A method for predicting change in an operating state, e.g. state of life, for an electrical energy storage device includes establishing a plurality of values for an operating parameter, e.g. current, of the electrical energy storage device and, for each respective value, determining a corresponding change in the operating state for the energy storage device based upon the respective value. Preferably, change in the state of life is determined based upon an integration of electrical current, a depth of discharge of the energy storage device, and an operating temperature factor of the electrical energy storage device.