Battery capacity calculating method, battery capacity calculating apparatus and battery capacity calculating program

• US 7,078,907 B2
• Filed: 11/05/2003
• Issued: 07/18/2006
• Est. Priority Date: 11/15/2002
• Status: Expired due to Term

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Tomita, Takashi, Uesaka, Shinichi, Ikeda, Tamon, Hatazawa, Tsuyonobu
• Primary Examiner(s): Berhane, Adolf Deneke
• Assistant Examiner(s): PIGGUSH, AARON C
• Application Number:
  US10/533,599
• Publication Number:
  US 20060022676A1
• Time in Patent Office: 986 Days
• Field of Search: 320/104, 320/132, 324/429, 324/427, 324/433, 702/63
• US Class Current: 324/429
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/3828 using current integration
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements

Abstract

A battery calculating method, apparatus, and program are provided. The battery capacity calculating method and apparatus can very accurately calculate a residual capacity of a secondary battery especially in the last stage of discharging independently of environmental conditions such as a temperature or a deteriorated state. the battery capacity calculating apparatus is equipped with a voltage measuring circuit which measures the terminal voltage (V_mea) of a battery at the time of discharging, a current measuring circuit which measures the current value (I) of the battery at the time of discharging, and a control circuit which calculates a residual capacity and/or residual power. The operation unit in the control circuit calculates a discharged capacity (Q_mea) and an apparent discharged capacity (Q_ocv) based on a terminal voltage (V_mea) and a current value (I) measured by the voltage measuring circuit and the current measuring circuit, respectively, estimates a discharge curve (C_pre) in the future including the last stage of discharging based on a capacity shift (ΔQ) being the difference between the discharged capacity (Q_mea) and the apparent discharged capacity (Q_ocv) during discharging, and calculates the residual capacity and/or the residual power of the battery based on the estimated discharge curve (C_pre).

Claims

1. A battery capacity calculating method for calculating a residual capacity and/or residual power of a secondary battery, comprising:

calculating an equilibrium voltage curve C_equ showing a relation between a discharged capacity and an equilibrium voltage in said secondary battery;

measuring a terminal voltage V_mea and a current value I of said secondary battery at a time of discharging;

calculating a discharged capacity Q_mea of said secondary battery based on the terminal voltage V_mea and the current value I;

calculating an apparent equilibrium voltage V_ocv by adding a voltage drop Δ

V_dc by a direct current resistance R_dc to the terminal voltage V_mea;

calculating an apparent discharged capacity Q_ocv corresponding to the apparent equilibrium voltage V_ocv calculated based on the equilibrium voltage curve C_equ;

calculating a capacity shift Δ

Q being a difference between the discharged capacity Q_mea and the apparent discharged capacity Q_ocv; and

estimating a discharge curve C_pre in a future based on the capacity shift Δ

Q calculated at said capacity shift calculating step.

2. The battery capacity calculating method according to claim 1, wherein when a state of said battery is close to the last stage of discharging, a reduction rate dQ of a capacity shift to a discharged capacity is calculated based on the discharged capacity Q_mea and the capacity shift Δ

Q, and the discharge curve C_pre in the future is estimated based on the capacity shift Δ

Q and the reduction rate dQ.

3. The battery capacity calculating method according to claim 2, wherein the capacity shift Δ

Q is expressed by a linear function of the discharged capacity Q_mea when the state of said battery is close to the last stage of discharging.

4. The battery capacity calculating method according to claim 1, wherein when a state of said battery is not in the last stage of discharging, the equilibrium voltage V_equ corresponding to the discharged capacity Q_mea is calculated based on the equilibrium voltage curve C_equ, and the discharge curve C_pre in the future is estimated based on the voltage drop Δ

V being the difference between the equilibrium voltage V_equ and the terminal voltage V_mea.

