METHOD AND APPARATUS FOR DETERMINING DETERIORATION OF SECONDARY BATTERY, AND POWER SUPPLY SYSTEM THEREWITH

• US 20080204031A1
• Filed: 03/17/2008
• Published: 08/28/2008
• Est. Priority Date: 09/16/2005
• Status: Active Grant

• Current Assignee: Furukawa Electric Company Limited
• Original Assignee: Furukawa Electric Company Limited
• Inventors: Watanabe, Yuichi, KIMURA, Atsushi, IWANE, Noriyasu, FUJIMURA, Koji, IWAHANA, Fumikazu, SATO, Toshiyuki, IlJIMA, Takashi
• Granted Patent: US 7,626,394 B2
• Time in Patent Office: Days
• US Class Current: 324/430
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• 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

A method for detecting SOC and SOH of a storage battery includes: calculating an SOC value of the storage battery with use of an SOC calculation unit based on a measured voltage value or a measured current value of the storage battery and calculating an SOH value of the storage battery with use of an SOH calculation unit based on the SOC value; further calculating a new SOC value with use of the SOC calculation unit based on the SOH value and calculating a new SOH value with use of the SOH calculation unit based on the new SOC value, these further calculations of SOC value and SOH value being repeated a prescribed n times of at least one so as to obtain an nth calculated SOC value and an nth calculated SOH value; outputting the nth calculated SOH value as an SOH output value and outputting the nth calculated SOH value as an SOC output value; and storing the SOH output value into a memory.

Claims

1. A method for detecting SOC and SOH of a storage battery comprising:

calculating an SOC value of the storage battery with use of an SOC calculation unit based on a measured voltage value or a measured current value of the storage battery and calculating an SOH value of the storage battery with use of an SOH calculation unit based on the SOC value;

further calculating a new SOC value with use of the SOC calculation unit based on the SOH value and calculating a new SOH value with use of the SOH calculation unit based on the new SOC value, these further calculations of SOC value and SOH value being repeated a prescribed n times of at least one so as to obtain an nth calculated SOC value and an nth calculated SOH value;

outputting the nth calculated SOH value as an SOH output value and outputting the nth calculated SOC value as an SOC output value; and

storing the SOH output value into a memory.

2. The method of claim 1, wherein the SOC output value is also stored in the memory.

3. The method of claim 1 or claim 2, wherein the SOC calculation is repeated until the new SOH value converges to a specified range.

4. The method of any one of claims 1 to 3, wherein a first calculated SOC value firstly obtained with use of the SOC calculation unit is obtained by correcting the measured voltage value or the measured current value based on either one of an initial SOH value set in advance and a previous SOH output value lastly stored in the memory.

5. The method of any one of claims 1 to 3, wherein the SOH calculation unit calculates the SOH value by correcting a measured internal impedance value of the storage battery based on the SOC value.

6. The method of claim 5, wherein the measured internal impedance value at a measurement temperature of the storage battery is corrected to a internal impedance value at a specified temperature.

7. The method of any one of claims 1 to 6, wherein the SOC calculation unit calculates the SOC value by substituting one of:

a measured value of an open-circuit voltage (OCV) of the storage battery; and

a corrected value obtained by correcting the measured value of the OCV based on an initial SOH value or a newest SOH value, into a functional expression.

8. The method of any one of claims 1 to 5, wherein the SOC calculation unit calculates a change in the SOC value based on a discharge current or a charge current of the storage battery, corrects the change in the SOC value in accordance with SOH value, and adds the corrected change in the SOC value to the SOC value obtained in the previous calculation so as to calculate the new SOC value.

9. The method of any one of claims 1 to 8, wherein, when the SOH output values in the memory three times or more are stored, a slope of the change of the SOH output values with respect to a number of the storing is determined, and

if the last stored SOH output value falls within an allowable range, the last stored SOH output value stored in the memory is decided as a true value, while if the last stored SOH output value is out of the allowable range, the last stored SOH output value is deleted from the memory, and then, a new SOC output value and a new SOH output value are determined through the measurement and/or calculation.

10. The method of any one of claims 1 to 8, wherein, when the SOH output values in the memory three times or more are stored, a slope of the change of the SOH output values with respect to a number of the storing is determined, and

if the last stored SOH output value is out of the allowable range, an alert is issued.

