Electrical energy storing system and corresponding engine vehicle

Electrical energy storing system (12) for an engine vehicle (2) comprising a brake pedal, an accelerator pedal and an engine starter (3), an alternator (4) and electrical equipments (8) connected to an electrical circuit (10) of the vehicle, the electrical energy storing system (12) comprising at least an internal electrical circuit (14), intended to be connected to said electrical circuit (10), a capacitor set (18) comprising at least one capacitor and being connected to the internal electrical circuit (14), at least one controlled switch (20) between the capacitor set and the internal electrical circuit, and a battery set (22) connected to the controlled switch (20), a control unit (24) adapted to control the controlled switch (20), wherein said control unit (24) is configured so that If the brake pedal of the motor vehicle is not activated and if the acceleration pedal is activated, the capacitor set (18) is charged with a current available from the alternator set (4) if the engine speed is greater than a minimum threshold value (S1) and if the charge of the capacitor set (18) is lower than a further threshold value (C1), wherein the minimum threshold value (S1) is an idling speed of the engine (2) and the further threshold (C1) is the maximum energy threshold value to which the capacitor set (18) can be charged.