Battery pack manager and method of detecting a line cut

• US 7,564,217 B2
• Filed: 11/14/2005
• Issued: 07/21/2009
• Est. Priority Date: 11/18/2004
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Kobayashi, Tetsuya, Tanigawa, Keisuke
• Primary Examiner(s): Ullah; Akm E
• Assistant Examiner(s): DIAO, M BAYE
• Application Number:
  US11/271,741
• Publication Number:
  US 20060103351A1
• Time in Patent Office: 1,345 Days
• Field of Search: 320/103, 320/104, 320/116, 320/117, 320/118, 320/119, 320/120, 320/121, 320/135, 320/136, 324/433, 324/434, 307/10.1, 307/10.7, 903/906, 903/907
• US Class Current: 320/118
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/00306 Overdischarge protection
• CPC Class Codes: H02J 7/00309 Overheat or overtemperature protection

Abstract

In a battery pack manager that manages series-connected rechargeable unit cells, a cell equalizer equalizes the cell voltages by individually discharging the unit cells according to deviations from reference voltages. An overcharge/overdischarge detector detects an overcharge and an overdischarge state of each unit cell. An inhibit circuit prevents the cell equalizer from discharging the unit cells when the overcharge/overdischarge detector is activated to reduce the cell voltage variability, which would otherwise occur as a result of interference from the overcharge/overdischarge detector, so that the overcharge/overdischarge states of all unit cells can be determined with precision. Connecting lines of the unit cells are monitored to detect a line-cut. The inhibit circuit further inhibits the cell equalizer when the connecting lines are being monitored to reduce the cell voltage variability, which would otherwise occur as a result of interference from the line-cut detection, so that false line-cut detection is avoided.

Claims

1. A battery pack manager for a plurality of rechargeable unit cells connected in series, wherein said unit cells are divided into a plurality of battery-pack modules, comprising a battery-pack controller, connected to said battery-pack modules via a pair of battery-pack connecting lines and a plurality of module-connecting lines, that successively detects a voltage value of each of said battery-pack modules, determines that a line-cut has occurred on one of said battery-pack connecting lines if a single zero-voltage value is detected and determines that a line-cut has occurred on one of said module-connecting lines if two zero-voltage values are detected in succession.

2. The battery pack manager of claim 1, further comprising a plurality of module controllers connected to said battery-pack modules respectively via said pair of battery-pack connecting lines and said plurality of module-connecting lines,

wherein each of said module controllers comprises an overcharged, overdischarge detector, connected to said unit cells of the associated battery-pack module via said module-connecting lines and a plurality of cell-connecting lines, that makes a decision on whether said unit cells of each battery-pack module are overcharged or overdischarged,

wherein said battery-pack controller inhibits reading of an output signal from the overcharge/overdischarge detectors of a pair of adjacent module controllers when said battery-pack controller determines that a line-cut has occurred on one of said module-connecting lines, and inhibits reading of an output signal from the overcharge/overdischarge detector of one of said module controllers when said battery-pack controller determines that a line-cut has occurred on one of said battery-pack connecting lines.

3. The battery pack manager of claim 1, wherein each of said module controllers comprises a cell equalizer connected to the unit cells of the associated battery-pack module via said plurality of cell-connecting lines for individually causing the unit cells to discharge when voltages developed by the unit cells differ from reference voltages,

wherein said battery-pack controller inhibits said cell equalizer of all of said module controllers when said battery-pack controller is making a determination that a line-cut has occurred on any of said connecting lines.

4. The battery pack manager of claim 1, wherein said battery-pack controller makes a comparison between a most recent voltage value and a previous voltage value of each battery-pack module to detect a match or a mismatch, repeats said comparison on each of said battery-pack modules, and determines that a line-cut has occurred on one of said connecting lines if said match is repeatedly detected.