11. An apparatus for detecting SOC and SOH of a storage battery comprising:

an SOC calculation unit configured to;

execute a first calculation of an SOC value of the storage battery based on a measured voltage value or a measured current value of the storage battery;

execute a second calculation of an SOC value by correcting the measured voltage value or the measured current value of the storage battery in accordance with an SOH value of the storage battery;

repeat the second calculation a prescribed n times of at least two; and

output an nth calculated SOC value as an SOC output value;

an SOH calculation unit configured to;

repeatedly calculate an SOH value of the storage battery based on the calculated SOC value the prescribed n times corresponding to a repeat number of the SOC calculation; and

output an nth calculated SOH value as an SOH output value; and

a memory for storing at least a plurality of the SOH output values among the SOH and SOC output values, respectively obtained in the nth calculation.

12. The apparatus of claim 11, further comprising a control unit configured to:

determine a slope of a change of the SOH output values with respect to a number of the storing times in the memory when the SOH output value is stored in the memory three times or more;

decide a newest SOH output value as a true value if the newest stored SOH output value of the stored values falls within an allowable range; and

delete the newest SOH output value and obtain again an SOC output value and an SOH output value through the measurement and/or the calculation if the newest SOH output value is out of the allowable range.

13. A method for determining SOH of a secondary battery according to an internal impedance or an internal resistance of the secondary battery supplying power to a load, comprising:

preparing in advance a specified temperature characteristic function which contains at least one exponential terms and one adjustment parameter and expresses a temperature dependency of the internal impedance or the internal resistance;

calculating the internal impedance or the internal resistance based on a measured current value or a measured voltage value at the time when the secondary battery is charged or discharged with a specified current;

determining a value of the adjustment parameter by substituting the measured temperature at the time when the secondary battery is charged or discharged with the specified current and the calculated internal impedance or the internal resistance to the temperature characteristic function;

calculating a reference internal impedance or a reference internal resistance by substituting the determined adjustment parameter value and a specified reference temperature into the temperature characteristic function; and

determining the SOH of the secondary battery based on the calculated reference internal impedance or the calculated reference internal resistance.

14. The method of claim 13, wherein the temperature characteristic function is expressed by:

Z(Temp) or R(Temp)=f(C)×

exp{g(C)/Temp}+C

where Z is the internal impedance, R is the internal resistance, C is the adjustment parameter, and f and g express a specified function respectively.

15. The method of claim 13 or claim 14, further comprising:

setting in advance a first threshold for determining the SOH based on the reference internal impedance and a second threshold for determining the SOH based on the reference internal resistance, respectively;

judging which of the reference internal impedance and the first threshold is high when the reference internal impedance was calculated, and judging which of the reference internal resistance and the second threshold is high when the reference internal resistance was calculated; and

determining the SOH of the secondary battery based on either of two judged results.

16. The method of any one of claims 13 to 15, wherein the internal impedance is calculated based on the measured current value and the measured voltage value at the time when the secondary battery is charged or discharged at an AC of 100 Hz or more frequency as the specified current.

17. The method of any one of claims 13 to 15, wherein the secondary battery is charged or discharged with a pulse current as the specified current, and the internal resistance is calculated based on measured values of the current and voltage measured within 10 ms of starting the charge or discharge.

18. An apparatus for determining an SOH of a secondary battery based on an internal impedance or an internal resistance of the secondary battery supplying power to a load, comprising:

a charging circuit for charging the secondary battery with a specified current;

a discharging circuit for discharging the secondary battery with a specified current;

a current sensor for measuring a current of the secondary battery;

a voltage sensor for measuring a voltage of the secondary battery;

a temperature sensor for measuring a temperature of the secondary battery; and

a control unit configured to;

(i) receive a measured current value, a measured voltage value, and a measured temperature value from the current sensor, the voltage sensor, and the temperature sensor, respectively, at the time when the secondary battery is charged or discharged with the specified current by the charging circuit or the discharging circuit;

(ii) calculate the internal impedance or the internal resistance based on the measured current value and the measured voltage value;

(iii) determine a value of a adjustment parameter by substituting the calculated internal impedance or the calculated internal resistance and the measured temperature into a temperature characteristic function which contains at least one exponential terms and one adjustment parameter and expresses a temperature dependency of the internal impedance or the internal resistance;

(iv) calculate a reference internal impedance or a reference internal resistance by substituting the decided adjustment parameter value and a specified reference temperature into the temperature characteristic function; and

(v) determine an SOH of the secondary battery based on the calculated reference internal impedance or the calculated reference internal resistance.

19. The apparatus of claim 18, further comprising:

a storage unit storing in advance a first threshold for determining deterioration based on the reference internal impedance, and a second threshold for determining deterioration based on the reference internal resistance,

wherein the control unit compares the reference internal impedance and the first threshold read out from the storage unit when the reference internal impedance was calculated, compares the reference internal resistance and the second threshold read out from the storage unit when the reference internal resistance was calculated, and determines the SOH of the secondary battery based on either of two comparison results.

