Plug (5, 5') for electrically connecting an electrical cable to an electrical terminal (20, 21, 20', 21') of a battery module (2, 2'), comprising: - a conductive end fitting (51, 51') comprising, at a first end, means for mechanically and electrically connecting said plug with said electrical terminal, and being provided at a second end with a knob for rotating actuation of said end fitting (51, 51') and - a conductive element for connecting said electrical cable, provided with means for mechanically and electrically connecting said conductive element with said electrical cable, and provided with means for mechanically and electrically connecting with said end fitting (51, 51') ensuring a freedom of rotation of said end fitting (51, 51') with respect to said cable or to the conductive element connected to said cable, the connection/disconnection of said means of connecting said plug (5, 5') with said terminal (20, 20', 21, 21') being implemented by a rotational movement imparted by means of said knob, without rotating at least a part of the conductive element for connecting said electrical cable and/or said cable, said conductive element for connecting the cable comprises a lug, characterised in that the end fitting (51, 51') forms at its first end a rim (5111, 5111') with a protrusion which thus forms a stop facing and away from the knob (56, 56'), the lug being housed between said stop (5111, 5111') and the knob (56, 56'), and in that said plug (5, 5') comprises elastic return means, disposed between the knob (56, 56') and the lug, said elastic return means consist of a pressure spring compressing the lug against the stop (5111, 5111') by exerting an extension force in the axial direction of said end fitting (51, 51') so as to tension said means for connecting the end fitting (51, 51') with the terminal (20, 20', 21, 21'), while exerting a frictional force tending to prevent the rotation of said lug for connecting said electrical cable with respect to said end fitting (51, 51'); said knob being designed to permit a rotational movement of said end fitting (51, 51') relative to said lug by exerting a rotational force greater than said frictional forces. - a conductive end fitting (51, 51') comprising, at a first end, means for mechanically and electrically connecting said plug with said electrical terminal, and being provided at a second end with a knob for rotating actuation of said end fitting (51, 51') and - a conductive element for connecting said electrical cable, provided with means for mechanically and electrically connecting said conductive element with said electrical cable, and provided with means for mechanically and electrically connecting with said end fitting (51, 51') ensuring a freedom of rotation of said end fitting (51, 51') with respect to said cable or to the conductive element connected to said cable, the connection/disconnection of said means of connecting said plug (5, 5') with said terminal (20, 20', 21, 21') being implemented by a rotational movement imparted by means of said knob, without rotating at least a part of the conductive element for connecting said electrical cable and/or said cable, said conductive element for connecting the cable comprises a lug, characterised in that the end fitting (51, 51') forms at its first end a rim (5111, 5111') with a protrusion which thus forms a stop facing and away from the knob (56, 56'), the lug being housed between said stop (5111, 5111') and the knob (56, 56'), and in that said plug (5, 5') comprises elastic return means, disposed between the knob (56, 56') and the lug, said elastic return means consist of a pressure spring compressing the lug against the stop (5111, 5111') by exerting an extension force in the axial direction of said end fitting (51, 51') so as to tension said means for connecting the end fitting (51, 51') with the terminal (20, 20', 21, 21'), while exerting a frictional force tending to prevent the rotation of said lug for connecting said electrical cable with respect to said end fitting (51, 51'); said knob being designed to permit a rotational movement of said end fitting (51, 51') relative to said lug by exerting a rotational force greater than said frictional forces.