APPARATUS AND METHOD FOR ESTIMATING RESISTANCE CHARACTERISTICS OF BATTERY BASED ON OPEN CIRCUIT VOLTAGE ESTIMATED BY BATTERY VOLTAGE VARIATION PATTERN

• US 20100042345A1
• Filed: 06/15/2009
• Published: 02/18/2010
• Est. Priority Date: 08/14/2008
• Status: Active Grant

• Current Assignee: LG Energy Solution Limited (LG Corporation)
• Original Assignee: LG Chem Limited (LG Corporation)
• Inventors: KIM, Ju-Young, KANG, Jung-Soo
• Granted Patent: US 7,996,167 B2
• Time in Patent Office: Days
• US Class Current: 702/65
• 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

An apparatus for estimating resistance characteristics of a battery includes a data storing manager for obtaining and storing battery voltage, current and temperature data of a battery, whenever estimating a battery resistance characteristic; an open circuit voltage calculator for calculating battery open circuit voltage from a battery voltage variation pattern measured at the present and in the past; a weighted mean resistance calculator for calculating a battery resistance parameter from a battery current and a difference between the battery open circuit voltage and a battery voltage, and calculating a weighted mean resistance from battery resistance parameters calculated at the present and in the past; a weighted mean resistance convergence calculator for calculating a weighed mean resistance convergence value by repeatedly calculating a weighted mean sequence using the weighted mean resistance as an initial condition; and a resistance characteristic estimator for estimating a battery resistance from the weighted mean resistance convergence value.

Claims

1. An apparatus for estimating resistance characteristics of a battery based on a battery voltage variation pattern, comprising:

a data storing manager for obtaining and storing battery voltage, current and temperature data from a voltage sensor, a current sensor and a temperature sensor, which are coupled to a battery, whenever a resistance characteristic is estimated;

an open circuit voltage calculator for calculating a battery open circuit voltage from a battery voltage variation pattern measured at the present and in the past;

a weighted mean resistance calculator for calculating a battery resistance parameter from a battery current and a difference between the battery open circuit voltage and a battery voltage, and calculating a weighted mean resistance from battery resistance parameters calculated at the present and in the past;

a weighted mean resistance convergence calculator for calculating a weighed mean resistance convergence value by repeatedly calculating a weighted mean sequence using the weighted mean resistance as an initial condition; and

a resistance characteristic estimator for estimating a battery resistance from the weighted mean resistance convergence value.

2. The apparatus for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 1,

wherein the resistance characteristic estimator estimates the weighted mean resistance convergence value as a battery resistance.

3. The apparatus for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 1,

wherein the resistance characteristic estimator estimates a battery resistance by mapping a battery resistance corresponding to the calculated weighted mean resistance convergence value from a look-up table defining a battery resistance for each weighted mean resistance convergence value.

4. The apparatus for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 1,

wherein the resistance characteristic estimator estimates a battery resistance by inputting the calculated weighted mean resistance convergence value to a function using the weighted mean resistance convergence value and the battery resistance as an input parameter and an output parameter, respectively.

5. The apparatus for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 1,

wherein the resistance characteristic estimator estimates a battery resistance by relatively comparing the calculated weighted mean resistance convergence value with a weighted mean resistance convergence value corresponding to an initial battery resistance value when a battery was produced.

6. The apparatus for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 1, wherein the weighted mean resistance calculator calculates a weighted mean resistance (R_meanⁿ) according to the following Math Figure:

R_mean=(R^n-1×

weight+Rⁿ)÷

(weight+1)

R^n-1=|V^n-1−

OCV^n-1|÷

|I^n-1|

Rⁿ=|Vⁿ−

OCVⁿ|÷

|Iⁿ|

where Rⁿ and R^n-1 are battery resistance parameters respectively calculated at n^th time and n-1^th time,

where Vⁿ and V^n-1 are battery voltages respectively measured at n^th time and n-1^th time,

where OCVⁿ and OCV^n-1 are open circuit voltages of a battery, respectively calculated at n^th time and n-1^th time, and

where Iⁿ and I^n-1 are battery currents respectively measured at n^th time and n-1^th time.

