METHOD AND DEVICE FOR DETERMINING STATE OF BATTERY, AND BATTERY POWER SUPPLY SYSTEM THEREWITH

• US 20080120050A1
• Filed: 11/05/2007
• Published: 05/22/2008
• Est. Priority Date: 11/21/2006
• Status: Active Grant

• Current Assignee: Furukawa Electric Company Limited
• Original Assignee: Furukawa Electric Company Limited
• Inventors: MORII, Keisuke, CHIKAZAWA, Keiko, IWANE, Noriyasu
• Granted Patent: US 7,593,823 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• 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
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health

Abstract

Coefficients A and B are calculated from the measured temperature and the measured state of charge. Next, a response voltage Vc is calculated by substituting the measured internal impedance X into a response-voltage correlation equation. Besides, by comparing the response voltage Vc with a predetermined threshold V0, if Vc is bigger than or equal to V0, the battery is determined as normal. By substituting the measured values of internal impedance, temperature, and SOC into the internal impedance calculation formula, a final internal impedance calculation formula is determined by calculating the value of C by an iterating operation. Next, in the case of determining SOH of a battery, by substituting a standard temperature and a standard SOC into the final internal impedance calculation formula, the internal impedance to determine the SOH is calculated. By comparing the internal impedance with SOH determination threshold, the SOH of the battery is determined.

Claims

1. A method for determining state of a battery by estimating response voltage when a predetermined discharge current pattern is applied, to determine SOF (State Of Function) or SOH (State Of Health) of a battery, comprising the steps of:

preparing in advance a prescribed correlative equation, a plurality of coefficients of which are given by functions of the temperature and the SOC (State Of Charge) of the battery, which calculates the response voltage when the predetermined discharge current pattern is applied, by using the measured value of either the internal impedance or the internal resistance of the battery;

determining the values of the coefficients by measuring the temperature and the SOC of the battery;

substituting the measured value of either the internal impedance or the internal resistance in the correlative equation with the values of the coefficients incorporated to calculate the response voltage when the predetermined discharge current pattern is applied; and

determining the SOF and the SOH of the battery based on the response voltage thus calculated.

2. The method according to claim 1, wherein the correlative equation is expressed in at least one of a polynomial function, an exponential function, and a reciprocal function.

3. The method according to claim 1, wherein the coefficients of the correlative equation are expressed in at least one of a polynomial function, an exponential function, and a reciprocal function of the temperature and the SOC.

4. The method according to claim 1, wherein the coefficients of the correlative equation are expressed in functions of the temperature, and the coefficients of the functions of the temperature are expressed in functions of the SOC.

5. The method according to claim 4, wherein the functions of the temperature or the functions of the SOC comprise at least one of a polynomial function, an exponential function, and a reciprocal function.

6. The method according to claim 1, wherein the coefficients of the correlative equation are expressed in functions of the SOC, and the coefficients of the functions of the SOC are expressed in functions of the temperature.

7. The method according to claim 6, wherein the functions of the SOC or the function of the temperature comprise at least one of a polynomial function, an exponential function, and a reciprocal function.

8. A device for monitoring state of a battery, the device comprising:

an internal impedance measurement unit configured to measure either internal impedance or internal resistance of a battery;

a temperature sensor configured to measure temperature of the battery;

an SOC sensor configured to measure SOC of the battery; and

a controller in which a prescribed correlative equation is memorized in advance, a plurality of coefficients of which are given by functions of temperature and SOC (State Of Charge) of the battery, which calculates the response voltage when a predetermined discharge current pattern is applied, by using a measured value of either internal impedance or internal resistance of the battery, the values of the coefficients is determined by measuring the temperature and the SOC of the battery, the measured value of either the internal impedance or the internal resistance is substituted in the correlative equation with the values of the coefficients incorporated to calculate the response voltage when the predetermined discharge current pattern is applied, and the SOF and the SOH of the battery are determined based on the response voltage value thus calculated.

9. A battery power supply system including the battery and the device for monitoring a battery state according to claim 8.

10. A method for determining a battery state, comprising the steps of:

preparing in advance a calculation formula to calculate internal resistance or internal impedance of a battery expressed by a predetermined function including at least one of a polynomial function, an exponential function, and a reciprocal function of temperature and SOC, a plurality of coefficients thereof being functions of one specified parameter;

obtaining respective measured values by simultaneously measuring one of the internal resistance and the internal resistance, as well as the temperature and the SOC of the battery;

calculating the specified parameter value by substituting the respective measured values into the calculation formula;

determining the coefficients from the calculated specified parameter value;

substituting the predetermined temperature and the predetermined SOC in a complete calculation formula using determined coefficients to estimate either the internal resistance or the internal impedance; and

applying either the estimated internal resistance or the estimated internal impedance as an index to determine the SOH of the battery.

