Battery pack

• US 6,664,000 B1
• Filed: 09/27/2000
• Issued: 12/16/2003
• Est. Priority Date: 09/30/1999
• Status: Expired due to Term

• Current Assignee: Envision AESC Energy Devices Ltd.
• Original Assignee: NEC Mobile Energy Corporation (NEC Corporation)
• Inventors: Sonobe, Satoshi
• Primary Examiner(s): CHANEY, CAROL DIANE
• Application Number:
  US09/669,837
• Time in Patent Office: 1,175 Days
• Field of Search: 429/61, 429/100, 429/99, 429/98, 429/97, 429/96, 320/134, 320/136
• US Class Current: 429/61
• CPC Class Codes: H01M 10/425 Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing printed circuits H05K1/00
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 50/581 in response to temperature
• CPC Class Codes: H01M 50/583 in response to current, e.g. fuses
• CPC Class Codes: H01M 6/42 Grouping of primary cells into batteries H01M6/40 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery pack arranged to make a judgment concerning a loss of functional status and to perform selectively charge-and-discharge control and forced discharge control according to the judgment. The battery pack includes a charge-and-discharge control device for charging and discharging a battery, a forced discharge control device for forcedly discharging each cell, a function detecting device for detecting a functional status of the battery pack, a judging device for making a judgment concerning a loss of functional status detected by the function detecting device, and a control device for selectively controlling the charge-and-discharge control device and the forced discharge control device according to the judgment concerning a loss of functional status made by the judging device. A battery pack having lost its function owing to the completion of the span of life and a marked degradation in function is judged to be one having lost its functional status, and charge-and-discharge control and forced discharge control are selectively performed according to the judgment.

Claims

1. A battery pack arranged to make a decision concerning a loss of functional status and to perform selectively charge-and-discharge control and forced discharge control according to the decision, said battery pack comprising:

charge-and-discharge control means for charging and discharging a battery;

forced discharge control means for forcedly discharging each cell;

function detecting means for detecting a functional status of said battery pack;

judging means for making a decision concerning a loss of functional status detected by said function detecting means; and

control means for selectively controlling said charge-and-discharge control means and forced discharge control means according to the decision concerning a loss of functional status made by said judging means, whereby charge-and-discharge control and forced discharge control are selectively performed according to the decision concerning a loss of functional status, wherein the loss of functional status is when a usable life of the battery pack is determined as approaching an end as determined by an elapsed time since manufacture of the battery pack or a number of charge-discharge cycles exceeds a predetermined number.

2. A battery pack according to claim 1, wherein said function detecting means includes timer means for measuring an elapsed time since a date of manufacture,

wherein said judging means judges whether or not there is a loss of functional status according to whether or not said elapsed time is more than a predetermined value.

3. A battery pack according to claim 2, wherein said timer means includes a non-volatile memory, so that said elapsed time is stored n said non-volatile memory before measurement is suspended owing to a drop in battery voltage, and when the battery voltage is restored by charging, time is measured in succession to said elapsed time.

4. A battery pack according to claim 3, wherein said timer means estimates a period of time during which the measurement was suspended and adds the estimated period of time to said elapsed time.

5. A battery pack according to claim 2, wherein said timer means includes:

storage means for storing a date of manufacture;

communication means for acquiring a present date from an external device by communication; and

computing means for calculating an elapsed time from said date of manufacture to said present date.

6. A battery pack according to any one of claims 2 to 5, wherein said function detecting means includes, in addition to said timer means, one of:

counting means for counting a number of charge/discharge cycles;

temperature detecting means for detecting an average temperature of said battery pack; and

measuring means for measuring a charging rate of said battery pack;

wherein said elapsed time is corrected by one of said number of charge/discharge cycles, said average temperature and said charging rate.

7. A battery pack according to claim 1, wherein said function detecting means includes:

temperature detecting means for detecting an average temperature; and

timer means for measuring an elapsed time since a date of manufacture in accordance with a doubling rule by which a period of time elapsed is doubled for every 10°

C. rise in said average temperature;

wherein said judging means judges whether or not there is a loss of functional status according to whether or not said elapsed time is more than a predetermined value.

8. A battery pack according to claim 1, wherein said function detecting means includes counting means for counting a number of charge/discharge cycles,

wherein said judging means judges whether or not there is a loss of functional status according to whether or not said number of charge/discharge cycles is more than a predetermined value.

