A method and apparatus for measuring battery depletion in an implantable medical device is presented. The apparatus includes first and second switch pairs disposed in series between the battery and a load, and connected in a parallel arrangement with respect to one another. A capacitor is connected in a first polarity between the battery and the load when only first and fourth switches are closed and in a second polarity when only second and third switches are closed. A comparator circuit causes the switches to reverse the capacitor's polarity based on a comparison of the voltage drop across the capacitor to a threshold value. A counter counts the number of times the capacitor reverses polarity, which is proportional to the amount of charge transferred from the battery during its lifetime in the device and indicative of the battery's level of depletion.