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

• US 20120265462A1
• Filed: 01/27/2012
• Published: 10/18/2012
• Est. Priority Date: 09/16/2005
• Status: Active Grant

• Current Assignee: Furukawa Electric Company Limited
• Original Assignee: Furukawa Electric Company Limited
• Inventors: IWANE, Noriyasu, FUJIMURA, Koji
• Granted Patent: US 9,091,739 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• 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 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.

2. The method of claim 1, 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.

3. The method of claim 2, 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.

4. The method of claim 3, 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.

5. The method of claim 4, 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.

6. The method of claim 4 or claim 5, wherein the functions f1(c), f2(c), . . . , g1(c), g2(c), . . . of the adjustment parameter c are respectively expressed by linear function of c.

7. The method of any one of claims 1 to 5, 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.

8. 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.

9. A power supply system comprising the apparatus for estimating the deterioration level or the discharge capability of the battery according to claim 8.