Method and apparatus using a circuit model to evaluate cell/battery parameters

0Associated
Cases 
0Associated
Defendants 
0Accused
Products 
27Forward
Citations 
0
Petitions 
0
Assignments
First Claim
1. Apparatus for determining one or more parameters of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry coupled to said response sensing circuitry and adapted to utilize said response to evaluate elements of a circuit model comprising the series combination of a series RL subcircuit and a plurality of parallel GC subcircuits, said computation circuitry further adapted to evaluate one or more said parameters from values of one or more said elements.
0 Assignments
0 Petitions
Accused Products
Abstract
Testing apparatus senses the timevarying electrical response of an electrochemical cell/battery to timevarying electrical excitation. The cell/battery may, or may not, be in service. Computation circuitry responsive to the timevarying electrical response evaluates elements of a unique circuit model representation of the cell/battery. Performance parameters and physical parameters are computed from these element values. Computed performance parameters include, but are not limited to, “total storage capacity”, “absolute stored charge”, “stateofcharge”, “absolute cranking current”, “fully charged cranking current”, and “stateofhealth”. Computed physical parameters include, but are not limited to, “exchange current”, “maximum exchange current”, “charge transfer conductance”, “maximum charge transfer conductance”, “double layer capacitance”, and “maximum double layer capacitance”. Computed parameters are either displayed to the user, employed to initiate an alarm, or used to control a process such as charging the cell/battery.
59 Citations
View as Search Results
METHOD AND APPARATUS FOR DETECTING CELL DETERIORATION IN AN ELECTROCHEMICAL CELL OR BATTERY  
Patent #
US 20110208451A1
Filed 02/25/2010

Current Assignee
Keith S Champlin

Sponsoring Entity
Keith S Champlin

Method and circuitry to adaptively charge a battery/cell  
Patent #
US 8,368,357 B2
Filed 10/12/2011

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Method and circuitry to calculate the state of charge of a battery/cell  
Patent #
US 8,427,112 B2
Filed 10/12/2011

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Method and circuitry to adaptively charge a battery/cell  
Patent #
US 8,513,921 B2
Filed 02/14/2013

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Method and circuitry to adaptively charge a battery/cell  
Patent #
US 8,638,070 B2
Filed 05/19/2011

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Method and circuitry to calculate the state of charge of a battery/cell  
Patent #
US 8,791,669 B2
Filed 06/24/2011

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Method and circuitry to calculate the state of charge of a battery/cell  
Patent #
US 8,970,178 B2
Filed 02/05/2012

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Method and circuitry to adaptively charge a battery/cell  
Patent #
US 8,975,874 B2
Filed 01/23/2014

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Method and circuitry to calculate the state of charge of a battery/cell  
Patent #
US 9,035,621 B2
Filed 07/02/2014

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Method and circuitry to determine temperature and/or state of health of a battery/cell  
Patent #
US 9,063,018 B1
Filed 10/22/2012

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Method and circuitry to adaptively charge a battery/cell using the state of health thereof  
Patent #
US 9,121,910 B2
Filed 03/26/2012

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Method and circuitry to adaptively charge a battery/cell  
Patent #
US 9,142,994 B2
Filed 09/25/2012

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

BATTERY STATE OF HEALTH ESTIMATION USING CHARGING RESISTANCE EQUIVALENT  
Patent #
US 20150362561A1
Filed 06/11/2014

Current Assignee
GM Global Technology Operations LLC

Sponsoring Entity
GM Global Technology Operations LLC

Method and circuitry to determine the relaxation time of a battery/cell  
Patent #
US 9,373,972 B2
Filed 02/06/2015

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Method and circuitry to determine the relaxation time of a battery/cell  
Patent #
US 9,385,555 B2
Filed 09/11/2015

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Method and circuitry to adaptively charge a battery/cell using a chargetime parameter  
Patent #
US 9,461,492 B1
Filed 04/14/2014

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Method and apparatus for detecting cell deterioration in an electrochemical cell or battery  
Patent #
US 9,588,185 B2
Filed 02/25/2010

Current Assignee
Keith S Champlin

Sponsoring Entity
Keith S Champlin

Method and circuitry to calculate the state of charge of a battery/cell  
Patent #
US 9,702,940 B2
Filed 02/06/2015

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Method and circuitry to determine temperature and/or state of health of a battery/cell  
Patent #
US 9,726,554 B1
Filed 05/14/2015

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Parameter estimation device using filter  
Patent #
US 9,784,794 B2
Filed 07/14/2011

Current Assignee
Calsonic Kansei Corporation

Sponsoring Entity
Calsonic Kansei Corporation

Method and circuitry to adaptively charge a battery/cell  
Patent #
US 9,787,122 B2
Filed 08/17/2015

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Method and circuitry to adjust, correct and/or compensate an SOC of a battery based on relaxation time thereof  
Patent #
US 9,791,513 B2
Filed 04/11/2015

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Battery state of health estimation using charging resistance equivalent  
Patent #
US 10,042,006 B2
Filed 06/11/2014

Current Assignee
GM Global Technology Operations LLC

Sponsoring Entity
GM Global Technology Operations LLC

Method and circuitry to adaptively charge a battery/cell using the state of health thereof  
Patent #
US 10,067,198 B2
Filed 06/26/2015

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Method and circuitry to adaptively charge a battery/cell  
Patent #
US 10,128,678 B2
Filed 08/18/2017

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Battery state estimation systems and methods using a nonlinear resistance element  
Patent #
US 10,345,385 B2
Filed 10/20/2015

Current Assignee
GM Global Technology Operations LLC

Sponsoring Entity
GM Global Technology Operations LLC

Method and circuitry to adaptively charge a battery/cell  
Patent #
US 10,389,156 B2
Filed 10/11/2017

Current Assignee
Qnovo Inc.

Sponsoring Entity
Qnovo Inc.

Battery testing and classification  
Patent #
US 6,526,361 B1
Filed 07/05/2000

Current Assignee
SnapOn Incorporated

Sponsoring Entity
SnapOn Incorporated

Signal detector employing mean energy and variance of energy content comparison for noise detection  
Patent #
US 5,323,337 A
Filed 08/04/1992

Current Assignee
Lockheed Martin Corporation

Sponsoring Entity
LORAL AEROSPACE CORPORATION

Telephone network access adapter  
Patent #
US 6,600,815 B1
Filed 09/24/1999

Current Assignee
WSOU Investments LLC

Sponsoring Entity
Alcatel USA Sourcing Incorporated

Battery voltage regulation circuit  
Patent #
US 6,531,848 B1
Filed 05/25/2001

Current Assignee
ARRIS International plc

Sponsoring Entity
ARRIS International plc

Current sensing device  
Patent #
US 6,081,109 A
Filed 11/07/1997

Current Assignee
Core Brands LLC

Sponsoring Entity
Xantech Corporation

Capacitive remote vehicle starter  
Patent #
US 6,679,212 B2
Filed 03/20/2001

Current Assignee
Vanair Manufacturing Incorporated

Sponsoring Entity
Goodall Mfg. LLC

DC to DC converter and power management system  
Patent #
US 6,628,011 B2
Filed 07/27/2001

Current Assignee
International Power Systems Inc

Sponsoring Entity
International Power Systems Inc

Battery recycling  
Patent #
US 6,618,644 B2
Filed 12/21/2001

Current Assignee
HewlettPackard Development Company L.P.

Sponsoring Entity
HewlettPackard Development Company L.P.

Battery clamp connection detection method and apparatus  
Patent #
US 6,667,624 B1
Filed 09/06/2002

Current Assignee
SPX Corporation

Sponsoring Entity
SPX Corporation

Engine shut off system for a hybrid electric vehicle  
Patent #
US 6,356,042 B1
Filed 07/05/2000

Current Assignee
Visteon Global Technologies Incorporated

Sponsoring Entity
Visteon Global Technologies Incorporated

Jump start battery pack and enclosure therefor  
Patent #
US 6,222,342 B1
Filed 07/28/2000

Current Assignee
SnapOn Technologies Incorporated

Sponsoring Entity
SnapOn Technologies Incorporated

Method and apparatus for charging a valveregulated lead acid battery  
Patent #
US 6,211,651 B1
Filed 03/15/2000

Current Assignee
GS Yuasa International Ltd.

Sponsoring Entity
Japan Storage Battery Company Limited

Battery terminal gripping assembly  
Patent #
US 6,238,253 B1
Filed 03/06/2000

Current Assignee
Qualls Phillip L.

Sponsoring Entity
Qualls Phillip L.

Vehicle with supplemental energy storage system for engine cranking  
Patent #
US 6,242,887 B1
Filed 08/31/2000

Current Assignee
KOLD BAN INTERNATIONAL LTD.

Sponsoring Entity
KOLD BAN INTERNATIONAL LTD.