5. The battery pack manager of claim 4, wherein said battery-pack controller monitors output signals of said overcharge/overdischarge detector of each of said module controllers, and determines that a line-cut has occurred on one of said module-connecting lines if a pair of adjacent module controllers alternately produce overcharge and overdischarge signals.

6. The battery pack manager of claim 5, wherein each of said module controllers further comprises a plurality of overcharge/overdischarge comparators respectively connected to the unit cells of the associated battery-pack module via said cell-connecting lines for generating output signals indicating whether the unit cells of the associated battery-pack module are overcharged or overdischarged,

wherein said battery-pack controller monitors output signals of said overcharge/overdischarge comparators of each of said module controllers, and determines that a line-cut has occurred on one of said cell-connecting lines if a pair of adjacent overcharge/overdischarge comparators alternately produce overcharge and overdischarge signals.

7. The battery pack manager of claim 6, wherein each of said module controllers further comprises logic circuitry, connected to said overcharge/overdischarge comparators of the module controller, that divides overcharge output signals from said comparators into a first odd-numbered group and a first even-numbered group, divides overdischarge output signals from said comparators into a second odd-numbered group and a second even-numbered group, analyzes transition states of output signals that occur in sequence from said first odd-numbered group, said first even-numbered group, second odd-numbered group and said second even-numbered group, and determines that said line-cut has occurred on one of said cell-connecting lines depending on the analyzed transition states.

8. A method of detecting a line-cut on a plurality of connecting lines connecting a plurality of series-connected rechargeable unit cells to control circuitry, wherein said unit cells are divided into a plurality of battery-pack modules, comprising the steps of:

a) successively detecting a voltage value of each of said battery-pack modules; and

b) determining that a line-cut has occurred on one of said battery-pack connecting lines if a single zero-voltage value is detected or that a line-cut has occurred on one of said module-connecting lines if two zero-voltage values are detected in succession.

9. The method of claim 8, wherein said control circuitry includes a plurality of module controllers connected to said battery-pack modules respectively via said pair of battery-pack connecting lines and said plurality of module-connecting lines,

d) performing a decision on whether said unit cells of each battery-pack module are overcharged or overdischarged,

e) inhibiting reading of a result of the decision by step (d) performed on a pair of adjacent module controllers if step (b) determines that a line-cut has occurred on one of said module-connecting lines;

and

f) inhibiting reading of a result of the decision by step (d) performed on one of said module controllers if step (b) determines that a line-cut has occurred on one of said battery-pack connecting lines.

10. The method of claim 9, wherein each of said module controllers comprises a cell equalizer connected to the unit cells of the associated battery-pack module via said plurality of cell-connecting lines for individually causing the unit cells to discharge when voltages developed by the unit cells differ from reference voltages, further comprising the step of inhibiting said cell equalizer of all of said module controllers when step (b) is being performed.

11. The method of claim 9, wherein step (b) comprises the steps of:

making a comparison between a most recent voltage value and a previous voltage value of each battery-pack module to detect a match or a mismatch;

repeating said comparison on each of said battery-pack modules; and

determining that a line-cut has occurred on one of said connecting lines if said match is repeatedly detected.

12. The method of claim 9, wherein step (b) comprises the step of determining that a line-cut has occurred on one of said module-connecting lines if the decision of step (d) performed on a pair of adjacent module controllers alternately indicates overcharge and overdischarge of one of said unit cells.

13. The method of claim 9, wherein each of said module controllers further comprises a plurality of overcharge/overdischarge comparators respectively connected to the unit cells of the associated battery-pack module via said cell-connecting lines for generating output signals indicating whether the unit cells of the associated battery-pack module are overcharged or overdischarged,

wherein step (a) comprises monitoring output signals of said overcharge/overdischarge comparators of each of said module controllers, and step (b) comprises determining that a line-cut has occurred on one of said cell-connecting lines if a pair of adjacent overcharge/overdischarge comparators alternately produce overcharge and overdischarge signals.