An apparatus and a method for managing the energy supplied to a low-voltage system of a vehicle. The low-voltage system includes a battery, which supplies the first voltage on a low-voltage bus. A system for charging the battery includes an alternator for supplying a charging voltage to the battery, and motor-vehicle loads supplied by the battery and/or by the alternator. A high-voltage system operates at a second voltage higher than said first voltage. The high-voltage system includes the vehicle energy-recovery stage. The second voltage is supplied through an intermediate energy-storage system and a DC-DC converter. A control module that carries out energy-management operations at least by the alternator. The second voltage of the DC-DC converter is regulated via a control procedure of a hysteretic type.