Bicolor led trailer connector circuit protector and indicator  
Patent #
US 6,259,170 B1
Filed 06/11/1999

Current Assignee
DrawTite Incorporated

Sponsoring Entity
DrawTite Incorporated

Sensing apparatus for cable termination devices in power distribution systems  
Patent #
US 6,031,368 A
Filed 09/12/1996

Current Assignee
SC Electric Company

Sponsoring Entity
SC Electric Company

Bypass apparatus and method for series connected energy storage devices  
Patent #
US 6,046,514 A
Filed 07/25/1997

Current Assignee
Avestor

Sponsoring Entity
3M Innovative Properties Company

Touchscreen display system for a test instrument  
Patent #
US 6,064,372 A
Filed 11/27/1996

Current Assignee
LinkRunner LLC

Sponsoring Entity
Fluke Corporation

Shared memory initialization method for system having multiple processor capability  
Patent #
US 6,158,000 A
Filed 09/18/1998

Current Assignee
Hewlett Packard Enterprise Development LP

Sponsoring Entity
Compaq Computer Corporation

Electrical connector  
Patent #
US 5,865,638 A
Filed 09/05/1997

Current Assignee
AEES Incorporated

Sponsoring Entity


Portable electrical energy source  
Patent #
US 5,982,138 A
Filed 12/17/1998

Current Assignee
Vector Products Incorporated

Sponsoring Entity
Vector Products Incorporated

Method and apparatus for synchronizing files  
Patent #
US 5,978,805 A
Filed 05/14/1997

Current Assignee
Clouding Corporation

Sponsoring Entity
MICROCOM SYSTEMS INC.

Method and system for monitoring and controlling an electrical distribution network  
Patent #
US 6,005,759 A
Filed 03/16/1998

Current Assignee
ABB Incorporated

Sponsoring Entity
ABB Power TD Limited

Electronic security system  
Patent #
US 5,745,044 A
Filed 04/09/1992

Current Assignee
Medeco Security Locks Incorporated

Sponsoring Entity
Medeco Security Locks Incorporated

Apparatus and method for maximizing power delivered by a photovoltaic array  
Patent #
US 5,747,967 A
Filed 02/22/1996

Current Assignee
Midwest Research Institute

Sponsoring Entity
Midwest Research Institute

Clamp assembly for a battery booster cable  
Patent #
US 5,772,468 A
Filed 09/27/1996

Current Assignee
Coleman Cable Incorporated

Sponsoring Entity
COLEMAN CABLE SYSTEMS INC.

Electric car drive system provided with hybrid battery and control method  
Patent #
US 5,780,980 A
Filed 04/09/1996

Current Assignee
Hitachi Ltd.

Sponsoring Entity
Hitachi Ltd.

Super capacitor battery clone  
Patent #
US 5,850,113 A
Filed 04/15/1997

Current Assignee
United States Of America As Represented By The Secretary Of The Air Force

Sponsoring Entity
United States Air Force

Dual voltage power supply  
Patent #
US 5,412,308 A
Filed 03/15/1994

Current Assignee
HP Inc.

Sponsoring Entity
HP Inc.

Washer for establishing electrical continuity between conductive components having nonconductive coatings  
Patent #
US 5,453,027 A
Filed 01/23/1995

Current Assignee
Hoffman Enclosures Incorporated

Sponsoring Entity
FederalHoffman Inc.

Network for minimizing current imbalances in a faradaic battery  
Patent #
US 5,313,152 A
Filed 06/19/1992

Current Assignee
Ford Global Technologies LLC

Sponsoring Entity
Ford Motor Company

Automatic rechargeable battery monitoring system  
Patent #
US 5,325,041 A
Filed 01/21/1993

Current Assignee
Briggs James B.

Sponsoring Entity
Briggs James B.

