Patent ID: 7730984

Claim:
Method for operating a hybrid electric powertrain including an electrical energy storage device configured 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 electro-mechanical transmission having four fixed gear ratios and two continuously variable operating modes, comprising: establishing a state-of-life parameter associated with the electrical energy storage device; providing a present state-of-life of the electrical energy storage device; establishing a life target for the electrical energy storage device as a predetermined limit in a predetermined metric at a predetermined state-of-life of the electrical energy storage device; determining a state-of-life gradient with respect to the predetermined metric which converges the state-of-life of the electrical energy storage device to the life target; and operating the electric machines such that the electrical energy storage device state-of-life substantially tracks the state-of-life gradient.