Method for checking and modulating battery capacity and power based on discharging/charging characteristics

• US 8,823,325 B2
• Filed: 04/07/2011
• Issued: 09/02/2014
• Est. Priority Date: 11/25/2010
• Status: Active Grant

• Current Assignee: Kwang Yang Motor Company Limited
• Original Assignee: Industrial Technology Research Institute
• Inventors: Sun, Chein-Chung, Lai, Chiou-Chu, Ling, Welkin
• Primary Examiner(s): Tso, Edward
• Assistant Examiner(s): RAMADAN, RAMY O
• Application Number:
  US13/081,514
• Publication Number:
  US 20120133331A1
• Time in Patent Office: 1,244 Days
• Field of Search: 320/132, 320/149, 320156-158
• US Class Current: 320/132
• 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

Abstract

A method for checking and modulating battery capacity and power based on charging/discharging characteristics is provided. In terms of discharge, a relationship between an open circuit voltage and an output electric capacity of a battery is measured to obtain a first characteristic curve. A relationship between a voltage and the output electric capacity of a battery at a predetermined maximum charge/discharge current rate is measured to obtain a second characteristic curve. A characteristic boundary line passing the first and the second characteristic points respectively selected from the first and the second characteristic curves is established. A voltage value corresponding to the first characteristic point is higher than a voltage value corresponding to the second characteristic point. The first and the second characteristic curves, and the characteristic boundary line define an operation range. The battery is charged/discharged within the operation range.

Claims

1. A method for checking and modulating capacity and power based on battery charging/discharging characteristics, comprising:

measuring a relationship between an open circuit voltage and an output electric capacity of a battery to obtain a first characteristic curve;

measuring a relationship between a voltage and the output electric capacity of the battery at a predetermined maximum discharge current rate to obtain a second characteristic curve;

selecting a first characteristic point and a second characteristic point from the first characteristic curve and the second characteristic curve respectively, wherein a voltage value corresponding to the first characteristic point is higher than a voltage value corresponding to the second characteristic point;

establishing a characteristic boundary line passing the first characteristic point and the second characteristic point, wherein the first characteristic curve, the second characteristic curve, and the characteristic boundary line constitute a battery discharge boundary line to define an operation range; and

managing the battery discharge within a discharge voltage range according to the output electric capacity of the battery, so as to keep a voltage-capacity curve falling within the operation range.

2. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 1, wherein the characteristic boundary line is substantially a straight line or a curve passing the first characteristic point and the second characteristic point.

3. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 1, wherein a difference between an output electric capacity value at the first characteristic point and an output electric capacity value obtained by an integration of a current is a residual capacity of the battery.

4. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 1, wherein a difference between an output electric capacity value at the second characteristic point and an output electric capacity value obtained by an integration of a current is a usable capacity of the battery at the predetermined maximum discharge current rate.

5. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 1, wherein a method of selecting the first characteristic point comprises:

in an open circuit condition, measuring or calculating a resistance difference Δ

R of the battery bewteen an internal resistance (Rn) at a sampling point and an internal resistance (Rm) of the battery at a reference residual capacity; and

when Rn>

Rm and Δ

R/Rm exceeds a threshold value, determining that the sampling point is the first characteristic point, wherein the threshold value is from 0.1 to 5.

6. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 1, wherein a method of selecting the second characteristic point comprises:

at the predetermined maximum discharge current rate, measuring or calculating a resistance difference Δ

R between an internal resistance (Rn) at a sampling point and an internal resistance (Rm) of the battery at a reference residual capacity; and

when Rn>

Rm and Δ

R/Rm exceeds a threshold value, determining that the sampling point is the second characteristic point, wherein the threshold value is from 0.1 to 5.

7. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 1, wherein a method of selecting the first characteristic point comprises:

in an open circuit condition, calculating a ratio (Δ

V/Δ

Ah)n of a voltage difference (Δ

V) and an output electric capacity difference (Δ

Ah) of the battery at a sampling point and a ratio (Δ

V/Δ

Ah)m of a voltage difference (Δ

V) and an output electric capacity difference (Δ

Ah) of the battery at a reference residual capacity, wherein the sampling point corresponding to a ratio of the two ratios (Δ

V/Δ

Ah)n and (Δ

V/Δ

Ah)m greater than a threshold value (Y) is used as the first characteristic point, and the threshold value (Y) is from 1.1 to 5.

8. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 1, wherein a method of selecting the second characteristic point comprises:

at the predetermined maximum discharge current rate, calculating a ratio (Δ

V/Δ

Ah)n of a voltage difference (Δ

V) and an output electric capacity difference (Δ

Ah) of the battery at a sampling point and a ratio (Δ

V/Δ

Ah)m of a voltage difference (Δ

V) and an output electric capacity difference (Δ

Ah) of the battery at a reference residual capacity, wherein the sampling point corresponding to a ratio of the two ratios (Δ

V/Δ

Ah)n and (Δ

V/Δ

Ah)m greater than a threshold value (Y) is used as the second characteristic point, and the threshold value (Y) is from 1.1 to 5.

9. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to any one of claims 5 to 8, wherein the reference residual capacity is a residual capacity between 0% and 100%.

10. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 1, wherein the discharge characteristic curve partially overlaps the characteristic boundary line.

11. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 1, wherein a method of establishing the characteristic boundary line further comprises:

measuring the relationship between the voltage and the output electric capacity of the battery at the at least a discharge current rate to obtain at least a third characteristic curve, wherein the discharge current rate of the third characteristic curve is smaller than the predetermined maximum discharge current rate; and

selecting a third characteristic point from the third characteristic curve, and making the characteristic boundary line pass the third characteristic point.

12. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 11, wherein a method of selecting the third characteristic point comprises:

at the at least a discharge current rate, calculating a difference quantity Δ

R between an internal resistance (Rn) of the battery at a sampling point and an internal resistance (Rm) of the battery at a reference residual capacity; and

when Rn>

Rm and Δ

R/Rm exceeds a threshold value, determining the sampling point as the third characteristic point, wherein the threshold value is from 0.1 to 5.

13. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 11, wherein a method of selecting the third characteristic point comprises:

at the at least a discharge current rate, calculating a ratio (Δ

V/Δ

Ah)n of a voltage difference (Δ

V) and an output electric capacity difference (Δ

Ah) of the battery at a sampling point and a ratio (Δ

V/Δ

Ah)m of a voltage difference (Δ

V) and an output electric capacity difference (Δ

Ah) of the battery at a reference residual capacity, wherein the sampling point corresponding to a ratio between the two ratios (Δ

V/Δ

Ah)n and (Δ

V/Δ

Ah)m greater than a threshold value (Y) is used as the third characteristic point, and the threshold value (Y) is between 1.1 and 5.

14. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 12 or 13, wherein the reference residual capacity is a residual capacity between 0% and 100%.

15. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 1, wherein a method of establishing the characteristic boundary line further comprises establishing a plurality of characteristic boundary lines at different operation temperatures and selecting one of the characteristic boundary lines at different operation temperatures according to a practical operation temperature to define the operation range.

16. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 1, wherein on the characteristic boundary line, a discharge current(I) and an output electric capacity (Q) of the battery satisfy a linear function:

Q=a(T)I+b(T), and a and b change with a temperature.

17. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 16, further comprising:

measuring a measured output electric capacity when the battery stops discharging;

judging whether the measured output electric capacity value is the same as a calculated output electric capacity value calculated through the linear function; and

when the measured output electric capacity value and the calculated output electric capacity value are different, regarding a ratio of the measured output electric capacity value and the calculated output electric capacity value as an update factor t, and updating a(T) and b(T) respectively into a(T)×

t and b(T)×

t.

18. A method for checking and modulating capacity and power based on battery charging/discharging characteristics, comprising:

measuring a relationship between an open circuit voltage and an electric capacity of a battery to obtain a first characteristic curve;

measuring a relationship between a voltage and the electric capacity of the battery at a predetermined maximum charge current rate to obtain a second characteristic curve;

selecting a first characteristic point and a second characteristic point from the first characteristic curve and the second characteristic curve respectively, wherein a voltage value corresponding to the first characteristic point is lower than a voltage value corresponding to the second characteristic point;

establishing a characteristic boundary line passing the first characteristic point and the second characteristic point, wherein the first characteristic curve, the second characteristic curve, and the characteristic boundary line constitute a battery charge boundary line to define an operation range; and

charging the battery at least a charge current rate according to a charge characteristic curve, wherein the charge characteristic curve falls within the operation range.

19. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 18, wherein the characteristic boundary line is substantially a straight line or a curve passing the first characteristic point and the second characteristic point.

20. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 18, wherein a difference between an electric capacity value corresponding to the first characteristic point and an electric capacity value obtained by an integration of a current is a residual capacity of the battery.

21. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 18, wherein a difference between an electric capacity value corresponding to the second characteristic point and an electric capacity value obtained by an integration of a current is a usable capacity of the battery at the predetermined maximum charge current rate.

22. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 18, wherein a method of selecting the first characteristic point comprises:

calculating or measuring a difference quantity Δ

R between an internal resistance (Rn) of the battery at a sampling point and an internal resistance (Rin) of the battery at a reference residual capacity in an open circuit condition; and

when Rn>

Rm and Δ

R/Rm exceeds a threshold value, determining that the sampling point is the first characteristic point, wherein the threshold value is from 0.1 to 5.

23. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 18, wherein a method of selecting the second characteristic point comprises:

at the predetermined maximum charge current rate, calculating or measuring a difference quantity Δ

R between an internal resistance (Rn) of the battery at a sampling point and an internal resistance (Rm) of the battery at a reference residual capacity; and

when Rn>

Rm and Δ

R/Rm exceeds a threshold value, determining that the sampling point is the second characteristic point, wherein the threshold value is from 0.1 to 5.

24. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 18, wherein a method of selecting the first characteristic point comprises:

in an open circuit condition, calculating a ratio (Δ

V/Δ

Ah)n of a voltage difference (Δ

V) and an electric capacity difference (Δ

Ah) of the battery at a sampling point and a ratio (Δ

V/Δ

Ah)m of a voltage difference (Δ

V) and an electric capacity difference (Δ

Ah) of the battery at a reference residual capacity, wherein the sampling point corresponding to a ratio of the two ratios (Δ

V/Δ

Ah)n and (Δ

V/Δ

Ah)m greater than a threshold value (Y) is used as the first characteristic point, and the threshold value (Y) is from 1.1 to 5.

25. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 18, wherein the selecting the second characteristic point comprises:

at the predetermined maximum charge current rate, calculating a ratio (Δ

V/Δ

Ah)n of a voltage difference (Δ

V) and an electric capacity difference (Δ

Ah) of the battery at a sampling point and a ratio (Δ

V/Δ

Ah)m of a voltage difference (Δ

V) and an electric capacity difference (Δ

Ah) of the battery at a reference residual capacity, wherein the sampling point corresponding to a ratio between the two ratios (Δ

V/Δ

Ah)n and (Δ

V/Δ

Ah)m greater than a threshold value (Y) is used as the second characteristic point, and the threshold value (Y) is from 1.1 to 5.

26. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to any one of claims 22 to 25, wherein the reference residual capacity is a residual capacity between 0% and 100%.

27. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 18, wherein the charge characteristic curve partially overlaps the characteristic boundary line.

28. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 18, wherein a method of establishing the characteristic boundary line further comprises:

measuring the relationship between the voltage and the electric capacity of the battery at least a discharge current rate to obtain at least a third characteristic curve, wherein the charge current rate of the third characteristic curve is smaller than the predetermined maximum charge current rate; and

selecting a third characteristic point from the third characteristic curve, and making the characteristic boundary line pass the third characteristic point.

29. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 18, wherein a method of selecting the third characteristic point comprises:

at the at least a charge current rate, calculating a difference quantity Δ

R between an internal resistance (Rn) of the battery at a sampling point and an internal resistance (Rin) of the battery at a reference residual capacity; and

when Rn>

Rm and Δ

R/Rm exceeds a threshold value, determining the sampling point as the third characteristic point, wherein the threshold value is from 0.1 to 5.

30. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 18, wherein a method of selecting the third characteristic point comprises:

at the at least a charge current rate, calculating a ratio (Δ

V/Δ

Ah)n of a voltage difference (Δ

V) and an electric capacity difference (Δ

Ah) of the battery at a sampling point and a ratio (Δ

V/Δ

Ah)m of a voltage difference (Δ

V) and an electric capacity difference (Δ

Ah) of the battery at a reference residual capacity, wherein the sampling point corresponding to a ratio of the two ratios (Δ

V/Δ

Ah)n and (Δ

V/Δ

Ah)m greater than a threshold value (Y) is used as the third characteristic point, and the threshold value (Y) is from 1.1 to 5.

31. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 29 or 30, wherein the reference residual capacity is a residual capacity between 0% and 100%.

32. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 18, wherein a method of establishing the characteristic boundary line further comprises establishing a plurality of characteristic boundary lines at different operation temperatures and selecting one of the characteristic boundary lines at different operation temperatures according to a practical operation temperature to define the operation range.

33. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 18, wherein on the characteristic boundary line, a charge current (I) and the electric capacity (Q) of the battery satisfy a linear function:

Q=c(T)I+d(T), and c and d change with a temperature.

34. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 33, further comprising:

measuring measured electric capacity when the battery stops charging;

judging whether the measured electric capacity value is the same as a calculated electric capacity value calculated through the linear function; and

when the measured electric capacity value is different from the calculated electric capacity value, regarding a ratio of the measured electric capacity value and the calculated electric capacity value as an update factor t, and updating c(T) and d(T) respectively into c(T)×

t and d(T)×

t.

35. A method for checking and modulating capacity and power based on battery charging/discharging characteristics, comprising:

measuring a relationship between an open circuit voltage and an output electric capacity of a battery to obtain a first characteristic curve;

measuring a relationship between a voltage and the output electric capacity of the battery at a predetermined maximum discharge current rate to obtain a second characteristic curve;

selecting a first characteristic point and a second characteristic point from the first characteristic curve and the second characteristic curve respectively, wherein a voltage value corresponding to the first characteristic point is higher than a voltage value corresponding to the second characteristic point;

establishing a characteristic boundary line passing the first characteristic point and the second characteristic point, wherein the first characteristic curve, the second characteristic curve, and the characteristic boundary line define an operation range;

discharging the battery at least a discharge current rate according to a discharge characteristic curve, wherein the discharge characteristic curve falls within the operation range;

calculating a difference between an output electric capacity value corresponding to the first characteristic point and an output electric capacity value obtained by an integration of a current to obtain a residual capacity of the battery; and

calculating a difference between an output electric capacity value corresponding to the second characteristic point and an output electric capacity value obtained by an integration of the current to obtain a usable capacity of the battery at the predetermined maximum discharge current rate.

36. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 35, wherein a maximum discharge power (Pmax) of the battery at a sampling point is:

37. A method for checking and modulating capacity and power based on battery charging/discharging characteristics, comprising:

measuring a relationship between an open circuit voltage and an electric capacity of a battery to obtain a first characteristic curve;

measuring a relationship between a voltage and the electric capacity of the battery at a predetermined maximum charge current rate to obtain a second characteristic curve;

selecting a first characteristic point and a second characteristic point from the first characteristic curve and the second characteristic curve respectively, wherein a voltage value corresponding to the first characteristic point is lower than a voltage value corresponding to the second characteristic point;

establishing a characteristic boundary line passing the first characteristic point and the second characteristic point, wherein the first characteristic curve, the second characteristic curve, and the characteristic boundary line define an operation range;

charging the battery in at least a charge current rate according to a charge characteristic curve, wherein the charge characteristic curve falls within the operation range;

calculating a difference between an output electric capacity value corresponding to the first cutting-off point and an output electric capacity value obtained by an integration of the current to obtain a residual capacity of the battery; and

calculating a difference between an output electric capacity value corresponding to the second cutting-off point and the output electric capacity value obtained by an integration of the current to obtain a usable capacity of the battery at the predetermined maximum charge current rate.

38. The method for checking and modulating capacity and power based on battery charging/discharging characteristics according to claim 37, wherein a maximum charge power (Pmax) of the battery at a sampling point is: