Estimating remaining battery service life in an implantable medical device

• US 8,612,167 B2
• Filed: 01/18/2008
• Issued: 12/17/2013
• Est. Priority Date: 01/18/2008
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Schmidt, Craig L., Wahlstrand, John D., Crespi, Ann M., Younker, Gregory A., Busacker, James W.
• Primary Examiner(s): Armand, Marc
• Assistant Examiner(s): Ngon, Ricky
• Application Number:
  US12/743,394
• Publication Number:
  US 20110130984A1
• Time in Patent Office: 2,160 Days
• Field of Search: 702/63, 702/60, 702/64, 607/29, 607/27, 607/28, 607/9, 429/90, 429/92, 320/127, 320/132
• US Class Current: 702/63
• CPC Class Codes: A61N 1/3708 for power depletion
• CPC Class Codes: A61N 1/37252 Details of algorithms or data aspects of communication system, e.g. handshaking, transmitting specific data or segmenting data
• 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

Abstract

Methods for estimating a remaining service life of an implantable medical device (IMD) battery are presented. In one embodiment, a characteristic discharge model of the battery is employed. Systems employing the methods may include an external device coupled to the IMD, for example, via a telemetry communications link, wherein a first portion of a computer readable medium included in the IMD is programmed to provide instructions for the measurement, or tracking, of time and the measurement of battery voltage, and a second portion of the computer readable medium included in the external device is programmed to provide instructions for carrying out the calculations when the voltage and time data is transferred via telemetry from the IMD to the external device.

Claims

1. A system comprising an implantable medical device and a non-transitory computer readable medium programmed with instructions for executing a method to estimate a remaining service life of a battery of the implantable medical device, the battery having a known initial capacity and a known characteristic discharge model, the discharge model defining battery voltage as a function of an average current drain and discharged capacity, the method comprising:

tracking time;

determining battery voltage at least one point in time;

estimating an average current drain corresponding to the at least one point in time of the battery voltage measurement, the estimated average current drain based upon an incremented initial current drain, the initial current drain being characteristic of the battery prior to a start of service;

estimating a depth of discharged capacity based on the estimated average current drain, the known initial capacity and the time of the at least one point in time;

iteratively determining battery voltage until the calculated voltage converges on the battery voltage measured at the at least one point in time, wherein each iterative calculation is based on the characteristic discharge model, and wherein each subsequent iteration of the iterative calculation is further based on an incremented estimated depth of discharged capacity and a corresponding incremented estimated average current drain, each incremented estimated average current drain being based upon a difference between a previously calculated voltage of the iterative calculation and the measured voltage; and

determining an estimated time of remaining battery service life according to the incremented estimated depth of discharged capacity that corresponds to the converged calculated battery voltage and the corresponding incremented estimated average current drain.

2. The system of claim 1, wherein the at least one point in time comprises a plurality of points in time, and the measured battery voltage corresponds to an average of battery voltage measurements, each measurement being made at one of each of the plurality of points in time.

3. The system of claim 2, wherein the plurality of points in time are spread over one day.

4. The system of claim 2, wherein the plurality of points in time are spread over about fourteen days.

5. The system of claim 2, wherein the plurality of points in time are spread over about seventy days.

6. The system of claim 1, wherein the method further comprises storing each measured battery voltage.

7. The system of claim 1, wherein the method further comprises providing a signal when the incremented estimated depth of discharged capacity that corresponds to the converged calculated battery voltage is about 85% of the initial capacity.

8. The system of claim 1, wherein:

the non-transitory computer readable medium is further programmed with an array of a plurality of times of remaining battery service life, each time of the array for a particular estimated average current drain and a particular depth of discharged capacity; and

the operation of determining the estimated time of remaining battery service life comprises referencing the array.

9. The system of claim 1, further comprising:

an external device coupled to the implanted device via a telemetry communication link; and

wherein a first portion of the non-transitory computer readable medium is included in the implanted device and is programmed with instructions for the operations of tracking time and measuring battery voltage;

a second portion of the non-transitory computer readable medium is included in the external device and is programmed with instructions for the operations of estimating the average current drain, estimating the depth of discharged capacity, iteratively determining battery voltage, and determining the estimated time of remaining battery service life; and

the telemetry communication link transfers tracked times and measured battery voltages to the external device.

10. The system of claim 9, wherein the method further comprises storing each battery voltage measurement, the first portion of the non-transitory computer readable medium being programmed with instructions for the storing operation.

11. The system of claim 9, wherein:

the second portion of the non-transitory computer readable medium is further programmed with an array of a plurality of times of remaining battery service life, each time of the array for a particular estimated average current drain and a particular depth of discharged capacity; and

the operation of determining the estimated time of remaining battery service life comprises referencing the array.

