Device and method of testing an internal resistance of a battery pack

• US 8,723,526 B2
• Filed: 10/19/2010
• Issued: 05/13/2014
• Est. Priority Date: 10/29/2009
• Status: Active Grant

• Current Assignee: BYD Company Limited
• Original Assignee: BYD Company Limited
• Inventors: Shen, Xiaofeng, Peng, Junna
• Primary Examiner(s): Hollington, Jermele M
• Application Number:
  US12/907,156
• Publication Number:
  US 20110101986A1
• Time in Patent Office: 1,302 Days
• Field of Search: None
• US Class Current: 324/430
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H01M 50/213 adapted for cells having curved cross-section, e.g. round or elliptic H01M50/209, H01M50/216 take precedence
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 7/0045 concerning the insertion or the connection of the batteries
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

An internal resistance testing device includes an excitation source and a battery pack, an adjustable resistance R, a sampling unit, and a control unit. The excitation source and the battery pack form a loop circuit. The adjustable resistance R may be located at the loop circuit formed by the excitation source and the battery pack. The sampling unit samples the voltage between two sides of the battery pack, the voltage between two sides of the adjustable resistance R, and the value of the adjustable resistance R. The control unit calculates internal resistance of the battery pack according to the signal value collected by the sampling unit. The internal resistances of different voltage-ranges the battery pack are determined by adjusting the value of the adjustable resistance R to cause the actual excitation voltage to be equal to the range voltage of the sampling unit. The voltage between two sides of the adjustable resistance R is made equal to the range voltage of the sampling unit by adjusting the value of the adjustable resistance R, which effectively improves measurement accuracy of the internal resistance.

Claims

1. An internal resistance testing device, comprising:

an excitation source and a battery pack, which form a loop circuit;

an adjustable resistance R located in the loop circuit;

the excitation source located in the loop circuit and generating an excitation voltage;

a sampling unit configured to measure;

the voltage between two sides of the battery pack,

the voltage between two sides of the adjustable resistance R, and

a value of the adjustable resistance R; and

a control unit that calculates an internal resistance of the battery pack according to the voltages measured by the sampling unit and the value of the adjustable resistance R; and

wherein the control unit coarsely adjusts a value of the adjustable resistance R to cause the excitation voltage to be about equal to a maximum range voltage of the sampling unit, and wherein the control unit then finely adjusts the value of the adjustable resistance R to be equal to an average value of two voltages levels recorded when the adjustable resistance R was coarsely adjusted.

2. The device of claim 1, wherein the sampling unit includes a voltage and current measuring device.

3. The device of claim 1, wherein the excitation source is a sinusoidal excitation signal.

4. A method for determining an internal resistance of a battery pack, the battery pack contained in a loop circuit having an excitation source and an adjustable resistance R, the method comprising the steps of:

injecting an excitation signal into the loop circuit;

adjusting the value of the adjustable resistance R until the voltage V2 is equal to the range voltage V (standard);

increasing the value of the adjustable resistance R until the voltage V2 is less than the range voltage V (standard);

storing the value of the adjustable resistance in step (b) as R2;

storing the value of the adjustable resistance is R1 which causes the voltage V2 to be equal to the range voltage V (standard) at a previous measurement;

finely adjusting the value of the adjustable resistance R to cause an actual excitation, voltage between two sides of the battery pack to be equal to the range voltage V (standard); and

calculating the internal resistance of the battery pack according to the voltage V1 between two sides of the adjustable resistance, the value of the adjustable resistance, and the voltage V2 between two sides of the battery pack after adjusting;

sampling an excitation voltage V2 generated between two sides of the battery pack;

sampling an excitation voltage V1 between the two sides of the adjustable resistance R;

determining a value of the adjustable resistance R;

adjusting the value of the adjustable resistance R to cause the excitation voltage V2 to be equal to a range voltage V (standard); and

calculating the internal resistance of the battery pack based on the excitation voltage V2, the excitation voltage V1, and the adjusted value of the adjustable resistance R.

5. The method of claim 4, for a fine adjustment of the adjustable resistance, the method further comprises the steps of:

adjusting the adjustable resistance to cause the value of the adjustable resistance being equal to an average value R3 based on R1 and R2;

collecting a voltage V2a between two sides of the battery pack;

adjusting the value of the adjustable resistance according to the voltage V2a between two sides of the battery pack and the range voltage V (standard); and

calculating an internal resistance of the battery pack according to the value R of the adjustable resistance, the voltage V1 between two sides of the adjustable resistance, and the voltage V2 between two sides of the battery pack.

6. The method of claim 5, wherein when the voltage V2a between two sides of the battery pack is equal to V (standard), the method further comprises the steps of:

adjusting the adjustable resistance R to cause the value of the adjustable resistance R to be equal to an average value R5 based on R2 and R3,

wherein R5=m(a),

wherein m is a predetermined integer value,

wherein (a) is a minimum increment of fine adjustment of the adjustable resistance;

collecting the voltage V2b between two sides of the battery pack;

continuing to adjust the value of the adjustable resistance R according to the voltage V2b between two sides of the battery pack and the range voltage V (standard); and

calculating the internal resistance of the battery pack according to the value R of adjustable resistance, the voltage V1 between two sides of the adjustable resistance R, and the voltage V2 between two sides of the battery pack.