7. The apparatus for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 1,

wherein the weighted mean resistance convergence calculator calculates a weighted mean resistance convergence value (R_meanⁿ) according to the following weighted mean sequence (k is 1 or more):

R_meanⁿ_k+1=(R_meanⁿ<sub>k−

1</sub>−

weight+R_meanⁿ_k)/(weight+1),

wherein an initial condition (R_meanⁿ₁) of the weighted mean sequence is set by the following condition;

R_meanⁿ₁=(R^n-1×

weight+Rⁿ)÷

(weight+1),

wherein R_meanⁿ₀ is set as a weighted mean resistance convergence value at a last stage or an initial battery resistance value.

8. The apparatus for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 1,

wherein the resistance characteristic estimator estimates a relative ratio of the estimated battery resistance to an initial battery resistance value based on an allowable maximum resistance as a parameter representing battery resistance degradation.

9. The apparatus for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 1, wherein the open circuit voltage calculator includes:

an open circuit voltage variation calculating unit for calculating an open circuit voltage variation from a variation pattern of the stored battery voltages measured at the present and in the past by applying a mathematic model defining a correlation between a battery voltage variation pattern and an open circuit voltage variation, and estimating an open circuit voltage variation at a present stage by reflecting a correction factor corresponding to battery temperature on the calculated open circuit voltage variation; and

an open circuit voltage estimating unit for estimating a battery open circuit voltage at the present stage by reflecting the estimated open circuit voltage variation to a battery open circuit voltage estimated at a last stage.

10. The apparatus for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 9,

wherein the open circuit voltage estimating unit corrects an open circuit voltage by adding a difference between a weight mean value (a greater weight is endowed as battery voltage is measured earlier) for present and previous battery voltages and an open-circuit voltage at a last stage to the estimated open-circuit voltage at a present stage.

11. The apparatus for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 10,

wherein the previous battery voltage is a battery voltage at a last stage.

12. The apparatus for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 9,

wherein the estimated open circuit voltage variation is calculated by multiplying the calculated open circuit voltage variation by the correction factor corresponding to temperature.

13. The apparatus for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 9,

wherein the battery voltage variation pattern includes at least the battery voltages V_n, V_n-1 and V_n-2 measured at a present stage, at a last stage and at the stage before last.

14. The apparatus for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 9,

wherein the mathematical model is defined by a mathematical operation between a battery voltage variation between a present stage and a previous stage and a pattern function defined by each voltage of the battery voltage variation pattern.

15. The apparatus for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 9,

wherein the correction factor is calculated by inputting a battery temperature into a mathematical model using the battery temperature (T) as an input parameter and the correction factor of the battery open circuit voltage variation as an output parameter.

16. A method for estimating resistance characteristics of a battery based on a battery voltage variation pattern, comprising:

(a) obtaining and storing battery voltage, current and temperature data from a voltage sensor, a current sensor and a temperature sensor, which are coupled to a battery, whenever a resistance characteristic is estimated;

(b) calculating a battery open circuit voltage from a battery voltage variation pattern measured at the present and in the past;

(c) calculating a battery resistance parameter from a battery current and a difference between the battery open circuit voltage and a battery voltage, and calculating a weighted mean resistance from battery resistance parameters calculated at the present and in the past;

(d) calculating a weighed mean resistance convergence value by repeatedly calculating a weighted mean sequence using the weighted mean resistance as an initial condition; and

(e) estimating a battery resistance from the weighted mean resistance convergence value.

17. The method for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 16,

wherein, in the step (e), the weighted mean resistance convergence value is estimated as a battery resistance.

18. The method for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 16,

wherein, in the step (e), a battery resistance is estimated by mapping a battery resistance corresponding to the calculated weighted mean resistance convergence value from a look-up table defining a battery resistance for each weighted mean resistance convergence value.

