System and method for maintenance charging of battery cells

• US 6,194,874 B1
• Filed: 09/15/1999
• Issued: 02/27/2001
• Est. Priority Date: 03/17/1999
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Wolf, Mats, Wendelrup, Heino, Kalogeropoulos, Sarandis, Hansson, Magnus, Forsberg, Charles, Ptasinski, Kristoffer, Mercke, Johan, Andersson, Richard
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): LUK, LAWRENCE W
• Application Number:
  US09/397,001
• Time in Patent Office: 531 Days
• Field of Search: 320/160, 320/137, 320/136, 320/127, 320/128
• US Class Current: 320/160
• CPC Class Codes: H02J 7/0071 with a programmable schedule

Abstract

A method and apparatus for maintenance charging a battery is disclosed. A battery is fully charged using conventional CC-CV techniques and subsequently is maintenance charged by applying a first maintenance voltage to the battery for a first predetermined time period. If desired, a second maintenance voltage may be applied to the battery for a second predetermined time period. An apparatus for maintenance charging a battery utilizes a timer and a charge controller to apply a maintenance voltage to a battery for a predetermined time period.

Claims

1. A method for charging a battery, comprising the steps of:

(a) charging the battery to a predetermined charge level; and

(b) applying a first maintenance voltage to the battery for a first predetermined time period,

wherein the first maintenance voltage is less than a predetermined reference voltage, and wherein the first predetermined time period is a function of a self-discharge curve associated with the battery.

2. A method according to claim 1, wherein the step of charging the battery to a predetermined charge level further comprises the step of:

applying a constant current to the battery until the battery reaches a predetermined voltage and then applying a constant voltage until the battery reaches a predetermined charge level.

3. A method according to claim 1, wherein:

the battery is charged to the predetermined charge level of 4.2 V; and

the first maintenance voltage of 4.15 V is applied to the battery for the first predetermined time period.

4. A method according to claim 1, wherein:

the reference voltage is a function of a self-discharge curve associated with the battery.

5. A method according to claim 1, wherein:

the first predetermined time period is approximately 60 hours.

6. A method according to claim 1, further comprising the step of:

(c) applying a second maintenance voltage for a second predetermined time period, wherein the second maintenance voltage is less than a predetermined reference voltage.

7. A method according to 6, wherein:

the second predetermined time period is a function of a discharge curve characteristic associated with the battery.

8. A method according to 6, wherein:

the second predetermined time period is approximately 200 hours.

9. A method according to claim 1, further comprising the step of:

iteratively reducing the first maintenance voltage for at least one predetermined time period, such that the maintenance voltage remains less than a predetermined reference voltage.

10. An apparatus for charging a battery cell, comprising:

a current source;

a timer;

a charge controller for charging the battery cell; and

a maintenance charge controller for applying a first maintenance voltage to the battery cell for a first predetermined time period, wherein the first maintenance voltage is less than a reference voltage of the battery cell in a fully-charged state, wherein the first predetermined time period is a function of a self-discharge curve associated with the battery.

11. The apparatus of claim 10, wherein:

the maintenance charge controller further applies a second maintenance voltage to the battery cell for a second predetermined time period, wherein the second maintenance voltage is less than the first maintenance voltage.

12. The apparatus of claim 10, wherein:

the current source comprises an ac/dc converter.

13. The apparatus of claim 10, wherein:

the timer, the charge controller, and the maintenance charge controller reside on the printed circuit board of a mobile communication device.

14. The apparatus of claim 10, wherein:

the reference voltage is a function of a self-discharge curve associated with the battery.

15. The apparatus of claim 10, wherein:

the maintenance charge controller iteratively reduces the first maintenance voltage for at least one predetermined time period, such that the maintenance voltage remains less than a predetermined reference voltage.

16. A method for charging a battery, comprising the steps of:

(a) charging the battery to a predetermined charge level; and

(b) applying a first maintenance voltage to the battery for a first predetermined time period,

wherein the first maintenance voltage is less than a predetermined reference voltage, and wherein the reference voltage is a function of a self-discharge curve associated with the battery.

17. A method according to claim 16, wherein the step of charging the battery to a predetermined charge level further comprises the step of:

applying a constant current to the battery until the battery reaches a predetermined voltage and then applying a constant voltage until the battery reaches a predetermined charge level.

18. A method according to claim 16, wherein:

the battery is charged to the predetermined charge level of 4.2 V; and

the first maintenance voltage of 4.15 V is applied to the battery for the first predetermined time period.

19. A method according to claim 17, wherein:

the first predetermined time period is a function of a self-discharge curve associated with the battery.

20. A method according to claim 16, wherein:

the first predetermined time period is approximately 60 hours.

21. A method according to claim 16, further comprising the step of:

(c) applying a second maintenance voltage for a second predetermined time period, wherein the second maintenance voltage is less than a predetermined reference voltage.

22. A method according to 16, wherein:

the second predetermined time period is a function of a discharge curve characteristic associated with the battery.

23. A method according to 22, wherein:

the second predetermined time period is approximately 200 hours.

24. A method according to claim 16, further comprising the step of:

iteratively reducing the first maintenance voltage for at least one predetermined time period, such that the maintenance voltage remains less than a predetermined reference voltage.

25. An apparatus for charging a battery cell, comprising:

a current source;

a timer;

a charge controller for charging the battery cell; and

a maintenance charge controller for applying a first maintenance voltage to the battery cell for a first predetermined time period, wherein the first maintenance voltage is less than a reference voltage of the battery cell in a fully-charged state, wherein the reference voltage is a function of a self-discharge curve associated with the battery.

26. The apparatus of claim 25, wherein:

the maintenance charge controller further applies a second maintenance voltage to the battery cell for a second predetermined time period, wherein the second maintenance voltage is less than the first maintenance voltage.

27. The apparatus of claim 25, wherein:

the current source comprises an ac/dc converter.

28. The apparatus of claim 25, wherein:

the timer, the charge controller, and the maintenance charge controller reside on the printed circuit board of a mobile communication device.

29. The apparatus of claim 25, wherein:

the first predetermined time period is a function of a self-discharge curve associated with the battery.

30. The apparatus of claim 25, wherein:

the reference voltage is a function of a self-discharge curve associated with the battery.

31. The apparatus of claim 25, wherein:

the maintenance charge controller iteratively reduces the first maintenance voltage for at least one predetermined time period, such that the maintenance voltage remains less than a predetermined reference voltage.