Apparatus and method for sensing leakage current of battery

• US 8,421,466 B2
• Filed: 06/02/2010
• Issued: 04/16/2013
• Est. Priority Date: 09/01/2008
• Status: Active Grant

• Current Assignee: LG Energy Solution Limited (LG Corporation)
• Original Assignee: LG Chem Limited (LG Corporation)
• Inventors: Kang, Ju-Hyun, Kim, Jee-Ho, Lee, Sang-Hoon, Kwon, Dong-Keun
• Primary Examiner(s): PATEL, PARESH H
• Application Number:
  US12/792,253
• Publication Number:
  US 20100237872A1
• Time in Patent Office: 1,049 Days
• Field of Search: None
• US Class Current: 324/429
• CPC Class Codes: B60L 3/0069 relating to the isolation, e.g. ground fault or leak current
• CPC Class Codes: G01R 27/18 Measuring resistance to earth , i.e. line to ground
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/42 Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells H01M10/60 takes precedence
• 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 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 50/569 Constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals battery terminal connectors with integrated measuring arrangements G01R31/364
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

An apparatus for sensing a leakage current of a battery comprises a floating capacitor charged with voltage detected from a cathode or anode terminal of a battery, a cathode terminal selection switching unit for selecting a voltage detection path for the cathode terminal and charging the floating capacitor with a detection voltage of the cathode terminal, an anode terminal selection switching unit for selecting a voltage detection path for the anode terminal and charging the floating capacitor with a detection voltage of the anode terminal, a DC voltage applying unit for applying DC voltage through the voltage detection path for the anode terminal, a voltage measuring unit for measuring the charged detection voltage of the cathode or anode terminal, and a leakage current determining unit for determining the occurrence of leakage current based on the measured detection voltages of the cathode and anode terminals.

Claims

1. An apparatus for sensing a leakage current of a battery, comprising:

a floating capacitor charged with a voltage detected from a cathode terminal or an anode terminal of a battery;

a cathode terminal selection switching unit for selecting a voltage detection path for the cathode terminal and charging the floating capacitor with a detection voltage of the cathode terminal;

an anode terminal selection switching unit for selecting a voltage detection path for the anode terminal and charging the floating capacitor with a detection voltage of the anode terminal;

a DC (Direct Current) voltage applying unit for applying a DC voltage through the selected voltage detection path for the anode terminal;

a voltage measuring unit for measuring the detection voltage of the cathode terminal or the anode terminal, charged to the floating capacitor; and

a leakage current determining unit for determining the occurrence of a leakage current based on the detection voltages of the cathode terminal and the anode terminal, measured by the voltage measuring unit.

2. The apparatus for sensing a leakage current of a battery according to claim 1, further comprising:

a first line connecting the cathode terminal and the anode terminal of the battery;

a first voltage distribution node located on the first line; and

a second line diverged from the first voltage distribution node.

3. The apparatus for sensing a leakage current of a battery according to claim 2,

wherein the cathode terminal selection switching unit comprises:

a first switch installed between the first voltage distribution node and the cathode terminal of the battery; and

a second switch installed on the second line.

4. The apparatus for sensing a leakage current of a battery according to claim 3,

wherein, when the voltage detection path for the cathode terminal is selected, the first and second switches are turned on at the same time under the control of the leakage current determining unit.

5. The apparatus for sensing a leakage current of a battery according to claim 2,

wherein the anode terminal selection switching unit comprises:

a third switch installed between the first voltage distribution node and the anode terminal of the battery; and

a fourth switch installed on a third line diverged from the second line.

6. The apparatus for sensing a leakage current of a battery according to claim 5,

wherein, when the voltage detection path for the anode terminal is selected, the third and fourth switches are turned on at the same time under the control of the leakage current determining unit.

7. The apparatus for sensing a leakage current of a battery according to claim 2,

wherein a second voltage distribution node is located on the second line, and

wherein the floating capacitor is installed between the second voltage distribution node and the ground.

8. The apparatus for sensing a leakage current of a battery according to claim 1,

wherein the DC voltage applying unit is installed between the anode terminal selection switching unit and the ground.

9. The apparatus for sensing a leakage current of a battery according to claim 1,

wherein the voltage measuring unit is a voltage follower that outputs an analog voltage signal corresponding to a voltage level charged to the floating capacitor.

10. The apparatus for sensing a leakage current of a battery according to claim 1,

wherein the detection voltage of the cathode terminal and the anode terminal, charged to the floating capacitor, have the same polarity.

11. The apparatus for sensing a leakage current of a battery according to claim 1, further comprising:

a relay capacitor charged with the detection voltage of the cathode terminal or the anode terminal, charged to the floating capacitor;

a charge switching unit for applying the voltage charged to the floating capacitor to the relay capacitor for relay charging; and

a voltage apply switching unit for applying the detection voltage of the cathode terminal or the anode terminal, charged to the relay capacitor, to the voltage measuring unit.

12. The apparatus for sensing a leakage current of battery according to claim 11,

wherein the charge switching unit is turned off before the voltage apply switching unit turns on under the control of the leakage current determining unit.

13. The apparatus for sensing a leakage current of a battery according to claim 11,

wherein the voltage measuring unit is a differential amplifier that outputs an analog voltage signal corresponding to a difference of voltages at both terminals of the relay capacitor.

14. The apparatus for sensing a leakage current of a battery according to claim 11,

wherein the detection voltages of the cathode terminal and the anode terminal, charged to the relay capacitor, have the same polarity.