9. A battery pack according to claim 1, wherein said function detecting means includes capacity detecting means for detecting a full-charge capacity,

wherein said judging means judges whether or not there is a loss of functional status according to whether or not said full-charge capacity is less than a predetermined value.

10. A battery pack according to claim 1, wherein said function detecting means includes means for accumulating a discharge or charge capacity,

wherein said judging means judges whether or not there is a loss of functional status according to whether or not said accumulated capacity value is more than a predetermined value.

11. A battery pack according to claim 1, wherein said function detecting means includes means for measuring a temperature and an electric current,

wherein said judging means judges whether or not there is a loss of functional status according to whether or not a charge-and-discharge efficiency at a predetermined temperature and a predetermined current value measured by said means is less than a predetermined current value.

12. A battery pack according to claim 1, wherein said function detecting means includes means for measuring a temperature and an electric current,

wherein said judging means judges whether or not there is a loss of functional status according to whether or not a self-discharge current from the battery at a predetermined temperature measured by said means is more than a predetermined value.

13. A battery pack according to claim 1, wherein said function detecting means includes for detecting an electric current,

wherein said judging means judges whether or not there is a loss of functional status from a value of charge/discharge current measured by said means.

14. A battery pack according to claim 13, wherein said judging means judges whether or not there is a loss of functional status according to whether or not a peak current exceeding a predetermined value has flowed as said charge/discharge current for more than a predetermined period of time or more than a predetermined number of times.

15. A battery pack according to claim 14, wherein said control means temporarily disables charging and discharging through said charge-and-discharge control means on condition that said judging means has judged that there that there is a loss of functional status, and after a predetermined period of time has passed, said control means enables charging and discharging permanently according to a peak current value.

16. A battery pack according to claim 13, wherein said judging means judges whether or not there is a loss of functional status according to whether or not said battery pack is incapable of being fully charged even if an electric current has flowed for a specified period of time.

17. A battery pack according to claim 1, wherein said function detecting means includes means for detecting a cell voltage,

wherein said judging means judges whether or not there is a loss of functional status from a value of said cell voltage.

18. A battery pack according to claim 17, wherein said judging means judges whether or not there is a loss of functional status according to whether or not any of cell voltages is less than a minimum value.

19. A battery pack according to claim 17, wherein said judging means judges whether or not there is a loss of functional status according to whether or not any of cell voltages is more than a maximum value.

20. A battery pack according to claim 17, wherein said judging means judges whether or not there is a loss of functional status according to whether or not a difference between a minimum cell voltage and a maximum cell voltage is more than a desired operating value.

21. A battery pack according to claim 1, wherein said function detecting means includes detecting means for detecting a battery voltage and an electric current,

wherein said judging means judges whether or not there is a loss of functional status from the battery voltage and electric current value detected by said detecting means.

22. A battery pack according to claim 21, wherein said judging means judges whether or not there is a loss of functional status according to whether or not a precharge time is longer than a predetermined period of time when said battery pack is precharged with a voltage less than a specified voltage and a specified electric current.

23. A battery pack according to claim 21, wherein said judging means calculates a value of electric current other than a charge/discharge current on a basis of a variation in battery voltage and an electric current, and judges whether or not there is a loss of functional status according to whether or not said value of electric current is more than a variation value.

24. A battery pack according to claim 1, wherein said function detecting means includes means for detecting a temperature,

wherein said judging means judges whether or not there is a loss of functional status according to whether or not a temperature of said battery pack or a temperature of the cell is more than an operating limit, or whether or not a time interval during which the temperature of said battery pack or the temperature of the cell is more than an operating limit for more than a given period of time.

25. A battery pack according to claim 1, wherein

said function detecting means includes means for detecting a temperature at each of at least three points,

wherein said judging means judges whether or not there is a loss of functional status according to whether or not a difference between a temperature at one of the three points and an

average value of temperatures at the other two of said three points is more than a differential.

26. A battery pack according to claim 1, wherein said function detecting means includes means for measuring an internal impedance at a predetermined temperature,

wherein said judging means judges whether or not there is a loss of functional status according to whether or not said internal impedance is more than a specified impedance.

27. A battery pack according to claim 1, wherein

said function detecting means includes means for detecting a battery voltage, an electric current and a temperature,

wherein when there is a variation in said battery voltage, a sampling period for detection of a battery voltage, an electric current and a temperature is shortened.

