A connecting device is provided, including a control apparatus, an energy storage apparatus, an input connection, and an output connection, the input connection being connected to the energy storage apparatus by means of a charging apparatus, the charging apparatus being configured for controlled charging of the energy storage apparatus, the control apparatus being configured, after reaching a preset charge state of the energy storage apparatus, to connect the energy storage apparatus to the input connection; and the control apparatus also being configured, during and/or following connection of the energy storage apparatus to the input connection, to connect the input connection to the output connection.