Railway vehicle comprising a power supply device, an electrical traction engine, first electrical auxiliary equipment (16, 17), and a connector for connecting to an electrical power source external to the vehicle, wherein the power supply device comprises: - an electrical converter connected to the connector; - a first medium-voltage electricity network to which the first auxiliary electrical equipment is connected, - a first electrical storage element connected (40, 38, 42) to the first medium-voltage electricity network so as to supply electricity to or draw electricity from the first network; the electrical converter comprising a first output connected to the first medium-voltage electricity network so as to supply the first network with medium-voltage current; the vehicle further comprising second auxiliary electrical equipment, and the power supply device further comprises: - a second low-voltage electricity network to which the second equipment is connected; and - a second electrical storage element connected to the second low-voltage electricity network so as to supply electricity to or draw electricity from the second network; the second storage element being also connected (50, 48, 52) to the first medium-voltage electricity network so as to draw electricity from the first network; the railway vehicle being characterized in that: - the electrical converter also comprises a second output configured for supplying the electrical traction engine with high-voltage current; and - the power supply device comprises a first reversible charger, interposed between the first electrical storage element and the first medium-voltage electricity network, wherein the first charger is suited to transfer electricity to one or the other of the first element and the first network. - an electrical converter connected to the connector; - a first medium-voltage electricity network to which the first auxiliary electrical equipment is connected, - a first electrical storage element connected (40, 38, 42) to the first medium-voltage electricity network so as to supply electricity to or draw electricity from the first network; the electrical converter comprising a first output connected to the first medium-voltage electricity network so as to supply the first network with medium-voltage current; the vehicle further comprising second auxiliary electrical equipment, and the power supply device further comprises: - a second low-voltage electricity network to which the second equipment is connected; and - a second electrical storage element connected to the second low-voltage electricity network so as to supply electricity to or draw electricity from the second network; - a second low-voltage electricity network to which the second equipment is connected; and - a second electrical storage element connected to the second low-voltage electricity network so as to supply electricity to or draw electricity from the second network; the second storage element being also connected (50, 48, 52) to the first medium-voltage electricity network so as to draw electricity from the first network; the railway vehicle being characterized in that: - the electrical converter also comprises a second output configured for supplying the electrical traction engine with high-voltage current; and - the power supply device comprises a first reversible charger, interposed between the first electrical storage element and the first medium-voltage electricity network, wherein the first charger is suited to transfer electricity to one or the other of the first element and the first network. - the electrical converter also comprises a second output configured for supplying the electrical traction engine with high-voltage current; and - the power supply device comprises a first reversible charger, interposed between the first electrical storage element and the first medium-voltage electricity network, wherein the first charger is suited to transfer electricity to one or the other of the first element and the first network.