change profile corresponding to the plurality of voltages measured after the inflection point is identified, and estimate a voltage corresponding to a predetermined time as the reference voltage by using the approximation function.

10. The apparatus for estimating a DOD of a secondary battery according to claim 8, wherein the control unit is configured to estimate the DOD by using a lookup table or a lookup function which defines a correlation between the reference voltage and the DOD in advance.

11. The apparatus for estimating a DOD of a secondary battery according to claim 8, wherein the control unit is configured to identify the inflection point when a voltage change rate (dV/dt) with respect to time is at the maximum in the voltage change profile.

12. The apparatus for estimating a DOD of a secondary battery according to claim 8, wherein the secondary battery has an open-circuit voltage profile including at least one inflection point or a discharge resistance profile including a convex pattern.

13. The apparatus for estimating a DOD of a secondary battery according to claim 8, further comprising:

a storage unit configured to store the estimated DOD;

a display unit configured to display the estimated DOD;

or

a communication interface configured to transmit the estimated DOD to the outside.

14. An electric-powered device, which comprises the apparatus for estimating a DOD of a secondary battery as defined in the claim 8.

15. A method for estimating a DOD of a secondary battery, comprising:

(a) receiving a plurality of voltages of a secondary battery, which have been repeatedly measured at time intervals when the secondary battery including a blended cathode material containing at least first and second cathode materials is in an operation state or in an idle state;

(b) identifying an inflection point indicative of changing of a cathode material reacting with working ions in a voltage change over time profile corresponding to the plurality of voltages;

(c) selecting a voltage, measured a predetermined time after the inflection point is identified, as a reference voltage; and

(d) estimating a DOD of the secondary battery by using the reference voltage.

16. The method for estimating a DOD of a secondary battery according to claim 15, wherein in the step (b), the inflection point is identified when a voltage change rate (dV/dt) with respect to time is at the maximum in the voltage change profile.

17. The method for estimating a DOD of a secondary battery according to claim 15, wherein in the step (c), a voltage measured after a predetermined time since the inflection point is identified is selected as a reference voltage.

18. The method for estimating a DOD of a secondary battery according to claim 15, wherein in the step (d), the DOD is estimated by using a lookup table or a lookup function which defines a correlation between the reference voltage and the DOD in advance.

19. The method for estimating a DOD of a secondary battery according to claim 15, further comprising:

storing, displaying or transmitting the estimated DOD.

20. A method for estimating a DOD of a secondary battery, comprising:

(a) receiving a plurality of voltages of a secondary battery, which have been repeatedly measured at time intervals when the secondary battery including a blended cathode material containing at least first and second cathode materials is in an operation state or in an idle state;

(b) identifying an inflection point indicative of changing of a cathode material reacting with working ions in a voltage change over time profile corresponding to the plurality of voltages;

(c) estimating a reference voltage, which is to be used for estimating a DOD of the secondary battery, by means of extrapolation from a plurality of voltages measured at predetermined times after the inflection point is identified; and

(d) estimating the DOD by using the estimated reference voltage.

21. The method for estimating a DOD of a secondary battery according to claim 20, wherein in the step (b), the inflection point is identified when a voltage change rate (dV/dt) with respect to time is at the maximum in the voltage change profile.

22. The method for estimating a DOD of a secondary battery according to claim 20, wherein in the step (c), an approximation function for approximating a voltage change profile corresponding to the plurality of voltages measured after the inflection point is identified is determined, and a voltage corresponding to a predetermined time is estimated as the reference voltage by using the approximation function.

23. The method for estimating a DOD of a secondary battery according to claim 20, wherein in the step (d), the DOD is estimated by using a lookup table or a lookup function which defines a correlation between the reference voltage and the DOD in advance.

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

storing, displaying or transmitting the estimated DOD.