19. The method for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 16,

wherein, in the step (e), a battery resistance is estimated by inputting the calculated weighted mean resistance convergence value to a function using the weighted mean resistance convergence value and the battery resistance as an input parameter and an output parameter, respectively.

20. The method for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 16,

wherein, in the step (e), a battery resistance is estimated by relatively comparing the calculated weighted mean resistance convergence value with a weighted mean resistance convergence value corresponding to an initial battery resistance value when a battery was produced.

21. The method for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 16, wherein, in the step (c), a weighted mean resistance (R_meanⁿ) is calculated according to the following Math Figure:

R_meanⁿ=(R^n-1×

weight+Rⁿ)÷

(weight+1)

R^n-1=|V^n-1−

OCV^n-1|÷

|I^n-1|

Rⁿ=|Vⁿ−

OCVⁿ|÷

|Iⁿ|

where Rⁿ and R^n-1 are battery resistance parameters respectively calculated at n^th time and n-1^th time,

where Vⁿ and V^n-1 are battery voltages respectively measured at n^th time and n-1^th time,

where OCVⁿ and OCV^n-1 are open circuit voltages of a battery, respectively calculated at n^th time and n-1^th time, and

where Iⁿ and I^n-1 are battery currents respectively measured at n^th time and n-1^th time.

22. The method for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 16,

wherein, in the step (d), a weighted mean resistance convergence value (R_meanⁿ) is calculated according to the following weighted mean sequence (k is 1 or more):

R_meanⁿ_k+1=(R_meanⁿ<sub>k−

1</sub>×

weight+R_meanⁿ_k)/(weight+1),

wherein an initial condition (R_meanⁿ₁) of the weighted mean sequence is set by the following condition;

R_meanⁿ₁=(R^n-1×

weight+Rⁿ)÷

(weight+1),

wherein R_meanⁿ₀ is set as a weighted mean resistance convergence value at a last stage or an initial battery resistance value.

23. The method for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 16, further comprising:

estimating a relative ratio of the estimated battery resistance to an initial battery resistance value based on an allowable maximum resistance as a parameter representing battery resistance degradation.

24. The method for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 16, wherein the step (b) includes:

calculating an open circuit voltage variation from a variation pattern of the stored battery voltages measured at the present and in the past by applying a mathematic model defining a correlation between a battery voltage variation pattern and an open circuit voltage variation, and estimating an open circuit voltage variation at a present stage by reflecting a correction factor corresponding to battery temperature on the calculated open circuit voltage variation; and

estimating a battery open circuit voltage at the present stage by reflecting the estimated open circuit voltage variation to a battery open circuit voltage estimated at a last stage.

25. The method for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 24, further comprising:

correcting an open circuit voltage by adding a difference between a weight mean value (a greater weight is endowed as battery voltage is measured earlier) for present and previous battery voltages and an open-circuit voltage at a last stage to the estimated open-circuit voltage at a present stage.

26. The method for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 25,

wherein the previous battery voltage is a battery voltage at a last stage.

27. The method for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 24,

wherein the estimated open circuit voltage variation is calculated by multiplying the calculated open circuit voltage variation by the correction factor corresponding to temperature.

28. The method for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 24,

wherein the battery voltage variation pattern includes at least voltages V_n, V_n-1 and V_n-2 measured at a present stage, at a last stage and at the stage before last.

29. The method for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 24,

wherein the mathematical model is defined by a mathematical operation between a battery voltage variation between a present stage and a previous stage and a pattern function defined by each voltage of the battery voltage variation pattern.

30. The method for estimating resistance characteristics of a battery based on a battery voltage variation pattern according to claim 24,

wherein the correction factor is calculated by inputting a battery temperature into a mathematical model using the battery temperature (T) as an input parameter and the correction factor of the battery open circuit voltage variation as an output parameter.