143 Claims
 1. Apparatus for determining one or more parameters of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry coupled to said response sensing circuitry and adapted to utilize said response to evaluate elements of a circuit model comprising the series combination of a series RL subcircuit and a plurality of parallel GC subcircuits, said computation circuitry further adapted to evaluate one or more said parameters from values of one or more said elements.  View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 39. A method for determining one or more parameters of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate elements of a circuit model of said cell or battery comprising the series combination of a series RL subcircuit and a plurality of parallel GC subcircuits; and
, determining values of one or more said parameters from values of one or more said elements.  View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76)
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 77. Apparatus for determining one or more parameters of an electrochemical cell or battery adapted to perform the method according to claim 39.
 78. Apparatus for determining absolute stored charge of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry coupled to said response sensing circuitry and adapted to utilize said response to evaluate elements of a circuit model containing a plurality of parallel GC subcircuits connected in series, said computation circuitry further adapted to evaluate said absolute stored charge from the value of the capacitance element of a particular parallel GC subcircuit.
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 79. Apparatus for determining an exchange current of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry coupled to said response sensing circuitry and adapted to utilize said response to evaluate elements of a circuit model containing a plurality of parallel GC subcircuits connected in series, said computation circuitry further adapted to evaluate said exchange current from the value of the conductance element of a particular parallel GC subcircuit.
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 80. Apparatus for determining stateofcharge of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry coupled to said response sensing circuitry and adapted to utilize said response to evaluate elements of a circuit model containing a plurality of parallel GC subcircuits connected in series, said computation circuitry further adapted to evaluate said stateofcharge from the value of the conductance element of a particular parallel GC subcircuit and the value of the capacitance element of a different parallel GC subcircuit.
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 81. Apparatus for determining total storage capacity of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry coupled to said response sensing circuitry and adapted to utilize said response to evaluate elements of a circuit model containing a plurality of parallel GC subcircuits connected in series, said computation circuitry further adapted to evaluate said total storage capacity from the value of the conductance element of a particular parallel GC subcircuit and the value of the capacitance element of a different parallel GC subcircuit.
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 82. Apparatus for determining maximum exchange current of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry coupled to said response sensing circuitry and adapted to utilize said response to evaluate elements of a circuit model containing a plurality of parallel GC subcircuits connected in series, said computation circuitry further adapted to evaluate said maximum exchange current from the value of the conductance element of a particular parallel GC subcircuit and the value of the capacitance element of a different parallel GC subcircuit.
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 83. Apparatus for determining absolute cranking current of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry coupled to said response sensing circuitry and adapted to utilize said response to evaluate elements of a circuit model containing a series RL subcircuit in series with a plurality of parallel GC subcircuits, said computation circuitry further adapted to evaluate said absolute cranking current from the value of the resistance element of said series RL subcircuit.  View Dependent Claims (84, 85, 86, 87, 88, 89)
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 90. Apparatus for determining a charge transfer conductance of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry coupled to said response sensing circuitry and adapted to utilize said response to evaluate elements of a circuit model containing a plurality of parallel GC subcircuits connected in series, said computation circuitry further adapted to evaluate said charge transfer conductance from the value of the conductance element of a particular parallel GC subcircuit.
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 91. Apparatus for determining a double layer capacitance of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry coupled to said response sensing circuitry and adapted to utilize said response to evaluate elements of a circuit model containing a plurality of parallel GC subcircuits connected in series, said computation circuitry further adapted to evaluate said double layer capacitance from the value of the capacitance element of a particular parallel GC subcircuit.
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 92. Apparatus for determining a maximum charge transfer conductance of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry coupled to said response sensing circuitry and adapted to utilize said response to evaluate elements of a circuit model containing a plurality of parallel GC subcircuits connected in series, said computation circuitry further adapted to evaluate said maximum charge transfer conductance from the values of the capacitance element of a particular parallel GC subcircuit and the conductance element of a different parallel GC subcircuit.
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 93. Apparatus for determining a maximum double layer capacitance of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry coupled to said response sensing circuitry and adapted to utilize said response to evaluate elements of a circuit model containing a plurality of parallel GC subcircuits connected in series, said computation circuitry further adapted to evaluate said maximum double layer capacitance from the values of the capacitance element of a particular parallel GC subcircuit and the conductance element of a different parallel GC subcircuit.
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 94. A method for determining the absolute stored charge of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate the capacitance element of a particular parallel GC subcircuit of an electrical circuit representation of said cell or battery containing a plurality of said GC subcircuits; and
, determining the value of said absolute stored charge from the value of said capacitance element.
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 95. A method for determining an exchange current of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate the conductance element of a particular parallel GC subcircuit of an electrical circuit representation of said cell or battery; and
, determining the value of said exchange current from the value of said conductance element.
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 96. A method for determining the stateofcharge of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate the capacitance element of a particular parallel GC subcircuit and the conductance element of a different parallel GC subcircuit of an electrical circuit representation of said cell or battery; and
, determining the value of said stateofcharge from the value of said capacitance element and the value of said conductance element.
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 97. A method for determining the total storage capacity of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate the capacitance element of a particular parallel GC subcircuit and the conductance element of a different parallel GC subcircuit of an electrical circuit representation of said cell or battery; and
, determining the value of said total storage capacity from the value of said capacitance element and the value of said conductance element.
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 98. A method for determining the maximum exchange current of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate the capacitance element of a particular parallel GC subcircuit and the conductance element of a different parallel GC subcircuit of an electrical circuit representation of said cell or battery; and
, determining the value of said maximum exchange current from the value of said capacitance element and the value of said conductance element.
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 99. A method for determining the absolute cranking current of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate the resistance element of a series RL subcircuit of an electrical circuit representation of said cell or battery; and
, determining the value of said absolute cranking current from the value of said resistance element.  View Dependent Claims (100, 101, 102, 103, 104, 105)
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 106. A method for determining a double layer capacitance of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate the capacitance element of a particular parallel GC subcircuit of an electrical circuit representation of said cell or battery containing a plurality of said GC subcircuits; and
, determining the value of said double layer capacitance from the value of said capacitance element.
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 107. A method for determining a charge transfer conductance of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate the conductance element of a particular parallel GC subcircuit of an electrical circuit representation of said cell or battery; and
, determining the value of said charge transfer conductance from the value of said conductance element.
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 108. A method for determining a maximum double layer capacitance of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate the capacitance element of a particular parallel GC subcircuit and the conductance element of a different parallel GC subcircuit of an electrical circuit representation of said cell or battery; and
, determining the value of said maximum double layer capacitance from the value of said capacitance element and the value of said conductance element.
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 109. A method for determining a maximum charge transfer conductance of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate the capacitance element of a particular parallel GC subcircuit and the conductance element of a different parallel GC subcircuit of an electrical circuit representation of said cell or battery; and
, determining the value of said maximum charge transfer conductance from the value of said capacitance element and the value of said conductance element.
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 110. Apparatus for determining the absolute stored charge of an electrochemical cell or battery adapted to perform the method according to claim 94.
