Battery recharge estimator using battery impedance response

• US 9,252,465 B2
• Filed: 05/24/2011
• Issued: 02/02/2016
• Est. Priority Date: 05/24/2011
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Hariharan, Krishnan S
• Primary Examiner(s): Breene, John
• Assistant Examiner(s): BLOSS, STEPHANIE E
• Application Number:
  US13/114,336
• Publication Number:
  US 20120303208A1
• Time in Patent Office: 1,715 Days
• Field of Search: 702/63
• US Class Current: 1/1
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• 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: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

An exemplary embodiment includes a method for determining a time to recharge a rechargeable battery system including providing impedance data over a frequency range, said impedance data characterizing the operation of a rechargeable battery within a selected time window; analyzing said impedance data for predetermined behavior of said impedance data indicating an approaching state of discharge of said battery; and, determining from said predetermined behavior of said impedance data whether a recharge of said rechargeable battery is indicated.

Claims

1. A method for determining whether a recharge of a rechargeable battery system is indicated comprising:

providing impedance data over a frequency range, said impedance data characterizing operation a rechargeable battery within a selected time window;

analyzing said impedance data for predetermined behavior of said impedance data indicating an approaching state of discharge of said battery; and

,

determining from said predetermined behavior of said impedance data whether a recharge of said rechargeable battery indicated; and

recharging said rechargeable battery if a recharge of said rechargeable battery is indicated by said impedance data.

2. The method of claim 1, wherein said impedance data is calculated from a Fourier transform of current and voltage data characterizing discharge behavior of said battery system.

3. The method of claim 1, wherein said step of analyzing comprises presenting said impedance data as imaginary impedance versus frequency data and characterizing a slope of said data near zero frequency.

4. The method of claim 3, wherein said characterizing comprises determining whether said slope is negative.

5. The method of claim 3, wherein said step of analyzing comprises presenting said impedance data as imaginary impedance versus real impedance plot over said frequency range and characterizing a low frequency portion of said plot.

6. The method of claim 5, wherein said characterizing comprises determining whether said low frequency portion extends outward of a radius of a semicircle comprising said plot.

7. The method of claim 1, wherein said step of analyzing comprises presenting said impedance data as imaginary impedance versus real impedance plot over said frequency range and characterizing a low frequency portion of said plot.

8. The method of claim 1, wherein said rechargeable battery comprises a lithium containing cathode on discharge.

9. The method of claim 1, wherein said rechargeable battery comprises a vehicle battery system.

10. The method of claim 1, wherein said steps of providing, analyzing, and determining are implemented by programmable instructions executed by one or more on board vehicle controllers.

11. The method of claim 1, further comprising determining an estimated time within which said recharge should take place.

12. A method for determining whether a recharge of a rechargeable battery system is indicated comprising:

providing impedance data over a frequency range, said impedance data characterizing operation a rechargeable battery within a selected time window;

analyzing said impedance data for predetermined behavior of said impedance data indicating an approaching state of discharge of said battery; and

,

determining from said predetermined behavior of said impedance data whether a recharge of said rechargeable battery is indicated including determining an estimated time within which said recharge should take place; and

recharging said rechargeable battery at said estimated time if a recharge of said rechargeable battery is indicated by said impedance data.

13. The method of claim 12, wherein said impedance data is calculated from a Fourier transform of current and voltage data characterizing discharge behavior of said battery system.

14. The method of claim 12, wherein said step of analyzing comprises characterizing a slope of an imaginary portion of said impedance data versus frequency data near zero frequency.

15. The method of claim 14, wherein said characterizing comprises determining whether said slope is negative.

16. The method of claim 12, wherein said step of analyzing wherein said step of analyzing comprises presenting said impedance data as imaginary impedance versus real impedance plot over said frequency range and characterizing a low frequency portion of said plot.

17. The method of claim 12, wherein said rechargeable battery comprises a lithium containing cathode on discharge.

18. The method of claim 12, wherein said rechargeable battery comprises a vehicle battery system.

19. The method of claim 12, wherein said steps of providing, analyzing, and determining are implemented by programmable instructions executed by one or more on board vehicle controllers.

20. A vehicle system for determining whether a recharge of a rechargeable battery system is indicated comprising:

an on-board controller in communication with a vehicle battery system, said controller programmed to determine impedance data over a frequency range, said impedance data characterizing operation a rechargeable battery within a selected time window;

said controller further programmed to analyze said impedance data for predetermined behavior of said impedance data indicating an approaching state of discharge of said battery system;

said controller further programmed to determine from said predetermined behavior of said impedance data whether a recharge of said rechargeable battery is indicated;

wherein said controller is further programmed to output at least one of a signal and a numerical value in response to a determination that said recharge is indicated by said impedance data.