STATE OF CHARGE DETECTION DEVICE

• US 20140229130A1
• Filed: 09/26/2012
• Published: 08/14/2014
• Est. Priority Date: 01/31/2012
• Status: Active Grant

• Current Assignee: Primearth EV Energy Company Limited (Toyota Motor Corporation)
• Original Assignee: Primearth EV Energy Company Limited (Toyota Motor Corporation)
• Inventors: Takeda, Sachio, Maegawa, Katsunori, Koba, Daisuke, Osaka, Tetsuya
• Granted Patent: US 10,429,444 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• 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
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H02J 7/00716 in response to integrated charge or discharge current
• CPC Class Codes: H02J 7/04 Regulation of charging current or voltage
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

The present invention pertains to the detection of the state of charge of a battery, whereby the complex impedance in the diffusion region of the battery is used. An arithmetic device such as a computer determines the slope of the complex impedance at least two different frequencies in the diffusion region of a rechargeable battery when a straight-line approximation has been made. The state of charge of the rechargeable battery is detected by using the slope that has been determined, and the relationship between the state of charge and slopes that have been stored in advance in a storage means.

Claims

1. A device for detecting a state of charge of a battery, comprising:

measurement means for measuring complex impedances in a diffusion region of the battery;

detection means for calculating a slope of a straight light or an approximate straight line which connects together two complex impedances or more of different frequencies in the diffusion region of the battery measured by the measurement means; and

storage means that preliminarily stores correlations between a slope and a state of charge, wherein the detection means detects the state of charge of the battery by use of the calculated slope and the correlations between the slope and the state of charge stored in the storage means.

2. The device for detecting a state of charge of a battery according to claim 1, wherein the detection means calculates the slope of the straight line or the approximate straight line that connects together the two complex impedances or more of different frequencies by use of a two-dimensional plane which employs a real-axis component and an imaginary-axis component for axes.

3. A device for detecting a state of charge of a battery comprising:

measurement means for measuring a complex impedance, in a diffusion region of the battery, whose frequency is identical with a frequency of a reference complex impedance which is a complex impedance in a diffusion region of a base battery that serves as a reference on occasion of comparison of the battery;

detection means for detecting a distance between the reference complex impedance and the complex impedance measured by the measurement means; and

storage means that preliminarily stores correlations between a distance and a state of charge, wherein

the detection means detects the state of charge of the battery by use of the calculated distance and the correlations between the distance and the state of charge stored in the storage means.

4. The device for detecting a state of charge of a battery according to claim 3, wherein the detection means detects a distance between the reference complex impedance and the complex impedance measured by the measurement means by use of a two-dimensional plane which employs a real-axis component and an imaginary-axis component for axes.

5. The device for detecting a state of charge of a battery according to claim 3, wherein the detection means detects a slope of a straight line that connects together the reference complex impedance and the complex impedance measured by the measurement means and also a distance between the reference complex impedance and the complex impedance measured by the measurement means;

the storage means preliminarily stores correlations between a slope and a state of charge as well as correlations between a distance and a state of charge; and

the detection detects the state of charge of the battery by use of the calculated slope and the correlations between the slope and the state of charge stored in the storage means as well as the calculated distance and the correlations between the distance and the state of charge stored in the storage means.

6. The device for detecting a state of charge of a battery according to claim 5, wherein the detection means calculates the slope of a straight line that connects the reference complex impedance to the complex impedance measured by the measurement means, by use of a two-dimensional plane that employs a real-axis component and an imaginary-axis component for axes.