28. A battery pack according to claim 1, wherein said function detecting means and judging means have a non-volatile memory for storing detecting data and judgement data when there is a drop in battery voltage.

29. A battery pack according to claim 1, wherein said function detecting means includes a label to be stuck on said battery pack or cell, said label having a conductor wire or a thin conductive film disposed all over a reverse side thereof,

wherein said judging means judges whether or not there is a loss of functional status according to whether or not said label is separated or whether or not the conductor wire is broken.

30. A battery pack according to claim 1, wherein said function detecting means includes a pressure sensor or an impact sensor,

wherein when judging that there is a loss of functional status, said judging means compares a voltage, an electric current and a temperature measured after before judging the loss of functional status with those measured before judging the loss of functional status to judge whether or not there is a sharp variation in voltage, electric current or temperature, and said control means temporarily disables charging or both charging and discharging through said charge-and-discharge control means on condition that said judging means had judged that there is a loss of functional status, and if there is not said sharp variation thereafter, said control means restores charging and discharging functions.

31. A battery pack according to claim 30, wherein

said function detecting means includes means for detecting a voltage, an electric current and a temperature,

wherein when judging that there is a loss of functional status, said judging means compares a voltage, an electric current and a temperature measured after judging the loss of functional status with those measured before judging the loss of function status to judge whether or not there is a variation in voltage, electric current or temperature, and said control means temporarily disables charging or both charging and

discharging through said charge-and-discharge control means on condition that said judging means has judged that there is a loss of functional status, and if there is not

said sharp variation thereafter, said control means restores charging and discharging functions.

32. A battery pack according to claim 31, wherein said function detecting means shortens a sampling period during the time interval between the instant when said judging means judges that there is a loss of functional status and the instant when said control means restores charging and discharging functions.

33. A battery pack according to claim 1, wherein said function detecting means includes a strain sensor for detecting a strain on said battery pack,

wherein said judging means judges whether or not there is a loss of functional status according to whether or not said strain is more than a predetermined value.

34. A battery pack according to claim 1, wherein said function detecting means includes a gas sensor for detecting a leakage of an electrolyte,

wherein said judging means judges whether or not there is a loss of functional status according to whether or not a value of detecting gas leakage is more than a predetermined value.

35. A battery pack according to claim 1, wherein said function detecting means includes one or a plurality of thermal fuses disposed at places on a circuit board where heat may be generated,

wherein said judging means judges that there is a loss of functional status from fusing of any of said thermal fees.

36. A battery pack according to claim 1, wherein said control means disables charging or both charging and discharging through charge-and-discharge control means on condition that said judging means has judged that there is a loss of functional status.

37. A battery pack according to claim 1, wherein, on condition that said judging means has judged that there is a loss of functional status, said control means disables charging or both charging and discharging through said charge-and-discharge control means and moreover forcedly discharges each cell of said battery pack through said forced discharge control means.

38. A battery pack according to claim 36 or 37, wherein said charge-and-discharge control means disables charging or both charging and discharging through a semiconductor device for on-off controlling charging and discharging or a thermal fuse inserted in a current path for charging and discharging, said thermal fuse being fused when charging or both charging and discharging are to be disabled.

39. A battery pack according to claim 1, wherein, according to the decision concerning a loss of functional status made by said judging means, said control means performs one of an operation of disabling charging or both charging and discharging, an operation of inhibiting charging or both charging and discharging and an operation of stopping charging or discharging by controlling said charge-and-discharge control means and forcedly discharges each cell by controlling said forced discharge control means and further performs control for issuing an alarm according to need.

40. A battery pack according to claim 1, wherein said control means performs control for filling a flame-resisting substance into said battery pack according to the decision concerning a loss of functional status made by said judgment means.

41. A battery pack arranged to make a decision concerning a loss of functional status and to perform selectively charge-and-discharge control and forced discharge control according to the decision, said battery pack comprising:

charge-and-discharge control means for charging and discharging a battery;

forced discharge control means for forcedly discharging each cell;

liquid detecting means for detecting a liquid leakage in said battery pack; and

control means for disabling charging or both charging and discharging by controlling said charge-and-discharge control means and for forcedly discharging each cell of said battery pack by controlling said forced discharge control means on condition that a liquid leakage has been detected by said liquid detecting means.

42. A battery pack according to claim 41, wherein control for disabling charging or both charging and discharging is performed through a fusible portion that is fused by detecting a liguid.