Patent ID: 7550946

Claim:
Method to determine state-of-life of an electrical energy storage device operative to exchange electrical energy with a hybrid vehicular powertrain including first and second electric machines each machine operable to impart torque to a two-mode, compound-split electromechanical transmission having four fixed gear ratios and two continuously variable operating modes, comprising: monitoring electrical current through the electrical energy storage device; monitoring a state-of-charge of the electrical energy storage device; monitoring temperature of the electrical energy storage device during periods of vehicle activity; monitoring temperature of the electrical energy storage device during periods of vehicle inactivity; determining a state-of-life of the electrical energy storage device based upon the electrical current, the state-of-charge, and the temperature of the electrical energy storage device during periods of vehicle activity and during periods of vehicle inactivity, wherein determining state-of-life includes fixing state-of-life to a predetermined value when said internal resistance indicates incipient end of life of the electrical energy storage device; detecting an internal resistance change over time that is greater than a minimum amount; and fixing the state-of-life to the predetermined value when the internal resistance is greater than the minimum amount.