Abstract: A method for minimizing a fuel consumption rate of a vehicle and a method for tracking an optimal state of charge function for a hydrostatic accumulator are provided. The first method includes the steps of providing a motor and pump, determining an efficiency of the motor and pump using an efficiency map, providing a power source, and controlling the motor independent from the pump with a controller. The controller employs the efficiency of the motor and the pump to minimize the fuel consumption rate of the vehicle. The second method includes the steps of determining the optimal state of charge control function, calculating an optimal state of charge of the hydrostatic accumulator, determining a state of charge error, calculating a corrective value, and adjusting a state of a charge based on the corrective value and the state of charge error by adjusting the charge of the hydrostatic accumulator.