5. The battery capacity calculating method according to claim 4, wherein the discharge curve C_pre is estimated by subtracting the voltage drop Δ

V from the equilibrium voltage curve C_equ.

6. The battery capacity calculating method according to claim 4, wherein the discharge curve C_pre is estimated using a maximum voltage drop Δ

V_max corresponding to a maximum load by present in place of the voltage drop Δ

V.

7. The battery capacity calculating method according to claim 1, further comprising calculating the residual capacity and/or the residual power of said secondary battery based on the discharge curve C_pre.

8. The battery capacity calculating method according to claim 1, further comprising performing a judgment whether a state of said battery is near the last stage of discharging or not based on the apparent equilibrium voltage V_ocv to switch an estimating method of the discharge curve C_pre according to a judgment result.

9. The battery capacity calculating method according to claim 8, wherein the apparent equilibrium voltage V_ocv is compared with a predetermined threshold value to perform the judgment whether the state of said battery is near the last stage of discharging or not.

10. The battery capacity calculating method according to claim 1, wherein the direct current resistance R_dc is calculated based on voltage changes according to current changes.

11. The battery capacity calculating method according to claim 1, wherein the direct current resistance R_dc is calculated based on an average voltage and an average current value.

12. The battery capacity calculating method according to claim 1, wherein the equilibrium voltage curve C_equ is calculated based on equilibrium voltages at least two points and a capacity between the equilibrium voltages.

13. The battery capacity calculating method according to claim 12, wherein a shrinkage ratio S expressed by a quotient obtained by dividing a fully charged capacity of the secondary battery by a fully charged capacity of an initial battery which is not deteriorated based on the equilibrium voltages at the at least two points and a capacity between the equilibrium voltages.

14. The battery capacity calculating method according to claim 1, wherein charging is compulsorily stopped and an equilibrium voltage is obtained based on a subsequent voltage change.

15. The battery capacity calculating method according to claim 1, wherein the calculated residual capacity and/or the calculated residual power are transmitted to an electronic apparatus using said secondary battery as its power supply.

16. A battery capacity calculating apparatus for calculating a residual capacity and/or residual power of a secondary battery, comprising:

voltage measuring means for measuring a terminal voltage V_mea of said secondary battery at a time of discharging;

current measuring means for measuring a current value I of said secondary battery at the time of discharging; and

operation processing means for calculating the residual capacity and/or the residual power of said secondary battery,

wherein said operation processing means calculates an equilibrium voltage curve C_equ showing a relation between a discharged capacity and an equilibrium voltage in said secondary battery, calculates a discharged capacity Q_mea of said secondary battery based on the terminal voltage V_mea measured with said voltage measuring means and the current value I measured with said current measuring means, calculates an apparent equilibrium voltage V_ocv by adding a voltage drop Δ

V_dc by a direct current resistance R_dc to the terminal voltage V_mea, calculates an apparent discharged capacity Q_ocv corresponding to the apparent equilibrium voltage V_ocv based on the equilibrium voltage curve C_equ, calculates a capacity shift Δ

Q being a difference between the discharged capacity Q_mea and the apparent discharged capacity Q_ocv, and estimates a discharge curve C_pre in a future based on the capacity shift Δ

Q.

17. The battery capacity calculating apparatus according to claim 16, wherein, when a state of said battery is close to the last stage of discharging, said operation processing means calculates a reduction rate dQ of a capacity shift to a discharged capacity based on the discharged capacity Q_mea and the capacity shift Δ

Q, and estimates the discharge curve C_pre in the future based on the capacity shift Δ

Q and the reduction rate dQ.

18. The battery capacity calculating apparatus according to claim 17, wherein the capacity shift Δ

Q is expressed by a linear function of the discharged capacity Q_mea when the state of said battery is close to the last stage of discharging.

