Method for estimating states and parameters of an electrochemical cell

• US 7,109,685 B2
• Filed: 09/17/2003
• Issued: 09/19/2006
• Est. Priority Date: 09/17/2003
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Frisch, Damon R., Koch, Brian J., Verbrugge, Mark W., Tate, Edward D. Jr.
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US10/664,287
• Publication Number:
  US 20050057255A1
• Time in Patent Office: 1,098 Days
• Field of Search: 320/132, 320/149, 320/DIG.21, 324/426, 324/427, 324/430, 324/433
• US Class Current: 320/132
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• 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 10/486 for measuring temperature
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A method of estimating a state of charge (SOC) and a state of health (SOH) of an electrochemical cell (EC) includes modeling the EC with a linear equation, measuring a terminal current of the EC, measuring a terminal voltage of the EC and measuring a temperature of the EC. The linear equation is processed through a time-varying state and parameter estimator based on the terminal current, the terminal voltage and the temperature to determine states and parameters of the EC.

Claims

1. A method of estimating a state of charge (SOC) and a state of health (SOH) of an electrochemical cell (EC), comprising:

modeling said EC with a state prediction model and a parameter prediction model;

measuring a terminal current of said EC;

measuring a terminal voltage of said EC;

measuring a temperature of said EC; and

processing said state prediction model and said parameter prediction model through a time-varying state and parameter estimator based on said terminal current, said terminal voltage and said temperature to determine states and parameters of said EC, wherein said parameters include charge and discharge variables.

2. The method of claim 1 wherein said states include said SOC and ohmic resistance of said EC.

3. The method of claim 1 further comprising determining said SOH based on said charge variable and said discharge variable.

4. The method of claim 1 wherein said state prediction model and said parameter prediction model are process models that model changes in states and parameters of said EC based on current.

5. The method of claim 1 further comprising determining synthesized inputs based on said terminal current, said terminal voltage and said temperature wherein said processing is further based on said synthesized inputs.

6. The method of claim 1 wherein said step of processing said state prediction model and said parameter prediction model comprises:

predicting current states based on prior states;

predicting current error of said states based on prior errors of said states;

determining current state gains based on said current error of said states; and

updating said current states based on said prior states and said current state gains to provide said states of said EC.

7. The method of claim 6 wherein said states include said SOC and ohmic resistance of said EC.

8. The method of claim 6 wherein said state errors are continuously updated.

9. The method of claim 1 wherein said step of processing said state prediction model and said parameter prediction model comprises:

predicting current parameters based on prior parameters;

predicting current error of said parameters based on prior errors of said parameters;

determining current parameter gains based on said current error of said parameters; and

updating said current parameters based on said prior parameters and said current parameter gains to provide said parameters of said EC.

10. The method of claim 9 wherein said parameter errors are continuously updated.

11. A method of estimating states and parameters of an electrochemical cell (EC), comprising:

modeling said EC with a state prediction model and a parameter prediction model;

measuring a terminal current of said EC;

measuring a terminal voltage of said EC;

measuring a temperature of said EC;

determining initial states and initial parameters; and

processing said state prediction model and said parameter prediction model through a Kalman filter (KF)-based state and parameter estimator based on said terminal current, said terminal voltage, said temperature, said initial states and said initial parameters to determine said states and said parameters, wherein said parameters include charge and discharge variables.

12. The method of claim 11 wherein said states include a state of charge (SOC) and ohmic resistance of said EC.

13. The method of claim 11 further comprising determining a state of health (SOH) based on said charge variable and said discharge variable.

14. The method of claim 11 wherein said state prediction model and said parameter prediction model are process models that model changes in said states and parameters of said EC based on current.

15. The method of claim 11 further comprising determining synthesized inputs based on said terminal current, said terminal voltage and said temperature wherein said processing is further based on said synthesized inputs.

16. The method of claim 11 wherein said step of processing said state prediction model and said parameter prediction model comprises:

predicting current states based on prior states;

predicting current error of said states based on prior errors of said states;

determining current state gains based on said current error of said states; and

updating said current states based on said prior states and said current state gains to provide said states of said EC.

17. The method of claim 16 wherein said states include a state of charge (SOC) and ohmic resistance of said EC.

18. The method of claim 16 wherein said state errors are continuously updated.

19. The method of claim 11 wherein said step of processing said state prediction model and said parameter prediction model comprises:

predicting current parameters based on prior parameters;

predicting current error of said parameters based on prior errors of said parameters;

determining current parameter gains based on said current error of said parameters; and

updating said current parameters based on said prior parameters and said current parameter gains to provide said parameters of said EC.

20. The method of claim 19 wherein said parameter errors are continuously updated.

21. The method of claim 11 wherein said initial states and parameters are determined based on minimizing an initial error between said initial states and parameters and actual states and parameters.

22. A method of estimating states and parameters of an electrochemical cell (EC), comprising:

modeling said EC with a state prediction model and a parameter prediction model based on characterization data of said EC;

measuring a terminal current of said EC;

measuring a terminal voltage of said EC;

measuring a temperature of said EC; and

processing said linear equation through a Kalman filter (KF)-based state and parameter estimator based on said terminal current, said terminal voltage, said temperature to determine said states and said parameters, wherein said parameters include charge and discharge variables.

23. The method of claim 22 wherein said characterization data includes the rate of change of a parameter based on a state.