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Method for monitoring end of life for battery

  • US 6,631,293 B2
  • Filed: 04/23/2001
  • Issued: 10/07/2003
  • Est. Priority Date: 09/15/1997
  • Status: Expired due to Fees
First Claim
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1. A process for estimating a level of power depletion in a system having a lithium battery, a cardiac pacing device 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 and calculating a rate of charge storage, said process comprising;

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

    determining a rate of charging in said storage capacitor during said quiescent period, including determining said rate of charging over a time period beginning when the capacitor is not fully discharged and has a predetermined minimum charge differential across the capacitor so that the storage capacitor is discharged to at least said predetermined minimum upon initiation of an episodic charging event; and

    determining a value for an internal impedance of said battery using known relationships with respect to said rate of charging for said battery.

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