SYSTEM AND METHOD FOR SENSING BATTERY CAPACITY

• US 20160116543A1
• Filed: 11/02/2015
• Published: 04/28/2016
• Est. Priority Date: 12/06/2010
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Barsukov, Yevgen, Zhang, Yandong, Blackwell, Dale Allen
• Granted Patent: US 10,203,374 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

One embodiment of the invention includes a battery sense system. The system includes a temperature sensor configured to measure a temperature of a battery and a memory configured to store predetermined data associated with steady-state and transient behaviors of the battery relative to a depth of discharge (DOD) of the battery. The system also includes a controller configured to measure a voltage of the battery and to calculate a state of charge (SOC) of the battery based on the voltage, the predetermined data, and the temperature.

Claims

1. A battery sense system comprising:

a temperature sensor configured to measure a temperature of a battery;

a memory configured to store predetermined data associated with steady-state and transient behaviors of the battery relative to a depth of discharge (DOD) of the battery; and

a controller configured to measure a voltage of the battery and to calculate a state of charge (SOC) of the battery based on the voltage, the predetermined data, and the temperature.

2. The system of claim 1, wherein the controller is configured to measure the voltage and calculate the SOC at each of a plurality of sampling times, and wherein the predetermined data associated with steady-state and transient behaviors of the battery comprises a temperature dependent resistance of the battery, the controller being configured to estimate a current generated by the battery based on the voltage and the temperature dependent resistance of the battery, and being further configured to calculate the SOC of the battery at a current sampling time based on the estimated current at a previous sampling time.

3. The system of claim 1, wherein the predetermined data associated with the steady-state and transient behaviors of the battery is determined based on modeling the battery as a dynamic battery model comprising a steady-state circuit portion and a transient circuit portion, the dynamic battery model comprising at least one RC network.

4. The system of claim 3, wherein the at least one RC network comprises:

a first RC network associated with the steady-state circuit portion configured as a first resistor and a first capacitor coupled in series; and

at least one second RC network associated with the transient circuit portion, each of the at least one second RC network being configured as a second resistor and a second capacitor coupled in parallel.

5. The system of claim 4, wherein the predetermined data associated with the steady-state and transient behaviors of the battery comprises a ratio of capacitance values of the first and second capacitors, a ratio of resistance values of the first and second resistors, temperature-dependent linear equation variables for a voltage across the first capacitor, and temperature-dependent exponential equation variables associated with a total resistance of the battery, all as a function of a plurality of DOD points of the battery.

6. The system of claim 5, wherein the controller is configured to calculate the resistance values of the first and second resistors of the dynamic battery model based on the ratio of resistance values of the first and second resistors and the temperature-dependent exponential equation variables associated with a total resistance of the battery as a function of the temperature of the battery, and to calculate the capacitance values of the first and second capacitors of the dynamic battery model based on the ratio of capacitance values of the first and second capacitors and the temperature-dependent linear equation variables for the voltage across the first capacitor as a function of the temperature of the battery.

7. The system of claim 6, wherein the controller is further configured to update the temperature-dependent exponential equation variables associated with a total resistance of the battery as a function of the temperature of the battery in the memory to account for aging of the battery.

8. The system of claim 6, wherein the controller is further configured to estimate a current generated by the battery at a current sampling time based on the resistance values of the first and second resistors of the dynamic battery model and the capacitance values of the first and second capacitors of the dynamic battery model and based on the estimated current through the battery at a previous sampling time.

9. The system of claim 8, wherein the controller is further configured to calculate the SOC of the battery based on the estimated current of the battery and the DOD of the battery at the previous sampling time.

10. The system of claim 3, wherein at least a portion of the predetermined data associated with the steady-state and transient behaviors of the battery is determined based on applying a predetermined load to the dynamic battery model and measuring a change in a voltage associated with the dynamic battery model as a function of a current through the predetermined load.

11. The system of claim 10, wherein at least a portion of the predetermined data associated with the steady-state and transient behaviors of the battery is determined based on measuring a voltage response associated with the dynamic battery model upon removing the predetermined load.

12. A method for calculating a state of charge (SOC) of a battery, the method comprising:

modeling the battery as a dynamic battery model comprising a steady-state circuit portion and a transient circuit portion to determine predetermined data associated with steady-state and transient behaviors of the battery relative to a depth of discharge (DOD) of the battery;

determining a temperature of the battery;

measuring a voltage of the battery;

accessing the predetermined data from a memory; and

calculating the SOC of the battery based on the voltage, the predetermined data, and the temperature.

13. The method of claim 12, wherein modeling the battery comprises:

modeling the steady-state circuit portion as a first resistor and a first capacitor coupled in series;

modeling the transient circuit portion as a second resistor and a second capacitor coupled in parallel; and

calculating values of the first and second capacitors and the first and second resistors as a function of the DOD of the battery, the values of the first and second capacitors and the first and second resistors forming a portion of the predetermined data associated with the steady-state and transient behaviors of the battery.

14. The method of claim 13, wherein modeling the battery further comprises generating the predetermined associated with the steady-state and transient behaviors of the battery as a ratio of capacitance values of the first and second capacitors, a ratio of resistance values of the first and second resistors, temperature-dependent linear equation variables for a voltage across the first capacitor, and temperature-dependent exponential equation variables associated with a total resistance of the battery, all as a function of a plurality of DOD points of the battery.

15. The method of claim 14, wherein calculating the SOC comprises:

calculating the resistance values of the first and second resistors of the dynamic battery model based on the ratio of resistance values of the first and second resistors and the temperature-dependent exponential equation variables associated with a total resistance of the battery as a function of the temperature of the battery; and

calculating the capacitance values of the first and second capacitors of the dynamic battery model based on the ratio of capacitance values of the first and second capacitors and the temperature-dependent linear equation variables for the voltage across the first capacitor as a function of the temperature of the battery.

16. The method of claim 15, wherein calculating the SOC further comprises:

estimating a current generated by the battery at a current sampling time based on the resistance values of the first and second resistors of the dynamic battery model and the capacitance values of the first and second capacitors of the dynamic battery model and based on the estimated current through the battery at a previous sampling time; and

calculating the SOC of the battery based on the estimated current generated by the battery and the DOD of the battery at the previous sampling time.