 111. Apparatus for determining an exchange current of an electrochemical cell or battery adapted to perform the method according to claim 95.
 112. Apparatus for determining stateofcharge of an electrochemical cell or battery adapted to perform the method according to claim 96.
 113. Apparatus for determining the total storage capacity of an electrochemical cell or battery adapted to perform the method according to claim 97.
 114. Apparatus for determining the maximum exchange current of an electrochemical cell or battery adapted to perform the method according to claim 98.
 115. Apparatus for determining the absolute cranking current of an electrochemical cell or battery adapted to perform the method according to claim 99.
 116. Apparatus for determining fully charged cranking current of an electrochemical cell or battery adapted to perform the method according to claim 100.
 117. Apparatus for determining stateofhealth of an electrochemical cell or battery adapted to perform the method according to claim 101.
 118. Apparatus for determining stateofhealth of an electrochemical cell or battery adapted to perform the method according to claim 103.
 119. Apparatus for determining a double layer capacitance of an electrochemical cell or battery adapted to perform the method according to claim 106.
 120. Apparatus for determining a charge transfer conductance of an electrochemical cell or battery adapted to perform the method according to claim 107.
 121. Apparatus for determining a maximum double layer capacitance of an electrochemical cell or battery adapted to perform the method according to claim 108.
 122. Apparatus for determining a maximum charge transfer conductance of an electrochemical cell or battery adapted to perform the method according to claim 109.
 123. Apparatus for determining stateofcharge of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry responsive to said timevarying response and adapted to evaluate a charge transfer conductance and a double layer capacitance, said computation circuitry further adapted to determine said stateofcharge by combining values of said charge transfer conductance and said double layer capacitance.
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 124. A method for determining stateofcharge of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate a double layer capacitance and a charge transfer conductance; and
, determining said stateofcharge by combining values of said double layer capacitance and said charge transfer conductance.
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 125. Apparatus for determining stateofcharge of an electrochemical cell or battery adapted to perform the method according to claim 124.
 126. Apparatus for determining total storage capacity of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry responsive to said timevarying response and adapted to evaluate a charge transfer conductance and a double layer capacitance, said computation circuitry further adapted to determine said total storage capacity by combining values of said charge transfer conductance and said double layer capacitance.
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 127. A method for determining total storage capacity of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate a double layer capacitance and a charge transfer conductance; and
, determining said total storage capacity by combining values of said double layer capacitance and said charge transfer conductance.
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 128. Apparatus for determining total storage capacity of an electrochemical cell or battery adapted to perform the method according to claim 127.
 129. Apparatus for determining absolute stored charge of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry responsive to said timevarying response and adapted to evaluate a double layer capacitance, said computation circuitry further adapted to determine said absolute stored charge from the value of said double layer capacitance.
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 130. A method for determining absolute stored charge of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate a double layer capacitance; and
, determining said absolute stored charge from the value of said double layer capacitance.
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 131. Apparatus for determining absolute stored charge of an electrochemical cell or battery adapted to perform the method according to claim 130.
 132. Apparatus for determining an exchange current of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry responsive to said timevarying response and adapted to evaluate a charge transfer conductance, said computation circuitry further adapted to determine said exchange current from the value of said charge transfer conductance.
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 133. A method for determining an exchange current of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate a charge transfer conductance; and
, determining said exchange current from the value of said charge transfer conductance.
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 134. Apparatus for determining an exchange current of an electrochemical cell or battery adapted to perform the method according to claim 133.
 135. Apparatus for determining a maximum double layer capacitance of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry responsive to said timevarying response and adapted to evaluate a double layer capacitance and a charge transfer conductance, said computation circuitry further adapted to determine said maximum double layer capacitance from the values of said double layer capacitance and said charge transfer conductance.
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 136. A method for determining a maximum double layer capacitance of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate a double layer capacitance and a charge transfer conductance; and
, determining said maximum double layer capacitance from the values of said double layer capacitance and said charge transfer conductance.
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 137. Apparatus for determining a maximum double layer capacitance of an electrochemical cell or battery adapted to perform the method according to claim 136.
 138. Apparatus for determining a maximum charge transfer conductance of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry responsive to said timevarying response and adapted to evaluate a double layer capacitance and a charge transfer conductance, said computation circuitry further adapted to determine said maximum charge transfer conductance from the values of said double layer capacitance and said charge transfer conductance.
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 139. A method for determining a maximum charge transfer conductance of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate a double layer capacitance and a charge transfer conductance; and
, determining said maximum charge transfer conductance from the values of said double layer capacitance and said charge transfer conductance.
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 140. Apparatus for determining a maximum charge transfer conductance of an electrochemical cell or battery adapted to perform the method according to claim 139.
 141. Apparatus for determining a maximum exchange current of an electrochemical cell or battery comprising:
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
, computation circuitry responsive to said timevarying response and adapted to evaluate a double layer capacitance and a charge transfer conductance, said computation circuitry further adapted to determine said maximum exchange current from the values of said double layer capacitance and said charge transfer conductance.
 response sensing circuitry coupled to said cell or battery and adapted to sense timevarying electrical response of said cell or battery generated as a result of timevarying electrical excitation of said cell or battery; and
 142. A method for determining a maximum exchange current of an electrochemical cell or battery comprising:
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
processing said timevarying electrical response to evaluate a double layer capacitance and a charge transfer conductance; and
, determining said maximum exchange current from the values of said double layer capacitance and said charge transfer conductance.
 sensing timevarying electrical response to timevarying electrical excitation of said cell or battery;
 143. Apparatus for determining a maximum exchange current of an electrochemical cell or battery adapted to perform the method according to claim 142.
1 Specification
[0001] This is a ContinuationInPart of patent application Ser. No. 09/940,684 filed Aug. 27, 2001 which is a Divisional of patent application Ser. No. 09/388,501 filed Sep. 1, 1999, which issued as U.S. Pat. No. 6,313,607 on Nov. 6, 2001 and also claims priority to U.S. provisional application Ser. No. 60/299,876 filed Jun. 21, 2001, the contents of which are hereby incorporated by reference in their entirety.
BACKGROUND OF THE INVENTION[0002] “Total storage capacity” (TSC), “absolute stored charge” (ASC), “stateofcharge” (SOC), “absolute cranking current” (ACC), “fully charged cranking current” (FCCC) and “stateofhealth” (SOH) are important performance parameters of an electrochemical cell/battery. These six parameters are assumed herein to have the following definitions:
[0003] “Total storage capacity” (TSC) denotes the total amount of charge that a fully charged battery can supply under specified discharge conditions. TSC is usually expressed in amperehours or in reserve capacity minutes.
[0004] “Absolute stored charge” (ASC)—also expressed in amperehours or reserve capacity minutes—denotes the amount of charge that a battery can supply in its current charge state. As a battery is discharged, its ASC decreases—much like the level of liquid in a fuel tank.
[0005] “Stateofcharge” (SOC), or “relative stored charge”, is the ratio of a battery's ASC to its TSC—generally expressed as a percentage. A battery's SOC indicates whether charging is advisable and identifies the point at which charging should be discontinued.
[0006] “Absolute cranking current” (ACC) denotes the highrate discharge current in amperes that a battery can sustain at a specified voltage for a specified time in its present charge state. As a battery discharges, its ACC decreases.
[0007] “Fully charged cranking current” (FCCC) denotes the value that the ACC would assume if the battery were fully charged.
[0008] “Stateofhealth” (SOH) describes a battery's full charge capability, either its TSC or its FCCC, visàvis its rated specifications. SOH identifies the point at which battery replacement is advisable.
[0009] Both ASC and TSC have traditionally been measured by performing timeddischarge tests on batteries that are partially or fully charged, respectively. Because of the time and expense involved in performing complete discharge tests, other techniques for determining ASC and TSC have been proposed. In U.S. Pat. No. 6,255,801, Chalasani claims to determine battery capacity from observations of the coup de fouet effect. O'Sullivan, in U.S. Pat. No. 6,211,654, discloses a method for predicting battery capacity from the discharge characteristics over a relatively short time period at the beginning of a full discharge.
