Method and apparatus for calibrating a rechargeable battery

• US 6,630,814 B2
• Filed: 05/16/2001
• Issued: 10/07/2003
• Est. Priority Date: 12/19/2000
• Status: Expired due to Term

• Current Assignee: Optis Cellular Technology LLC (Brevet Capital)
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Andersson, Rickard, Carlson, Jeremy, Demers, David, Liddle, Derek, Evers, Petrus, Kalogeropoulos, Sarandis, Langberg, Anders, Forsberg, Charles, Ptasinski, Kristoffer
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/859,237
• Publication Number:
  US 20020167293A1
• Time in Patent Office: 874 Days
• Field of Search: 320/132, 320/149
• US Class Current: 320/132
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Method and apparatus for calibrating a rechargeable battery for mobile telephones and other electronic devices. Calibration is accomplished during a process of completely charging the battery by determining the total amount of charge accepted by the battery during the charging process, and providing a value of total charge capacity of the battery based, at least in part, on the total amount of charge accepted by the battery. The total charge capacity of the battery is used to calculate remaining battery capacity and to predict the remaining operational time of the device. Alternative calibration procedures are provided if the battery is not completely discharged before charging or if the battery is not fully charged by the charging process. The calibration procedures of the invention require no interaction from a user (other than his initiating the normal charging process), and typically permits a calibration to be carried out notwithstanding varying usage habits of different users.

Claims

1. A method for calibrating a rechargeable battery for an electronic device comprising:

charging the battery by a charging process;

determining a total amount of charge accepted by the battery during the charging process; and

providing a value of total battery capacity of the battery based, at least in part, on the total amount of charge accepted by the battery.

2. The method according to claim 1, wherein said battery is completely discharged before said charging step is initiated.

3. The method according to claim 2, and further including the step of completely discharging said battery before said charging step is initiated, and wherein said charging step comprises fully charging said battery such that the total amount of charge accepted by said battery comprises the total battery capacity value.

4. The method according to claim 1, wherein said determining step comprises determining a net current fed into the battery during the charging process and a duration of the charging process to determine the total amount of charge accepted by the battery.

5. The method according to claim 4, wherein said step of determining a net current fed into the battery comprises measuring a charging current and a current consumption of the electronic device, and calculating therefrom the net current fed into the battery.

6. The method according to claim 1, and further including the step of updating a total battery capacity parameter using said provided value of total battery capacity.

7. The method according to claim 6, and further including the step of predicting a remaining operational time of said device using said updated total battery capacity parameter.

8. The method of claim 7, wherein said device comprises a mobile telephone, and wherein said step of predicting a remaining operational time comprises predicting a remaining talk/standby time of said mobile telephone.

9. The method according to claim 1, and further including the step of providing a value of remaining battery capacity of the battery prior to initiation of the charging step, and wherein the step of providing a value of total battery capacity comprises the step of adding the provided remaining battery capacity value and the total amount of charge accepted by the battery during the charging process to provide the total battery capacity value.

10. The method according to claim 9, wherein said battery includes at least one battery cell, and wherein said step of providing a value of remaining battery capacity comprises the steps of determining a voltage across said at least one cell, and determining said remaining battery capacity value as a function of said voltage across said at least one cell.

11. The method according to claim 10, wherein said step of determining a voltage across said at least one cell comprises the step of measuring battery voltage when battery current is sufficiently low that said battery voltage is substantially equal to said voltage across said at least one cell.

12. The method according to claim 11, wherein said sufficiently low battery current is less than about 10 mA.

13. The method according to claim 11, and further including the step of waiting a period of time after said battery current is sufficiently low before measuring said battery voltage to stabilize chemical reactions in said at least one cell.

14. The method according to claim 13, wherein said period of time is at least about 10 minutes.

15. The method according to claim 1, wherein said charging step comprises the step of fully charging said battery, and wherein said method further includes the step of calibrating said battery by an alternative calibration procedure if said charging step does not fully charge said battery.

16. The method according to claim 15, wherein said alternative calibration procedure comprises a calibration procedure based on ageing of the battery.

17. The method according to claim 15, wherein said alternative calibration procedure includes monitoring said battery during use of said device.

18. The method according to claim 17, wherein said monitoring step includes the steps of predicting a remaining battery capacity value of the battery, and calculating a difference between said predicted remaining battery capacity value and a remaining battery capacity value determined by a fuel gauge of said device, and updating the total battery capacity value in accordance with said difference.

