Systems and Methods for Determining Battery State of Charge

• US 20170123012A1
• Filed: 11/15/2016
• Published: 05/04/2017
• Est. Priority Date: 07/23/2009
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Yao, Chidong
• Granted Patent: US 10,527,680 B2
• Time in Patent Office: Days
• CPC Class Codes: G01R 31/3647 for determining the ability of a battery to perform a critical function, e.g. cranking
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

Systems (50, 200) and methods for determining a state of charge of a battery (52, 102, 150, 202) are provided. The system (50, 200) includes a power source (56, 206) configured to provide a charging current to a battery (52, 102, 150, 202). A controller (54, 104, 204) is included and configured to determine a state of charge of the battery (52, 102, 150, 202) based on impedance of a battery (52, 102, 150, 202) during a discharge time period based on an impedance and a state of charge relationship of a battery (52, 102, 150, 202) during a charge time period.

Claims

1. A system for determining a state of charge of a battery comprising:

a power source configured to provide a charging current to a battery; and

a controller configured to determine a state of charge based on impedance of a battery during a discharge time period based on an impedance and a state of charge relationship of a battery during a charge time period.

2. The system of claim 1, wherein the impedance of the battery during the charge time period for a given time instance is determined based at least on a measured voltage of the battery at the given time instance, the state of charge of the battery at the given time instance and a current provided by the power source at the given time instance.

3. The system of claim 2, wherein the controller is configured to determine impedances of the battery for a plurality of different time instances during the charge time period to determine an average scaling factor for the battery that is employed by the controller to predict an impedance of the battery.

4. The system of claim 1, wherein the controller is configured to store the relationship between the impedance of the battery and the state of charge of the battery.

5. The system of claim 1, wherein the impedance of the battery varies as a function of the state of charge of the battery.

6. The system of claim 5, wherein the controller employs the state of charge of the battery and a change in the state of charge of the battery to determine a subsequent state of charge of the battery for a given time instance.

7. The system of claim 6, wherein the controller employs the subsequent state of charge for the given time instance to determine an open circuit voltage for the subsequent state of charge.

8. The system of claim 7, wherein the controller accesses a lookup table to determine the relationship between the given state of charge of the battery and the open circuit voltage for the subsequent state of charge of the battery.

9. The system of claim 8, wherein the controller calculates an impedance of the battery for the given time instance with the equation:

10. The system of claim 1, wherein the controller is configured to determine a remaining battery run time of the battery based on the state of charge of the battery.

11. A system determining a state of charge of a battery, the system comprising:

a power source configured to provide the battery with a charging current; and

a controller configured to determine a plurality of impedances of the battery during a charge period, wherein each impedance of the plurality of impedances of the battery corresponds with a given state of charge of the battery.

12. The system of claim 11, wherein the controller is further configured to store the plurality of impedances and the corresponding states of charge of the battery.

13. The system of claim 12, wherein the controller is further configured to determine a state of charge of the battery during a discharge time period based on the stored plurality of impedances and the corresponding states of charge of the battery.

14. The system of claim 11, wherein a given impedance of the plurality of impedances of the battery is based on the state of charge for the battery corresponding to the given impedance, a measured voltage of the battery and the charging current of the battery.

15. The system of claim 14, wherein the controller is further configured to report a remaining battery run time for a given time instance via a battery status indicator based on a state of charge of the battery at the given time instance.

16. A method for determining a state of charge of a battery, the method comprising:

providing a charging current to the battery;

determining an initial state of charge (SOC) for the battery;

charging the battery for a predetermined time interval;

determining a subsequent SOC for the battery;

determining an open circuit voltage (OCV) corresponding to the subsequent SOC of the battery; and

calculating an impedance for the battery corresponding to the subsequent SOC of the battery.

17. The method of claim 16, further comprising determining a scaling factor for the battery based on one or more calculated impedances of the battery.

18. The method of claim 17, further comprising predicting an impedance associated with a given SOC of the battery based on the scaling factor.

19. The method of claim 16, further comprising:

detecting a disconnection from a power outlet; and

determining an SOC for the battery near the time of the disconnection.

20. The method of claim 19, further comprising:

determining an impedance of the battery for a given instance of time during a discharge time period;

determining a state of charge for the battery based on the correspondence between the impedance of the battery and the SOC of the battery.