Patent ID: 8565881

Claim:
A method comprising: estimating an amount of energy depleted during operation of an implantable medical device based on a first depletion amount and a second depletion amount, wherein the first depletion amount is calculated based on application of first electrical charge depletion rate information associated with an idle mode of the implantable medical device to one or more periods of operation of the implantable medical device in the idle mode, and wherein the second depletion amount is calculated based on application of second electrical charge depletion rate information associated with a stimulation mode of the implantable medical device to one or more periods of operation of the implantable medical device in the stimulation mode; determining whether a measured voltage across an energy storage device of the implantable medical device is greater than or equal to a transition voltage of the energy storage device; when the measured voltage is greater than or equal to the transition voltage, determining an amount of energy remaining in the energy storage device based on the estimated amount of energy depleted; and when the measured voltage is less than the transition voltage, determining the amount of energy remaining in the energy storage device based on a difference between the measured voltage and a voltage associated with end of service of the energy storage device.