11. The method according to claim 10, wherein as the predetermined temperature and the predetermined SOC, a standard temperature and a standard SOC for determining the SOH of the battery are used.

12. The method according to claim 10, wherein the temperature and the SOC at a time when the SOF of the battery is determined are used as the predetermined temperature and the predetermined SOC.

13. The method according to claim 10, wherein the calculation formula for calculating either the internal resistance or the internal impedance is expressed by first function including at least one of a polynomial function, an exponential function, and a reciprocal function of the temperature, and at the same time at least one of the coefficients of the first function is expressed by second function including at least one of a polynomial function, an exponential function, and a reciprocal function of the SOC, and further a plurality of coefficients of the first function and the second function are expressed by functions of the specified parameter.

14. The method according to claim 10, wherein the calculation formula for calculating either the internal resistance or the internal impedance is expressed by third function including at least one of a polynomial function, an exponential function, and reciprocal function of the SOC, and at the same time at least one coefficient of the third function is expressed by forth function including at least one of a polynomial function, an exponential function, and a reciprocal function of the temperature, and further a plurality of coefficients of the third function and the fourth function are expressed by functions of the specified parameter.

15. A device for determining state of a battery by estimating either internal resistance or internal impedance of a battery at the predetermined temperature and the predetermined SOC, and applying either the estimated internal resistance or the estimated internal impedance as an index to determine the state of a battery, the device comprising:

an internal impedance measurement unit configured to measure either an internal impedance or an internal resistance of a battery;

a temperature sensor configured to measure the temperature of the battery;

an SOC sensor configured to measure the SOC of the battery; and

a controller configured to prepare in advance and store a calculation formula for calculating either the internal resistance or the internal impedance expressed by a function including at least one of a polynomial function, an exponential function, and a reciprocal function of the temperature and the SOC with a plurality of coefficients thereof expressed by functions of one specified parameter, input respective measured values of either the internal resistance or the internal impedance, as well as the temperature and the SOC which are simultaneously measured by the internal impedance measurement unit, the temperature sensor and the SOC sensor, substitute the measured values of either the internal resistance or the internal impedance, as well as the temperature and the SOC in the calculation formula to calculate the specified parameter, and substitute the predetermined temperature and the predetermined SOC in a complete calculation formula using the coefficients determined from the calculated specified parameter to estimate either the internal resistance or the internal impedance.

16. The device according to claim 15, wherein the controller, using a standard temperature and a standard SOC as the predetermined temperature and the predetermined SOC for determining the SOH of the battery, is configured to substitute the standard temperature and the standard SOC in the complete calculation formula to estimate either the internal resistance or the internal impedance, and apply either the estimated internal resistance or the estimated internal impedance as an index to determine the SOH of the battery.

17. The device according to claim 15, wherein the controller, using the temperature and the SOC at the time when the SOF of the battery is measured as the predetermined temperature and the predetermined SOC, is configured to substitute the temperature and the SOC at the time when SOF of the battery is measured in the complete calculation formula to estimate the internal resistance or the internal impedance, and apply the estimated internal resistance or the internal impedance as an index to determine the SOF of the battery.

18. The device according to claim 15, wherein the controller is configured to use a calculation formula for calculating either the internal resistance or the internal impedance expressed by first function including at least one of a polynomial function, an exponential function, and a reciprocal function of the temperature, and at least one of a plurality of coefficients of the first function is expressed by second function including at least one of a polynomial function, an exponential function, and a reciprocal function of the SOC, and further a plurality of coefficients of the first function and the second function are expressed by functions of the specified parameter.

19. The device according to claim 15, wherein the controller configured to use a calculation formula calculating either the internal resistance or the internal impedance expressed by third function including at least one of a polynomial function, an exponential function, and a reciprocal function of the SOC, and at least one of a plurality of coefficients of the third function is expressed by forth function including at least one of a polynomial function, exponential function, and reciprocal function of the temperature, and further a plurality of coefficients of the third function and the forth function are expressed by functions of the specified parameter.

20. A battery power supply system including the device for determining state of a battery according to claim 15.