19. The method according to claim 18, wherein said step of predicting the remaining battery capacity value is made when the remaining battery capacity value determined by said fuel gauge is at a specified value.

20. The method according to claim 19, wherein said specified value is about 10% of the total battery capacity value of said battery programmed into said device.

21. The method according to claim 18, wherein said updating step comprises updating said total battery capacity value by no more than a specified maximum amount as a result of any one calibration procedure.

22. The method according to claim 17, wherein said alternative calibration procedure comprises determining either an actual remaining battery capacity of said battery after a fuel gauge of said device indicates that said battery is empty, or a remaining battery capacity value indicated by said fuel gauge when said battery is actually empty, and updating a total battery capacity value as a result of said determination.

23. The method according to claim 22, wherein said updating step is by no more than a predetermined maximum value during any one calibration procedure.

24. The method according to claim 1, wherein said device comprises a mobile terminal.

25. The method according to claim 24, wherein said mobile terminal comprises a mobile telephone.

26. The method according to claim 1, wherein said battery comprises a smart battery.

27. The method according to claim 1, wherein said battery comprises a dumb battery.

28. An apparatus for calibrating a rechargeable battery for an electronic device comprising:

a charging circuit for charging said battery,

a determiner which determines the total amount of charge accepted by the battery during charging; and

a provider which provides a total battery capacity value for said battery based, at least in part, on the total amount of charge accepted by the battery.

29. An apparatus according to claim 28, wherein said charging circuit includes a discharger for fully discharging said battery before being charged.

30. An apparatus according to claim 28, and further including a memory for storing a remaining battery capacity value prior to charging said battery, and wherein said provider provides said total battery capacity value based on both said remaining battery capacity value and said total amount of charge accepted by said battery during charging.

31. An apparatus according to claim 29, and further including a monitor which monitors said battery during use of said device and determines said remaining battery capacity value.

32. The apparatus according to claim 28, and further including a user advising member for advising a user of the device of remaining operational time of said device using on said total battery capacity value.

33. The apparatus according to claim 32, wherein said advising member comprises a display on said device.

34. The apparatus according to claim 33, wherein said device comprises a mobile telephone, and wherein said display displays remaining talk/standby time of said telephone.

35. A method for determining remaining battery capacity of a battery for an electronic device, said battery including at least one battery cell, the method comprising:

determining a voltage across said at least one battery cell; and

determining a remaining battery capacity value as a function of said voltage across said at least one battery cell, wherein said step of determining a voltage across said at least one battery cell comprises measuring battery voltage when said battery current is sufficiently low that said battery voltage is substantially equal to said voltage across said at least one battery cell.

36. The method according to claim 35, wherein said sufficiently low battery current is less than about 10 mA.

37. The method according to claim 35, and further including the step of waiting a period of time after said battery current is sufficiently low before measuring said battery voltage to stabilize any chemical reactions in said at least one cell.

38. The method according to claim 37, wherein said period of time comprises at least about 10 minutes.

39. A method for calibrating a battery of an electronic device, comprising:

monitoring used battery capacity of said battery during use of said device and

providing a monitored remaining battery capacity value therefrom;

predicting a remaining battery capacity value of said battery, calculating a difference between said predicted remaining battery capacity value and said monitored remaining battery capacity value; and

updating a total capacity value of said battery as a result of said difference.

40. The method according to claim 39, wherein said prediction is made when said monitored remaining battery capacity value is at a specified amount.

41. The method according to claim 40, wherein said specified amount is about 10% of a total battery capacity value programmed into said device.

42. The method according to claim 39, wherein said updating step updates said total battery capacity value by no more than a predetermined amount as a result of any one calibration.

43. A method for calibrating a battery of an electronic device, comprising:

monitoring said battery during use of said device to determine a difference between a remaining battery capacity value indicated by a fuel gauge of said device and an actual remaining battery capacity value; and

updating a total battery capacity value stored in said device as a result of said difference.

44. The method according to claim 43, wherein said monitoring step comprises measuring an additional charge capacity of said battery after said fuel gauge indicates that said battery is empty.

45. The method according to claim 43, wherein said monitoring step comprises determining the total battery capacity value indicated by said fuel gauge when said battery is actually empty.

46. The method according to claim 43, wherein said updating step updates a stored total battery capacity value by no more than a predetermined maximum amount as a result of any one calibration procedure.