Battery pack diagnostic method and battery pack diagnostic apparatus

• US 6,509,718 B2
• Filed: 07/17/2001
• Issued: 01/21/2003
• Est. Priority Date: 07/18/2000
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Sakai, Kenichi, Sugimoto, Tomonaga
• Primary Examiner(s): Tso, Edward H.
• Assistant Examiner(s): Luk, Lawrence
• Application Number:
  US09/906,141
• Publication Number:
  US 20020011822A1
• Time in Patent Office: 553 Days
• Field of Search: 320/134, 320/116, 320/118, 320/132, 320/165, 320/DIG.20, 320/DIG.21, 324/429, 324/430, 324/433
• US Class Current: 320/134
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/0047 with monitoring or indicating devices or circuits
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/005 Detection of state of health [SOH]
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A battery pack diagnostic apparatus that performs diagnosis on a plurality of cells constituting a battery pack measures the current flowing through the battery pack and starts a cell voltage measurement at the terminals of each cell when the absolute value of the measured current flowing through the battery pack has sustained a level equal to or lower than a predetermined value over a specific length of time. By detecting a faulty cell based upon the measured cell voltage value at individual cells thus obtained, a cell failure occurring while the battery pack is used in a normal state such as while the vehicle is in a running state can be detected reliably.

Claims

1. A battery pack diagnostic apparatus that performs diagnosis on a plurality of cells constituting a battery pack, comprising:

a current measuring instrument that measures current flowing through the battery pack;

a voltage measuring instrument that measures a cell voltage at the terminals of each cell;

a measurement control device that starts a cell voltage measurement by the voltage measuring instrument when an absolute value of the current flowing through the battery pack measured by the current measuring instrument has sustained a level equal to or lower than a predetermined value over a specific length of time; and

a faulty cell detection device that detects a faulty cell based upon the cell voltage measured during the cell voltage measurement at individual cells performed by the voltage measuring instrument.

2. A battery pack diagnostic apparatus according to claim 1, wherein;

the specific length of time is set in correspondence to the type of the battery pack.

3. A battery pack diagnostic apparatus according to claim 2, further comprising:

a temperature measuring instrument that measures a temperature of the battery pack; and

a depletion detection device that detects an extent of depletion at the battery pack, wherein;

the specific length of time set in correspondence to the type of the battery pack is corrected in conformance to the temperature of the battery pack measured by the temperature measuring instrument and the extent of depletion of the battery pack detected by the depletion detection device.

4. A battery pack diagnostic apparatus according to claim 1, wherein;

the predetermined value for the current flowing through the battery pack is a current value so that a faulty cell detection can be performed even when the cell voltage changes as a result of a change in the current.

5. A battery pack diagnostic apparatus according to claim 1, wherein;

the measurement control device starts measurement of cell voltages anew if the absolute value of the current flowing through the battery pack exceeds the predetermined value during the cell voltage measurement performed by the voltage measuring instrument.

6. A battery pack diagnostic apparatus according to claim 1, wherein;

the measurement control device starts the cell voltage measurement anew if an absolute value of the difference between a maximum value and a minimum value of the current flowing through the battery pack exceeds a predetermined value during the cell voltage measurement performed by the voltage measuring instrument.

7. A battery pack diagnostic apparatus that performs diagnosis on a plurality of cells constituting a battery pack, comprising:

a current measurement means for measuring current flowing through the battery pack;

a voltage measurement means for measuring cell voltage at the terminals of each cell;

a measurement control means for starting a cell voltage measurement by the voltage measurement means when an absolute value of the current flowing through the battery pack measured by the current measurement means has sustained a level equal to or lower than a predetermined value over a specific length of time; and

a faulty cell detection means for detecting a faulty cell based upon the cell voltage measured during the cell voltage measurement at individual cells performed by the voltage measuring means.

8. A battery pack diagnostic apparatus that performs diagnosis on a plurality of cells constituting a battery pack, comprising:

a current measuring instrument that measures current flowing through the battery pack;

a voltage measuring instrument that measures cell voltage at the terminals of each cell;

a measurement control device that starts a cell voltage measurement by the voltage measuring instrument when an absolute value of the current flowing through the battery pack measured by the current measuring instrument has sustained a level equal to or lower than a predetermined value over a specific length of time; and

a faulty cell detection device that detects a faulty cell based upon the cell voltage measured during the cell voltage measurement at individual cells performed by the voltage measuring instrument, wherein;

the measurement control device starts cell voltage measurement anew if the absolute value of the current flowing through the battery pack exceeds the predetermined value or an absolute value of a difference between a maximum value and a minimum value of the current flowing through the battery pack exceeds a predetermined value during a cell voltage measurement performed by the voltage measuring instrument.

9. A battery pack diagnostic apparatus according to claim 8, wherein;

a current value that enables a faulty cell detection even when the cell voltage changes as a result of a change in the current is set as the predetermined value for the current flowing through the battery pack.

10. A battery pack diagnostic method for performing diagnosis on a plurality of cells constituting a battery pack, comprising the steps of:

measuring the current flowing through the battery pack;

measuring cell voltage at the terminals of each cell when an absolute value of the measured current flowing through the battery pack has sustained a level equal to or lower than a predetermined value over a specific length of time; and

detecting a faulty cell based upon the cell voltages measured during the cell voltage measurement.

11. A battery pack diagnostic method for performing diagnosis on a plurality of cells constituting a battery pack, comprising;

measuring the current flowing through the battery pack,

measuring a cell voltage at the terminals of each cell when the absolute value of the measured current flowing through the battery pack has sustained a level equal to or lower than a predetermined value over a specific length of time;

measuring the cell voltage anew if the absolute value of the current flowing through the battery pack exceeds the predetermined value or if an absolute value of the difference between a maximum value and a minimum value of the measured current flowing through the battery pack exceeds a predetermined value during cell voltage measurement; and

detecting a faulty cell based upon the cell voltage measured during the cell voltage measurement.