SYSTEM AND METHOD FOR ESTIMATING BATTERY CAPACITY

• US 20120197341A1
• Filed: 01/28/2011
• Published: 08/02/2012
• Est. Priority Date: 01/28/2011
• Status: Active Grant

• Current Assignee: LivaNova USA, Inc. (LivaNova Plc)
• Original Assignee: Cyberonics, Inc
• Inventors: Cowley, Anthony W., Hussain, Saadat
• Granted Patent: US 8,577,459 B2
• Time in Patent Office: Days
• US Class Current: 607/45
• CPC Class Codes: A61N 1/378 Electrical supply
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

A method for estimating capacity of a battery in an implantable medical device includes obtaining a characteristic curve of voltage versus resistance for the battery, periodically determining voltage and resistance of the battery, and comparing the resistance with a third derivative function of the characteristic curve, the third derivative function having roots representing near depletion of the battery and end of service of the battery, respectively. Remaining time of service of the battery can also be determined by comparing the resistance value with a curve of battery capacity versus resistance for the battery.

Claims

1. A method for estimating capacity of a battery in an implantable medical device, comprising:

a) obtaining a characteristic curve of voltage versus resistance for the battery;

b) periodically determining voltage and resistance of the battery; and

c) comparing the resistance with a third derivative function of the characteristic curve, the third derivative function having roots representing near depletion of the battery and end of service of the battery, respectively.

2. A method in accordance with claim 1, further comprising wirelessly transmitting the voltage and resistance of the battery to an external computing device, the external computing device having the characteristic curve stored in memory therein, and comparing the resistance with the third derivative function.

3. A method in accordance with claim 2, wherein the external computing device includes at least one of a PDA, a smartphone, a laptop computer, and a special purpose portable computing device.

4. A method in accordance with claim 2, further comprising wirelessly transmitting data from the external computing device via a wireless communications network.

5. A method in accordance with claim 1, further comprising:

d) comparing the resistance with the characteristic curve; and

e) recalculating the characteristic curve to create an adapted characteristic curve intended to match actual varying resistance in the battery; and

f) wherein comparing the resistance with the third derivative function comprises comparing the resistance with a third derivative of the adapted characteristic curve.

6. A method in accordance with claim 5, further comprising repeating (b) through (f) throughout the life of the battery in the implantable medical device.

7. A method in accordance with claim 1, further comprising providing an indication to a user of the implantable medical device of a position of the measured value relative to at least one of the near depletion and end of service points, respectively.

8. A method in accordance with claim 7, further comprising comparing the resistance with a battery capacity curve, and determining an estimate of time to end of service of the battery.

9. A method in accordance with claim 1, further comprising comparing the resistance with a battery capacity curve, and determining an estimate to time to end of service of the battery.

10. A method in accordance with claim 1, wherein obtaining the characteristic curve comprises:

measuring voltage and resistance of a plurality of batteries of a same type as the battery;

plotting an individual battery characteristic curve of voltage versus resistance for each of the plurality of batteries; and

calculating a statistical measure of central tendency of the individual battery characteristic curves to obtain the characteristic curve.

11. A method in accordance with claim 1, wherein the reference voltage includes at least one of an open circuit voltage, a low power mode voltage, and a voltage measured at a pre-defined operating mode.

12. An implantable system, comprising:

an implantable device, having a battery, and a battery circuit capable of measuring voltage and calculating a resistance of the battery; and

a computer program product, stored in a tangible storage medium, comprising machine-readable instructions for;

measuring a reference voltage and calculating a resistance value of the battery;

comparing the voltage and resistance values with a characteristic curve of resistance versus voltage for the battery; and

estimating future performance characteristics of the battery based upon a third derivative of the characteristic curve and a position of the voltage and resistance values thereon; and

an output mechanism, adapted to provide an indication to a user of the future performance characteristics.

13. A system in accordance with claim 12, wherein the output mechanism comprises an external computing device having a microprocessor and digital memory for storing at least a part of the computer program product, and comparing the voltage and resistance values with the characteristic curve and estimating future performance characteristics of the battery are performed by the external computing device.

14. A system in accordance with claim 13, wherein the external computing device includes at least one of a PDA, a smartphone, a laptop computer, and a special purpose portable computing device.

15. A system in accordance with claim 12, wherein the computer program product further comprises instructions for creating a modified characteristic curve based upon the voltage and resistance values, and estimating future performance characteristics of the battery comprises estimating future performance characteristics of the battery based upon a third derivative of the modified characteristic curve.

16. A system in accordance with claim 12, wherein the computer program product further comprises instructions for comparing the resistance value to a curve of battery capacity, and estimating future performance characteristics of the battery comprises estimating a time to end of service of the battery.

17. A system in accordance with claim 12, wherein the future performance characteristics of the battery include time to depletion of the battery and time to end of service of the battery.

18. A system in accordance with claim 12, wherein the implantable device comprises a pulse generator of a vagus nerve stimulation system.

19. A method for managing a battery of an implantable device, the method being carried out by a computer, associated with the implantable device, having a microprocessor and digital memory containing machine-readable program instructions for causing the computer to perform the steps of:

a) periodically determining a reference voltage and resistance of the battery in the implantable device;

b) comparing the voltage and resistance with a characteristic curve of voltage versus resistance for the battery;

c) creating a modified characteristic curve based upon the voltage and resistance;

d) comparing the voltage and resistance with a third derivative of the modified characteristic curve, the third derivative curve indicating a relative condition of the battery;

e) comparing the resistance with a battery capacity curve, the battery capacity curve indicating remaining power of the battery; and

f) providing an output to a user indicating at least one of the condition of the battery and the remaining power of the battery.

20. A method in accordance with claim 19, wherein the indication of remaining power of the battery includes at least one of time to near depletion of the battery, and time to end of service of the battery.

21. A method in accordance with claim 20, wherein the time to depletion of the battery, and time to end of service of the battery are determined relative to roots of the third derivative curve.

22. A method in accordance with claim 19, wherein the step of periodically determining voltage and resistance of the battery is performed by the implantable device, and (b) through (f) are performed by an external device in wireless communication with the implanted device, the implanted device and the external device each including a microprocessor and digital memory containing machine-readable program instructions for performing the respective steps.