State of charge detection device

Patent metadata

Field	Value
Publication number	US-10429444-B2
Application number	US-201214343743-A
Country	US
Kind code	B2
Filing date	Sep 26, 2012
Priority date	Jan 31, 2012
Publication date	Oct 1, 2019
Grant date	Oct 1, 2019

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.

First claim

The invention claimed is:

1. A rechargeable battery system, comprising:
a rechargeable battery formed by a nickel-metal hydride battery;
an AC voltage source connected to the rechargeable battery, wherein the AC voltage source is configured to apply AC voltage at least at two frequencies;
an impedance analyzer connected to the rechargeable battery;
a processing unit configured to calculate a slope of a straight line or an approximate straight line which connects together two or more complex impedances of different frequencies in the diffusion region of the battery measured by the impedance analyzer, wherein the diffusion region defines a plot of complex impedances of the battery at frequencies lower than about 10 Hertz; and
a memory that preliminarily stores correlations between a slope and a state of charge, wherein the slope decreases as the state of charge increases,
wherein the processing unit changes a detection method of the state of charge of the battery between when the state of charge is less than or equal to a specific threshold value of 0 to 10% and when the state of charge exceeds the threshold value, such that the processing unit detects and outputs the state of charge of the battery by comparing the calculated slope and the correlations between the slope and the state of charge stored in the memory when the state of charge of the battery is less than or equal to the threshold value and detects and outputs the state of charge of the battery in another method without using the calculated slope; and
recycling the rechargeable battery based on the calculated state of charge.

2. The rechargeable battery system according to claim 1 , wherein the processing unit 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. The rechargeable battery system of claim 1 , wherein the diffusion region defines a plot of complex impedances of the battery, which includes a curved portion and a nearly-straight portion, at frequencies lower than a point of inflection of the nearly-straight portion.

4. The rechargeable battery system of claim 1 , wherein the correlations include correlations of slope angles in the diffusion region of the complex impedances with respect to the state of charge.

5. A hybrid or electric vehicle, comprising the rechargeable battery system of claim 1 .

Assignees

• Primearth Ev Energy Co Ltd

Inventors

• KOBA Daisuke
• Takeda Sachio
• Maegawa Katsunori
• Osaka Tetsuya

Classifications

• H02J7/947

  in response to integrated charge or discharge current · CPC title

• H01M10/48

  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 title

• G01R31/392

  Determining battery ageing or deterioration, e.g. state of health · CPC title

• G01R31/3648 Primary

  comprising digital calculation means, e.g. for performing an algorithm · CPC title

• G01R31/367

  Software therefor, e.g. for battery testing using modelling or look-up tables · CPC title