Systems and methods for detecting charge switching element failure in a battery system

• US 7,436,151 B2
• Filed: 12/23/2004
• Issued: 10/14/2008
• Est. Priority Date: 12/23/2004
• Status: Active Grant

• Current Assignee: Dell Products LP (Dell Technologies Inc.)
• Original Assignee: Dell Products LP (Dell Technologies Inc.)
• Inventors: Wang, Ligong, Miller, Bruce A., Sterz, Stephen D.
• Primary Examiner(s): Berhane; Adolf
• Assistant Examiner(s): DIAO, M BAYE
• Application Number:
  US11/021,926
• Publication Number:
  US 20060139006A1
• Time in Patent Office: 1,391 Days
• Field of Search: 320/132, 320/134, 320/136, 320/DIG.12
• US Class Current: 320/134
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/00308 Overvoltage protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence

Abstract

Systems and methods for detection of charge switching element failure (e.g., charge FET switching element) in a battery system, such as a battery system of an information handling system (e.g. notebook computer), in which an increase in cell voltage is employed as a criteria for detecting charge switching element failure.

Claims

1. A method of detecting charge switching element failure in a battery system, comprising:

monitoring for the presence of a battery charging current flowing to one or more battery cells of said battery system;

monitoring voltage of said one or more battery cells of said battery system;

using a combination of said monitored voltage and said monitored battery charging current to sense failure of said charge switching element and without disabling the battery system due to a false charging current indication; and

taking one or more failure state actions only if both of the following conditions are detected to exist at the same time when said charge switching element of said battery system is supposed to be in a state that prevents flow of battery charging current to said one or more, battery cells of said battery system and not taking said one or more failure state actions if both of the following conditions are not detected to exist at the same time when said charge switching element of said battery system is supposed to be in a state that prevents flow of battery charging current to said one or more battery cells of said battery system;

(i) battery charging current is flowing to said one or more battery cells, and

(ii) voltage of said one or more battery cells is detected to be increasing;

wherein said charge switching element forms a part of a charge circuit that is controllable to allow or disallow charging current to said one or more battery cells from said battery charging apparatus; and

wherein said method further comprises controlling said charge switching element to allow or disallow charging current to said one or more battery cells.

2. The method of claim 1, wherein said failure state action comprises permanently disabling said battery system.

3. The method of claim 2, further comprising only taking said failure state action if a measured value of said battery charging current detected exceeds a selected threshold current value.

4. The method of claim 3, wherein said step of monitoring comprises monitoring for the presence of a battery charging current flowing at a first time to one or more battery cells of said battery system;

and wherein said method further comprises;

monitoring for the presence of a battery charging current flowing at a second time to said one or more battery cells of said battery system; and

only taking said failure state action if a first measured value of said battery charging current detected at said first time exceeds a first selected threshold current value and a second measured value of said battery charging current detected at said second time exceeds a second selected threshold current value;

wherein said second time is a later time than said first time; and

wherein said second selected threshold current value is the same or different value than said first selected threshold current value.

5. The method of claim 3, wherein said battery system is a replaceable battery pack of a portable information handling system.

6. The method of claim 2, wherein said battery system is a replaceable battery pack of a portable information handling system;

wherein said battery system is coupled to a battery charging apparatus; and

wherein said replaceable battery pack comprises;

battery current control circuitry coupled between said battery charging apparatus and said one or more battery cells, said battery current control circuitry including said charge switching element, and said charge switching element comprising a charge FET switching element that forms a part of a charge circuit that is controllable to allow or disallow charging current to said one or more battery cells from said battery charging apparatus;

a battery management unit (BMU) including a microcontroller and an analog front end (AFE) circuitry, said BMU being coupled to said battery current control circuitry and being configured to control said charge FET switching element to allow or disallow charging current to said one or more battery cells, and said AFE being coupled to said one or more battery cells and being configured to monitor said battery charging current flow and to monitor said voltage of said one or more battery cells; and

an inline fuse coupled between said battery charging apparatus and said one or more battery cells, said BMU being coupled to permanently disable said battery system by changing the state of said fuse;

wherein said method further comprises using said BMU to permanently disable said battery system by changing the state of said inline fuse if both of the following conditions are detected to exist by said AFE when said charge FET switching element of said battery system is supposed to be off to prevent flow of battery charging current to said one or more battery cells of said battery system;

(i) battery charging current is flowing to said one or more battery cells, and

(ii) voltage of said one or more battery cells is detected to be increasing.

