Critical state estimation system and method for secondary cells

• US 20050194976A1
• Filed: 05/04/2005
• Published: 09/08/2005
• Est. Priority Date: 12/25/2003
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Yumoto, Daijiro, Nakamura, Hideo
• Granted Patent: US 7,358,704 B2
• Time in Patent Office: Days
• US Class Current: 324/433
• 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 a critical state of a performance under a prescribed working condition of a secondary cell, in consideration of an internal resistance of the secondary cell, the system comprising:

a variable data provider configured to provide a set of variable data on the performance, including

an available first data on a variant of the performance,

an available second data on a current of the secondary cell, and

an estimated third data on a dynamic characteristic of the internal resistance; and

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

a specified fourth data on a permissible range of the variant under the prescribed working condition, and

a set of exact data on the dynamic characteristic; and

a critical state estimator configured to process the set of variable data and the set of specified data for estimation of the critical state, the critical state estimator comprising

an internal resistance setter configured to process the second data and the third data to set a subset of the set of exact data defining the dynamic characteristic, and

an estimating element configured to process the first data, the fourth data, and the subset of exact data to estimate the critical state.

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 second data and the third data for calculation 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 dynamic characteristic in a non-linear manner, and to provide a result of the calculation as the third data, and

the internal resistance setter is configured to set the subset of exact data to be commensurate with the third data 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 first data represents an open-circuit voltage of the secondary cell, and the fourth 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 11, wherein

the variable data provider is configured to process the second data, the third data, and a data on a terminal voltage of the secondary cell, for estimation of the first data representing the open-circuit voltage.

13. A critical state estimation method adapted for estimation of a critical state of a performance under a prescribed working condition of a 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 available first data on a variant of the performance,

an available second data on a current of the secondary cell,

an estimated third data on a dynamic characteristic of the internal resistance; and

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

a specified fourth data on a permissible range of the variant under the prescribed working condition, and

a set of exact data on the dynamic characteristic; and

processing the set of variable data and the set of specified data for estimation of the critical state, the processing comprising

processing the second data and the third data to set a subset of the set of exact data defining the dynamic characteristic, and

processing the first data, the fourth data, and the subset of exact data to estimate the critical state.