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Method and apparatus for battery depletion monitoring

  • US 5,391,193 A
  • Filed: 02/05/1993
  • Issued: 02/21/1995
  • Est. Priority Date: 02/05/1993
  • Status: Expired due to Term
First Claim
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1. A method for metering remaining longevity of an implantable medical device battery, comprising the steps of:

  • (a) generating a first signal having a first value corresponding to a measured internal impedance of said battery;

    (b) generating a second signal having a second value corresponding to time-from-implant of said measured internal impedance;

    (c) defining a nomograph having a plurality of time lines, impedance curves, and constant current-drain lines therein, said nomograph relating each one of said plurality of constant current lines to an estimate of battery longevity;

    (d) locating in said nomograph an impedance curve corresponding to said first value;

    (e) locating in said nomograph an intersection point between said corresponding impedance curve and a time line corresponding to said second value;

    (f) repeating steps (a), (b), (d) and (e) at least once to locate a plurality of said intersection points;

    (g) nomographically extrapolating an estimate of battery longevity based upon said plurality of intersection points; and

    (h) generating a third signal having a third value corresponding to said longevity estimation.

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