Method for monitoring end of life for battery

• US 20010034541A1
• Filed: 04/23/2001
• Published: 10/25/2001
• Est. Priority Date: 09/15/1997
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Lyden, Michael J.
• Granted Patent: US 6,631,293 B2
• Time in Patent Office: Days
• US Class Current: 607/29
• CPC Class Codes: A61N 1/3708 for power depletion
• CPC Class Codes: G01R 31/3647 for determining the ability of a battery to perform a critical function, e.g. cranking
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health
• CPC Class Codes: H02J 2310/23 The load being a medical device, a medical implant, or a life supporting device
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/005 Detection of state of health [SOH]

Abstract

A system is described which has a battery, a device which is powered by the battery in an episodic manner, and a charge storage capacitor. The system has attached to the charge storage capacitor a device or devices capable of: reading the rate of charge storage; or measuring both time and charge stored or added to the charge storage capacitor so that a rate of charge storage may be calculated. The estimated replacement time for the battery, particularly for a lithium battery in a pacing device, is easily estimated. Also described herein is a process for estimating a level of energy depletion in the system. The process comprises: finding a relatively quiescent period in powering of the device in the episodic manner; determining a rate of charging in the storage capacitor during the quiescent period; and correlating the rate of charging in the storage capacitor to a value of internal impedance in the battery through a comparison with known relationships for the battery and rate of charging to determine a value for the internal impedance of the battery.

Claims

1. A system having a lithium battery, a device which is powered by said lithium batter in an episodic manner, and a charge storage capacitor, said system having attached to said charge storage capacitor a device or devices capable of:

reading the rate of charge storage;

or

measuring both time and charge stored or added to said charge storage capacitor so that a rate of charge storage may be calculated.

2. A cardiac pacing system having a lithium battery, a device which delivers electric current to a patient, which device is powered by said lithium battery in an episodic manner, and a charge storage capacitor, said system having attached to said charge storage capacitor a device or devices capable of:

reading the rate of charge storage;

or

measuring both time and charge stored or added to said charge storage capacitor so that a rate of charge storage may be calculated.

3. The pacing system of

claim 2

wherein said storage capacitor is a storage capacitor from which stored energy is used to apply a pace to a patient.

4. The pacing system of

claim 2

wherein said storage capacitor is substantially uninvolved in application of a pace to a patient and is present to provide a basis of measuring capacitor charge rate during a relatively quiescent period within a period of episodic power utilization by said device.

5. A process for estimating a level of power depletion in a system having a lithium battery, a cardiac pacing device which is powered by said lithium battery in an episodic manner, and a charge storage capacitor, said system having attached to said charge storage capacitor a device or devices capable of:

reading the rate of charge storage;

or

measuring both time and charge stored or added to said charge storage capacitor so that a rate of charge storage may be calculated,

said process comprising;

finding a relatively quiescent period in powering of said device in said episodic manner;

determining a rate of charging in said storage capacitor during said quiescent period; and

correlating said rate of charging in said storage capacitor to a value of internal resistance in said battery through a comparison with known relationships for said battery and rate of charging to determine a value for the internal impedance of said battery.

6. The process of

claim 5

wherein said comparison is done by use of a look-up table having predetermined quantitative comparisons of measured capacitor charge rates and Internal Impedance for a particular battery.

7. The process of

claim 5

wherein after determining a value for the Internal Impedance of said battery, said value for Internal AC Impedance of said battery is used to determine a value for expended energy from said battery.

8. The process of

claim 7

wherein the use of said value for Internal AC Impedance of said battery to determine a value for expended energy is effected by reference to a graphic representation of a relationship between Internal AC Impedance of said battery and energy expended from said battery.

9. The process of

claim 5

wherein said storage capacitor is used to store energy which is used to energize a pace from said pacing system to a patient.

10. The process of

claim 5

wherein said quiescent period immediately follows an atrial pace or atrial pulse.

11. The process of

claim 5

wherein said quiescent period immediately follows a ventricular pace or pulse.

12. The process of

claim 7

wherein said quiescent period immediately follows an atrial pace or atrial pulse.

13. The process of

claim 8

wherein said quiescent period immediately follows an atrial pace or atrial pulse.

14. The process of

claim 7

wherein said quiescent period immediately follows a ventricular pace or pulse.

15. The process of

claim 8

wherein said quiescent period immediately follows a ventricular pace or pulse.

18. The process of

claim 5

wherein said charge rate is determined over a time period beginning when the capacitor is not fully discharged and has a predetermined minimum charge differential across the capacitor so that upon initiation of an episodic charging event, the storage capacitor is discharged to at least said predetermined minimum.