19. The battery capacity calculating apparatus according to claim 16, wherein, when a state of said battery is not in the last stage of discharging, said operation processing means calculates the equilibrium voltage V_equ corresponding to the discharged capacity Q_mea based on the equilibrium voltage curve C_equ, and estimates the discharge curve C_pre in the future based on the voltage drop Δ

V being the difference between the equilibrium voltage V_equ and the terminal voltage V_mea.

20. The battery capacity calculating apparatus according to claim 19, wherein said operation processing means estimates the discharge curve C_pre by subtracting the voltage drop Δ

V from the equilibrium voltage curve C_equ.

21. The battery capacity calculating apparatus according to claim 19, wherein said operation processing means estimates the discharge curve C_pre using a maximum voltage drop Δ

V_max corresponding to a maximum load by present in place of the voltage drop Δ

V.

22. The battery capacity calculating apparatus according to claim 16, wherein said operation processing means calculates a residual capacity and/or the residual power of said secondary battery based on the estimated discharge curve C_pre.

23. The battery capacity calculating apparatus according to claim 16, wherein said operation processing means performs a judgment whether a state of said battery is near the last stage of discharging or not based on the apparent equilibrium voltage V_ocv to switch an estimating method of the discharge curve C_pre according to a judgment result.

24. The battery capacity calculating apparatus according to claim 23, wherein said operation processing means compares the apparent equilibrium voltage V_ocv with a predetermined threshold value to perform the judgment whether the state of said battery is near the last stage of discharging or not.

25. The battery capacity calculating apparatus according to claim 16, wherein said operation processing means calculates the direct current resistance R_dc based on voltage changes according to current changes.

26. The battery capacity calculating apparatus according to claim 16, wherein said operation processing means calculates the direct current resistance R_dc based on an average voltage and an average current value.

27. The battery capacity calculating apparatus according to claim 16, wherein said operation processing means calculates the equilibrium voltage curve C_equ based on equilibrium voltages at least two points and a capacity between the equilibrium voltages.

28. The battery capacity calculating apparatus according to claim 27, wherein said operation processing means calculates a shrinkage ratio S expressed by a quotient obtained by dividing a fully charged capacity of said secondary battery by a fully charged capacity of an initial battery which is not deteriorated based on the equilibrium voltages at the at least two points and a capacity between the equilibrium voltages.

29. The battery capacity calculating apparatus according to claim 16, wherein said operation processing means compulsorily stops charging and obtains an equilibrium voltage based on a subsequent voltage change.

30. The battery capacity calculating apparatus according to claim 16, further comprising transmitting means for transmitting the residual capacity and/or the residual power calculated by said operation processing means to an electronic apparatus using said secondary battery as its power supply.

31. A battery capacity calculating program capable of being executed by a computer for calculating a residual capacity and/or residual power of a secondary battery, comprising:

equilibrium voltage curve calculating processing for calculating an equilibrium voltage curve C_equ showing a relation between a discharged capacity and an equilibrium voltage of said secondary battery;

voltage current measuring processing for measuring a terminal voltage V_mea and a current value I of said secondary battery at a time of discharging;

discharged capacity calculating processing for calculating a discharged capacity Q_mea of said secondary battery based on the terminal voltage V_mea and the current value I, both measured by said voltage current measuring processing;

apparent equilibrium voltage calculating processing for calculating an apparent equilibrium voltage V_ocd by adding a voltage drop Δ

V_dc by a direct current resistance R_dc to the terminal voltage V_mea;

apparent discharged capacity calculating processing for calculating an apparent discharged capacity Q_ocv corresponding to the apparent equilibrium voltage V_ocv calculated by said equilibrium voltage calculating processing based on said equilibrium voltage curve C_equ calculated by said equilibrium voltage curve calculating processing;

capacity shift calculating processing for calculating a capacity shift Δ

Q being a difference between the discharged capacity Q_mea and the apparent discharged capacity Q_ocv; and

estimating processing for estimating a discharge curve C_pre in a future based on the capacity shift Δ

Q calculated by said capacity shift calculating processing.