METHOD OF DETERMINING THE STATE OF CHARGE OF A BATTERY OF AN ELECTRONIC APPLIANCE

• US 20150088443A1
• Filed: 09/23/2014
• Published: 03/26/2015
• Est. Priority Date: 09/25/2013
• Status: Active Grant

• Current Assignee: STMicroelectronics International N.V. (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Grenoble 2 SAS (STMicroelectronics NV)
• Inventors: Lorin, Christophe, Garnier, Jean-Francois, MAZARD, Aurlien
• Granted Patent: US 10,073,144 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• 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 state of charge of a battery is estimated in several iterations, each iteration including: acquiring a measurement of intensity of current supplied by the battery, acquiring a measurement of voltage supplied by the battery, estimating a first state of charge of the battery based on a first estimated state of charge obtained upon a previous iteration and on the current intensity measurement, estimating a value of intensity of current supplied by the battery based on the voltage measurement and on a state of charge of the battery obtained upon the previous iteration, and calculating a corrected state of charge by adding to the first estimated state of charge a corrective term obtained by the product of a first correction gain multiplied by a factor representative of a difference between the estimated and measured current intensities.

Claims

1. A method, comprising:

iteratively estimating a state of charge of a battery, at least one iteration of the estimating including;

receiving an indication of an intensity of current supplied by the battery;

receiving an indication of a voltage supplied by the battery;

estimating a first state of charge of the battery during the iteration based on an estimated first state of charge of a previous iteration and on the received indication of the intensity of current supplied by the battery;

estimating an intensity of current supplied by the battery based on the received indication of the voltage supplied by the battery and on a corrected state of charge of the battery of the previous iteration, and

calculating a corrected state of charge of the iteration by adding to the estimated first state of charge of the iteration a corrective term, the corrective term being based on a product of a first correction gain and a factor representative of a difference between the estimated intensity of current and the received indication of the intensity of current supplied by the battery.

2. The method according to claim 1 wherein the iteration comprises estimating a second state of charge of the battery during the iteration based on a second estimated state of charge of the previous iteration and on the estimated intensity of current and the factor is determined based on a difference between the first and second estimated states of charge.

3. The method according to claim 2 wherein the first and second estimated states of charge are values integrated over a first period, and the factor is determined by deriving over the first period the difference between the first and second estimated states of charge.

4. The method according to claim 3 wherein the indication of the voltage is based on a measurement acquired in a second period, and the indication of the current intensity is based on a measurement acquired in a third period, the first period being greater than or equal to the second period and the second period being greater than or equal to the third period.

5. The method according to claim 4 wherein the first period is a multiple of the second period and of the third period.

6. The method according to claim 1 wherein the estimated intensity of current is based on the following equation:

7. The method according to claim 1 wherein the iteration comprises determining a corrected capacity value of the battery by adding to a corrected capacity value of the previous iteration a second corrective term, the second corrective term being based on a product of a second correction gain and a difference between the corrected state of charge of the iteration and the estimated first state of charge of the previous iteration, the estimated first state of charge being based on a corrected capacity value of the previous iteration.

8. The method according to claim 1 wherein the iteration comprises determining a corrected internal impedance value of the battery by adding to an internal impedance value of the previous iteration a corrective impedance term, the corrective impedance term being based on a product of an impedance correction gain and the factor, the estimated current intensity being based on a corrected internal impedance value of the previous iteration.

9. The method of claim 1, comprising:

determining, for a given iteration, whether to calculate a corrected state of charge based on whether the factor has a value greater than a threshold value.

10. The method according to claim 1, comprising determining the correction gain using at least one of the algorithms belonging to the group comprising LMS, RLS, NLMS, and extended Kalman filter.

11. A device, comprising:

a memory; and

processing circuitry, which, in operation, iteratively estimates a state of charge of a battery, at least one iteration of the estimating including;

receiving an indication of an intensity of current;

receiving an indication of a voltage;

estimating a first state of charge during the iteration based on an estimated first state of charge of a previous iteration and on the received indication of the intensity of current;

estimating an intensity of current based on the received indication of the voltage and on a corrected state of charge of the previous iteration, and

calculating a corrected state of charge of the iteration by adding to the estimated first state of charge of the iteration a corrective term, the corrective term being based on a product of a first correction gain and a factor representative of a difference between the estimated intensity of current and the received indication of the intensity of current.

