Electrical circuit for a motor vehicle that comprises an internal combustion engine and electrical devices , including a starter for starting the internal combustion engine, the electrical circuit comprising: - a first terminal to be connected to the starter in order to supply electric current thereto, - at least one second terminal to be connected to another of said electrical devices in order to supply electric current thereto, - a first electric battery (B1), comprising an accumulator module (B11) connected to the first terminal by way of a first controlled switch (K1) and connected to the second terminal by way of a second controlled switch (K2), - a second electric battery (B2), connected to the second terminal , and - an electronic control unit able to control the first and second controlled switches (K1, K2), characterized in that the control unit is programmed to: - control the first and second switches (K1, K2) into an open state when the motor vehicle is in a prolonged parked state, and - control the first switch (K1) into a closed state in a phase of starting the internal combustion engine , and - in at least one operating mode of the vehicle in which the vehicle is moving, control the second switch (K2) into a closed state so as to connect the first and second batteries (B1, B2) to one another in parallel, and in that the first and second batteries are such that, when the state of charge (SOC2) of the second battery (B2) is within an interval corresponding to a full charge (int2), the open-circuit voltage (U2) across the terminals of the second battery (B2) is equal to the open-circuit voltage (U1) across the terminals of the first battery (B1), while the state of charge (SOC1) of the first battery is within an interval corresponding to a partial charge (int1). - a first terminal to be connected to the starter in order to supply electric current thereto, - at least one second terminal to be connected to another of said electrical devices in order to supply electric current thereto, - a first electric battery (B1), comprising an accumulator module (B11) connected to the first terminal by way of a first controlled switch (K1) and connected to the second terminal by way of a second controlled switch (K2), - a second electric battery (B2), connected to the second terminal , and - an electronic control unit able to control the first and second controlled switches (K1, K2), - control the first and second switches (K1, K2) into an open state when the motor vehicle is in a prolonged parked state, and - control the first switch (K1) into a closed state in a phase of starting the internal combustion engine , and - in at least one operating mode of the vehicle in which the vehicle is moving, control the second switch (K2) into a closed state so as to connect the first and second batteries (B1, B2) to one another in parallel, and in that the first and second batteries are such that, when the state of charge (SOC2) of the second battery (B2) is within an interval corresponding to a full charge (int2), the open-circuit voltage (U2) across the terminals of the second battery (B2) is equal to the open-circuit voltage (U1) across the terminals of the first battery (B1), while the state of charge (SOC1) of the first battery is within an interval corresponding to a partial charge (int1). <EOS>