19. The process of

claim 12

wherein said charge rate is determined over a time period beginning when the capacitor is not fully discharged and has a minimum charge differential across the capacitor so that upon initiation of an episodic charging event, the storage capacitor is discharged to at least said predetermined minimum.

20. The process of

claim 14

wherein said charge rate is determined over a time period beginning when the capacitor is not fully discharged and has a minimum charge differential across the capacitor so that upon initiation of an episodic charging event, the storage capacitor is discharged to at least said predetermined minimum.

21. The process of

claim 5

wherein internal impedance is compared.

22. The process of

claim 7

wherein attainment of a predetermined amount of expended energy from said battery causes an ERT flag to be effected.

23. The process of

claim 22

wherein a charge time measurement is used to create said ERT flag.

24. The process of

claim 23

wherein said ERT flag is transmitted to a programmer.

16. A process for indicating estimated replacement time for a battery in a cardiac pacing system, said system having a) a battery, b) a device which delivers electric current to a patient, which device is powered by said battery in an episodic manner, and c) a means which is capable of estimating pacing current, whereby after estimating said pacing current, the estimated current is considered with programmed pulse rates or programmed pace rates in said cardiac pacing system to estimate a replacement time for said battery.

25. The process of

claim 16

wherein the pacing currents are selected from the group consisting of pacing rate, pacing mode, lead impedance, pulse width, and pulse amplitude.

17. A process for estimating a level of energy depletion in a system having a battery, a device which is powered by said battery in an episodic manner, and a charge storage capacitor, said system having attached to said charge storage capacitor a device or devices capable of:

reading the rate of charge storage;

or

measuring both time and charge stored or added to said charge storage capacitor so that a rate of charge storage may be calculated,

said process comprising;

finding a relatively quiescent period in powering of said device in said episodic manner;

determining a rate of charging in said storage capacitor during said quiescent period; and

correlating said rate of charging in said storage capacitor to a value of internal resistance in said battery through a comparison with known relationships for said battery and rate of charging to determine a value for the internal resistance of said battery.

26. The process of

claim 17

wherein said battery comprises a battery characterized by having an internal impedance characteristic curve which is initially substantially linear as a function of energy depletion, but which asymptotically approaches an energy production limit and increasing internal impedance.

27. The process of

claim 26

wherein said battery comprises a lithium battery.

28. A system having a battery characterized by having an internal resistance characteristic curve which is initially substantially linear as a function of energy depletion, but which asymptotically approaches an energy production limit and increasing internal resistance, a device which is powered by said battery in an episodic manner, and a charge storage capacitor, said system having attached to said charge storage capacitor a device or devices capable of:

reading the rate of charge storage;

or

measuring both time and charge stored or added to said charge storage capacitor so that a rate of charge storage may be calculated.

29. A process for estimating a level of power depletion in a cardiac pacing system having a lithium battery, a first cardiac pacing device electrically connected to said lithium battery and said first cardiac pacing device operating in an episodic manner and powered by said lithium battery, and a charge storage capacitor electrically connected to said lithium battery, said cardiac pacing system having at least one second device attached to said charge storage capacitor, and the second device:

reads a rate of charge storage within said storage capacitor without disconnecting the electrical connection between said charge storage capacitor and said lithium battery;

or

measures both charge added to said charge storage capacitor and a time during which said charge is added to said charge storage capacitor, said measuring of both charge added to said charge storage capacitor and a time during which said charge is added to said charge storage capacitor being performed without disconnecting the electrical connection between said charge storage capacitor and said lithium battery, and calculating a rate of charge storage in said charge storage capacitor,

said process comprising the steps of adding charge to said charge storage capacitor from said lithium battery and;

finding a relatively quiescent period in powering of said first device in said episodic manner;

determining a rate of said charge storage in said charge storage capacitor during said relatively quiescent period; and

correlating said rate of charging in said charge storage capacitor to a value of internal resistance in said lithium battery to determine a value for the internal impedance of said lithium battery,

said internal impedance estimating a level of energy depletion in the cardiac pacing system having said lithium battery.

30. The process of

claim 29

wherein said lithium battery has an internal impedance, and said determining a rate of said charge storage is done by use of a look-up table having predetermined quantitative comparisons of measured capacitor charge rates for said charge storage capacitor and internal impedance for said lithium battery.

31. The process of

claim 29

wherein said internal resistance is an internal AC impedance, and after determining a value for internal AC impedance of said lithium battery, said value for internal AC impedance of said lithium battery is used to determine a value for expended energy from said lithium battery.