7. The method of claim 3, wherein said method further comprises:

measuring a value of battery charging current flowing to one or more battery cells of said battery system;

then comparing said measured value of battery charging current to a selected threshold current value;

then checking for the state of said charge switching element if said measured value of battery charging current exceeds said selected threshold current value;

then recording a first voltage value of said one or more battery cells measured at a first time if said charge switching element of said battery system is supposed to be in a state that prevents flow of battery charging current to said one or more battery cells of said battery system;

then comparing said first voltage value measured at a first time with a second voltage value of said one or more battery cells measured at a second time to detect if said voltage of said one or more battery cells is increasing, said second time being later than said first time and being separated from said first time by a time delay;

then permanently disabling said battery system if said measured value of battery charging current exceeds said selected threshold current value.

8. The .method of claim 7, wherein said battery system is a replaceable battery pack of a portable information handling system.

21. The method of claim 3, wherein said method further comprises:

measuring a first value of battery charging current flowing to one or more battery cells of said battery system;

then comparing said measured first value of battery charging current to a first selected threshold current value;

then checking for the state of said charge switching element if said first measured value of battery charging current exceeds said first selected threshold current value;

then recording a first voltage value of said one or more battery cells measured at a first time if said charge switching element of said battery system is supposed to be in a state that prevents flow of battery charging current to said one or more battery cells of said battery system;

then comparing said first voltage value measured at a first time with a second voltage value of said one or more battery cells measured at a second time to detect if said voltage of said one or more battery cells is increasing, said second time being later than said first time and being separated from said first time by a time delay; and

then proceeding as follows if said voltage of said one or more battery cells is detected to be increasing in the previous step;

measuring a second value of battery charging current flowing to one or more battery cells of said battery system at a time later than a time of said measurement of said first value of battery charging current flowing to said one or more battery cells of said battery system,

then comparing said measured second value of battery charging current to a second selected threshold current value, and

then permanently disabling said battery system if said second measured value of battery charging current exceeds said second selected threshold current value.

9. A battery system configured to be coupled to a battery charging apparatus, said battery system comprising:

one or more battery cells;

battery current control circuitry configured to be coupled between said battery charging apparatus and said one or more battery cells, said battery current control circuitry comprising at least one charge switching element configured to control flow of said charging current to said battery cells from said battery charging apparatus;

a switching element failure detector configured to use a combination of monitored voltage of said one or more battery cells and monitored battery charging current flowing to said one or more battery cells to sense failure of one or more charge switching elements without disabling the battery system due to a false charging current indication and configured to take one or more failure state actions only if both of the following conditions are detected to exist at the same time when said charge switching element of said battery system is supposed to be in a state that prevents flow of battery charging current to said one or more battery cells of said battery system and configured not to take said one or more failure state actions if both of the following conditions are not detected to exist at the same time when said charge switching element of said battery system is supposed to be in a state that prevents flow of battery charging current to said one or more battery cells of said battery system;

(i) battery charging current is flowing to said one or more battery cells, and

(ii) voltage of said one or more battery cells is detected to be increasing;

wherein said charge switching element forms a part of a charge circuit that is controllable to allow or disallow charging current to said one or more battery cells from said battery charging apparatus.

10. The battery system of claim 9, wherein said failure state action comprises permanently disabling said battery system.

11. The battery system of claim 10, wherein said switching element failure detector is configured to only take said failure state action if a measured value of said battery charging current exceeds a selected threshold current value.

12. The battery system of claim 11, wherein said switching element failure detector is configured to only take said failure state action if a first measured value of said battery charging current exceeds a first selected threshold current value and a second measured value of said battery charging current detected at a second time exceeds a second selected threshold current value;

wherein said second time is a later time than said first time; and

wherein said second selected threshold current value is the same or different value than said first selected threshold current value.

13. The battery system of claim 11, wherein said battery system is a replaceable battery pack of a portable information handling system.

14. The battery system of claim 10, wherein said battery system is a replaceable battery pack of a portable information handling system;

and wherein said replaceable battery pack further comprises;

a current sensor coupled to monitor for the presence of a battery charging current flowing to said one or more battery cells of said battery system, and coupled to provide a signal representative of said monitored current to said switching element failure detector;

a battery cell voltage detector coupled to monitor voltage of said one or more battery cells, and coupled to provide a signal representative of said monitored voltage to said switching element failure detector;

wherein said charge switching element comprises a charge FET switching element that forms a part of a charge circuit that is controllable to allow or disallow charging current to said one or more battery cells from said battery charging apparatus;

wherein said switching element failure detector comprises a microcontroller (uP) of a battery management unit (BMU), said BMU including an analog front end (AFE) circuitry and said microcontroller (uP), and said BMU being configured to control said charge FET switching element to allow or disallow charging current to said one or more battery cells;

wherein said AFE comprises said current sensor and said battery voltage detector.

