The invention relates to an electric circuit (CE) for a motor vehicle, comprising a first electric power storage element (1), a current generator (3) connected in parallel with the first electric power storage element (1) between a reference potential (M) and a first node (E) of the circuit (CE), a vehicle on-board network (RDB) comprising at least one electric power consumption member (8) mounted between a first node (S) of the circuit (CE) and the reference potential (M), a voltage regulator (5) mounted between the first node (E) and the second node (S), comprising an inlet terminal connected to the first node (E) and comprising an outlet terminal connected to the second node (S). The circuit is characterised in that the regulator comprises a by-pass switch (10) mounted in series between the first and second nodes (E and S) corresponding to the inlet (E) and outlet (S) terminals of the regulator (5), said by-pass switch including a switch (K) and a diode (D) mounted in parallel on the switch (K) and extending from the inlet terminal (E) to the outlet terminal (S) of the regulator (5). The circuit is also characterised in that the regulator (5) comprises a reversible DC-DC converter (11) mounted in series with a second electric power storage element (12), said converter being connected to the outlet terminal (S) of the regulator (5) and the second electric power storage element (12) being connected to the reference potential (M).