Patent ID: 7769455

Claim:
An implantable medical device, comprising: an energy storage device that provides power for an operation performed by the implantable medical device, characterized by a non-linear battery voltage depletion curve of voltage over time; a stimulation unit operatively coupled to the energy storage device that provides an electrical signal; and a controller operatively coupled to the stimulation unit and the energy storage device, the controller comprising: a charge depletion determination unit that determines an electrical charge depleted by the energy storage device during operation of the implantable medical device; a voltage determination unit that determines whether a measured voltage across the energy storage device has reached a transition voltage; and a useful life determination unit that determines a time period remaining in the energy storage device's useful life based upon at least one of 1) a function of the electrical charge depleted, and 2) a function of the measured voltage; wherein the useful life determination unit determines the time period remaining in the energy storage device's useful life based on the function of the electrical charge depleted when a measured voltage across the energy storage device is greater than or equal to the transition voltage, and the useful life determination unit determines the time period until the end of service of the energy storage device based on the function of the measured voltage when the measured voltage across the energy storage device is less than the transition voltage; wherein when the measured voltage is less than the transition voltage, the useful life determination unit calculates the time period remaining the energy storage device's useful life based upon the measured voltage, an end-of-service voltage, a percentage of energy storage device capacity remaining at a transition point of non-linearity in a battery voltage depletion curve representing the voltage across the energy storage device over time and at least one of the transition voltage, the total available electrical charge, and a consumption rate.