BATTERY STATE OF CHARGE TRACKING, EQUIVALENT CIRCUIT SELECTION AND BENCHMARKING

• US 20140244225A1
• Filed: 02/20/2014
• Published: 08/28/2014
• Est. Priority Date: 02/24/2013
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation), University of Connecticut (State of Connecticut)
• Original Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation), University of Connecticut (State of Connecticut)
• Inventors: BALASINGAM, Balakumar, FRENCH, Brian, BAR-SHALOM, Yaakov, PATTIPATI, Bharath, PATTIPATI, Krishna, MEACHAM, James, WILLIAMS, Travis, AVVARI, Gopi Vinod, HWANG, Tai-Sik
• Granted Patent: US 10,664,562 B2
• Time in Patent Office: Days
• US Class Current: 703/2
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G06F 30/367 Design verification, e.g. using simulation, simulation program with integrated circuit emphasis [SPICE], direct methods or relaxation methods

Abstract

A method includes calculating a first estimated state of charge (SOC) of a battery at a first time, receiving a voltage value representing a measured voltage across the battery at a second time, calculating a filter gain at the second time, and calculating a second estimated SOC of the battery at the second time based on the first estimated SOC, the voltage value, and the filter gain. Another method includes storing, in a memory, a library of equivalent circuit models representing a battery, determining an operational mode of a battery based on a load associated with the battery, selecting one of the equivalent circuit models based on the determined operational mode, and calculating a state of charge of charge (SOC) of the battery using the selected equivalent circuit model.

Claims

1. A method comprising:

storing, in a memory, a library of equivalent circuit models representing a battery;

determining an operational mode of a battery based on a load associated with the battery;

selecting one of the equivalent circuit models based on the determined operational mode; and

calculating a state of charge of charge (SOC) of the battery using the selected equivalent circuit model.

2. The method of claim 1, wherein

the operational mode is based on a high voltage load drawing variable current,

the operational mode includes a corresponding equivalent circuit model including a first resistance-current (RC) circuit and a second RC circuit.

3. The method of claim 1, wherein

the operational mode is based on a variable voltage load,

the operational mode includes a corresponding equivalent circuit model including a resistance-current (RC) circuit.

4. The method of claim 1, wherein

the operational mode is based on a variable voltage load,

the operational mode includes a corresponding equivalent circuit model including a resistor and a bias component.

5. The method of claim 1, wherein

the operational mode is based on a low voltage load,

the operational mode includes a corresponding equivalent circuit including a resistor.

6. The method of claim 1, wherein

at least one of the equivalent circuit models includes a hysteresis component, and

the hysteresis component is modeled as a open circuit voltage (OCV) calculation error.

7. The method of claim 1, further comprising:

measuring a terminal voltage of an equivalent battery during a discharge of the equivalent battery;

determining a linear equation based on the measured terminal voltage; and

calculating at least one parameter using a weighted least squared algorithm based on the linear equation, the calculating of the SOC of the battery is based on the at least one parameter.

8. The method of claim 1, further comprising:

benchmarking the SOC based on at least one of a coulomb counting error metric, an OCV-SOC error metric and a predicted time-to-voltage (TTV) error metric.

9. A system comprising:

a data store configured to store a library of equivalent circuit models representing a battery;

a model selection module configured to select an equivalent circuit model based on an operational mode of the battery; and

a filter module configured to calculate an estimated state of charge (SOC) of the battery based on the selected equivalent circuit model.

10. The system of claim 9, further comprising:

an operational mode module configured to determine an operational mode of the battery based on at least one of a current associated with the battery and a voltage associated with the battery.

11. The system of claim 9, wherein

the operational mode is based on a high voltage load drawing variable current, the operational mode includes a corresponding equivalent circuit model including a first resistance-current (RC) circuit and a second RC circuit.

12. The system of claim 9, wherein

the operational mode is based on a variable voltage load, the operational mode includes a corresponding equivalent circuit model including a resistance-current (RC) circuit.

13. The system of claim 9, wherein

the operational mode is based on a variable voltage load,

the operational mode includes a corresponding equivalent circuit model including a resistor and a bias component.

14. The system of claim 9, wherein

the operational mode is based on a low voltage load,

the operational mode includes a corresponding equivalent circuit including a resistor.

15. The method of claim 9, wherein

at least one of the equivalent circuit models includes a hysteresis component, and

the hysteresis component is modeled as a open circuit voltage (OCV) calculation error.

16. The system of claim 9, further comprising:

a model estimation module configured to calculate at least one voltage drop model parameter based on the selected equivalent model representing the battery, wherein the estimated SOC is calculated based on the at least one voltage drop model parameter.

17. The system of claim 9, further comprising a display configured to display the estimated SOC.

18. A computer readable medium including code segments that, when executed by a processor, cause the processor to:

select an equivalent circuit model from a library of equivalent circuit models representing a battery based on an operational mode of the battery; and

calculate a state of charge of charge (SOC) of the battery using the selected equivalent circuit model.

19. The computer readable medium of claim 38, further including code segments that cause the processor to:

calculate at least one voltage drop model parameter based on the selected equivalent model, wherein the SOC is calculated based on the at least one voltage drop model parameter.

20. The computer readable medium of claim 38, wherein at least one of the equivalent circuit models includes a hysteresis component, the code segments further cause the processor to:

calculate at least one voltage drop model parameter based on the selected equivalent model; and

vary the at least one voltage drop model parameter to reduce an open circuit voltage (OCV) error indicating hysteresis.