State and parameter estimation for an electrochemical cell

• US 8,103,485 B2
• Filed: 11/11/2004
• Issued: 01/24/2012
• Est. Priority Date: 11/11/2004
• Status: Active Grant

• Current Assignee: LG Energy Solution Limited (LG Corporation)
• Original Assignee: LG Chem Limited (LG Corporation)
• Inventors: Plett, Gregory L.
• Primary Examiner(s): Shah, Kamini S
• Assistant Examiner(s): GEBRESILASSIE, KIBROM K
• Application Number:
  US10/985,617
• Publication Number:
  US 20060100833A1
• Time in Patent Office: 2,630 Days
• Field of Search: 320/137, 320/146, 320/148, 320/163, 320/118, 320/127, 320/132, 320/149, 320/152, 324/430, 324/434, 324/616, 703/2
• US Class Current: 703/2
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A system and a method for computing an estimated state of charge and an estimated cell resistance of an electrochemical cell are provided. The method includes predicting a first cell resistance value indicating a present resistance of the electrochemical cell utilizing a first nonlinear cell model. The method further includes predicting a first state of charge value indicating a present state of charge of the electrochemical cell utilizing a second nonlinear cell model. The method further includes measuring a voltage and, a current associated with the electrochemical cell to obtain a voltage value and a current value, respectively. The method further includes estimating a second state of charge value indicating the present state of charge of the electrochemical cell utilizing the second nonlinear cell model based on the first state of charge value, the first cell resistance value, the voltage value, and the current value. The method further includes estimating a second cell resistance value indicating the present resistance of the electrochemical cell utilizing the first nonlinear cell model based on the first cell resistance value, the first state of charge value, the voltage value, and the current value.

Claims

1. A method for determining an estimated state of charge value and an estimated cell resistance value associated with an electrochemical cell comprising:

predicting a first cell resistance value indicating a present resistance of the electrochemical cell utilizing a first nonlinear cell model;

predicting a first state of charge value indicating a present state of charge of the electrochemical cell utilizing a second nonlinear cell model;

measuring a voltage associated with the electrochemical cell to obtain a voltage value;

measuring a current associated with the electrochemical cell to obtain a current value;

calculating a second state of charge value associated with the electrochemical cell, utilizing an inverse open circuit voltage function having a parameter determined from the voltage value and the current value;

calculating the estimated state of charge value indicating the present state of charge of the electrochemical cell utilizing the second nonlinear cell model based on the first state of charge value, the second state of charge value, the first cell resistance value, the voltage value, and the current value;

calculating the estimated cell resistance value indicating the present resistance of the electrochemical cell utilizing the first nonlinear cell model based on the first cell resistance value, the first state of charge value, the second state of charge value, the voltage value, and the current value, and

storing the estimated state of charge value and the estimated cell resistance value in a storage medium.

2. The method of claim 1, further comprising:

predicting a first voltage polarization value indicating a present voltage polarization level of the electrochemical cell utilizing the second nonlinear cell model; and

estimating a second voltage polarization value indicating the present voltage polarization level of the electrochemical cell utilizing the second nonlinear cell model based on the first voltage polarization value, the first state of charge value, the voltage value, and the current value.

3. The method of claim 1, further comprising:

predicting a first hysteresis value indicating a present hysteresis of the electrochemical cell utilizing the second nonlinear cell model; and

estimating a second hysteresis value indicating the present hysteresis of the electrochemical cell utilizing the second nonlinear cell model based on the first hysteresis value, the first state of charge value, the voltage value, and the current value.

4. The method of claim 1, further comprising:

predicting a first capacity value indicating a present capacity the electrochemical cell utilizing the first nonlinear cell model; and

estimating a second capacity value indicating the present capacity of the electrochemical cell utilizing the first nonlinear cell model based on the first capacity value, the first state of charge value, the voltage value, and the current value.

5. A system for determining an estimated state of charge value and an estimated cell resistance value associated with of an electrochemical cell, comprising:

an arithmetic circuit configured to predict a first cell resistance value indicating a present resistance of the electrochemical cell utilizing a first nonlinear cell model;

the arithmetic circuit further configured to predict a first state of charge value indicating a present state of charge of the electrochemical cell utilizing a second nonlinear cell model;

a voltage sensor configured to measure a voltage associated with the electrochemical cell to obtain a voltage value, the voltage sensor coupled to the arithmetic circuit;

a current sensor configured to measure a current associated with the electrochemical cell to obtain a current value, the current sensor coupled to the arithmetic circuit;

the arithmetic circuit further configured to calculate a second state of charge value associated with the electrochemical cell utilizing an inverse open circuit voltage function having a parameter determined from the voltage value and the current value;

the arithmetic circuit further configured to calculate the estimated state of charge value indicating the present state of charge of the electrochemical cell utilizing the second nonlinear cell model based on the first state of charge value, the second state of charge value, the first cell resistance value, the voltage value, and the current value;

the arithmetic circuit further configured to calculate the estimated cell resistance value indicating the present resistance of the electrochemical cell utilizing the first nonlinear cell model based on the first cell resistance value, the first state of charge value, the second state of charge value, the voltage value, and the current value; and

the arithmetic circuit further configured to store the estimated state of charge value and the estimated cell resistance value in a storage medium.

6. The system of claim 5, wherein

the arithmetic circuit further configured to predict a first voltage polarization value indicating a present voltage polarization level of the electrochemical cell utilizing the second nonlinear cell model;

and

the arithmetic circuit further configured to estimate a second voltage polarization value indicating the present voltage polarization level of the electrochemical cell utilizing the second nonlinear cell model based on the first voltage polarization value, the first state of charge value, the voltage value, and the current value.

7. The system of claim 5, wherein

the arithmetic circuit further configured to predict a first hysteresis value indicating a present hysteresis of the electrochemical cell utilizing the second nonlinear cell model;

and

the arithmetic circuit further configured to estimate a second hysteresis value indicating the present hysteresis of the electrochemical cell utilizing the second nonlinear cell model based on the first hysteresis value, the first state of charge value, the voltage value, and the current value.

8. The system of claim 5, wherein

the arithmetic circuit further configured to predict a first capacity value indicating a present capacity the electrochemical cell utilizing the first nonlinear cell model;

and

the arithmetic circuit further configured to estimate a second capacity value indicating the present capacity of the electrochemical cell utilizing the first nonlinear cell model based on the first capacity value, first state of charge value, the voltage value, and the current value.