Method and apparatus for estimating the charge/discharge electricity amount of secondary batteries

• US 7,728,598 B2
• Filed: 06/04/2009
• Issued: 06/01/2010
• Est. Priority Date: 07/29/2003
• Status: Active Grant

• Current Assignee: Panasonic EV Energy Company, Limited (Toyota Motor Corporation)
• Original Assignee: Panasonic EV Energy Company, Limited (Toyota Motor Corporation)
• Inventors: Murakami, Yusai, Yamabe, Norito
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): RAMADAN, RAMY O
• Application Number:
  US12/478,221
• Publication Number:
  US 20090261836A1
• Time in Patent Office: 362 Days
• Field of Search: None
• US Class Current: 324/429
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery

Abstract

An apparatus estimates charge/discharge electricity amount without being affected by current measurement error. Under specific selection conditions, a no-load voltage calculation part uses pairs of data consisting of current data I(n) and voltage data V(n) corresponding to the current data to calculate a no-load voltage V_sep as the voltage intercept at a current of zero in a straight-line approximation obtained by statistical processing such as regression analysis using a least squares method. If specific current conditions exist for a certain amount of time, an open circuit voltage calculation part calculates the terminal voltage of the secondary battery as the open circuit voltage V_oc. An estimated charge/discharge electricity amount calculation part uses a preset change-in-voltage adjustment constant ΔV_bc/adjustment coefficient K_b, change-in-electromotive-force constant K_eq and polarization voltage generation constant K_pol to calculate the estimated charge/discharge electricity amount ΔQ_e as a function of the change ΔV_b in the no-load or open circuit voltage over a predetermined period of time.

Claims

1. A method for estimating a charge/discharge electricity amount of a secondary battery comprising:

measuring a pair of data consisting of a current flowing through the secondary battery and a terminal voltage of the secondary battery corresponding to the current, thus obtaining a plurality of pairs of data;

if specific selection conditions are satisfied, the specific selection conditions including (i) the current in charging and discharging the secondary battery is within a first predetermined range, (ii) a number of the plurality of pairs of data greater than or equal to a predetermined number, and (iii) a charge/discharge electricity amount during collection of the plurality of pairs of data is within a second predetermined range, calculating a no-load voltage as a voltage intercept at a current of zero in a straight-line approximation obtained by statistical processing with respect to the plurality of pairs of data;

if the specific selection conditions are not satisfied and if one of specific current conditions or voltage conditions continue to be met for a certain amount of time, calculating an open circuit voltage from the terminal voltage of the secondary battery, the component resistance of the secondary battery and an average current;

calculating a change (Δ

V_b) in the no-load voltage or the open circuit voltage over a predetermined period of time;

calculating an estimated charge/discharge electricity amount (Δ

Q_e) of the secondary battery based on the change in the no-load voltage or the open circuit voltage; and

calculating a measured charge/discharge electricity amount over the predetermined period of time from the current flowing through the secondary battery.

2. The method for estimating a charge/discharge electricity amount of a secondary battery according to claim 1, further comprising calculating a polarization voltage of the secondary battery based on the measured charge/discharge electricity amount.

3. The method for estimating a charge/discharge electricity amount of a secondary battery according to claim 2, further comprising calculating an electromotive force of the secondary battery based on the measured charge/discharge electricity amount.

4. The method for estimating a charge/discharge electricity amount of a secondary battery according to claim 3, further comprising calculating a change in the polarization voltage and a change in the electromotive force over the predetermined period of time.

5. The method for estimating a charge/discharge electricity amount of a secondary battery according to claim 4, wherein calculating the estimated charge/discharge electricity amount is performed based on the change in the polarization voltage, the change in the electromotive force and the change in the no-load voltage or the open circuit voltage.

6. The method for estimating a charge/discharge electricity amount of a secondary battery according to claim 5 wherein calculating the estimated charge/discharge electricity amount comprises:

calculating a compensation coefficient with respect to the measured charge/discharge electricity amount based on the change in the polarization voltage, the change in the electromotive force and the change in the no-load voltage or the open circuit voltage; and

multiplying the measured charge/discharge electricity amount by the compensation coefficient.

7. The method for estimating a charge/discharge electricity amount of a secondary battery according to claim 6, wherein, when Δ

V_pol is the change in the polarization voltage, Δ

V_eq is the change in the electromotive force, Δ

V_b is the change in the no-load voltage or the open circuit voltage, and α

is the compensation coefficient, the compensation coefficient α

is expressed as α

=Δ

V_b/(Δ

V_pol+Δ

V_eq).

8. The method for estimating a charge/discharge electricity amount of a secondary battery according to claim 5, wherein:

calculating the polarization voltage is performed based on the measured charge/discharge electricity amount; and

calculating the polarization voltage is performed based on the estimated charge/discharge electricity amount calculated for the previous predetermined amount of time.

9. The method for estimating a charge/discharge electricity amount of a secondary battery according to claim 5, wherein:

calculating the electromotive force is performed based on the measured charge/discharge electricity amount; and

calculating the electromotive force is performed based on the estimated charge/discharge electricity amount calculated for the previous predetermined amount of time.

10. The method for estimating a charge/discharge electricity amount of a secondary battery according to claim 5, wherein calculating the polarization voltage is performed with reference to a polarization voltage-charge/discharge electricity amount characteristic prepared in advance with temperature as a parameter.

11. The method for estimating a charge/discharge electricity amount of a secondary battery according to claim 5, wherein calculating the electromotive force is performed with reference to an electromotive force-state of charge characteristic prepared in advance with temperature as a parameter, based on the sum of the measured charge/discharge electricity amount and the state of charge calculated for the previous predetermined amount of time.

12. An apparatus for estimating a charge/discharge electricity amount of a secondary battery, comprising:

a current measurement part that measures current flowing through the secondary battery as current data;

a voltage measurement part that measures a terminal voltage of the secondary battery as voltage data;

a no-load voltage calculation part that obtains a plurality of pairs of data consisting of current data from the current measurement part and voltage data corresponding to this current data from the voltage measurement part, and that, in the case that specific selection conditions are satisfied, the specific selection conditions including (i) the current in charging and discharging the secondary battery is within a first predetermined range, (ii) a number of the plurality of pairs of data greater than or equal to a predetermined number, and (iii) a charge/discharge electricity amount during collection of the plurality of pairs of data is within a second predetermined range, calculates a no-load voltage as a voltage intercept at a current of zero in a straight-line approximation obtained by statistical processing with respect to the plurality of pairs of data;

an open circuit voltage calculation part that, in the case that the specific selection conditions are not satisfied and specific current conditions or voltage conditions continue to be met for a certain amount of time, calculates an open circuit voltage from the terminal voltage of the secondary battery, the component resistance of the secondary battery and an average current;

a change-in-measured-voltage calculation part that calculates a change (Δ

V_b) in the no-load voltage or the open circuit voltage over a predetermined period of time;

an estimated charge/discharge electricity amount calculation part that calculates an estimated charge/discharge electricity amount (Δ

Q_e) of the secondary battery based on the change in the no-load voltage or the open circuit voltage; and

a measured charge/discharge electricity amount calculation part that calculates a measured charge/discharge electricity amount over the predetermined period of time from the current flowing through the secondary battery.

13. The apparatus for estimating a charge/discharge electricity amount of a secondary battery according to claim 12, further comprising a polarization voltage calculation part that calculates a polarization voltage of the secondary battery based on the measured charge/discharge electricity amount.

14. The apparatus for estimating a charge/discharge electricity amount of a secondary battery according to claim 13, further comprising an electromotive force calculation part that calculates an electromotive force of the secondary battery based on the measured charge/discharge electricity amount.

15. The apparatus for estimating a charge/discharge electricity amount of a secondary battery according to claim 14, further comprising a change-in-polarization-voltage calculation part that calculates a change in the polarization voltage over the predetermined period of time.

16. The apparatus for estimating a charge/discharge electricity amount of a secondary battery according to claim 15, further comprising a change-in-electromotive-force calculation part that calculates a change in the electromotive force over the predetermined period of time.

17. The apparatus for estimating a charge/discharge electricity amount of a secondary battery according to claim 16, wherein the estimated charge/discharge electricity amount calculation part calculates the estimated charge/discharge electricity amount based on the change in the polarization voltage, the change in the electromotive force and the change in the no-load voltage or the open circuit voltage.

18. The apparatus for estimating a charge/discharge electricity amount of a secondary battery according to claim 17, wherein the estimated charge/discharge electricity amount calculation part comprises a compensation coefficient calculation part that calculates a compensation coefficient with respect to the measured charge/discharge electricity amount based on the change in the polarization voltage, the change in the electromotive force and the change in the no-load voltage or the open circuit voltage, and the estimated charge/discharge electricity amount is calculated by multiplying the measured charge/discharge electricity amount by the compensation coefficient.

19. The apparatus for estimating a charge/discharge electricity amount of a secondary battery according to claim 18, wherein when Δ

V_pol is the change in the polarization voltage, Δ

V_eq is the change in the electromotive force, Δ

V_b is the change in the no-load voltage or the open circuit voltage, and α

is the compensation coefficient, the compensation coefficient α

is expressed as α

Δ

V_b/(Δ

V_pol+Δ

V_eq).

20. The apparatus for estimating a charge/discharge electricity amount of a secondary battery according to claim 17, wherein the polarization voltage calculation part calculates the polarization voltage based on the measured charge/discharge electricity amount and the polarization voltage calculated based on the estimated charge/discharge electricity amount calculated for the previous predetermined amount of time.

21. The apparatus for estimating a charge/discharge electricity amount of a secondary battery according to claim 17, wherein the electromotive force calculation part calculates the electromotive force based on the measured charge/discharge electricity amount and the electromotive force calculated based on the estimated charge/discharge electricity amount calculated for the previous predetermined amount of time.

22. The apparatus for estimating a charge/discharge electricity amount of a secondary battery according to claim 17, further comprising a temperature measurement part that measures a temperature of the secondary battery as temperature data, wherein the polarization voltage calculation part calculates the polarization voltage with reference to a polarization voltage-charge/discharge electricity amount characteristic prepared in advance with the temperature data from the temperature measurement part as a parameter.

23. The apparatus for estimating a charge/discharge electricity amount of a secondary battery according to claim 17, further comprising a temperature measurement part that measures a temperature of the secondary battery as temperature data, wherein the electromotive force calculation part calculates the electromotive force with reference to an electromotive force-state of charge characteristic prepared in advance with the temperature data from the temperature measurement part as a parameter, based on the sum of the measured charge/discharge electricity amount and the state of charge calculated for the previous predetermined amount of time.