[0010] Techniques employing timevarying signals have also been proposed. Sharaf, in U.S. Pat. No. 3,808,522, purportedly determines the amperehour capacity of a leadacid battery from ac measurements of its internal resistance. Yang, in U.S. Pat. No. 5,126,675, also uses singlefrequency internal resistance measurements to predict battery capacity. Muramatsu reports in U.S. Pat. No. 4,678,998 that he can determine both the remaining amphour capacity and the remaining service life of a battery from measurements of the magnitude of the ac impedance at two different frequencies. Fang, in U.S. Pat. No. 5,241,275, teaches a method for determining remaining capacity from complex impedance measured at two or three frequencies in the range from 0.001 to 1.0 Hz. Hampson, et al., in U.K. Patent Application GB 2,175,700A, report determining battery capacity from the frequency of the maximum value of capacitive reactance in the “impedance characteristic curve”. Yoon et al., in U.S. Pat. Nos. 6,208,147 and 6,160,382, claim that a battery's capacity can be found by analyzing the complete impedance spectrum over a wide frequency range. Presumably, any of these techniques, if effective, could also be used to determine SOH by comparing the TSC thus determined with a rated value.
[0011] Champlin, in U.S. Pat. No. 5,140,269, shows that the percent capacity of a standby battery—and hence its SOH—can be determined from its ac conductance measured at a single frequency if the ac conductance of a reference, fully charged, identically constructed, new battery is known. This method, although quite effective, requires that such ac conductance data be available, apriori.
[0012] “Absolute cranking current” (ACC) and “fully charged cranking current” (FCCC) have been traditionally measured with timed, highrate, discharge tests. Such tests have many disadvantages, however. They require heavy and cumbersome equipment, cause dangerous sparking, give imprecise results, and leave the battery in a significantly worse condition than existed before the test was performed. In response to the need for a better method, Champlin pioneered a testing technique based upon singlefrequency ac conductance measurements. Various aspects of this wellaccepted methodology have been disclosed in U.S. Pat. Nos. 3,873,911, 3,909,708, 4,816,768, 4,825,170, 4,881,038, 4,912,416, 5,572,136, 5,585,728, 5,598,098, and 5,821,756.
[0013] With leadacid batteries, SOC has been traditionally evaluated by observing the battery's opencircuit voltage or the specific gravity of its electrolyte. However, neither of these quantities provides information about the battery's TSC, ASC, ACC, FCCC, or SOH. Furthermore, specific gravity measurements are messy and impossible to perform on sealed cells. Moreover, opencircuit voltage cannot be measured under load conditions and, at any rate, is imprecisely related to SOC because both “surface charge” and temperature affect it.
[0014] Because of these drawbacks, several techniques for correcting voltage of leadacid batteries to obtain SOC have been proposed. These include techniques described by Christianson et al. in U.S. Pat. No. 3,946,299, by Reni et al. in U.S. Pat. No. 5,352,968, and by Hirzel in U.S. Pat. No. 5,381,096. However, such voltage correction methods are not very accurate. Furthermore, they are of little help with electrochemical systems other than leadacid in which voltage may bear little relationship to SOC.
[0015] Due to these and other problems, techniques based upon ac or timevarying signals have been proposed for determining SOC. For example, Latner claims to determine SOC of NiCd batteries from ac bridge measurements of farad capacitance in U.S. Pat. No. 3,562,634. U.S. Pat. No. 3,984,762 to Dowgiallo purports to determine SOC from the phase angle of the complex impedance at a single frequency. In U.S. Pat. No. 4,743,855, Randin et al. assert that SOC can be determined from the argument (i.e., phase angle) of the difference between complex impedances measured at two different frequencies. Bounaga, in U.S. Pat. No. 5,650,937, reportedly determines SOC from measurements of the imaginary part of the complex impedance at a single frequency. Basell et al. purport to determine SOC from the rate of change of impedance with frequency in U.S. Pat. No. 5,717,336. Ding et al., in U.S. Pat. No. 6,094,033, broadly assert that SOC can be determined from a battery's “impedance response, which can include series and parallel equivalent circuit parameters, i.e., resistance, capacitance, and phase angle, among others”. Finally, techniques purporting to determine SOC from the transient response to an applied pulsed voltage and/or current are disclosed by Andrieu and Poignant in U.S. Pat. No. 5,530,361 and by Simon in French Patent Application FR 2,749,396A. The fact that none of these methods has gained wide acceptance, however, suggests that they may not be altogether satisfactory methods for determining SOC.
SUMMARY OF THE INVENTION[0016] Testing apparatus senses the timevarying electrical response of an electrochemical cell/battery to timevarying electrical excitation. The cell/battery may, or may not, be in service. Computation circuitry responsive to the timevarying electrical response evaluates elements of a unique circuit model representation of the cell/battery. Performance parameters and physical parameters are computed from these element values. Computed performance parameters include, but are not limited to, “total storage capacity”, “absolute stored charge”, “stateofcharge”, “absolute cranking current”, “fully charged cranking current”, and “stateofhealth”. Computed physical parameters include, but are not limited to, “exchange current”, “maximum exchange current”, “charge transfer conductance”, “maximum charge transfer conductance”, “double layer capacitance”, and “maximum double layer capacitance”. Computed parameters are either displayed to the user, employed to initiate an alarm, or used to control a process such as charging the cell/battery.
BRIEF DESCRIPTION OF THE DRAWINGS[0017] <crossreference>FIG. 1</crossreference> is a block diagram of apparatus for evaluating performance parameters and physical parameters of an electrochemical cell or battery in accordance with one embodiment of the present invention.
[0018] <crossreference>FIG. 2</crossreference> depicts a generic 2nelement small signal circuit model representation of an electrochemical cell or battery employed in the present invention.
[0019] <crossreference>FIG. 3</crossreference> depicts the sixelement small signal circuit model representation of a particular fully charged 12V VRLA battery determined from complex immittance measurements at 5 Hz, 50 Hz, and 500 Hz.
[0020] <crossreference>FIG. 4</crossreference> is a plot of the variation of the three subcircuit timeconstants defined in <crossreference>FIG. 3</crossreference> as charge is removed from the battery.
[0021] <crossreference>FIG. 5</crossreference> is a plot of values of the three conductances defined in <crossreference>FIG. 3</crossreference> as charge is removed from the battery.
[0022] <crossreference>FIG. 6</crossreference> is plot of values of capacitances C2 and C3 defined in <crossreference>FIG. 3</crossreference> as charge is removed from the battery.
[0023] <crossreference>FIG. 7</crossreference> is a plot of the “exchange current” i<highlight><subscript>0 </subscript></highlight>derived from “charge transfer conductance” G3 of <crossreference>FIG. 5</crossreference> as charge is removed from the battery.
[0024] <crossreference>FIG. 8</crossreference> is a plot of the “stateofcharge” SOC derived from “charge transfer conductance” G3 of <crossreference>FIG. 5</crossreference> and “double layer capacitance” C2 of <crossreference>FIG. 6</crossreference> as charge is removed from the battery.
[0025] <crossreference>FIG. 9</crossreference> is a plot of the “absolute stored charge” ASC determined from “double layer capacitance” C2 of <crossreference>FIG. 6</crossreference> as charge is removed from the battery.
[0026] <crossreference>FIG. 10</crossreference> is a plot of the “total storage capacity” TSC derived from “charge transfer conductance” G3 of <crossreference>FIG. 5</crossreference> and “double layer capacitance” C2 of <crossreference>FIG. 6</crossreference> as charge is removed from the battery.
[0027] <crossreference>FIG. 11</crossreference> is a plot of the “absolute cranking current” ACC derived from series conductance G1=1/R1 of <crossreference>FIG. 5</crossreference> as charge is removed from the battery.
[0028] <crossreference>FIG. 12</crossreference> is a plot of the function used to correct the “absolute cranking current” ACC for “stateofcharge” SOC to obtain the “fully charged cranking current” FCCC of <crossreference>FIG. 13</crossreference>.
[0029] <crossreference>FIG. 13</crossreference> is a plot of the corrected “fully charged cranking current” FCCC as charge is removed from the battery.
[0030] <crossreference>FIG. 14</crossreference> is a diagram of the “commonly accepted” circuit model showing the placement of a “charge transfer resistance” and “double layer capacitance” in parallel with one another.
[0031] <crossreference>FIG. 15</crossreference> is a diagram of the n=3 circuit model according to the present invention showing the placement of the “charge transfer conductance” and the “double layer capacitance” in two separate GC subcircuits that are actually in series with one another.
[0032] <crossreference>FIG. 16</crossreference> is a block diagram of apparatus for evaluating performance and physical parameters of an electrochemical cell or battery wherein an external source produces timevarying electrical excitation
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS[0033] Method and apparatus for quickly and accurately determining performance parameters and physical parameters that does not discharge the battery, does not require the battery to be fully charged, and tests batteries while “on line” would be of great value. The present invention addresses this need. It is based upon teachings disclosed by Champlin in U.S. Pat. Nos. 6,002,238, 6,037,777, 6,172,483, 6,222,369, 6,262,563, 6,313,607, and U.S. patent application Ser. Nos. 60/299,876 and 09/940,684, all of which are incorporated herein by reference.
[0034] <crossreference>FIG. 1</crossreference> discloses a block diagram of apparatus 5 for evaluating performance parameters and/or physical parameters according to one embodiment of the present invention. Measuring circuitry 10 electrically couples to cell/battery 20 at positive terminal 15 and negative terminal 25 by means of currentcarrying contacts A and B and voltagesensing contacts C and D. Cell/battery 20 may, or may not, be in service. Under control of microcontroller circuitry 30 via control path 35, measuring circuitry 10 passes periodic timevarying excitation current i(t) through contacts A and B and senses periodic timevarying response voltage v(t) across contacts C and D. Amplification and analog to digital conversion circuitry contained within measuring circuitry 10 formulates digital representations of i(t) and v(t) samples and communicates them to microcontroller circuitry 30 via data path 40.
[0035] By appropriately processing these digital representations, microcontroller circuitry 30 computes real and imaginary parts of complex immittance—either impedance Z or admittance Y—at a measuring frequency f<highlight><subscript>k</subscript></highlight>; where f<highlight><subscript>k </subscript></highlight>is a discrete frequency contained in the periodic waveforms of i(t) and v(t). Microcontroller circuitry 30 commands measuring circuitry 10 to repeat these measurements at each one of n discrete measuring frequencies, where n is an integer number equal to or greater than 3. This action defines 2n experimental quantities: the values of the n real parts and the n imaginary parts of complex immittance at each of the n measuring frequencies. Microcontroller circuitry 30 then employs algorithms disclosed in U.S. Pat. Nos. 6,037,777 and 6,222,369 to numerically combine the 2n experimental quantities to evaluate the 2n elements of the circuit model representation of the cell/battery disclosed in <crossreference>FIG. 2</crossreference>. This unique circuit model comprises a single series RL subcircuit in series with a plurality, n1, of parallel GC subcircuits.
[0036] Microcontroller circuitry 30 computes one or more performance and/or physical parameters of cell/battery 20 from values of one or more elements of this circuit model representation of <crossreference>FIG. 2</crossreference>. Additionally, microcontroller circuitry 30 can compare one or more computed parameters with battery rating information inputted by a user on input device 45 to determine the battery's “stateofhealth” SOH. Finally, microcontroller circuitry 30 can output appropriate performance or physical parameters to a user on display 50, and/or apply one or more computed parameters to initiate an alarm 55 or to control a process 60 such as charging of the battery.
[0037] <crossreference>FIG. 3</crossreference> discloses the sixelement circuit model of a fully charged 12V battery as determined with the apparatus of <crossreference>FIG. 1</crossreference> using n=3. The experimental battery was a VRLA (valveregulated leadacid) automotive battery of spiralgrid construction that was rated 700 CCA, 95 minutes reserve capacity, and 50 Ah capacity @ 20 hour rate. The three measurement frequencies were 5, 50, and 500 Hz.
[0038] One notes from <crossreference>FIG. 3</crossreference> that the n=3 circuit model comprises three twoelement subcircuits in series:
[0039] A series R1L1 subcircuit.
[0040] A parallel G2C2 subcircuit.
[0041] A parallel G3C3 subcircuit.
[0042] One notes further that the three subcircuits are characterized by three very different time constants. The shortest time constant, τ<highlight><subscript>1</subscript></highlight>=L1/R1=215.4 μS, belongs to the series R1L1 subcircuit. The next longest time constant, τ<highlight><subscript>2</subscript></highlight>=C2/G2=3.33 mS, belongs to the parallel G2C2 subcircuit; and the longest timeconstant, τ<highlight><subscript>3</subscript></highlight>=C3/G3=51.3 mS, belongs to the parallel G3C3 subcircuit. Accordingly, the three subcircuits represent quite different physical processes that can be differentiated from one another by their time constants.
[0043] By analyzing similar threefrequency measurements on many leadacid batteries, a consistent physical interpretation of the circuit model of <crossreference>FIG. 3</crossreference> has emerged. The theoretical basis for this interpretation can be found in the paper by Champlin and Bertness, “Results of Discrete Frequency Immittance Spectroscopy (DFIS) Measurements of Lead Acid Batteries”, Proceedings of the 23<highlight><superscript>rd </superscript></highlight>International Telecommunications Energy Conference (INTELEC), Edinburgh Scotland, paper 53, (October 2001).
[0044] According to this interpretation, series resistance R1 represents the currentinduced drop in electric potential across the metal connectors, plates, separators, active material, and electrolyte—with the majority of R1 associated with the active material and electrolyte. Accordingly, conductance G1=1/R1 correlates directly with highrate loadtest current such as coldcranking amps (CCA). Series inductance L1 describes energy storage in the battery's surrounding magnetic field, with no electrochemical component to L1 yet observed.
[0045] Both the parallel G2C2 subcircuit and the parallel G3C3 subcircuit are believed to be linearized representations of nonlinear electrochemical processes occurring at the negative electrode surfaces. These two subcircuits together describe the response of negative electrode surfaces to changes in an externally applied electrochemical overpotential.
[0046] Electrochemical overpotential at an electrode surface consists of two parts: an electrical overpotential and a chemical overpotential. The electrical part arises from electrical forces on charged particles, and the chemical part arises from concentration differences. The faster G2C2 subcircuit responds to the electrical part of an electrochemical overpotential and the slower G3C3 subcircuit responds to the chemical part. These two subcircuits add in series in the circuit model of <crossreference>FIG. 3</crossreference> because the electrical overpotential and the chemical overpotential add together to form the electrochemical overpotential. Voltages (potentials) add in series.
[0047] <crossreference>FIGS. 4, 5</crossreference>, and 6 display the results of threefrequency immittance measurements performed on the battery whose model is depicted in <crossreference>FIG. 3</crossreference> during a discharge sequence. The battery was initially charged, allowed to reach equilibrium, and was then repeatedly discharged at an approximate 8hr rate in increments of approximately 3 amperehours. The battery was permitted to rest for 2.5 hours after each discharge period before the threefrequency immittance measurements were taken.
[0048] <crossreference>FIG. 4</crossreference> is a plot of the variation of the three time constants defined in <crossreference>FIG. 3</crossreference> as charge is removed from the battery. One notes that the time constants remain widely separated as charge is removed, and that the longest of the three, τ<highlight><subscript>3</subscript></highlight>, is nearly independent of stateofcharge.
[0049] <crossreference>FIG. 5</crossreference> discloses the variation of the three conductances, G1=1/R1, G2, and G3 as charge is removed from the battery. Of particular interest is the fact that G3 becomes small near full charge as well as near full discharge. This remarkable behavior sets G3 apart from G1 and G2, both of which reach maxima at full charge. Such unusual behavior can be explained by assuming that G3 describes faradaic processes occurring at the negative electrode surfaces and considering the kinetics of such processes.
[0050] The ButlerVolmer equation for faradaic processes at the negative electrode surfaces can be written:
<inlineformula>i=i<highlight><subscript>f</subscript></highlight>−i<highlight><subscript>b</subscript></highlight>=i<highlight><subscript>0</subscript></highlight>(e<highlight><superscript>αnfV</superscript></highlight><highlight><superscript><highlight><subscript>3</subscript></highlight></superscript></highlight>−e<highlight><superscript>−{1α}nfV</superscript></highlight><highlight><superscript><highlight><subscript>3</subscript></highlight></superscript></highlight>) (1) </inlineformula>
[0051] In equation (1), i is the current in the external circuit (assumed positive in the “charge” direction) while i<highlight><subscript>f </subscript></highlight>and i<highlight><subscript>b </subscript></highlight>are “forward” and “backward” ionic “reaction” currents, respectively, in the electrolyte. Physical parameter i<highlight><subscript>0 </subscript></highlight>is the “exchange current”; α is “charge transfer coefficient” (less than unity) n is the number of electrons transferred per molecule reactant (two); and f=(F/RT), with F being Faraday's constant, R the universal gas constant, and T the absolute (Kelvin) temperature. Voltage V<highlight><subscript>3 </subscript></highlight>in equation (1) is believed to be the chemical component of the electrochemi cal overpotential (positive for “charge” and negative for “discharge”) at the negative electrode surfaces.
[0052] The chemical overpotential, V<highlight><subscript>3</subscript></highlight>, drives the two ionic reaction currents. Under charging conditions (V<highlight><subscript>3</subscript></highlight>>0) , the forward ionic current, i<highlight><subscript>f</subscript></highlight>=i<highlight><subscript>0 </subscript></highlight>exp(αnfV<highlight><subscript>3</subscript></highlight>), is larger than i<highlight><subscript>0</subscript></highlight>; while the backward ionic current, i<highlight><subscript>b</subscript></highlight>=i<highlight><subscript>0 </subscript></highlight>exp(−{1a}nfV<highlight><subscript>3</subscript></highlight>) is less than i<highlight><subscript>0</subscript></highlight>. Accordingly, their difference yields a positive (“charging”) current in the external circuit. Under discharging conditions (V<highlight><subscript>3</subscript></highlight><0), the opposite is true. In equilibrium (V<highlight><subscript>3</subscript></highlight>=0), both forward and backward ionic currents are equal to the exchange current i<highlight><subscript>0</subscript></highlight>, and the current in the external circuit is zero. Note that even with i=O, there are still two equal ionic “exchange currents” flowing in opposite directions on the electrolyte side of the electrode/electrolyte interface.
[0053] For small variations in V<highlight><subscript>3</subscript></highlight>, the equilibrium smallsignal faradaic conductance, or “charge transfer conductance”, follows by differentiating equation (1) with respect to (N<highlight><subscript>C</subscript></highlight>V<highlight><subscript>3</subscript></highlight>), where N<highlight><subscript>C </subscript></highlight>is the number of battery cells in series, and evaluating this derivative at V<highlight><subscript>3</subscript></highlight>=0. The result is<mathcwu><number>1</number><math><mtable><mtr><mtd><mrow><mi>G3</mi><mo>=</mo><mrow><mrow><mfrac><mrow><mo>ⅆ</mo><mi>i</mi></mrow><mrow><mo>ⅆ</mo><mrow><mo>(</mo><mrow><msub><mi>N</mi><mi>C</mi></msub><mo></mo><msub><mi>V</mi><mn>3</mn></msub></mrow><mo>)</mo></mrow></mrow></mfrac><mo></mo><msub><mo></mo><mrow><msub><mi>V</mi><mn>3</mn></msub><mo>=</mo><mn>0</mn></mrow></msub></mrow><mo>=</mo><mrow><mfrac><msub><mi>nfi</mi><mn>0</mn></msub><msub><mi>N</mi><mi>C</mi></msub></mfrac><mo>=</mo><mrow><mrow><mo>(</mo><mrow><mrow><mi>nF</mi><mo>/</mo><msub><mi>N</mi><mi>C</mi></msub></mrow><mo></mo><mi>RT</mi></mrow><mo>)</mo></mrow><mo>·</mo><msub><mi>i</mi><mn>0</mn></msub></mrow></mrow></mrow></mrow></mtd><mtd><mrow><mo>(</mo><mn>2</mn><mo>)</mo></mrow></mtd></mtr></mtable></math><mathematicafile></mathematicafile><image></image></mathcwu>
[0054] One sees that at any given temperature, the “charge transfer conductance” G3 is proportional to the “exchange current” i<highlight><subscript>0</subscript></highlight>. The “charge transfer conductance” and electrode “exchange current” are both physical parameters of great importance.
[0055] Equation (2) can be inverted to yield the “exchange current” i<highlight><subscript>0 </subscript></highlight>in terms of “charge transfer conductance” G3. For a 12V (6cell) battery at room temperature (T=293° K.), equation (2) yields
<inlineformula>i<highlight><subscript>0</subscript></highlight>=(N<highlight><subscript>C</subscript></highlight>RT/nF)·G3=(0.07574)·G3 amperes (3) </inlineformula>
[0056] <crossreference>FIG. 7</crossreference> displays i<highlight><subscript>0 </subscript></highlight>calculated from equation (3) using the experimental G3 data of <crossreference>FIG. 5</crossreference>. One sees that i<highlight><subscript>0 </subscript></highlight>approaches zero at both full charge and full discharge and reaches a maximum value of i<highlight><subscript>0max</subscript></highlight>=27.5 amperes at approximately 50% stateofcharge.