7. The method of claim 6, wherein when the voltage V2b between two sides of the battery pack is equal to V (standard), the method further comprises the steps of:

adjusting the adjustable resistance R to cause the value of the adjustable resistance R=(m+1)(a);

collecting the voltage V2c between two sides of the battery pack; and

when V2c<

V (standard), the value of the adjustable resistance R is adjusted to be (m+1)(a), the internal resistance of the battery pack is calculated according to a signal value collected.

8. The method of claim 7, wherein when V2c=V (standard), the value of the adjustable resistance R is adjusted, and the method further comprises the steps of:

when the value R of the adjustable resistance R=(m+x−

1) (a), wherein x is a count of the number of fine adjustment iterations, the voltage between two sides of the battery pack is equal to V (standard); and

when the voltage between two sides of the battery pack is less than V and R=(m+x) (a), the value of the adjustable resistance is adjusted to be (m+x)(a); and

calculating the internal resistance of the battery pack according to the signal value collected.

9. The method of claim 6, wherein when the voltage between two sides of the battery pack V2b<

V (standard), the method further comprises the steps of;

adjusting the adjustable resistance to cause the value of the adjustable resistance R=(m−

1) (a);

collecting the voltage between two sides of the battery pack V2g;

when V2g=V (standard), the value of the adjustable resistance R is adjusted to be (m−

1) (a); and

calculating the internal resistance of the battery pack according to the signal value collected.

10. The method of claim 9, wherein when V2g<

V (standard), the value of the adjustable resistance R is adjusted, and the method further comprises the steps of;

when the value of the adjustable resistance R=(m−

z−

1) (a), wherein z is a count of a number of fine adjustment iterations, the voltage between two sides of the battery pack is equal to V (standard), and when R=(m−

z)(a), the voltage between two sides of the battery pack is less than V (standard), so that

when the value of the adjustable resistance R is adjusted to be equal to (m−

z−

1) (a), calculating the internal resistance of the battery pack according to the signal value collected.

11. The method of claim 5, wherein when the voltage between two sides of the battery pack V2b<

V (standard), the method further comprises the steps of;

adjusting the adjustable resistance to cause the value of the adjustable resistance R to be equal to an average value R4 based on R1 and R3,

wherein n is a predetermined integer variable,

wherein (a) is a minimum increment of fine adjustment of the adjustable resistance R;

collecting the voltage V2d between two sides of the battery pack;

adjusting the value of the adjustable resistance R according to the voltage V2d between two sides of the battery pack and the range voltage V (standard);

calculating the internal resistance of the battery pack according to the value of the adjustable resistance R, the voltage V1 between two sides of the adjustable resistance R and the voltage V2 between two sides of the battery pack collected.

12. The testing method of claim 11, wherein when the voltage between two sides of the battery pack V2d=V (standard), the method further comprises the steps of:

adjusting the adjustable resistance to cause the value of the adjustable resistance R=(n+1) (a);

collecting the voltage between two sides of the battery pack V2e; and

when V2e<

V (standard) and the value of the adjustable resistance R is adjusted to be (n+1) (a), calculating the internal resistance of the battery pack according to the signal value collected.

13. The method of claim 12, wherein when V2e=V (standard) and the value of the adjustable resistance R is adjusted, the method further comprises the steps of:

when the value of the adjustable resistance R=(n+w−

1) (a),

wherein w is a count of the number of fine adjustment iterations,

the voltage between two sides of the battery pack is equal to V (standard),

R=(n+w) (a),

the voltage between two sides of the battery pack is less than V (standard);

the value of the adjustable resistance R is adjusted to be equal to (n+w) (a); and

calculating the internal resistance of the battery pack according to a signal value collected.

14. The method of claim 11, wherein when the voltage between two sides of the battery pack collected by the sample unit V2d<

V (standard), the method further comprises the steps of;

adjusting the adjustable resistance to cause the value of the adjustable resistance R=(n−

1)(a);

collecting the voltage between two sides of the battery pack V2f; and

when V2f=V (standard) and the value of the adjustable resistance R is adjusted to be (n−

1)(a), calculating the internal resistance of the battery pack according to the signal value collected.

15. The method of claim 14, wherein when V2f<

V (standard), the value of the adjustable resistance R is adjusted, and the method further comprises the steps of;

when the value of the adjustable resistance R (n−

y−

1)(a),

wherein y is a count of the number of fine adjustment iterations, the voltage between two sides of the battery pack is equal to V (standard),

wherein R=(n−

y)(a) and the voltage between two sides of the battery pack is less than V (standard),

the value of the adjustable resistance R is adjusted to be =(n−

y−

1)(a); and

calculating the internal resistance of the battery pack according to the signal value collected.

16. The method of claim 4, wherein the internal resistance of the battery pack R=PF*V2/I, wherein I=V1/R, and wherein I is the current in the loop circuit, PF is a power coefficient.