Energy supply device for providing electrical energy, having: - a two-stroke diesel engine for providing mechanical energy, which has a crankshaft for providing the mechanical energy, and - a first rotating electric machine for converting the mechanical energy into electrical energy, wherein the first rotating electric machine has a first rotor that is arranged so as to be rotatable in a first stator and that has a first rotor shaft, wherein the first rotor shaft is mechanically coupled to the crankshaft, and wherein the first rotating electric machine has a first electrical winding that can be electrically coupled to a first network branch of a DC voltage network in order to supply the electrical energy to the DC voltage network, - a second rotating electric machine for converting the mechanical energy into electrical energy, wherein the second rotating electric machine has a second rotor that is arranged so as to be rotatable in a second stator and that has a second rotor shaft, wherein the second rotor shaft is mechanically coupled to the crankshaft, and wherein the second rotating electric machine has a second electrical winding that can be electrically coupled to a second network branch of the DC voltage network in order to supply the electrical energy to the DC voltage network, - a first and a second energy converter (38, 40) for electrically coupling the first and the second electrical winding (24, 36) to the DC voltage network, characterized by - a first and a second electrical switching unit (42, 44) for electrically coupling the first and the second electrical winding (24, 36) to the DC voltage network via the first and the second energy converter (38, 40), - a further electrical switching unit for electrically coupling the first network branch to the second network branch, and - a control device for controlling the first and the second rotating electric machine (16, 28) and the at least first and second energy converter (38, 40) and the at least one further electrical switching unit and the first and the second electrical switching unit (42, 44) that is configured to activate the second rotating electric machine to convert the energy at least when the first rotating electric machine is deactivated, wherein the first electrical switching unit is opened and the further electrical switching unit is closed. - a two-stroke diesel engine for providing mechanical energy, which has a crankshaft for providing the mechanical energy, and - a first rotating electric machine for converting the mechanical energy into electrical energy, wherein the first rotating electric machine has a first rotor that is arranged so as to be rotatable in a first stator and that has a first rotor shaft, wherein the first rotor shaft is mechanically coupled to the crankshaft, and wherein the first rotating electric machine has a first electrical winding that can be electrically coupled to a first network branch of a DC voltage network in order to supply the electrical energy to the DC voltage network, - a second rotating electric machine for converting the mechanical energy into electrical energy, wherein the second rotating electric machine has a second rotor that is arranged so as to be rotatable in a second stator and that has a second rotor shaft, wherein the second rotor shaft is mechanically coupled to the crankshaft, and wherein the second rotating electric machine has a second electrical winding that can be electrically coupled to a second network branch of the DC voltage network in order to supply the electrical energy to the DC voltage network, - a first and a second energy converter (38, 40) for electrically coupling the first and the second electrical winding (24, 36) to the DC voltage network, - a first and a second electrical switching unit (42, 44) for electrically coupling the first and the second electrical winding (24, 36) to the DC voltage network via the first and the second energy converter (38, 40), - a further electrical switching unit for electrically coupling the first network branch to the second network branch, and - a control device for controlling the first and the second rotating electric machine (16, 28) and the at least first and second energy converter (38, 40) and the at least one further electrical switching unit and the first and the second electrical switching unit (42, 44) that is configured to activate the second rotating electric machine to convert the energy at least when the first rotating electric machine is deactivated, wherein the first electrical switching unit is opened and the further electrical switching unit is closed.