Self-diagnosis system for an energy storage device

• US 20040232884A1
• Filed: 06/16/2004
• Published: 11/25/2004
• Est. Priority Date: 05/25/2001
• Status: Active Grant

• Current Assignee: Bathium Canada Inc. (Bolloré SE)
• Original Assignee: Avestor (Bolloré SE)
• Inventors: Choquette, Yves, Parent, Michel, Geoffroy, Sebastien, Richard, Monique, Potvin, Estelle, Lague, Frederic, Vaillancourt, Jean-Pierre
• Granted Patent: US 6,956,355 B2
• Time in Patent Office: Days
• US Class Current: 320/132
• CPC Class Codes: G01R 31/364 Battery terminal connectors with integrated measuring arrangements
• 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 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/005 Detection of state of health [SOH]
• CPC Class Codes: H02J 9/06 with automatic change-over , e.g. UPS systems
• CPC Class Codes: H02J 9/061 for DC powered loads
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A self-diagnosis system for an energy storage device, the latter including a plurality of electrochemical cells connected in series or parallel to form a cell string. The self-diagnosis system correlates a state of health of the battery based on the internal resistance value of each electrochemical cell of the energy storage device and determines a corresponding battery initial capacity which enables the self-diagnosis system to evaluate the exact capacity of the battery at any given time.

Claims

1. - A self-diagnosis system for an energy storage device, the energy storage device including a plurality of electrochemical cells forming a cell string, said system comprising:

a. a current source providing a constant current;

b. a cell selector switch operative to select a particular one of the electrochemical cells within the cell string;

c. a voltage measurement means for measuring an initial voltage and a second voltage of said particular cell;

d. a processing unit coupled to said voltage measurement means, said processing unit operative to calculate an internal resistance of said particular cell on a basis of the constant current value and the initial and second voltages;

e. said electronic self-diagnosis system capable to determine a state of health of said energy storage device on the basis of the internal resistance of each cell of said cell string.

2. - A system as defined in claim 1, wherein said processing unit includes a memory for storing data representative of electrochemical cell capacity fade as a function of internal resistance, said processing unit correlating the highest calculated internal resistance of the cell string to a corresponding state of health value stored in said memory to define an overall state of health of said energy storage device.

3. - An energy storage device comprising a housing, a plurality of electrochemical cells each having a positive, a negative electrode and an electrolyte separator therebetween;

said plurality of electrochemical cells connected in series or parallel to form a cell string within said housing; and

an electronic self-diagnosis system comprising a processing unit, a current source, a voltage measurement means, a cell selector switch adapted to select a single electrochemical cell within said cell string;

said electronic self-diagnosis system measuring an internal resistance of each cell of said cell string, one cell at a time, to determine a state of health of said energy storage device;

wherein said cell selector switch selects a first cell of said cell string, said voltage measurement means measures an initial voltage and a second voltage of said selected cell, said current source provides a constant current;

the constant current value, the initial and second voltage measurement being processed by said processing unit wherein said processing unit calculates the internal resistance of said selected cell using on Ohmn'"'"'s law, said processing unit further comprising a memory for storing electrochemical cell'"'"'s capacity fade as a function of its internal resistance, said processing unit correlating the highest calculated internal resistance of said cell string to a corresponding state of health value stored in said memory to define an overall state of health of said energy storage device.

4. - An energy storage device as defined in claim 3 wherein said current source provides a small charge at constant current to said selected cell.

5. - An energy storage device as defined in claim 4 wherein a resulting increase in voltage of said selected cell is measured at a predetermined time after said small charge at constant current is applied.

6. - An energy storage device as defined in claim 4 wherein after said small charge at constant current, a voltage relaxation occurs and provokes a drop in voltage within said selected cell, wherein said voltage drop is measured by said voltage measurement means at a predetermined time for calculation of the internal resistance of said selected cell.

7. - An energy storage device as defined in claim 3 wherein said current source provides a small discharge of said selected cell at constant current

8. - An energy storage device as defined in claim 7 wherein a resulting decrease in voltage of said selected cell is measured at a predetermined time after said small discharge at constant current is applied.

