Quasi-adaptive method for determining a battery's state of charge

• US 6,359,419 B1
• Filed: 12/27/2000
• Issued: 03/19/2002
• Est. Priority Date: 12/27/2000
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Sarbacker, Shawn D., Koch, Brian James, Verbrugge, Mark William, Tate, Edward Dean Jr.
• Primary Examiner(s): TOATLEY, GREGORY J
• Application Number:
  US09/748,097
• Time in Patent Office: 447 Days
• Field of Search: 320/132, 324/427, 324/428, 702/63
• US Class Current: 320/132
• CPC Class Codes: B60K 6/44 Series-parallel type
• CPC Class Codes: B60K 6/52 Driving a plurality of drive axles, e.g. four-wheel drive
• CPC Class Codes: B60L 2210/14 Boost converters
• CPC Class Codes: B60L 2210/40 DC to AC converters
• CPC Class Codes: B60L 2220/14 Synchronous machines
• CPC Class Codes: B60L 2220/18 Reluctance machines
• CPC Class Codes: B60L 2240/36 Temperature of vehicle components or parts
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2260/28 Four wheel or all wheel drive
• CPC Class Codes: B60L 2260/56 Temperature prediction, e.g. for pre-cooling
• CPC Class Codes: B60L 3/0046 relating to electric energy storage systems, e.g. batteries or capacitors
• CPC Class Codes: B60L 50/16 with provision for separate direct mechanical propulsion
• CPC Class Codes: B60L 50/61 by batteries charged by engine-driven generators, e.g. series hybrid electric vehicles
• CPC Class Codes: B60L 58/13 Maintaining the SoC within a determined range
• CPC Class Codes: B60L 58/18 of two or more battery modules
• CPC Class Codes: B60L 58/21 having the same nominal voltage
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 20/13 in order to stay within battery power input or output limits; in order to prevent overcharging or battery depletion
• CPC Class Codes: B60W 2510/244 Charge state
• CPC Class Codes: G01R 31/367 : Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/3828 : using current integration
• CPC Class Codes: G01R 35/005 : Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence
• CPC Class Codes: Y02T 10/62 : Hybrid vehicles
• CPC Class Codes: Y02T 10/70 : Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 : Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 10/72 : Electric energy management in electromobility
• CPC Class Codes: Y10S 903/903 : having energy storing means, e.g. battery, capacitor
• CPC Class Codes: Y10S 903/907 : Electricity storage, e.g. battery, capacitor
• CPC Class Codes: Y10S 903/916 : with plurality of drive axles

Abstract

A method and apparatus for determining the state of charge of a battery including determining a current-based state of charge measurement based on coulomb integration, determining a voltage-based state of charge measurement based on the resistance of said battery and a hysteresis voltage, and combining the current-based state of charge measurement and the voltage-based state of charge measurement to generate the state of charge measurement of the battery.

Claims

1. A method of determining the state of charge of a battery comprising:

determining a current-based state of charge measurement based on coulomb integration;

determining a voltage-based state of charge measurement based on the resistance of the battery and a hysteresis voltage; and

combining the current-based state of charge measurement and the voltage-based state of charge measurement with a weighting factor to generate the state of charge of the battery.

2. The method of claim 1 wherein the step of determining the current-based state of charge is based on the equation:

${\mathrm{SOC}}_C<br><br>\left(t\right)=\mathrm{SOC}<br><br>\left(t-\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>t\right)-\left[100<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{\left[\left({\mathrm{\eta <br><br>}}_I<br><br>I_{t-1}+{\mathrm{\eta <br><br>}}_I<br><br>I_t\right)/2\right]}{A<br><br>\text{\hspace{1em}<br><br>}<br><br>h_{\mathrm{nominal}}}+{\left(S_D\right)}_{t-\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>t}\right]<br><br>\frac{\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>t}{3600}.$

3. The method of claim 1 wherein the step of determining a voltage-based state of charge further comprises determining the battery voltage using the open circuit voltage of the battery and the ohmic drop of the battery.

4. The method of claim 3 wherein the step of determining a voltage-based state of charge further comprises determining the open circuit voltage of the battery as a function of temperature, hysteresis voltage and an initial state of charge of the battery.

5. The method of claim 1 wherein the battery is a nickel/metal hydride battery.

6. A method of determining the state of charge of a nickel/metal hydride battery comprising:

determining a first state of charge measurement based on coulomb integration;

determining a second state of charge measurement based on a voltage model;

determining a weighting factor to be used in combining said first state of charge measurement and said second stage of charge measurement; and

combining said first state of charge measurement and said second stage of charge measurement to determine the state of charge of the nickel/metal hydride battery.

7. The method of claim 6 wherein the step of determining the second state of charge measurement comprises:

determining the standard cell potential of the nickel/metal hydride battery;

determining the entropy of the cell reaction of the nickel/metal hydride battery; and

determining a hysteresis voltage of the nickel/metal hydride battery.

8. The method of claim 6 further wherein the step of combining said first state of charge measurement and said second stage of charge measurement to determine the state of charge of the nickel/metal hydride battery comprises using the equation:

9. The method of claim 6 wherein the step of determining the hysteresis voltage comprises monitoring the voltage and current of the battery.

10. A vehicle powertrain control system comprising:

a battery pack;

a power inverter coupled to said battery pack;

a controller controlling said power inverter, said controller monitoring the state of charge of said battery pack; and

a state of charge algorithm included in said controller, said state of charge algorithm based on a coulomb integration method and a voltage based model.

11. The vehicle powertrain control system of claim 10 wherein said battery pack comprises at least one nickel/metal hydride battery.

12. The vehicle powertrain control system of claim 10 wherein said battery pack comprises a plurality of nickel/metal hydride batteries connected in series.

13. The vehicle powertrain control system of claim 10 wherein said battery pack comprises at least one lead acid battery.

14. The vehicle powertrain control system of claim 10 wherein said battery pack comprises at least one lithium battery.

15. The vehicle powertrain control system of claim 10 wherein said controller is capable of communicating over an automotive communications network.

16. The vehicle powertrain control system of claim 15 wherein said automotive communications network comprises a CAN network.

17. The vehicle powertrain control system of claim 10 further comprising a motor/generator coupled to said inverter.