32. The process of

claim 31

wherein after determining said value for internal AC impedance of said lithium battery, said determined value is used to determine a value for expended energy by reference with said determined value to a graphic representation of a relationship between internal AC impedance of said lithium battery and energy expended from said lithium battery.

33. The process of

claim 29

wherein said storage capacitor is used to store energy and said stored energy is used to energize a pace from said cardiac pacing system to a patient, and a pace is provided to said patient with energy stored in said charge storage capacitor.

34. The process of

claim 29

wherein an atrial pace or atrial pace is provided to a patient from said charge storage capacitor, and said quiescent period immediately follows said atrial pace or atrial pulse.

35. The process of

claim 29

wherein a ventricle pulse or ventricle pace is provided to a patient from said charge storage capacitor, and said quiescent period immediately follows said ventricular pace or ventricular pulse.

36. The process of

claim 31

wherein an atrial pulse or atrial pace is provided to a patient from said charge storage capacitor, and said quiescent period immediately follows an atrial pace or atrial pulse.

37. The process of

claim 32

wherein an atrial pulse or atrial pace is provided to a patient from said charge storage capacitor, and said quiescent period immediately follows an atrial pace or atrial pulse.

38. The process of

claim 31

wherein a ventricle pulse or ventricle pace is provided to a patient from said charge storage capacitor, and said quiescent period immediately follows a ventricular pace or ventricular pulse.

39. The process of

claim 32

wherein a ventricle pulse or ventricle pace is provided to a patient from said charge storage capacitor, and said quiescent period immediately follows a ventricular pace or ventricular pulse.

41. The process of

claim 29

wherein said charge rate is determined over a time period beginning when the capacitor is not fully discharged and has a predetermined minimum charge differential across the capacitor so that upon initiation of an episodic charging event of at least adding charge to a charge storage capacitor and then discharging charge from said charge storage capacitor, the storage capacitor is discharged to at least said predetermined minimum.

42. The process of

claim 36

wherein said charge rate is determined over a time period beginning when the capacitor is not fully discharged and has a minimum charge differential across the capacitor so that upon initiation of an episodic charging event, the storage capacitor is discharged to at least said predetermined minimum.

43. The process of

claim 38

wherein said charge rate is determined over a time period beginning when the capacitor is not fully discharged and has a minimum charge differential across the capacitor so that upon initiation of an episodic charging event, the storage capacitor is discharged to at least said predetermined minimum.

44. The process of

claim 29

wherein said value for the internal impedance of said battery is compared to known relationships between the internal impedance of the battery and energy depletion from said battery.

45. The process of

claim 31

wherein reaching a stage of a predetermined amount of expended energy from said battery causes an estimated replacement time (ERT) flag to signal that an estimated replacement time has been approached.

46. The process of

claim 45

wherein after a charge time measurement has been made by said second device, a predetermined value of charge time measurement causes said second device to activate said ERT flag.

47. The process of

claim 46

wherein said second device transmits said ERT flag to a programmer.

40. A process for estimating a level of energy depletion in a battery in a system having a lithium battery, a first device operating in an episodic manner electrically connected to and powered by said lithium battery, and a charge storage capacitor electrically connected to said lithium battery, said system having at least one second device attached to said charge storage capacitor, and the process comprising said at least one second device:

reading a first rate of charge storage of said charge storage capacitor;

or

measuring both charge added to said charge storage capacitor and a time during which said charge is added to said charge storage capacitor, said measuring of both charge added to said charge storage capacitor and a time during which said charge is added to said charge storage capacitor being performed without disconnecting the electrical connection between said charge storage capacitor and said lithium battery, and calculating a second rate of charge storage,

said process further comprising the steps of adding charge to said charge storage capacitor from said lithium battery and;

finding a relatively quiescent period in powering of said first device in said episodic manner;

determining a third rate of charging in said charge storage capacitor during said relatively quiescent period;

correlating said third rate of charging in said charge storage capacitor to a value of internal impedance in said lithium battery to determine a value for internal impedance of said battery; and

comparing said value for internal impedance of said lithium battery with known relationships between said internal impedance of said lithium battery and depleted charge from said lithium battery to estimate the level of depletion of said lithium battery.

48. The process of

claim 40

wherein said battery comprises a battery having an internal resistance characteristic curve, wherein the curve is initially substantially linear as a function of energy depletion, but wherein the curve asymptotically approaches an energy production limit and increasing internal resistance.

49. The process of

claim 48

wherein said battery comprises a lithium battery.