Electrochemical reactor, comprising: - a stack of electrochemical cells each comprising two electrodes (3, 4) separated from each other by an electrolyte and in electrical contact with bipolar plates (10, 20), and comprising at least one abutment mechanism (7; 8; 14, 24) or an abutting through-orifice (15, 25) of an electrochemical cell; and - at least one electrical connector, providing an electrical connection with the said electrochemical cell of the said stack of electrochemical cells, the electrical connector comprising an end part inserted into the stack of electrochemical cells and occupying a position referred to as engaged, the said end part comprising: o an electrical contact portion, being in electrical contact with a bipolar plate (10; 20) of the said electrochemical cell when the end part occupies the engaged position; and o a blocking portion, cooperating with the said electrochemical cell in order to ensure the maintenance of the end part in the engaged position, characterized in that the blocking portion comprises: ▪ either a blocking through-orifice receiving by insertion the said abutment mechanism (7; 8; 14, 24) of the electrochemical cell, ▪ or a blocking mechanism introduced by insertion into the said abutting through-orifice (15; 25) of the electrochemical cell, the said insertion, leading to the formation of an abutment opposing the retraction of the end part out of the engaged position, and in that the end part is composed of an electrical cable comprising a conducting core in the form of a strip having two faces opposite to each other coated with an insulating sheath, and has an average thickness, between two main faces of the end part substantially parallel and opposite to each other, less than the width and length dimensions of the said main faces. - a stack of electrochemical cells each comprising two electrodes (3, 4) separated from each other by an electrolyte and in electrical contact with bipolar plates (10, 20), and comprising at least one abutment mechanism (7; 8; 14, 24) or an abutting through-orifice (15, 25) of an electrochemical cell; and - at least one electrical connector, providing an electrical connection with the said electrochemical cell of the said stack of electrochemical cells, the electrical connector comprising an end part inserted into the stack of electrochemical cells and occupying a position referred to as engaged, the said end part comprising: o an electrical contact portion, being in electrical contact with a bipolar plate (10; 20) of the said electrochemical cell when the end part occupies the engaged position; and o a blocking portion, cooperating with the said electrochemical cell in order to ensure the maintenance of the end part in the engaged position, characterized in that the blocking portion comprises: ▪ either a blocking through-orifice receiving by insertion the said abutment mechanism (7; 8; 14, 24) of the electrochemical cell, ▪ or a blocking mechanism introduced by insertion into the said abutting through-orifice (15; 25) of the electrochemical cell, the said insertion, leading to the formation of an abutment opposing the retraction of the end part out of the engaged position, o an electrical contact portion, being in electrical contact with a bipolar plate (10; 20) of the said electrochemical cell when the end part occupies the engaged position; and o a blocking portion, cooperating with the said electrochemical cell in order to ensure the maintenance of the end part in the engaged position, ▪ either a blocking through-orifice receiving by insertion the said abutment mechanism (7; 8; 14, 24) of the electrochemical cell, ▪ or a blocking mechanism introduced by insertion into the said abutting through-orifice (15; 25) of the electrochemical cell,