METHOD FOR DETERMINING A STATE OF A RECHARGEABLE BATTERY DEVICE IN REAL TIME

• US 20120101674A1
• Filed: 10/26/2010
• Published: 04/26/2012
• Est. Priority Date: 10/26/2010
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: VERBRUGGE, MARK W., WANG, SHUOQIN, WANG, JOHN S., LIU, PING
• Granted Patent: US 9,091,735 B2
• Time in Patent Office: Days
• US Class Current: 701/22
• 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 of determining and predicting a state of a rechargeable battery device in real time involves measuring a current and a voltage of the rechargeable battery in real time, inputting the measured current and voltage into an algorithm, and applying the algorithm to determine the state of the rechargeable battery. The algorithm includes a first mathematical model based on a direct solution of at least one differential equation characterizing an equivalent RC circuit of the battery as a function of time. The first model generates a plurality of parameters that are usable to determine the state of the battery. The algorithm further includes a second mathematical model configured to regress the parameters over time, and a third mathematical model configured to estimate the state of the battery.

Claims

1. A method of determining and predicting a state of a rechargeable battery device in real time, comprising:

via respective measuring devices, measuring a current and a voltage of the rechargeable battery in real time;

via a processor operatively coupled to memory and to a computer-readable medium encoded with an algorithm for determining the state of the rechargeable battery device in real time, utilizing the measured current and voltage in the algorithm, wherein the algorithm comprises;

a first mathematical model based on a direct solution of at least one differential equation characterizing an equivalent RC circuit of the rechargeable battery as a function of time, wherein the first mathematical model is configured to generate a plurality of parameters that are usable to determine the state of the rechargeable battery; and

a second mathematical model configured to regress the plurality of parameters over time; and

a third mathematical model configured to estimate the state of the rechargeable battery; and

via the processor, applying the algorithm to determine the state of the rechargeable battery.

2. The method as defined in claim 1 wherein the first mathematical model is represented by:

3. The method as defined in claim 2 wherein the plurality of parameters include R, R_ct—

_c, R<sub>ct—

d</sub>, C_c, C_d, and V_oc.

4. The method as defined in claim 1 wherein the second mathematical model includes a weighted recursive least squares method configured to regress the model parameters using the measured current and voltage over time.

5. The method as defined in claim 1 wherein the state of the rechargeable battery is a state of charge (SOC), and wherein the third mathematical model is represented by:

i) SOC=w(SOC_c)+(1−

w)(SOC_v) during a charging state (c) of the rechargeable battery, and

wherein w is a weighting factor, and SOC_v is the state of charge with respect to an open circuit voltage (V_oc) of the rechargeable battery.

6. The method as defined in claim 5 wherein the state of charge during the charging state of the rechargeable battery (SOC_c) is represented by:

7. The method as defined in claim 1 wherein state of the rechargeable battery is a state of power (SOP), and wherein the third mathematical model is configured to:

i) estimate a charging power capability of the battery P_c, which is represented by;

P_c(t)=I_c(t)·

V_max; and

ii) estimate current as a function of time I(t), which is represented by;

8. The method as defined in claim 1 wherein state of the rechargeable battery is a state of power (SOP), and wherein the third mathematical model is configured to:

i) estimate a discharging power capability of the rechargeable battery P_d, which is represented by;

P_d(t)=I_c(t)·

V_min; and

ii) estimate current as a function of time I(t), which is represented by;

9. The method as defined in claim 1 wherein the applying of the algorithm includes solving for a charging state of the rechargeable battery by using only charging state data as input.

10. The method as defined in claim 1 wherein the applying of the algorithm includes solving for a discharging state of the rechargeable battery by using only discharging state data as input.

11. A control system for a vehicle, comprising:

a module including at least one rechargeable battery;

a first device for measuring a magnitude and direction of current flowing through the at least one rechargeable battery;

a second device for measuring a voltage of the at least one battery; and

a controller operatively associated with the module, the controller including a processor operatively coupled to memory and to a computer-readable medium encoded with an algorithm, the processor configured to execute the algorithm that utilizes measured current and voltage obtained from the first and second devices, respectively, to predict a state of the at least one rechargeable battery, the algorithm comprising;

a first mathematical model based on a direct solution of at least one differential equation characterizing an equivalent RC circuit of the at least one rechargeable battery as a function of time, wherein the first mathematical model is configured to generate a plurality of parameters that are usable to predict the state of the at least one rechargeable battery; and

a second mathematical model configured to regress the plurality of parameters over time; and

a third mathematical model configured to estimate the state of the at least one rechargeable battery.

12. The control system as defined in claim 11 wherein the first mathematical model is represented by:

13. The control system as defined in claim 12 wherein the plurality of parameters include R, R_ct—

_c, R<sub>ct—

d</sub>, C_c, C_d, and V_oc.

14. The control system as defined in claim 13 wherein the second mathematical model includes a weighted recursive least squares method configured to exponentially damp the measured current and voltage over time.

15. The control system as defined in claim 11 wherein the state of the at least one rechargeable battery is a state of charge (SOC), and wherein the third mathematical model is represented by:

i) SOC=w(SOC_c)+(1−

w)(SOC_v) during a charging state (c) of the at least one rechargeable battery, and

wherein w is a weighting factor, and SOC_v is the state of charge with respect to an open circuit voltage (V_oc) of the at least one rechargeable battery.

16. The control system as defined in claim 15 wherein:

i) the state of charge during the charging state of the at least one rechargeable battery (SOC_c) is represented by;

17. The control system as defined in claim 11 wherein:

i) state of the at least one rechargeable battery is a state of power (SOP), and wherein the third mathematical model is configured to;

estimate a charging power capability of the at least one rechargeable battery P_c, which is represented by;

P_c(t)=I_c(t)·

V_max; and

estimate current as a function of time I(t), which is represented by;

18. The method as defined in claim 11 wherein the applying of the algorithm includes solving for a charging state of the at least one rechargeable battery by assuming that a discharging state of the at least one rechargeable battery is zero.

19. The method as defined in claim 11 wherein the applying of the algorithm includes solving for a discharging state of the at least one rechargeable battery by assuming that a charging state of the at least one rechargeable battery is zero.

20. A computer-readable medium encoded with a computer program that includes computer-readable code for executing an algorithm for determining a state of a rechargeable battery device in real time, the algorithm comprising:

a first mathematical model based on a direct solution of at least one differential equation characterizing an equivalent RC circuit of the rechargeable battery as a function of time, wherein the first mathematical model is configured to generate a plurality of parameters that are usable to determine the state of the rechargeable battery; and

a second mathematical model configured to regress the plurality of parameters over time; and

a third mathematical model configured to estimate the state of the rechargeable battery.