20. The apparatus of claim 19,

wherein the storage unit stores a charge or discharge selection signal to select either the charge or the discharge of the secondary battery with the specified current, and

the control unit reads the charge or discharge selection signal from the storage unit and outputs a specified instruction signal to the charging circuit or the discharging circuit based on the charge or discharge selection signal.

21. The apparatus of claim 19 or claim 20,

wherein the storage unit stores a DC or AC selection signal to designate either an AC of 100 Hz or more frequency or a pulse current as the specified current, and

the control unit reads the DC or AC selection signal from the storage unit and selects either the AC of 100 Hz or more frequency or the pulse current in accordance with the DC or AC selection signal so as to output a specified control signal to the charging circuit or the discharging circuit.

22. The apparatus of claim 21,

wherein the storage unit stores at least one of a frequency of the AC and a pulse width of the pulse current, and

the control unit reads at least one of the frequency of the AC and the pulse width of the pulse current from the storage unit and sets at least one of the frequency of the AC and the pulse width of the pulse current in the charging circuit or the discharging circuit at the same time as or prior to the output of the specified control signal for the charging circuit or the discharging circuit.

23. A power supply system comprising the apparatus for determining an SOH of a secondary battery according to any one of claims 18 to 22.

24. The power supply system of claim 23, further comprising a display unit for display a determination result of the SOH of the secondary battery by receiving the result from the apparatus for determining an SOH of a secondary battery.

25. The power supply system of claim 23 or claim 24, further comprising an input unit for changing data stored in the storage unit,

wherein at least one or all of the first threshold for the determination, the second threshold for the determination, the charge or discharge selection signal, the DC or AC selection signal, the frequency of the AC, and the pulse width of the pulse current can be changed with the input unit.

26. A method for estimating a deterioration level or a discharge capability of a battery by comparing an impedance of the battery with a predetermined allowable range thereof, the method comprising:

measuring a current and a voltage of the battery;

calculating an impedance Za of the battery from the measured current value and the measured voltage value and calculating a superimposed DC component IDCa from the measured current value; and

estimating an impedance Zb of the case when a reference direct current IDCb value is superimposed, from the calculated impedance Za value and the calculated superimposed DC component IDCa value, based on a predetermined relational expression between a superimposed direct current IDC and a impedance Z so as to determine the deterioration level or a discharge capability of the battery.

27. The method of claim 26, wherein, in the relational expression between the superimposed direct current IDC and the impedance Z, the impedance Z is expressed by a function including at least one exponential term of the superimposed direct current IDC.

28. The method of claim 27, wherein the relational expression between the superimposed direct current IDC and the impedance Z is expressed by:

Z=a1×

exp(−

IDC/b1)+a2×

exp(−

IDC/b2)+ . . . +c.

29. The method of claim 28, wherein the coefficients a1, a2, . . . , b1, b2, . . . of the relational expression between the superimposed direct current IDC and the impedance Z are given by functions f1(c), f2(c), . . . , g1(c), g2(c), . . . , of one adjustment parameter c, respectively.

30. The method of claim 29, wherein a value of the adjustment parameter c is determined so that, when substituting the calculated superimposed DC component IDCa value into the direct current IDC of the relational expression, the impedance Z of the relational expression agrees with the calculated impedance Za.

31. The method of claim 29 or claim 30, wherein the functions f1(c), f2(c), . . . , g1(c), g2(c), . . . of the adjustment parameter c are respectively expressed by linear function of c.

32. The method of any one of claims 26 to 31, wherein the calculated superimposed DC component IDCa value is obtained by performing any of moving average operation, Fourier transfer operation, and Kalman filter operation on the measured current value.

33. An apparatus for estimating a deterioration level or a charge capability of a battery based on an impedance of the battery, comprising:

a current sensor for measuring a current of the battery;

a voltage sensor for measuring a voltage of the battery; and

a control unit configured to;

(i) receive a measured current value and a measured voltage value from the current sensor and the voltage sensor, respectively;

(ii) calculate a impedance Za of the battery from the measured current value and the measured voltage value and calculate a superimposed DC component IDCa from the measured current value;

(iii) estimate an impedance Zb of the case when a reference direct current IDCb value is superimposed, from the calculated impedance Za value and the calculated superimposed DC component IDCa value, based on a predetermined relational expression between a superimposed direct current IDC and a impedance Z so as to determine the deterioration level or a discharge capability of the battery.

34. A power supply system comprising the apparatus for estimating the deterioration level or the discharge capability of the battery according to claim 33.