NOVELTY - The apparatus has a controller (84) coupled to direct current (DC)-to-DC voltage converters (14, 20, 22). The controller determines a voltage level of a DC energy source (ES) (DC-ES) (12) e.g. fuel cell. The controller controls the second DC-to-DC voltage converter to draw energy from the ES to cause DC voltage output from the ES and supplied to the first DC-to-DC voltage converter to be below DC load voltage supplied to a DC link via the first DC-to-DC voltage converter if a voltage level of the DC link is less than the voltage level of the ES.    USE - Apparatus for transferring electrical energy from an ES e.g. DC-ES such as fuel cell, sodium metal halide battery, sodium nickel chloride battery, sodium sulfur battery, nickel metal hydride battery, lithium ion battery, lithium polymer battery, nickel cadmium battery, ultracapacitor cell, to a vehicle. Can also be used for a crane and a lift.    ADVANTAGE - The apparatus allows an interface to a utility grid for charging a source to be medium voltage or higher voltage that combines a pole mount distribution transformer with a secondary service transformer, thus reducing size, weight and cost of transformer components, while increasing efficiency of transmitting electric power from the grid for fast charging in an improved manner. The apparatus allows a contactor or switch to be closed by the controller to supply the voltage from the ES directly to the voltage converters, while bypassing the voltage converters to reduce power loss due to current from the ES passing through the voltage converters during an operation of the ES at high current loads or any time to determine that the voltage of the ES is below the DC link. The controller can close a switch and control voltage converter in a boost mode to increase voltage supplied to auxiliary loads within a desirable voltage range or voltage that is optimized to improve efficiency of a voltage range when output voltage of the ES is not sufficient to operate the auxiliary loads during a high power level operation of a traction system and the ES in an effective manner. The apparatus can be coupled between the ES and the switch so as to prevent current from a charging source from being directly coupled to the ES.    DETAILED DESCRIPTION - The DC-to-DC voltage converter is a bi-directional DC-to-DC voltage converter. INDEPENDENT CLAIMS are also included for the following:    (1) a method for fabricating an energy transfer system    (2) a system for transferring an electrical energy from an ES to a vehicle.    DESCRIPTION OF DRAWING(S) - The drawing shows a circuit block diagram of a traction system.    Traction system (10)    DC-ES (12)    DC-to-DC voltage converters (14, 20, 22)    Controller (84)    Charging source (120)