15. The battery system of claim 10, further comprising an inline fuse coupled between said battery charging apparatus and said one or more battery cells, said switching element failure detector being coupled to permanently disable said battery system by changing the state of said fuse if both of the following conditions are detected to exist when said charge switching element of said battery system is supposed to be in a state that prevents flow of battery charging current to said one or more battery cells of said battery system:

(i) battery charging current is flowing to said one or more battery cells, and

(ii) voltage of said one or more battery cells is detected to be increasing.

16. A portable information handling system comprising the battery system of claim 9.

22. The battery system of claim 11, wherein said battery system is configured to:

measure a value of battery charging current flowing to one or more battery cells of said battery system;

then compare said measured value of battery charging current to a selected threshold current value;

then check for the state of said charge switching element if said measured value of battery charging current exceeds said selected threshold current value;

then record a first voltage value of said one or more battery cells measured at a first time if said charge switching element of said battery system is supposed to be in a state that prevents flow of battery charging current to said one or more battery cells of said battery system;

then compare said first voltage value measured at a first time with a second voltage value of said one or more battery cells measured at a second time to detect if said voltage of said one or more battery cells is increasing, said second time being later than said first time and being separated from said first time by a time delay; and

wherein said switching element failure detector is configured to then permanently disable said battery system if said measured value of battery charging current exceeds said selected threshold current value and said comparison of said first and second voltage values indicates said one or more battery cells is increasing.

23. The replaceable battery pack of claim 11, wherein said battery system is configured to:

measure a first value of battery charging current flowing to one or more battery cells of said battery system;

then compare said measured first value of battery charging current to a first selected threshold current value;

then check for the state of said charge switching element if said measured first value of battery charging current exceeds said first selected threshold current value;

then record a first voltage value of said one or more battery cells measured at a first time if said charge switching element of said battery system is supposed to be in a state that prevents flow of battery charging current to said one or more battery cells of said battery system;

then compare said first voltage value measured at a first time with a second voltage value of said one or more battery cells measured at a second time to detect if said voltage of said one or more battery cells is increasing, said second time being later than said first time and being separated from said first time by a time delay;

then proceed as follows if said voltage of said one or more battery cells is detected to be increasing in the previous step;

measure a second value of battery charging current flowing to one or more battery cells of said battery system at a time later than a time of said measurement of said first value of battery charging current flowing to said one or more battery cells of said battery system,

then compare said measured second value of battery, charging current to a second selected threshold current value; and

wherein said switching element failure detector is configured to then permanently disable said battery system if said second measured value of battery charging current exceeds said second selected threshold current value.

17. A replaceable battery pack for a portable information handling system configured to be coupled to a battery charging apparatus, said replaceable battery pack comprising:

one or more battery cells;

a charge circuit configured to be coupled between said battery charging apparatus and said one or more battery cells, said charge circuit comprising a charge FET switching element and being configured to receive a charging current from said battery charging apparatus, said charge FET switching element forming a part of a charge circuit that is controllable to allow or disallow charging current to said one or more battery cells from said battery charging apparatus;

an inline fuse configured to be coupled between said battery charging apparatus and said one or more battery cells;

a battery management unit (BMU) coupled to said charge circuit, said BMU comprising a microcontroller and being configured to control said charge FET switching element to allow or disallow charging current to said one or more battery cells;

wherein said BMU is configured to sense failure of said charge FET switching element without disabling the battery system due to a false charging current indication and configured to control operation of said inline fuse so as to permanently disable said battery system only if both of the following conditions are detected to exist at the same time when said charge FET switching element of said battery system is supposed to be off to prevent flow of battery charging current to said one or more battery cells of said battery system and configured not to take said one or more failure state actions if both of the following conditions are not detected to exist at the same time when said charge FET switching element of said battery system is supposed to be in a state that prevents flow of battery charging current to said one or more battery cells of said battery system;

(i) battery charging current is flowing to said one or more battery cells, and

(ii) voltage of said one or more battery cells is detected to be increasing.

18. The replaceable battery pack of claim 17, wherein said BMU further comprises an analog front end (AFE) coupled to monitor said battery charging current flowing to said one or more battery cells, and coupled to monitor said voltage of said one or more battery cells.

19. The replaceable battery pack of claim 18, wherein said battery system is a battery pack of a portable information handling system.

20. A portable information handling system comprising the replaceable battery pack of claim 17.