Critical state estimation system and method for secondary cells

• US 7,358,704 B2
• Filed: 05/04/2005
• Issued: 04/15/2008
• Est. Priority Date: 12/25/2003
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Nakamura, Hideo, Yumoto, Daijiro
• Primary Examiner(s): Vu; Bao Q.
• Assistant Examiner(s): Zhang; Jue
• Application Number:
  US11/121,037
• Publication Number:
  US 20050194976A1
• Time in Patent Office: 1,077 Days
• Field of Search: 324/427, 324/433, 320/119, 320/132, 320/133, 702/182, 702/63
• US Class Current: 320/132
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• 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

Abstract

For estimation of a critical state of a performance under a working condition of a secondary cell, in consideration of an internal resistance of the cell, a variable data provider provides variable data on the performance, including a first data on a variant of the performance, a second data on a current of the cell, and an estimated third data on a dynamic characteristic of the internal resistance, a specified data provider provides specified data on the cell, including a fourth data on a permissible range of the variant under the prescribed working condition, and exact data on the dynamic characteristic, and a critical state estimator processes the variable and specified data for estimation of the critical state, and has an internal resistance setter to process the second and third data to set exact data as a function of second data defining the dynamic characteristic, and an estimating element to process the first, fourth, and exact data to estimate the critical state.

Claims

1. A critical state estimation system adapted for estimation of an inputtable power of a secondary cell that defines a limiting boundary of a permissible range for power to be input to the secondary cell and an outputtable power of the secondary cell that defines a limiting boundary of a permissible range for power to be output from the secondary cell, in consideration of an internal resistance of the secondary cell, the system comprising:

a current detector detecting a supply current from the secondary cell;

a voltage detector detecting a supply voltage from the secondary cell;

a variable data provider configured to provide a set of variable data on the secondary cell based on the supply current and the supply voltage, the variable data including

an estimated parameter on open-circuit voltaae of the secondary cell, and

an estimated parameter on the internal resistance of the secondary cell;

a specified data provider configured to provide a set of specified data on the secondary cell, the specified data including

a specified data on a minimum voltage to be permissible under a prescribed working condition of the secondary cell, and

a specified data on a maximum voltage to be permissible under the prescribed working condition of the secondary cell; and

a critical state estimator configured to process the set of variable data and the set of specified data for estimation of the inputtable power of the secondary cell and the outputtable power of the secondary cell, the critical state estimator comprising

an internal resistance setter configured to process the estimated parameter on the internal resistance of the secondary cell to set an internal resistance of the secondary cell as a function of a current of the secondary cell,

a critical current estimator configured to process the estimated parameter on the open-circuit voltage of the secondary cell, the specified data on the minimum voltage of the secondary cell, the specified data on the maximum voltage of the secondary cell, and the internal resistance of the secondary cell as the function of the current of the secondary cell to estimate an inputtable current of the secondary cell and an outputtable current of the secondary cell within the minimum voltage of the secondary cell and the maximum voltage of the secondary cell, respectively, and

a critical power estimator configured to process the specified data on the minimum voltage of the secondary cell, the specified data on the maximum voltage of the secondary cell, the inputtable current of the secondary cell and the outputtable current of the secondary cell to estimate the inputtable power of the secondary cell and the outputtable power of the secondary cell.

2. The critical state estimation system as claimed in claim 1, wherein

the critical state comprises one of an inputable current, an outputtable current, inputtable power, and outputtable power of the secondary cell.

3. The critical state estimation system as claimed in claim 1, wherein

the internal resistance setter is configured to process the estimated parameter on the internal resistance of the secondary cell to determine a representative value of the internal resistance as a function of a representative variant of the current, and set the subset of exact data to be commensurate with the representative value of the internal resistance.

4. The critical state estimation system as claimed in claim 3, wherein

the representative variant represents a magnitude of the current.

5. The critical state estimation system as claimed in claim 4, wherein

the internal resistance setter is configured for a correction of the function depending on a variable relationship between the magnitude of the current and the internal resistance.

6. The critical state estimation system as claimed in claim 5, wherein

the variable data provider comprises an internal resistance calculator for calculation to estimate the internal resistance in a non-linear manner, and to provide a result of the calculation as the estimated parameter on the internal resistance of the secondary cell, and

the internal resistance setter is configured to set the subset of exact data to be commensurate with the estimated parameter on the internal resistance of the secondary cell for the magnitude of the current not exceeding a reference value, and to be commensurate with the representative value of the internal resistance for the magnitude of the current exceeding the reference value.

7. The critical state estimation system as claimed in claim 6, wherein

the function comprises a linear expression representing a line segment defined with a slope and an intercept.

8. The critical state estimation system as claimed in claim 7, wherein

the correction of the function comprises a change of one of the slope and the intercept depending on the variable relationship.

9. The critical state estimation system as claimed in claim 7, wherein

the correction of the function comprises a shift of the line segment depending on the variable relationship.

10. The critical state estimation system as claimed in claim 5, wherein

the internal resistance setter is configured to execute the correction of the function for a significant residual time of the internal resistance in a prescribed range of the magnitude of the current.

11. The critical state estimation system as claimed in claim 2, wherein

the estimated parameter represents an open-circuit voltage of the secondary cell, and the specified data represents one of a possible maximum voltage and a possible minimum voltage of the secondary cell.

12. The critical state estimation system as claimed in claim 1, wherein

the variable data provider is configured to process the estimated parameter on the internal resistance of the secondary cell and a data on a terminal voltage of the secondary cell, for estimation of the estimated parameter on the open-circuit voltage of the secondary cell.

13. A critical state estimation method adapted for estimation of an inputtable power of a secondary cell that defines a limiting boundary of a permissible range for power to be input to the secondary cell and an outputtable power of the secondary cell that defines a limiting boundary of a permissible range for power to be output from the secondary cell, in consideration of an internal resistance of the secondary cell, the method comprising:

providing a set of variable data on the performance, including

an estimated parameter on an open-circuit voltage of the secondary cell based on a supply current from the secondary cell and a supply voltage from the secondary cell, the supply current from the secondary cell being detected by a current detector and the supply voltage from the secondary cell being detected by a voltage detector, and

an estimated parameter on the internal resistance of the secondary cell; and

providing a set of specified data on the secondary cell, including

a specified data on a minimum voltage to be permissible under the prescribed working condition, and

a specified data on a maximum voltage to be permissible under the prescribed working condition of the secondary cell; and

processing the set of variable data and the set of specified data for estimation of the inputtable power of the secondary cell and the outputtable power of the secondary cell, the processing comprising

processing the estimated parameter on the internal resistance of the secondary cell to set an internal resistance of the secondary cell as a function of a current of the secondary cell,

processing the estimated parameter on the open-circuit voltage of the secondary cell, the specified data on the minimum voltage of the secondary cell, the specified data on the maximum voltage of the secondary cell, and the internal resistance of the secondary cell as the function of the current of the secondary cell to estimate an inputtable current of the secondary cell and an outputtable current of the secondary cell within the minimum voltage of the secondary cell and the maximum voltage of the secondary cell, respectively, and

processing the specified data on the minimum voltage of the secondary cell, the specified data on the maximum voltage of the secondary cell, the inputtable current of the secondary cell and the outputtable current of the secondary cell to estimate the inputtable power of the secondary cell and the outputtable power of the secondary cell.