The invention relates to a modular by-pass device of an electrical component comprising a housing 2 possessing a movable means of sealing 3, 4 and equipped with conducting terminals T1-T3, one of whose ends is connected to one of the terminals of the electrical component circuit, the other end being fastened to the wall of the housing projecting into the interior of the housing and constituting a contact post P1, P2, P3, an actuator 9 providing transposition between two positions of a control device consisting of a plunger shaft 12 and comprising a spring 21 arranged in the space D2 formed between the plunger shaft 12 and the internal wall 6 of the housing, a trigger (10) comprising a retention device of the plunger shaft held in place by a fusible material, a reversing switch 11 comprising a contact zone providing electrical continuity between two contact posts of the terminals carried by the housing. The invention finds application more particularly in the isolation and short- circuiting of a battery element, which has become defective.