System with limited long-time-averaged battery charging rate

• US 6,137,268 A
• Filed: 06/30/1997
• Issued: 10/24/2000
• Est. Priority Date: 06/30/1997
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Compaq Computer Corporation (HP Inc.)
• Inventors: Mitchell, Nathan, Freiman, Joseph F.
• Primary Examiner(s): TIBBITS, PIA FLORENCE
• Assistant Examiner(s): Shin, K.
• Application Number:
  US08/885,215
• Time in Patent Office: 1,212 Days
• Field of Search: 320/149, 320/137, 320/155, 320/140, 320/141, 320/145, 320/146
• US Class Current: 320/149
• CPC Class Codes: H02J 7/00714 in response to battery charging or discharging current

Abstract

A battery charging system in which current is averaged over a long time period (seconds) to determine the maximum average charging rate. When the integral of charging current over this long period reaches the programmed maximum charge value for one period, current is simply cut off for the remainder of the fixed long period.

Claims

1. A method of charging a portable battery pack which includes a built-in cutoff transistor, comprising the steps of:

(a.) monitoring charge transferred into the battery pack during successive fixed durations; and

(b.) whenever the charge transferred into the battery pack during any one of said fixed durations exceeds a fixed maximum value, then cutting off current to the battery for the remainder of said one of said fixed durations; and

(c.) at the beginning of the next one of said fixed durations, applying current to said battery if further charging is needed, and repeating said steps (a.) and (b.).

2. The method of claim 1, wherein said cutoff transistor is always turned off at least once during each of said fixed durations.

3. The method of claim 1, wherein said battery pack has a capacity of 100 Watt-hours or less.

4. The method of claim 1, wherein charge is transferred into said battery pack at a maximum rate in the range of 0.5 C to 2 C, and wherein the ratio of said fixed duration in seconds to the battery size in Watt-hours is more than 0.01.

5. The method of claim 1, wherein charge is transferred into said battery pack at a maximum C rate in the range of 0.5 C to 2 C, and wherein the ratio of said fixed duration in seconds to the battery size in Watt-hours is more than 0.1.

6. The method of claim 1, wherein charge is transferred into said battery pack at a maximum C rate which is higher than 1 C, and wherein the ratio of said fixed duration in seconds to the battery size in Watt-hours is more than 0.1 divided by said maximum C rate.

7. A method of charging a battery pack of 100 Watt-hours or less, comprising the steps of:

(a.) connecting the battery pack to the available current from a power supply, while intermittently turning off a cutoff transistor as necessary to limit the average current into the battery pack;

(b.) performing a further charging step which does not conform to said step (a.);

wherein said step of turning off said cutoff transistor is performed no more than once per second.

8. The method of claim 7, wherein said cutoff transistor is always turned off at least once in every 30 seconds.

9. A method of charging a battery pack of 100 Watt-hours or less at a rate of 0.5 C or greater, comprising the steps of:

(a.) connecting the battery pack to the available current from a power supply, while intermittently turning off a cutoff transistor as necessary to limit the average current into the battery pack;

wherein said step of turning off said cutoff transistor is performed with a frequency which is greater than said charging rate.

10. The method of claim 9, wherein said cutoff transistor is always turned off at least once in every 30 seconds.

11. The method of claim 9, wherein said step (a.) is followed by a further charging step which does not conform to said step (a.).

12. A computer system comprising:

at least one programmable processor;

a battery connected to power said processor under at least some circumstances, and a battery charge subsystem which is configured

to monitor charge transferred into a battery pack during each one of successive fixed durations,

and to cut off current to said battery pack for the remainder of one of said fixed durations, whenever the charge transferred into said battery pack during said one of said fixed durations exceeds a fixed maximum value.

13. The system of claim 12, wherein current is always turned off for at least a fixed fraction of each of said fixed durations.

14. The system of claim 12, wherein said current is always turned off at least once during each of said fixed durations.

15. The system of claim 12, wherein said battery has a capacity of 100 Watt-hours or less.

16. The system of claim 12, wherein charge is transferred into said battery at a maximum rate in the range of 0.5 C to 2 C, and wherein the ratio of said fixed duration in seconds to the battery size in Watt-hours is more than 0.01.

17. The system of claim 12, wherein charge is transferred into said battery at a maximum C rate in the range of 0.5 C to 2 C, and wherein the ratio of said fixed duration in seconds to the battery size in Watt-hours is more than 0.1.

18. The system of claim 12, wherein charge is transferred into said battery at a maximum C rate which is higher than 1 C, and wherein the ratio of said fixed duration in seconds to the battery size in Watt-hours is more than 0.1 divided by said maximum C rate.

19. A computer system, comprising:

a microprocessor;

a memory system connected to be readable and writable by said microprocessor;

monitor circuitry to monitor charge transferred into a battery pack during successive first fixed durations of time, said battery pack being connected to power said microprocessor;

a cutoff transistor, connected to said monitor circuitry, and connected to cut off current to said battery pack for the remainder of one of said first fixed durations whenever the charge transferred into said battery pack during said one of said first fixed durations exceeds a fixed maximum value.

20. The system of claim 19, further comprising user input/output devices.

21. The system of claim 19, wherein current is always turned off for a second fixed duration during each of said first fixed durations.

22. The system of claim 19, wherein current is always turned off for at least a fixed fraction of each of said fixed durations.

23. The system of claim 19, wherein said current is always turned off at least once during each of said fixed durations.

24. The system of claim 19, wherein said battery pack has a capacity of 100 Watt-hours or less.

25. The system of claim 19, wherein charge is transferred into said battery at a maximum rate in the range of 0.5 C to 2 C, and wherein the ratio of said fixed duration in seconds to the battery size in Watt-hours is more than 0.01.

26. The system of claim 19, wherein charge is transferred into said battery at a maximum C rate in the range of 0.5 C to 2 C, and wherein the ratio of said fixed duration in seconds to the battery size in Watt-hours is more than 0.1.

27. The system of claim 19, wherein charge is transferred into said battery at a maximum C rate which is higher than 1 C, and wherein the ratio of said fixed duration in seconds to the battery size in Watt-hours is more than 0.1 divided by said maximum C rate.

28. A battery charging system, comprising:

a line which connects a battery pack to the available current from a power supply;

a cutoff transistor, connected to said line between said battery pack and said power supply and configured to limit the average current into the battery pack;

wherein said cutoff transistor is turned off no more than once per second;

wherein charge is transferred into said battery at a maximum rate in the range of 0.5 C to 2 C, and wherein the ratio of said fixed duration in seconds to the battery size in Watt-hours is more than 0.01.

29. The system of claim 28, wherein said cutoff transistor is always turned off at least once in every 30 seconds.

30. The system of claim 28, wherein charge is transferred into said battery at a maximum C rate in the range of 0.5 C to 2 C, and wherein the ratio of said fixed duration in seconds to the battery size in Watt-hours is more than 0.1.

31. The system of claim 28, wherein charge is transferred into said battery at a maximum C rate which is higher than 1 C, and wherein the ratio of said fixed duration in seconds to the battery size in Watt-hours is more than 0.1 divided by said maximum C rate.