Charged State Estimating Device and Charged State Estimating Method of Secondary Battery

• US 20090001992A1
• Filed: 11/30/2006
• Published: 01/01/2009
• Est. Priority Date: 12/27/2005
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Tsuchiya, Kenji
• Granted Patent: US 8,274,291 B2
• Time in Patent Office: Days
• US Class Current: 324/426
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/3828 using current integration
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

When a battery current is not larger than a limit current set depending on the battery temperature and is flowing continuously for a predetermined time set depending on the battery temperature or longer, a decision is made that a secondary battery is in stable state. When the secondary battery is in stabilized state, the battery voltage is considered to be equal to the open circuit voltage and SOC estimation is performed based on the open circuit voltage-SOC characteristics. When the product of the internal resistance of the secondary battery and the limit current is made substantially constant (constant voltage) by setting the limit current in association with temperature dependence of the internal resistance, estimation error can be kept within a predetermined range in the stabilized state even if SOC estimation is performed while the battery voltage is assumed as the open circuit voltage. Consequently, SOC can be estimated with high precision within a predetermined error by a simple and reliable system under stabilized state.

Claims

1. A device for estimating charged state of a secondary battery provided with a detector capable of detecting input/output current, an output voltage and battery temperature, comprising:

characteristic storing means for storing characteristic between open circuit voltage and remaining capacity of said secondary battery;

stable state determining means for determining whether it is a stable state in which said input/output current is maintained not higher than a limit current set in accordance with said battery temperature for at least a voltage stabilizing period set in accordance with said battery temperature or not; and

first charged state estimating means for estimating the remaining capacity of said secondary battery based on the characteristic stored in said characteristic storing means, regarding said output voltage as said open circuit voltage, when it is determined to be said stable state.

2. The device for estimating charged state of a secondary battery according to claim 1, further comprising

second charged state estimating means for estimating the remaining capacity of said secondary battery when it is determined not to be said stable state by said stable state determining means;

wherein

said second charged state estimating means estimates the remaining capacity of said secondary battery by a procedure of successively calculating amount of change in said remaining capacity based on an integrated value of said input/output current or a procedure based on a battery model using said input/output current, said output voltage and said battery temperature as input variables.

3. The device for estimating charged state of a secondary battery according to claim 2, wherein

said second charged state estimating means includes

first estimating means for estimating the remaining capacity of said secondary battery by calculating amount of change in said remaining capacity based on an integrated value of said input/output current,

second estimating means for estimating the remaining capacity of said secondary battery based on the battery model using said input/output current, said output voltage and said battery temperature as input variables, and timer means for measuring duration of continuous execution of the estimation of remaining capacity by said first estimating means;

and

said second charged state estimating means estimates said remaining capacity by selecting said first estimating means when said duration of continuous execution is within a first limit time period, and estimates said remaining capacity by selecting said second estimating means when said duration of continuous execution exceeds said first limit time period and said input/output current is in a prescribed range that allows use of the battery model.

4. The device for estimating charged state of a secondary battery according to claim 3, wherein

said second charged state estimating means estimates said remaining capacity by selecting said second estimating means, when said duration of continuous execution exceeds a second limit time period longer than said first limit time period, regardless of said input/output current.

5. The device for estimating charged state of a secondary battery according to claim 3, wherein

said second charged state estimating means estimates said remaining capacity by selecting said first estimating means, when said duration of continuous execution exceeds said first limit time period and said input/output current is out of said prescribed range that allows use of the battery model.

6. The device for estimating charged state of a secondary battery according to claim 1, wherein

said limit current in said stable state determining means is set relatively large as said battery temperature increases.

7. The device for estimating charged state of a secondary battery according to claim 1, wherein

said voltage stabilizing period in said stable state determining means is set relatively short as said battery temperature increases.

12. The device for estimating charged state of a secondary battery according to claim 1, wherein

said secondary battery is a lithium ion battery.

8. A device for estimating charged state of a secondary battery provided with a detector capable of detecting input/output current, an output voltage and battery temperature, comprising:

first estimating means for estimating the remaining capacity of said secondary battery by calculating amount of change in said remaining capacity based on an integrated value of said input/output current;

second estimating means for estimating the remaining capacity of said secondary battery based on a battery model using said input/output current, said output voltage and said battery temperature as input variables;

timer means for measuring duration of continuous execution of the estimation of remaining capacity by said first estimating means; and

selecting means for selecting one of said first and second estimating means for estimating said remaining capacity, based on determination as to whether said input/output current is within a prescribed range that allows use of the battery model or not and on said duration of continuous execution obtained by said timer means.