[0057] The remarkable variation of G3 disclosed in <crossreference>FIG. 5</crossreference> can now be explained. As the battery approaches full charge, the forward, or “charge”, component of reaction current goes to zero because the number of reaction sites available for the charge reaction (PbSO<highlight><subscript>4 </subscript></highlight>sites) approaches zero. Since forward and backward ionic currents are equal in equilibrium, the equilibrium backward current likewise goes to zero. Similarly, as the battery approaches full discharge, the backward, or “discharge”, component of reaction current goes to zero because the number of sites available for the discharge reaction (Pb sites) approaches zero. Again, since forward and backward ionic currents are equal in equilibrium, the equilibrium forward current likewise goes to zero. Accordingly, the “exchange current” i<highlight><subscript>0 </subscript></highlight>goes to zero in both cases. From equation (2), the “charge transfer conductance” G3—which is simply proportional to i<highlight><subscript>0</subscript></highlight>—likewise approaches zero at full charge and at full discharge, reaching maximum at 50% stateofcharge.
[0058] By reasoning in accordance with this mechanism, one can write “charge transfer conductance” G3 as
<inlineformula>G3=4·G3<highlight><subscript>max</subscript></highlight>·(N<highlight><subscript>Pb</subscript></highlight><highlight><superscript>−</superscript></highlight>/N<highlight><superscript>−</superscript></highlight>)·(N<highlight><subscript>PbSO</subscript></highlight><highlight><superscript><highlight><subscript>4</subscript></highlight></superscript></highlight><highlight><superscript>−</superscript></highlight>/N<highlight><superscript>−</superscript></highlight>) (4) </inlineformula>
[0059] where N<highlight><superscript>−</superscript></highlight>=N<highlight><subscript>Pb</subscript></highlight><highlight><superscript>−</superscript></highlight>+N<highlight><subscript>PbSO</subscript></highlight><highlight><superscript><highlight><subscript>4</subscript></highlight></superscript></highlight><highlight><superscript>−</superscript></highlight> is the total number of negativeelectrode reaction sites, N<highlight><subscript>Pb</subscript></highlight><highlight><superscript>−</superscript></highlight> is the number of such sites occupied by Pb molecules, and N<highlight><subscript>PbSO</subscript></highlight><highlight><superscript><highlight><subscript>4</subscript></highlight></superscript></highlight><highlight><superscript>−</superscript></highlight> is the number occupied by PbSO<highlight><subscript>4 </subscript></highlight>molecules. The factor 4 in equation (4) arises because G3 equals G3<highlight><subscript>max </subscript></highlight>when N<highlight><subscript>Pb</subscript></highlight><highlight><superscript>−</superscript></highlight>=N<highlight><subscript>PbSO</subscript></highlight><highlight><superscript><highlight><subscript>4</subscript></highlight></superscript></highlight><highlight><superscript>−</superscript></highlight>=N<highlight><superscript>−</superscript></highlight>/2.
[0060] I now define the performance parameter “stateofcharge” SOC as the fraction of negativeelectrode reaction sites occupied by Pb molecules. That is,
<inlineformula>SOC≡(N<highlight><subscript>Pb</subscript></highlight><highlight><superscript>−</superscript></highlight>/N<highlight><superscript>−</superscript></highlight>)=1−(N<highlight><subscript>PbSO</subscript></highlight><highlight><superscript><highlight><subscript>4</subscript></highlight></superscript></highlight><highlight><superscript>−</superscript></highlight>/N<highlight><superscript>−</superscript></highlight>) (5) </inlineformula>
[0061] Equation (4) can therefore be written
<inlineformula>G3=4·G3<highlight><subscript>max</subscript></highlight>·(SOC)·(1−SOC) (6) </inlineformula>
[0062] which obviously approaches zero when SOC approaches unity as well as zero.
[0063] <crossreference>FIG. 6</crossreference> discloses the variation of capacitance C2 and capacitance C3 as charge is removed from the battery. Capacitance C3 is seen to mimic the behavior of “charge transfer conductance” G3 over the complete range of Ah removed. This variation can be understood by noting that C3=τ<highlight><subscript>3</subscript></highlight>·G3, and that τ<highlight><subscript>3 </subscript></highlight>varies little as charge is removed (see <crossreference>FIG. 4</crossreference>). Time constant τ<highlight><subscript>3 </subscript></highlight>is believed closely related to the reaction time of faradaic processes at the negative electrode surfaces (See U.S. Pat. Nos. 6,137,269 and 6,294,697).
[0064] Capacitance C2 in <crossreference>FIG. 6</crossreference> is observed to vary in an entirely different manner from C3 as charge is removed. Instead of increasing and then decreasing, C2 assumes its largest value with zero amphours removed and simply decreases monotonically as charge is removed from the battery. Such behavior suggests that the G2C2 subcircuit is responsive to the nonfaradaic or electrical component of an electrochemical overpotential at the negativeelectrode surfaces. In this interpretation, capacitance C2 represents the negativeelectrode's ionic “double layer capacitance”—a physical parameter of considerable interest.
[0065] An ionic double layer can only form on metallic Pb molecules. It cannot form on nonconducting PbSO<highlight><subscript>4 </subscript></highlight>molecules. It follows that C2 is proportional to N<highlight><subscript>Pb</subscript></highlight><highlight><superscript>−</superscript></highlight>, the total number of reaction sites that are occupied by Pb molecules. Accordingly, “double layer capacitance” C2 can be written
<inlineformula>C2=C2<highlight><subscript>100</subscript></highlight>·(N<highlight><subscript>Pb</subscript></highlight><highlight><superscript>−</superscript></highlight>/N<highlight><superscript>−</superscript></highlight>)=C2<highlight><subscript>100</subscript></highlight>·SOC (7) </inlineformula>
[0066] where C2<highlight><subscript>100 </subscript></highlight>is “maximum double layer capacitance”—the value that would occur at 100% stateofcharge.
[0067] Equation (7) indicates that physical parameter C2<highlight><subscript>100 </subscript></highlight>relates to battery size and condition by being proportional to N<highlight><superscript>−</superscript></highlight>, the total number of reaction sites available for charge/discharge reactions. Similarly, equation (4) indicates that physical parameter G3<highlight><subscript>max </subscript></highlight>relates to size and condition by being proportional to (N<highlight><superscript>−</superscript></highlight>)<highlight><superscript>2</superscript></highlight>. Accordingly, I define the following useful quantity:<mathcwu><number>2</number><math><mtable><mtr><mtd><mrow><mi>ξ</mi><mo>≡</mo><mfrac><msup><mrow><mo>(</mo><msub><mi>C2</mi><mn>100</mn></msub><mo>)</mo></mrow><mn>2</mn></msup><mrow><mn>4</mn><mo>·</mo><msub><mi>G3</mi><mi>max</mi></msub></mrow></mfrac></mrow></mtd><mtd><mrow><mo>(</mo><mn>8</mn><mo>)</mo></mrow></mtd></mtr></mtable></math><mathematicafile></mathematicafile><image></image></mathcwu>
[0068] which, for any particular class of cell/battery, is independent of battery size, condition and “stateofcharge”. I have found that ξ≅1.368·10<highlight><superscript>−2 </superscript></highlight>for batteries of the type under consideration herein.
[0069] Equations (6), (7), and (8) can be combined algebraically to provide separate expressions for SOC, C2<highlight><subscript>100</subscript></highlight>, and G3<highlight><subscript>max </subscript></highlight>in terms of ξ, C2, and G3. The results are<mathcwu><number>3</number><math><mtable><mtr><mtd><mrow><mi>SOC</mi><mo>=</mo><mfrac><mn>1</mn><mrow><mn>1</mn><mo>+</mo><mrow><mi>ξ</mi><mo>·</mo><mrow><mo>(</mo><mrow><mi>G3</mi><mo>/</mo><msup><mi>C2</mi><mn>2</mn></msup></mrow><mo>)</mo></mrow></mrow></mrow></mfrac></mrow></mtd><mtd><mrow><mo>(</mo><mn>9</mn><mo>)</mo></mrow></mtd></mtr><mtr><mtd><mrow><mrow><msub><mi>C2</mi><mn>100</mn></msub><mo>=</mo><mrow><mi>C2</mi><mo>+</mo><mrow><mi>ξ</mi><mo>·</mo><mrow><mo>(</mo><mrow><mi>G3</mi><mo>/</mo><mi>C2</mi></mrow><mo>)</mo></mrow></mrow></mrow></mrow><mo></mo><mstyle><mtext> </mtext></mstyle><mo></mo><mi>and</mi></mrow></mtd><mtd><mrow><mo>(</mo><mn>10</mn><mo>)</mo></mrow></mtd></mtr><mtr><mtd><mrow><msub><mi>G3</mi><mi>max</mi></msub><mo>=</mo><mfrac><msup><mrow><mo>{</mo><mrow><mi>C2</mi><mo>+</mo><mrow><mi>ξ</mi><mo>·</mo><mrow><mo>(</mo><mrow><mi>G3</mi><mo>/</mo><mi>C2</mi></mrow><mo>)</mo></mrow></mrow></mrow><mo>}</mo></mrow><mn>2</mn></msup><mrow><mn>4</mn><mo>·</mo><mi>ξ</mi></mrow></mfrac></mrow></mtd><mtd><mrow><mo>(</mo><mn>11</mn><mo>)</mo></mrow></mtd></mtr></mtable></math><mathematicafile></mathematicafile><image></image></mathcwu>
[0070] By combining equation (3) and equation (11), “maximum exchange current” i<highlight><subscript>0max </subscript></highlight>can be written as<mathcwu><number>4</number><math><mtable><mtr><mtd><mrow><msub><mi>i</mi><msub><mn>0</mn><mi>max</mi></msub></msub><mo>=</mo><mfrac><mrow><mrow><mo>{</mo><mrow><msub><mi>N</mi><mi>C</mi></msub><mo></mo><mrow><mi>RT</mi><mo>/</mo><mi>nF</mi></mrow></mrow><mo>}</mo></mrow><mo>·</mo><mrow><mo>{</mo><mrow><mi>C2</mi><mo>+</mo><mrow><mi>ξ</mi><mo>·</mo><msup><mrow><mo>(</mo><mrow><mi>G3</mi><mo>/</mo><mi>C2</mi></mrow><mo>}</mo></mrow><mn>2</mn></msup></mrow></mrow></mrow></mrow><mrow><mn>4</mn><mo>·</mo><mi>ξ</mi></mrow></mfrac></mrow></mtd><mtd><mrow><mo>(</mo><mn>12</mn><mo>)</mo></mrow></mtd></mtr></mtable></math><mathematicafile></mathematicafile><image></image></mathcwu>
[0071] This physical parameter is of considerable theoretical interest since it describes the level of maximum chemical activity at the electrode/electrolyte interface.
[0072] <crossreference>FIG. 8</crossreference> displays performance parameter SOC (in percent) calculated from equation (9) by using the experimental G3 and C2 data disclosed in <crossreference>FIGS. 5 and 6</crossreference>. Note that combining G3 and C2 data to determine SOC resolves the multivalue ambiguity of equation (6). The “stateofcharge” determined in this manner varies from a maximum value of 93.6%, with zero amperehours removed from the battery, to a minimum value of 4.1% with 45.2 amperehours removed. The observed, nearly linear, variation of SOC with amperehours removed provides excellent corroboration of the theory.
[0073] The performance parameters “absolute stored charge” ASC and “total storage capacity” TSC are proportional to C2 and C2<highlight><subscript>100</subscript></highlight>, respectively. Accordingly, I write
<inlineformula>ASC=K<highlight><subscript>cs</subscript></highlight>·C2 (13) </inlineformula>
[0074] and, from equation (10)
<inlineformula>TSC=K<highlight><subscript>cs</subscript></highlight>·{C2+ξ·(G3/C2)} (14) </inlineformula>
[0075] where K<highlight><subscript>cs </subscript></highlight>is a “charge storage” constant that depends upon the battery type, and upon the units of charge storage (i.e., amperehours @ an 8 hr rate, amperehours @ a 20 hr rate, reserve capacity minutes, coulombs, etc.) I find that for batteries of the type under consideration herein, and with ASC and TSC expressed in amperehours @ an 8 hr rate, K<highlight><subscript>cs</subscript></highlight>≅11.3.
[0076] Taking the ratio of equation (13) to equation (14) shows that<mathcwu><number>5</number><math><mtable><mtr><mtd><mrow><mfrac><mi>ASC</mi><mi>TSC</mi></mfrac><mo>=</mo><mrow><mfrac><mi>C2</mi><mrow><mi>C2</mi><mo>+</mo><mrow><mi>ξ</mi><mo>·</mo><mrow><mo>(</mo><mrow><mi>G3</mi><mo>/</mo><mi>C2</mi></mrow><mo>)</mo></mrow></mrow></mrow></mfrac><mo>=</mo><mrow><mfrac><mn>1</mn><mrow><mn>1</mn><mo>+</mo><mrow><mi>ξ</mi><mo>·</mo><mrow><mo>(</mo><mrow><mi>G3</mi><mo>/</mo><msup><mi>C2</mi><mn>2</mn></msup></mrow><mo>)</mo></mrow></mrow></mrow></mfrac><mo>=</mo><mi>SOC</mi></mrow></mrow></mrow></mtd><mtd><mrow><mo>(</mo><mn>15</mn><mo>)</mo></mrow></mtd></mtr></mtable></math><mathematicafile></mathematicafile><image></image></mathcwu>
