Method and apparatus that detects state of charge (SOC) of a battery

• US 8,374,807 B2
• Filed: 11/11/2009
• Issued: 02/12/2013
• Est. Priority Date: 11/13/2008
• Status: Active Grant

• Current Assignee: Leidos Innovations Technology, Inc.
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Hall, A. Daniel
• Primary Examiner(s): NGHIEM, MICHAEL P
• Application Number:
  US12/616,593
• Publication Number:
  US 20100121591A1
• Time in Patent Office: 1,189 Days
• Field of Search: 702/63
• US Class Current: 702/63
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements

Abstract

A method and apparatus are provided for estimating a state of charge (SOC) of a battery. Curves are generated to expresses a relationship between a first parameter and an SOC over a region of interest. A voltage and a current of the battery during a period of time are measured to create a set of voltage and current data, which is then processed to create a set of processed data. The processed data is then combined with the generated curves to generate processed data as a function of SOC. A curve is generated that evaluates each SOC for accuracy and chance likelihood of fit. An SOC that minimizes both the error and chance is selected and output for display to the user on a user interface.

Claims

1. A method for estimating a state of charge (SOC) of a battery, comprising:

generating one or more curves with a processor, the generated one or more curves expressing an a priori relationship between a first parameter and the SOC of a battery over a region of interest;

taking a derivative with the processor of the generated one or more curves with respect to the SOC to generate a derived parameter with the SOC of the battery over the region of interest;

transforming with the processor a combination of the generated one or more curves into one or more supplemental curves to express the a priori relationship based on cell chemistry between a second parameter and one or more of current (I), polarization current (Ip), and open circuit voltage (OCV), and a voltage slope with respect to SOC(dOCV/dSOC);

measuring a voltage and a current of the battery during a period of time to create a set of voltage and current data;

processing with the processor the set of voltage and current data to create a set of processed data;

combining with the processor the one or more generated curves with the processed data to generate processed data as a function of SOC;

regressing with the processor the process data at multiple SOCs over the region of interest with respect to an equation which is representative of the battery to generate a curve that evaluates each SOC for accuracy;

selecting the SOC that minimizes errors; and

outputting the selected SOC for display to a user on a user-interface;

wherein Rp1(SOC,Ip)*Rp2(T) and Rohmic is used to track pulse (discharge) and regen (charge) peak power or track pulse (discharge) and regen (charge) power at any current or voltage discharge, where Rp1(SOC,Ip) is polarization resistance relative to SOC, Rp2(T) is polarization resistance relative to temperature, and Rohrnic is ohmic resistance.

2. The method of claim 1, wherein the SOC that minimizes the error is an SOC that minimizes an F statistic.

3. The method of claim 1, wherein the battery-operated device is one of a car, a truck, an aircraft, a motorcycle, a scooter, a boat, a military transport or combatant, a portable computer, a mobile telephone, a satellite telephone, a satellite, a spacecraft, a submarine, a MP3 player, a personal digital assistant (PDA), a portable communication device, a portable radio, and a portable television.

4. A battery-operated device, comprising:

a battery;

a user interface; and

a battery state of charge determination unit that generates one or more curves that express an a priori relationship between a first parameter and a state of charge (SOC) of the battery over a region of interest,

takes a derivative of the generated one or more curves with respect to the SOC to generate a derived parameter with the SOC of the battery over the region of interest,

transforms a combination of the generated one or more curves into one or more supplemental curves that express the a priori relationship between a second parameter with one or more of current (I), polarization current (Ip) and open circuit voltage (OCV), and a voltage slope with respect to SOC (dOCV/dSOC),

measures a voltage and a current of the battery during a period of time to create a set of voltage and current data,

processes the set of voltage and current data to create a set of processed data,

combines one or more generated curves with the processed data to generate processed data as a function of SOC,

regresses the process data function at multiple SOCs over the region of interest with respect to an equation which is representative of the battery to generate a curve that evaluates each SOC for accuracy,

selects the SOC that minimizes errors, and

outputs the selected SOC for display to a user on the user-interface, wherein Rp1(SOC,Ip)*Rp2(T) and Rohmic is used to track pulse (discharge) and regen (charge) peak power or track pulse (discharge) and regen (charge) power at any current or voltage discharge, where Rp1(SOC,Ip) is polarization resistance relative to SOC, Rp2(T) is polarization resistance relative to temperature, and Rohmic is ohmic resistance.

5. The battery-operated device of claim 4, wherein the SOC that minimizes both the error and chance occurrence is the SOC that minimizes an F statistic.

6. The battery-operated device of claim 4, wherein the battery-operated device is one of a car, a truck, an aircraft, a motorcycle, a scooter, a boat, a military transport or combatant, a portable computer, a mobile telephone, a satellite telephone, a satellite, a spacecraft, a submarine, a MP3 player, a personal digital assistant (PDA), a portable communication device, a portable radio, and a portable television.

7. A non-transitory computer-readable medium storing instructions for controlling a computing device for estimating a state of charge (SOC) of a battery, the instructions comprising:

generating one or more curves that express an a priori relationship between a first parameter and the SOC of a battery over a region of interest;

taking a derivative of the generated one or more curves with respect to the SOC to generate a derived parameter with the SOC of the battery over the region of interest;

transforming a combination of the generated one or more curves into one or more supplemental curves to express the a priori relationship based on cell chemistry between a second parameter with one or more of current (I), polarization current (Ip), and open circuit voltage (OCV), a voltage slope with respect to SOC (dOCV/dSOC);

measuring a voltage and a current of the battery during a period of time to create a set of voltage and current data;

processing the set of voltage, ‘

rod current data to create a set of processed data;

combining one or more generated curves with the processed data to generate processed data as a function of SOC;

regressing the process data function at multiple SOCs over the region of interest with respect to an equation which is representative of the battery to generate a curve that evaluates each SOC for accuracy;

selecting the SOC that minimizes errors; and

outputting the selected SOC for display to the user on a user-interface,

wherein Rp1(SOC,Ip)*Rp2(T) and Rohmic is used to track pulse (discharge) and regen (charge) peak power or track pulse (discharge) and regen (charge) power at any current or voltage discharge, where Rp1(SOC,Ip) is polarization resistance relative to SOC, Rp2(T) is polarization resistance relative to temperature, and Rohmic is ohmic resistance.