Method and apparatus for generalized recursive least-squares process for battery state of charge and state of health

• US 7,324,902 B2
• Filed: 02/18/2003
• Issued: 01/29/2008
• Est. Priority Date: 02/18/2003
• Status: Expired due to Term

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Frisch, Damon R., Koch, Brian J., Verbrugge, Mark W., Tate, Edward D. Jr.
• Primary Examiner(s): Barlow; John
• Assistant Examiner(s): Cherry; Stephen J.
• Application Number:
  US10/368,869
• Publication Number:
  US 20040162683A1
• Time in Patent Office: 1,806 Days
• Field of Search: 702/64, 700/286, 324/436, 324/428, 324/427, 322/11, 322/18, 320/116, 320/132, 320/136, 318/139
• US Class Current: 702/64
• CPC Class Codes: G01R 31/006 on road vehicles, e.g. automobiles or trucks testing of ignition installations peculiar to internal combustion engines F02P17/00
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/3828 using current integration
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health

Abstract

A method for determining a voltage based or current based state of charge (SOC) and state of health (SOH) of a battery system is provided. The method includes: providing a model of the battery system including an equivalent circuit having both low frequency and high frequency elements; establishing a plurality of functional relationships comprising relationship of the equivalent circuit with SOC; reducing at least part of the plurality of functional relationships into a set of time segmented recursive functional relationships, wherein a state at a first time t can be modeled by a functional presentation of a state at a second time t−Δt that occurred before the first time t; and computing a set of data points based upon the set of time segmented recursive functional relationships using a matrix for operation in matrix algebra.

Claims

1. A method for determining a voltage based state of charge (SOC) and state of health (SOH) of a battery system, comprising:

providing a model of said battery system including an equivalent circuit having both low frequency and high frequency elements;

establishing a plurality of functional relationships including relationship of said equivalent circuit with SOC;

reducing at least part of said plurality of functional relationships into a set of time segmented recursive functional relationships, wherein a first state at a first timet can be modeled by a functional presentation of a second state at a second time t−

Δ

t that occurred before said first time t;

computing a set of data points based upon said set of time segmented recursive functional relationships using a matrix for operation in matrix algebra; and

performing at least one of indicating a SOC of the battery system, regulating limits of a battery pack, and charging a battery pack based on said set of data points.

2. The method of claim 1, further comprising:

repeating said computing step based upon a later time segment;

establishing a plurality of data points based upon the repetition of said computing step; and

assigning a weight to said plurality of data points.

3. The method of claim 1, comprising providing a set of starting values for said plurality of functional relationships.

4. The method of claim 1, wherein said establishing step includes the following functional relationships:

V_oc(T, SOC, V_o, V_hyst);

V_o(T, SOC);

V_hyst(I);

R, (T, SOC);

R_ct, [sign(I), T, SOC]; and

C_D[sign(I), T, SOC];

wherein V is open circuit voltage, T is temperature, V_o is open circuit voltage without hysteresis contribution, and V_hyst is hysteresis voltage of the battery system, R is series resistance, R_ct is parallel resistance, and C_D is parallel capacitance.

5. A method for determining a state of charge (SOC) or state of health (SOH) of a battery system using a generalized regression method, comprising:

determining a current-based SOC result based on Coulomb integration or Coulomb counting, wherein said Coulomb integration or counting includes self discharge and current efficiency computations;

determining a voltage based SOC result based on measurements or previous computations as a starting point, and using a recursive adaptive filter for extracting a plurality of parameter values, including;

providing a model of said battery system comprising an equivalent circuit having both low frequency and high frequency elements;

establishing a plurality of functional relationships comprising relationship of said equivalent circuit with SOC;

reducing at least part of said plurality of functional relationships into a set of time segmented recursive functional relationships, wherein a state at a time can be modeled by a functional presentation of a state at a time that occurred before; and

computing a set of data points based upon said set of time segmented recursive functional relationships using a matrix for operation in matrix algebra;

combining current based Soc result and the voltage based SOC result with a weighting factor to generate said SOC of said battery; and

based on said SOC of said battery system, performing at least one of indicating said SOC of said battery system, regulating limits of a battery pack, and charging a battery pack.

6. The method of claim 5, including:

repeating said computing step based upon a later time segment;

establishing a plurality of data points based upon the repetition of said computing step; and

assigning a weight to said plurality of data points.

7. The method of claim 5, including providing a set of starting values for said plurality of functional relationships.

8. The method of claim 5, wherein said establishing step includes establishing a functional relationship of SOC with an open circuit voltage.