9. - An energy storage device as defined in claim 7 wherein after said small discharge at constant current, a voltage relaxation occurs and provokes a bump in voltage within said selected cell, wherein said voltage bump is measured by said voltage measurement means at a predetermined time for calculation of the internal resistance of said selected cell.

10. - An energy storage device as defined in claim 3 wherein said electronic self-diagnosis system further comprises an external link through which said extrapolated overall state of health may be transferred to a remote monitoring system and through which data or commands may be received from a remote system.

11. - An energy storage device as defined in claim 3 wherein said-processing unit selects from said memory an initial capacity corresponding to said overall state of health of said energy storage device, said processing unit determines a state of charge of said energy storage device by measuring energy flowing in or out of said energy storage device and adding or subtracting said energy from said state of charge to determine an exact capacity of said energy storage device.

12. - An energy storage device as defined in claim 11 wherein said energy flowing in is calculated as a current drawn from said energy storage device over time during a discharge, said energy flowing out is calculated as a current received by said energy storage device over time during a charge, said measured energy representative of the area under a corresponding discharge curve.

13. - An energy storage device as defined in claim 12 wherein said processing unit evaluates a remaining time the energy storage device can provide energy based on said corresponding discharge curve for a measured instantaneous rate of discharge.

14. - An energy storage device as defined in claim 3 wherein said electronic self-diagnosis system further comprises a cell selector sequencer, a current source processor, a bi-directional current source, a voltage cell signal processor, a current signal processor, and an A/D signal conversion unit adapted to transform analog signals into readable digital signals for processing unit.

15. - An energy storage device as defined in claim 7 wherein said small discharge is routed into an application to which said energy storage device is connected to reduce energy waste by internal resistance measurements.

16. - An energy storage device comprising a housing, a plurality of electrochemical cells each having a positive, a negative electrode and an electrolyte separator therebetween;

said plurality of electrochemical cells connected in series or parallel to form a cell string within said housing; and

an electronic self-diagnosis system;

said electronic self-diagnosis system correlating a measured internal resistance of said cell string to a state of health value representative of a capacity fade of said cell string;

said electronic self-diagnosis system selecting an initial capacity of said energy storage device corresponding to said state of health value;

said electronic self-diagnosis system monitoring a state of charge of said energy storage device by measuring, energy flowing in or out of said energy storage device and adding or subtracting said energy to determine an exact battery capacity.

17. - An energy storage device as defined in claim 16 wherein said energy flowing in is calculated as a current drawn from said energy storage device over time during a discharge, said energy flowing out is calculated as a current received by said energy storage device over time during a charge, said measured energy representative of the area under a corresponding discharge curve.

18. - An energy storage device as defined in claim 17 wherein said electronic self-diagnosis system measures said internal resistance of each electrochemical cells of said cell string, one cell at a time, by selecting a first cell of said cell string, measuring an initial voltage and a second voltage for a constant current;

the constant current value, the initial and second voltage measurement being processed by said electronic self-diagnosis system wherein said electronic self-diagnosis system calculates the internal resistance of said selected cell using on Ohm'"'"'s law, said electronic self-diagnosis system further comprising a memory for storing electrochemical cell'"'"'s capacity fade as a function of its internal resistance, said electronic self-diagnosis system correlating the highest calculated internal resistance of said cell string to a corresponding state of health value stored in said memory to define an overall state of health of said energy storage device.

19. - An energy storage device as defined in claim 18 wherein said electronic self-diagnosis system comprises a processing unit, a current source, a voltage measurement means, a cell selector switch adapted to select a single electrochemical cell within said cell string and a current measurement means.

20. - A method for determining a state of health of an energy storage device, the energy storage device including a plurality of electrochemical cells forming a cell string, the energy storage device characterized by a state of health value representative of a capacity fade of the cell string, said method comprising:

a correlating a measured internal resistance of the cell string to the state of health value;

b. selecting an initial capacity of the energy storage device corresponding to the, state of health value

c. monitoring a state of charge of the energy storage device by measuring energy flowing in or out of said energy storage device and adding or subtracting the energy to determine an exact battery capacity.