12. The device of claim 11 wherein the at least one iteration comprises estimating a second state of charge during the iteration based on a second estimated state of charge of the previous iteration and on the estimated intensity of current and the factor is determined based on a difference between the first and second estimated states of charge.

13. The device of claim 12 wherein the processing circuitry comprises one or more integrators, the first and second estimated states of charge are values integrated by the one or more integrators over a first period, and the factor is determined by deriving over the first period the difference between the first and second estimated states of charge.

14. The device of claim 13 wherein the indication of the voltage is based on a measurement acquired in a second period, and the indication of the current intensity is based on a measurement acquired in a third period, the first period being greater than or equal to the second period and the second period being greater than or equal to the third period.

15. The device of claim 14 wherein the first period is a multiple of the second period and of the third period.

16. The device of claim 11 wherein the estimated intensity of current is based on the following equation:

17. The device of claim 16 wherein the processing circuitry comprises an adder and the iteration includes determining a corrected capacity value by adding to a corrected capacity value of the previous iteration a second corrective term, the second corrective term being based on a product of a second correction gain and a difference between the corrected state of charge of the iteration and the estimated first state of charge of the previous iteration, the estimated first state of charge being based on a corrected capacity value of the previous iteration.

18. The device of claim 11 wherein the processing circuitry comprises an adder and the iteration includes determining a corrected internal impedance value by adding to an internal impedance value of the previous iteration a corrective impedance term, the corrective impedance term being based on a product of an impedance correction gain and the factor, the estimated current intensity being based on a corrected internal impedance value of the previous iteration.

19. The device of claim 11 wherein, in operation, the processing circuitry determines whether to calculate a corrected state of charge for a given iteration based on whether the factor has a value greater than a threshold value.

20. The device of claim 11, comprising:

a voltage measuring circuit;

a current intensity measuring circuit; and

an analog-digital converter coupled to the processing circuitry and which, in operation, provides samples of current intensity measurements and of voltage measurements based on measurements provided by the current and voltage measuring circuits to the processing circuitry.

21. The device of claim 20, comprising a multiplexer coupled to the voltage measuring circuit, the current intensity measuring circuit and the analog-digital converter.

22. The device according to claim 11, comprising:

one voltage measuring circuit per cell of the battery;

one current measuring circuit per parallel branch of series-connected cells of the battery;

one current intensity estimating circuit per cell of the battery;

one circuit to estimate a first state of charge per parallel branch of the battery; and

one circuit to calculate a corrected state of charge per cell of the battery.

23. The device of claim 11 wherein the processing circuitry comprises:

at least one integrator;

current intensity prediction circuitry;

drift calculation circuitry;

state of charge calculation circuity; and

at least one adder.

24. A non-transitory computer-readable memory medium whose contents cause one or more processing devices to, in operation, iteratively estimate a state of charge of a battery, at least one iteration of the estimating including:

receiving an indication of an intensity of current;

receiving an indication of a voltage;

estimating a first state of charge during the iteration based on an estimated first state of charge of a previous iteration and on the received indication of the intensity of current;

estimating an intensity of current based on the received indication of the voltage and on a corrected state of charge of the previous iteration, and calculating a corrected state of charge of the iteration by adding to the estimated first state of charge of the iteration a corrective term, the corrective term being based on a product of a first correction gain and a factor representative of a difference between the estimated intensity of current and the received indication of the intensity of current.

25. The medium of claim 24 wherein the iteration comprises estimating a second state of charge of the battery during the iteration based on a second estimated state of charge of the previous iteration and on the estimated intensity of current and the factor is determined based on a difference between the first and second estimated states of charge.

26. The medium of claim 25 wherein the first and second estimated states of charge are values integrated over a first period, and the factor is determined by deriving over the first period the difference between the first and second estimated states of charge.

27. The medium of claim 24 wherein the contents cause the processing circuitry, in operation, to determine whether to calculate a corrected state of charge for a given iteration based on whether the factor has a value greater than a threshold value.