Method for monitoring end of life for battery

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.

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.

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.

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.