9. The device for estimating charged state of a secondary battery according to claim 8, wherein

said selecting means estimates said remaining capacity by selecting said first estimating means when said duration of continuous execution is within a first limit time period, and estimates said remaining capacity by selecting said second estimating means when said duration of continuous execution exceeds said first limit time period and said input/output current is in said prescribed range that allows use of the battery model.

10. The device for estimating charged state of a secondary battery according to claim 9, wherein

said selecting manes estimates said remaining capacity by selecting said second estimating means, when said duration of continuous execution exceeds a second limit time period longer than said first limit time period, regardless of said input/output current.

11. The device for estimating charged state of a secondary battery according to claim 9, wherein

said selecting manes estimates said remaining capacity by selecting said first estimating means, when said duration of continuous execution exceeds said first limit time period and said input/output current is out of said prescribed range that allows use of the battery model.

13. A method of estimating charged state of a secondary battery provided with a detector capable of detecting input/output current, an output voltage and battery temperature, comprising:

the stable state determining step of determining whether it is a stable state in which said input/output current is maintained not higher than a limit current set in accordance with said battery temperature for at least a voltage stabilizing period set in accordance with said battery temperature or not; and

the first charged state estimating step of estimating the remaining capacity of said secondary battery based on characteristic between open circuit voltage and remaining capacity of said secondary battery, regarding said output voltage as the open circuit voltage of said secondary battery, when it is determined to be the stable state.

14. The method of estimating charged state of a secondary battery according to claim 13, further comprising

the second charged state estimating step of estimating the remaining capacity of said secondary battery when it is determined not to be said stable state at said stable state determining step;

wherein

at said second charged state estimating step, the remaining capacity of said secondary battery is estimated by a procedure of successively calculating amount of change in said remaining capacity based on an integrated value of said input/output current or a procedure based on a battery model using said input/output current, said output voltage and said battery temperature as input variables.

15. The method of estimating charged state of a secondary battery according to claim 14, wherein

said second charged state estimating step includes

the first estimating step of estimating the remaining capacity of said secondary battery by calculating amount of change in said remaining capacity based on an integrated value of said input/output current,

the second estimating step of estimating the remaining capacity of said secondary battery based on the battery model using said input/output current, said output voltage and said battery temperature as input variables, and

the time measuring step of measuring duration of continuous execution of the estimation of remaining capacity by said first estimating step;

and

at said second charged state estimating step, said remaining capacity is estimated by selecting said first estimating step when said duration of continuous execution is within a first limit time period, and estimates said remaining capacity by selecting said second estimating step when said duration of continuous execution exceeds said first limit time period and said input/output current is in a prescribed range that allows use of the battery model.

16. The method of estimating charged state of a secondary battery according to claim 13, wherein

said limit current at said stable state determining step is set relatively large as said battery temperature increases.

17. The method of estimating charged state of a secondary battery according to claim 13, wherein

said voltage stabilizing period at said stable state determining step is set relatively short as said battery temperature increases.

20. The method of estimating charged state of a secondary battery according to claim 13, wherein

said secondary battery is a lithium ion battery.

18. A method of estimating charged state of a secondary battery provided with a detector capable of detecting input/output current, an output voltage and battery temperature, comprising:

the first estimating step of estimating the remaining capacity of said secondary battery by calculating amount of change in said remaining capacity based on an integrated value of said input/output current;

the second estimating step of estimating the remaining capacity of said secondary battery based on a battery model using said input/output current, said output voltage and said battery temperature as input variables;

the time measuring step of measuring duration of continuous execution of the estimation of remaining capacity by said first estimating step; and

the selecting step of selecting one of said first and second estimating steps of estimating said remaining capacity, based on determination as to whether said input/output current is within a prescribed range that allows use of the battery model or not and on said duration of continuous execution obtained by said time measuring step.

19. The method of estimating charged state of a secondary battery according to claim 18, wherein

at said selecting step, said remaining capacity is estimated by selecting said first estimating step when said duration of continuous execution is within a first limit time period, and said remaining capacity is estimated by selecting said second estimating step when said duration of continuous execution exceeds said first limit time period and said input/output current is in said prescribed range that allows use of the battery model.