12. A computer-implemented method for estimating a remaining service life of a battery of an implantable medical device, the battery having a known initial capacity and a known characteristic discharge model, the discharge model defining battery voltage as a function of an average current drain and discharged capacity, and the method comprising:

tracking time;

measuring battery voltage at least one point in time;

estimating an average current drain corresponding to the at least one point in time of the battery voltage measurement, the estimated average current drain based upon an incremented initial current drain, the initial current drain being characteristic of the battery prior to a start of service;

estimating a depth of discharged capacity based on the estimated average current drain, the known initial capacity and the time of the at least one point in time;

iteratively determining battery voltage until the calculated voltage converges on the battery voltage measured at the at least one point in time, wherein each iterative calculation is based on the characteristic discharge model, and wherein each subsequent iteration of the iterative calculation is further based on an incremented estimated depth of discharged capacity and a corresponding incremented estimated average current drain, each incremented estimated average current drain being based upon a difference between a previously calculated voltage of the iterative calculation and the measured voltage; and

determining an estimated time of remaining battery service life according to the incremented estimated depth of discharged capacity that corresponds to the converged calculated battery voltage and the corresponding incremented estimated average current drain.

13. The method of claim 12, wherein the at least one point in time comprises a plurality of points in time, and the measured battery voltage corresponds to an average of battery voltage measurements, each measurement at one of each of the plurality of points in time.

14. The method of claim 13, wherein the plurality of points in time are spread over about one day.

15. The method of claim 13, wherein the plurality of points in time are spread over about fourteen days.

16. The method of claim 13, wherein the plurality of points in time are spread over about seventy days.

17. The method of claim 12, further comprising:

storing each measured battery voltage in a buffer of the implantable device;

establishing a communications link between the implantable medical device and an external device; and

transferring the tracked times and each measured battery voltage from the buffer to the external device for the operations of estimating the average current drain, estimating the depth of discharged capacity, iteratively determining battery voltage, and determining the estimated time of remaining battery service life.

18. The method of claim 12, further comprising providing a signal when the incremented estimated depth of discharged capacity that corresponds to the converged calculated battery voltage is about 85% of the initial capacity.

19. The method of claim 12, wherein the operation of determining the estimated time of remaining battery service life comprises referencing an array of a plurality of times of remaining battery service life, each time of the array for a particular estimated average current drain and a particular depth of discharged capacity.

20. A system comprising an implantable medical device and a non-transitory computer readable medium programmed with instructions for executing a method to estimate a remaining service life of a battery of the implantable medical device, the battery having a known initial capacity and a known characteristic discharge model, the discharge model defining battery voltage as a function of an average current drain and discharged capacity, the method comprising:

tracking time;

measuring battery voltage at least one point in time;

determining an average current drain from each measured battery voltage and the corresponding elapsed time of the measurement point in time;

estimating a depth of discharged capacity based on the determined average current drain, the known initial capacity and the elapsed time of the measurement point in time;

iteratively determining battery voltage until the battery voltage converges on the battery voltage measured at the at least one point in time, wherein each iterative calculation is based on the characteristic discharge model, and wherein each subsequent iteration of the iterative calculation is further based on an incremented estimated depth of discharged capacity and a corresponding incremented estimated average current drain, each incremented estimated average current drain being based upon a difference between a previously determined battery voltage of the iterative calculation and the measured battery voltage; and

determining an estimated time of remaining battery service life according to the estimated depth of discharged capacity that corresponds to the converged determined battery voltage and the corresponding incremented estimated average current drain.

21. The system of claim 20, wherein the at least one point in time comprises a plurality of points in time, and the measured battery voltage corresponds to an average of battery voltage measurements, each measurement being made at one of each of the plurality of points in time.

22. The system of claim 21, wherein the plurality of points in time are spread over one day.

23. The system of claim 21, wherein the plurality of points in time are spread over about fourteen days.

24. The system of claim 21, wherein the plurality of points in time are spread over about seventy days.

25. The system of claim 20, wherein the method further comprises storing each measured battery voltage.

26. The system of claim 20, wherein the method further comprises providing a signal when the estimated depth of discharged capacity is about 85% of the initial capacity.

27. The system of claim 20, wherein:

the non-transitory computer readable medium is further programmed with an array of a plurality of times of remaining battery service life, each time of the array for a particular average current drain and a particular depth of discharged capacity; and

the operation of determining the estimated time of remaining battery service life comprises referencing the array.

28. The system of claim 20, further comprising:

an external device coupled to the implanted device via a telemetry communication link; and

wherein a first portion of the non-transitory computer readable medium is included in the implanted device and is programmed with instructions for the operations of tracking time and measuring battery voltage;

a second portion of the non-transitory computer readable medium is included in the external device and is programmed with instructions for the operations of determining the average current drain, estimating the depth of discharged capacity, and determining the estimated time of remaining battery service life; and

the telemetry communication link transfers tracked times and measured battery voltages to the external device.

29. The system of claim 28, wherein the method further comprises storing each battery voltage measurement, the first portion of the computer readable medium being programmed with instructions for the storing operation.

30. The system of claim 28, wherein:

the second portion of the non-transitory computer readable medium is further programmed with an array of a plurality of times of remaining battery service life, each time of the array for a particular estimated average current drain and a particular depth of discharged capacity; and

the operation of determining the estimated time of remaining battery service life comprises referencing the array.