[0077] Thus, the performance parameter “stateofcharge” SOC, that is defined physically in terms of numbers of reaction sites by equation (5), is actually the ratio of the two performance parameters “absolute stored charge” ASC and “total storage capacity” TSC.
[0078] <crossreference>FIG. 9</crossreference> displays performance parameter “absolute stored charge” ASC (in amperehours) calculated from equation (13) using the experimental C2 data disclosed in <crossreference>FIG. 6</crossreference>. The “absolute stored charge” determined in this manner varies from a maximum value of 47.2 amperehours, with zero amperehours removed from the battery, to a minimum value of 1.9 amperehours with 45.2 amperehours removed. Note that “absolute stored charge” ASC decreases as the battery discharges—much like the level of liquid in a fuel tank. Accordingly, ASC would comprise an excellent “electric fuel gauge” readout.
[0079] <crossreference>FIG. 10</crossreference> displays the performance parameter “total storage capacity” TSC (in amperehours) calculated from equation (14) using the experimental G3 and C2 data disclosed in <crossreference>FIGS. 5 and 6</crossreference>. Note that the observed TSC varies very little as the battery is discharged. Ideally, TSC would not vary at all. The small variations observed are believed caused by minor inaccuracies in the n=3 model. Performing immittance measurements at four or five frequencies and then employing an eight or tenelement circuit model in the analysis greatly reduces such variations.
[0080] Performance parameter “absolute cranking current” ACC has been found experimentally to be proportional to G1=1/R1. Thus
<inlineformula>ACC=K<highlight><subscript>cc</subscript></highlight>·G1 (16) </inlineformula>
[0081] where K<highlight><subscript>cc </subscript></highlight>is a “cranking current” coefficient that depends upon the type of battery and the definition of “cranking current”. For batteries of the type under consideration, and with “cranking current” defined to be SAE “cold cranking amperes”, K<highlight><subscript>cc</subscript></highlight>≅2.7. <crossreference>FIG. 11</crossreference> displays performance parameter ACC determined from equation (16) by using the G1 data of <crossreference>FIG. 5</crossreference>. One sees that ACC decreases significantly as charge is removed from the battery.
[0082] For batteries that are less than fully charged, the performance parameter “fully charged cranking current” FCCC can be determined by correcting the ACC according to
<inlineformula>FCCC=ACC·F(SOC) (17) </inlineformula>
[0083] where F(SOC) is a “correction factor” that depends upon “stateofcharge”. <crossreference>FIG. 12</crossreference> discloses an emperically determined F(SOC) for correcting the ACC of batteries of the type under consideration. This function can be expressed mathematically as<mathcwu><number>6</number><math><mtable><mtr><mtd><mrow><mrow><mi>F</mi><mo></mo><mrow><mo>(</mo><mi>SOC</mi><mo>)</mo></mrow></mrow><mo>=</mo><mfrac><mn>1</mn><mrow><mn>1</mn><mo></mo><mrow><mn>0.5</mn><mo>·</mo><mrow><mo>(</mo><mrow><mi>SOC</mi><mo></mo><mn>1</mn></mrow><mo>)</mo></mrow></mrow><mo></mo><mrow><mn>1.0</mn><mo>·</mo><msup><mrow><mo>(</mo><mrow><mi>SOC</mi><mo></mo><mn>1</mn></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>+</mo><mrow><mn>0.4</mn><mo>·</mo><msup><mrow><mo>(</mo><mrow><mi>SOC</mi><mo></mo><mn>1</mn></mrow><mo>)</mo></mrow><mn>3</mn></msup></mrow></mrow></mfrac></mrow></mtd><mtd><mrow><mo>(</mo><mn>18</mn><mo>)</mo></mrow></mtd></mtr></mtable></math><mathematicafile></mathematicafile><image></image></mathcwu>
[0084] <crossreference>FIG. 13</crossreference> displays performance parameter FCCC obtained by correcting the data of <crossreference>FIG. 11</crossreference> according to equation (17) using the correction factor defined by equation (18) (<crossreference>FIG. 12</crossreference>). One sees that the corrected FCCC varies by only ±2.7% from 695 amperes over the entire range of discharge down to SOC=20%.
[0085] One determines the performance parameter “stateofhealth” SOH by either of two methods. The first method is to compare the computed “total storage capacity” TSC with an appropriate userinputted capacity rating such as the battery's rated “amperehour capacity” or rated “reserve capacity” in minutes. The second method is to compare the computed “fully charged cranking current” FCCC with an appropriate userinputted cranking rating such as the battery's rated “cold cranking amperes” (CCA). In either case, the battery is assumed to have “failed” the SOH test if the calculated parameter value is less than a predetermined fraction, say 75%, of the rated parameter value. Either SOH method, or both methods, may be employed—depending upon the type of service that the battery is expected to experience.
[0086] This completes the disclosure of my invention. <crossreference>FIGS. 14 and 15</crossreference>, however, will serve to place the innovative nature of my invention in perspective. <crossreference>FIG. 14</crossreference> illustrates the “commonly accepted” equivalent circuit model of a cell/battery at the present time. (See, e.g., U.S. Pat. No. 6,167,349 to Alvarez. See also E. Karden, et al., “A method for measurement and interpretation of impedance spectra for industrial batteries”, J Power Sources 85 (2000), pp. 7278.) The “commonly accepted” model, also known as the “Randles equivalent circuit”, places a “charge transfer resistance” and a “double layer capacitance” in parallel with one another. In my opinion, this model is fundamentally wrong and cannot possibly lead to correct evaluation of any of the performance parameters or physical parameters evaluated herein.
[0087] My measurements and analysis have shown that the “charge transfer conductance” (the reciprocal of “charge transfer resistance”) and the “double layer capacitance” are elements of two separate GC subcircuits that are actually in series with one another in the correct circuit model (see <crossreference>FIG. 15</crossreference>). Furthermore, the “double layer capacitance” of the correct model varies directly with the number of reaction sites available for the discharge reaction (equation (7)); while the “charge transfer conductance” of the correct model varies directly with both the number of sites available for the discharge reaction and also the number available for the charge reaction (equation (4)). These important new discoveries set my work totally apart from all of the prior art.
[0088] To summarize, I have herein disclosed new methods and apparatus for evaluating the following six performance parameters:
[0089] 1. “Absolute stored charge” ASC (equation (13)).
[0090] 2. “Total storage capacity” TSC (equation (14)).
[0091] 3. “Stateofcharge” SOC=ASC/TSC (equation (9)).
[0092] 4. “Absolute cranking current” ACC (equation (16)).
[0093] 5. “Fully Charged Cranking Current” FCCC (equation (17)).
[0094] 6. “StateOfHealth” SOH.
[0095] Furthermore, in the course of this disclosure I have also revealed new methods and apparatus for evaluating the following six important physical parameters:
[0096] 1. “Exchange current” i<highlight><subscript>0 </subscript></highlight>(equation (3)).
[0097] 2. “Maximum exchange current” i<highlight><subscript>0max </subscript></highlight>(equation (12)).
[0098] 3. “Charge transfer conductance” G3.
[0099] 4. “Maximum charge transfer conductance” G3<highlight><subscript>max </subscript></highlight>(equation (11)).
[0100] 5. “Double layer capacitance” C2.
[0101] 6. “Maximum double layer capacitance” C2<highlight><subscript>100 </subscript></highlight>(equation (10)).
[0102] My invention, however, is not limited to evaluating only these twelve parameters.
[0103] Although my disclosure has referred to particular apparatus and algorithms previously disclosed in U.S. Pat. Nos. 6,002,238, 6,037,777, 6,172,483, 6,222,369, and 6,262,563, other methods will be apparent to those skilled in the art. For example, one could evaluate elements of the correct circuit model by using pulsed or stepped excitation such as that described in U.S. Pat. No. 6,118,275 to Yoon or in U.S. Pat. No. 6,167,349 to Alvarez; or by using random or pseudorandom excitation such as that described in PCT Application WO 99/18448 to Scott. One could also employ bridges, frequency response analyzers, or other types of ac instrumentation to measure complex admittance or complex impedance at multiple frequencies. The range of measurement frequencies is unrestricted and could include frequencies in the millihertz and microhertz region (f<1) as well as frequencies in the range of hertz (f>1).
[0104] The embodiment disclosed in <crossreference>FIG. 1</crossreference> utilizes timevarying electrical excitation i(t) generated internally to apparatus 5 by internal measuring circuitry 10. Alternatively however, the requisite timevarying electrical excitation could be developed by an external source 65 as disclosed in <crossreference>FIG. 16</crossreference>. Such an external source could simply comprise normal “noise” currents flowing through a cell/battery during service, such as taught in PCT Application WO 93/22666 to Robinson. It could also comprise “ripple” signals arising from an unfiltered battery charger during benchcharging of the cell/battery or charging by an alternator in a vehicle. Although, timevarying current i(t) has been presented as an electrical excitation and timevarying voltage v(t) as an electrical response, the roles of i(t) and v(t) could be reversed. Timevarying voltage v(t) could be the electrical excitation and timevarying current i(t) the electrical response. All such modifications and variations are included in my invention.
[0105] It is well known that elements of any circuit model can be readily subdivided and rearranged to obtain a derivative circuit that appears to be quite different, but is in effect electrically equivalent to the original circuit. My invention includes all such derivative circuits that are electrically equivalent to the models of <crossreference>FIG. 2</crossreference> and/or <crossreference>FIG. 3</crossreference>. One could use a circuit model containing, e.g., eight or ten elements rather than the six elements treated herein. This straightforward modification is likewise included in my invention.
[0106] Instead of the algorithms disclosed in U.S. Pat. Nos. 6,037,777 and 6,222,369 to evaluate elements of the circuit model, one could simply employ a conventional “complex leastsquares curve fitting” procedure. If accuracy is not essential, one could even take advantage of the fact that the time constants are widely separated from one another and simply assume that the subcircuits are not coupled. Thus, with some batteries, it may be possible to obtain a reasonably accurate circuit model from a very simple computational analysis of measured timevarying electrical response.
[0107] The invention is not limited to the particular circuitry implementations disclosed herein. Measuring circuitry, electrical excitation circuitry, electrical response sensing circuitry, computational circuitry, etc., can be implemented in hardware, software, or combinations thereof. Such circuitry can share common elements or be implemented with common components such as a common microprocessor, microcontroller, or personal computer. Workers skilled in the art will recognize that these and other variations may be made in form and detail without departing from the true spirit and scope of my invention.