This study discusses a converter structure appropriate for charging the batteries of an electric vehicle (EV). The structure is obtained by a transformation of a conventional three-phase inverter, which is already present in an EV's power-train system. Since the motor inverter's semiconductor components and the electric motor's windings form the battery charger's circuit, a reduction in the power-train system's size and weight is achievable. The proposed fully integrated battery charger operates alternately in two modes, buck and boost, while providing power factor (PF) correction capability continuously. This study also proposes an input current control strategy that ensures smooth operating mode transitions, which occur during the operation of a battery charger. The control is entirely implemented within a microcontroller and ensures operation with a high PF and low total harmonic distortion of the input current. The performance of the discussed converter using the proposed control scheme was verified experimentally.