15. The apparatus for sensing a leakage current of a battery according to claim 1,

wherein the leakage current determining unit comprises:

a switch controller for controlling operations of the cathode terminal selection switching unit and the anode terminal selection switching unit;

an A/D (Analog/Digital) converter for converting an analog voltage signal corresponding to the detection voltages of the cathode terminal and the anode terminal, output from the voltage measuring unit, into a digital voltage signal; and

a CPU (Central Processing Unit) for receiving the digital voltage signal from the A/D converter and determining the occurrence of a leakage current based on the detection voltages of the cathode terminal and the anode terminal.

16. The apparatus for sensing a leakage current of a battery according to claim 1,

wherein the leakage current determining unit calculates a leakage resistance according to the following equation, and determines that a leakage current occurs in case the calculated leakage resistance is smaller than a criterion insulation resistance:

17. The apparatus for sensing a leakage current of a battery according to claim 1,

wherein the leakage current determining unit determines that a leakage current occurs in case the measured detection voltage of the cathode terminal or the anode terminal departs from a preset safe voltage range.

18. The apparatus for sensing a leakage current of a battery according to claim 1,

wherein the leakage current determining unit obtains a leakage resistance corresponding to the detection voltages of the cathode terminal and the anode terminal with reference to a look-up table in which leakage resistances are already defined for each detection voltage of the cathode terminal and the anode terminal under various conditions, and then determines that a leakage current occurs in case the obtained leakage resistance is smaller than a criterion insulation resistance.

19. The apparatus for sensing a leakage current of a battery according to claim 1,

wherein the leakage current determining unit further comprises a leakage current alarming unit for visually or audibly alarming the occurrence of a leakage current, and

wherein the leakage current alarming unit makes a visual or audible alarm in case a leakage current occurs.

20. A battery pack, which comprises the apparatus for sensing a leakage current of a battery as defined in claim 1.

21. A battery-driven apparatus, which comprises the apparatus for sensing a leakage current of a battery as defined in claim 1.

22. A method for sensing a leakage current of a battery, comprising:

(a) selecting a voltage detection path for a cathode terminal of a battery, charging a floating capacitor with a detection voltage of the cathode terminal of the battery, and then measuring the detection voltage of the cathode terminal;

(b) selecting a voltage detection path for an anode terminal of the battery, applying a DC voltage to the anode terminal of the battery to charge the floating capacitor with a detection voltage of the anode terminal of the battery, and then measuring the detection voltage of the anode terminal; and

(c) determining from the measured detection voltages of the cathode terminal and the anode terminal whether a leakage current occurs.

23. The method for sensing a leakage current of a battery according to claim 22,

wherein, in the step (c), a leakage resistance is calculated from the detection voltages of the cathode terminal and the anode terminal according to the following equation, and it is determined that a leakage current occurs in case the calculated leakage resistance is smaller than a criterion insulation resistance:

24. The method for sensing a leakage current of a battery according to claim 22,

wherein, in the step (c), it is determined that a leakage current occurs in case the measured detection voltage of the cathode terminal or the anode terminal departs from a preset safe voltage range.

25. The method for sensing a leakage current of a battery according to claim 22,

wherein the step (c) comprises:

obtaining a leakage resistance corresponding to the detection voltages of the cathode terminal and the anode terminal with reference to a look-up table in which leakage resistances are already defined for each detection voltage of the cathode terminal and the anode terminal under various conditions; and

determining that a leakage current occurs in case the obtained leakage resistance is smaller than a criterion insulation resistance.

26. The method for sensing a leakage current of a battery according to claim 22, further comprising:

making a visual or audible alarm in case it is determined that a leakage current occurs.

27. A method for sensing a leakage current of a battery, comprising:

(a) selecting a voltage detection path for a cathode terminal of a battery, primarily charging a floating capacitor with a detection voltage of the cathode terminal of the battery, and secondarily charging a relay capacitor with the charged detection voltage of the cathode terminal;

(b) measuring the detection voltage of the cathode terminal, secondarily charged to the relay capacitor, in a state that the relay capacitor is electrically separated from the battery;

(c) selecting a voltage detection path for an anode terminal of the battery, applying a DC voltage to the anode terminal of the battery to primarily charge the floating capacitor with a detection voltage of the anode terminal of the battery, and then secondarily charging a relay capacitor with the charged detection voltage of the anode terminal;

(d) measuring the detection voltage of the anode terminal, secondarily charged to the relay capacitor, in a state that the relay capacitor is electrically separated from the battery; and

(c) determining from the measured detection voltages of the cathode terminal and the anode terminal whether a leakage current occurs.

28. The method for sensing a leakage current of a battery according to claim 27,

wherein, in the step (e), a leakage resistance is calculated from the detection voltages of the cathode terminal and the anode terminal according to the following equation, and it is determined that a leakage current occurs in case the calculated leakage resistance is smaller than a criterion insulation resistance:

29. The method for sensing a leakage current of a battery according to claim 27,

wherein, in the step (e), it is determined that a leakage current occurs in case the measured detection voltage of the cathode terminal or the anode terminal departs from a preset safe voltage range.

30. The method for sensing a leakage current of a battery according to claim 27,

wherein the step (e) comprises:

obtaining a leakage resistance corresponding to the detection voltages of the cathode terminal and the anode terminal with reference to a look-up table in which leakage resistances are already defined for each detection voltage of the cathode terminal and the anode terminal under various conditions; and

determining that a leakage current occurs in case the obtained leakage resistance is smaller than a criterion insulation resistance.

31. The method for sensing a leakage current of a battery according to claim 27, further comprising:

making a visual or audible alarm in case it is determined that a leakage current occurs.