METHOD AND APPARATUS FOR DETECTING BATTERY STATE OF CHARGE

• US 20080136378A1
• Filed: 01/15/2008
• Published: 06/12/2008
• Est. Priority Date: 07/15/2005
• Status: Abandoned Application

• Current Assignee: Furukawa Electric Company Limited
• Original Assignee: Furukawa Electric Company Limited
• Inventors: Watanabe, Yuichi, Sato, Toshiyuki, Iijima, Takashi, Kimura, Atsushi, Iwahana, Fumikazu
• Application Number:
  US12/014,502
• Publication Number:
  US 20080136378A1
• Time in Patent Office: Days
• US Class Current: 320/153
• 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 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

A method for detecting the charged state of a battery based on the measurements of open circuit voltage in which the charged state of a battery can be detected precisely regardless of the degradation state of the battery. Internal impedance of a battery is measured, voltage of the battery is measured under stable state, measurement of the battery voltage under stable state is subjected to raising correction depending on the measurement of internal impedance, and then charged state of the battery is determined based on the corrected value of battery voltage under stable state.

Claims

1. A method for detecting a state of charge of a battery, comprising the steps of:

measuring an internal impedance of the battery;

measuring a stable-state voltage of the battery;

compensatively correcting the stable-state voltage in accordance with the internal impedance; and

determining the state of charge of the battery based on a corrected stable-state voltage.

2. The method of claim 1, wherein the step of determining the state of charge is performed by substituting the corrected stable-state voltage into a function showing a relation between the stable-state voltage and the state of charge.

4. The method of claim 2 or 3, wherein at least one of a coefficient and a constant of the function showing the relation between the stable-state voltage and the state of charge is corrected in accordance with the internal impedance.

5. The method of any one of claims 2 to 4, wherein the function is a linear function.

6. The method of claim 5, wherein, assuming the state of charge is y and the stable-state voltage is x, the linear function is expressed by y=ax+b (where a is the coefficient and b is the constant).

3. A method for detecting a state of charge of a battery, comprising the steps of:

measuring an internal impedance of the battery;

measuring a stable-state voltage of the battery; and

determining the state of charge of the battery by substituting the corrected stable-state voltage into a function showing a relation between the stable-state voltage and the state of charge.

7. A method for detecting a state of charge of a battery, comprising the steps of:

measuring an internal impedance of the battery;

measuring a stable-state voltage of the battery;

preparing, in advance, plurally divided state-of-charge ranges and matrix data of internal impedances and stable-state voltages associated with each of the state-of-charge ranges; and

determining the state of charge by specifying one of the state-of-charge ranges which includes the internal impedance and the stable-state voltage.

8. The method of claim 7,

further comprising, after the step of measuring the internal impedance, the step of measuring a temperature at a time when the internal impedance is measured, and

the internal impedance used in the step of determining the state of charge being a corrected internal impedance of a predetermined temperature obtained by correcting the internal impedance based on a previously obtained impedance-temperature relation.

9. The method of claim 7 further comprising,

after the step of measuring the internal impedance, the step of measuring a temperature at a time when the internal impedance is measured;

after the step of determining the state of charge, the step of correcting the internal impedance to a corrected internal impedance of a predetermined temperature based on a previously obtained impedance-temperature relation; and

determining the state of charge by specifying one of the state-of-charge ranges which includes the corrected internal impedance and the stable-state voltage.

10. A battery state-of-charge detecting apparatus comprising:

internal impedance measuring unit for measuring an internal impedance of a battery;

voltage measuring unit for measuring a stable-state voltage of the battery;

stable-state voltage correcting unit for correcting the stable-state voltage in accordance with the internal impedance measured by the internal impedance measuring unit; and

state-of-charge calculating unit for calculating out a state of charge of the battery based on a corrected stable-state voltage corrected by the stable-state voltage correcting unit.

11. The battery state-of-charge detecting apparatus of claim 10, wherein the state-of-charge calculating unit calculates out the state of charge by substituting the internal impedance measured by the internal impedance measuring unit into a function showing a relation between the stable-state voltage and the state of charge.

13. The battery state-of-charge detecting apparatus of claim 11 or 12, wherein at least one of a coefficient and a constant of the function showing the relation between the stable-state voltage and the state of charge is corrected in accordance with the internal impedance measured by the internal impedance measuring unit.

14. The battery state-of-charge detecting apparatus of any one of claims 11 to 13, wherein the function is a linear function.

15. The battery state-of-charge detecting apparatus of claim 14, wherein, assuming the state of charge is y and the stable-state voltage is x, the linear function is expressed by y=ax+b (where a is the coefficient and b is the constant).

17. The battery state-of-charge detecting apparatus of any one of claims 10 to 16, wherein the internal impedance measuring unit corrects, based on a temperature of the battery, the internal impedance measured by the internal impedance measuring unit to output a corrected internal impedance of a predetermined temperature.

18. The battery state-of-charge detecting apparatus of claim 17, wherein the internal impedance measuring unit corrects the corrected internal impedance of the predetermined temperature based on the state of charge calculated by the state-of-charge calculating unit to output a further corrected internal impedance.

19. The battery state-of-charge detecting apparatus of claim 17 or 18, further comprising a temperature sensor attached to the battery for detecting the temperature of the battery to output temperature data to the internal impedance measuring unit.

12. A battery state-of-charge detecting apparatus comprising:

internal impedance measuring unit for measuring an internal impedance of a battery;

voltage measuring unit for measuring a stable-state voltage of the battery; and

state-of-charge calculating unit for calculating out a state of charge of the battery by substituting the internal impedance measured by the internal impedance measuring unit into a function showing a relation between the stable-state voltage and the state of charge.

16. A battery state-of-charge detecting apparatus comprising:

internal impedance measuring unit for measuring an internal impedance of a battery;

voltage measuring unit for measuring a stable-state voltage of the battery;

data memory for storing matrix data of internal impedances and stable-state voltages associated with each of plurally divided state-of-charge ranges; and

state-of-charge calculating unit for calculating out a state of charge by specifying one of the state-of-charge ranges which includes the internal impedance measured by the internal impedance measuring unit and the stable-state voltage measured by the voltage measuring unit.