Patent ID: 7533744

Claim:
A method for use in an electrically driven vehicle having a primary drivetrain and an auxiliary drivetrain, the auxiliary drivetrain being an electric only drivetrain having capabilities to power an electric motor used to drive the vehicle with energy from a limited supply of stored energy, the method comprising: controlling a driving characteristic of the auxiliary drive train based on a first performance limiting strategy, the first performance limiting strategy based in part on future availability of the primary drivetrain; and switching control of the driving characteristic to a second performance limiting strategy associated with future unavailability of the primary drivetrain, the second performance limiting strategy associated with controlling power consumption of the electric motor in such a manner as to limit consumption of the stored energy for all motor power demands and not only motor power demands associated with particular vehicle speeds; wherein the second performance limiting strategy includes setting a plurality of maximum vehicle speed ranges based on battery state of charge, the battery state of charge for a battery of the auxiliary drivetrain.