APPARATUS AND METHOD FOR DETECTING CHARGED STATE OF ELECTRIC STORAGE DEVICE

• US 20100023285A1
• Filed: 02/13/2008
• Published: 01/28/2010
• Est. Priority Date: 04/19/2007
• Status: Active Grant

• Current Assignee: Panasonic EV Energy Company, Limited (Toyota Motor Corporation)
• Original Assignee: Panasonic EV Energy Company, Limited (Toyota Motor Corporation)
• Inventors: Nakanishi, Toshiaki
• Granted Patent: US 8,521,458 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• 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

Provided is an apparatus for detecting state of charge (SOC) of a battery. A voltage of a battery pack (100) is detected by voltage sensors (120-1) to (120-n). A determining unit (160) samples currents at times when the battery voltage reaches predetermined threshold voltages (Vth1, Vth2) respectively, and calculates an open end voltage (Vocv), based on representative values (I1, I2) of the sampled currents and threshold voltages (Vth1, Vth2). Furthermore, based on a correspondence relationship between the voltage (Vocv) and the state of charge (SOC) which is determined in advance, the state of charge (SOC) that corresponds to the calculated voltage (Vocv) is calculated.

Claims

1. A device which detects a state of charge of an electric storage device, comprising:

a measuring unit which measures a first current value at a time when a voltage of the electric storage device becomes equal to a first predetermined voltage and a second current value at a time when the voltage of the electric storage device becomes equal to a second predetermined voltage; and

a detecting unit which detects the state of charge of the electric storage device based on the measured first current value and the measured second current value.

2. The detecting device of state of charge of electric storage device according to claim 1, wherein

the detecting unit comprises:

a unit which calculates a first representative current value through a predetermined statistical process based on a plurality of the measured first current values and calculates a second representative current value through a predetermined statistical process based on a plurality of the measured second current values;

a unit which calculates an open end voltage of the electric storage device based on the calculated first representative current value, the calculated second representative current value, the first predetermined voltage, and the second predetermined voltage;

a unit which stores, in advance, a correspondence relationship between an open end voltage and a state of charge; and

a unit which calculates a state of charge corresponding to the calculated open end voltage based on the calculated open end voltage and the correspondence relationship.

5. The detecting device of state of charge of electric storage device according to claim 1, wherein

the measuring unit measures a current value having a time lag of within 100 msec as the current values at the times when the voltage of the electric storage device becomes equal to the first predetermined voltage and the second predetermined voltage.

6. The detecting device of state of charge of electric storage device according to claim 2, wherein

the unit which calculates the first representative current value and the second representative current value extracts, among the plurality of measured first current values and the plurality of measured second current values, only current values within a certain range, and calculates the first representative current value and the second representative current value through the predetermined statistical process.

3. A method of detecting a state of charge of an electric storage device, comprising the steps of:

measuring a first current value at a time when a voltage of the electric storage device becomes equal to a first predetermined voltage and a second current value at a time when the voltage of the electric storage deice becomes equal to a second predetermined voltage; and

detecting the state of charge of the electric storage device based on the measured first current value and the measured second current value.

4. A computer-readable recording medium storing a computer program for detecting a state of charge of an electric storage device, which, when executed, causes a computer to execute a process comprising:

measuring a first current value at a time when a voltage of the electric storage device becomes equal to a first predetermined voltage;

measuring a second current value at a time when the voltage of the electric storage device becomes equal to a second predetermined voltage;

sequentially storing the measured first current value and the measured second current value in a memory;

instructing a calculating unit to calculate a first representative current value through a predetermined statistical process based on a plurality of the first current values stored in the memory and to calculate a second representative current value through a predetermined statistical process based on a plurality of the second current values;

instructing the calculating unit to calculate an open end voltage based on the first representative current value and the second representative current value obtained through the calculation; and

accessing a storage device which stores, in advance, a correspondence relationship between an open end voltage and a state of charge, to search for a state of charge corresponding to the open end voltage obtained through the calculation.

7. A device which detects a state of charge of an electric storage device, comprising:

a measuring unit which measures a first current value, a second current value, and a third current value at times when a voltage of the electric storage device becomes equal to a first predetermined voltage, a second predetermined voltage, and a third predetermined voltage, respectively; and

a detecting unit which detects the state of charge of the electric storage device based on the measured first current value, the measured second current value, and the measured third current value, wherein

the detecting unit comprises;

a unit which calculates a first representative current value through a predetermined statistical process based on a plurality of the measured first current values, calculates a second representative current value through a predetermined statistical process based on a plurality of the measured second current values, and calculates a third representative current value through a predetermined statistical process based on a plurality of the measured third current values;

a unit which calculates an open end voltage of the electric storage device based on the calculated first representative current value, the calculated second representative current value, the calculated third representative current value, the first predetermined voltage, the second predetermined voltage, and the third predetermined voltage;

a unit which stores, in advance, a correspondence relationship between an open end voltage and a state of charge; and

a unit which calculates a state of charge corresponding to the calculated open end voltage based on the calculated open end voltage and the correspondence relationship, and

the unit which calculates the first representative current value, the second representative current value, and the third representative current value calculates the representative current value based only on a plurality of current values, among the plurality of measured first current values, the plurality of measured second current values, and the plurality of measured third current values, having a degree of distribution of a certain value or less.

8. A device which detects a state of charge of an electric storage device, comprising:

a measuring unit which measures a current value at a time when a voltage of the electric storage device becomes equal to a predetermined voltage; and

a detecting unit which detects a state of charge of the electric storage device based on the measured current value.

9. The detecting device of state of charge of electric storage device according to claim 8, wherein

the detecting unit comprises:

a unit which calculates a representative current value through a predetermined statistical process based on a plurality of the measured current values;

a unit which stores, in advance, a correspondence relationship between a representative current value and a state of charge; and

a unit which calculates a state of charge corresponding to the calculated representative current value based on the correspondence relationship.