System for fastening a plurality of battery packs stacked on top of one another on board a vessel, the vessel comprising a battery room whose length extends along an X axis and is delimited by a back wall, the width extends along a Y axis and is delimited by two side walls (16, 17) and the height extends along a Z axis and is delimited by a floor and a ceiling; each battery pack has a substantially parallelepipedal shape defining two side walls (22-1, 22-2), a proximal wall, a distal wall, an upper wall, and a bottom wall, while each side wall (22-1, 22-2) defines a plurality of grooves; the battery packs being designed to be placed in several layers on the floor of the battery room between its side walls (16, 17) and against the back wall, the battery packs of the same layer being designed to be placed next to each other adjacent to their side walls (22-1, 22-2) so that the grooves of these side walls (22-1, 22-2) face each other so that the distal walls of these packs are adjacent to the back wall; wherein the system comprises: - a plurality of reinforcements, each reinforcement defining a through-hole between an upper end and a lower end, each reinforcement being designed to be inserted into a groove of a battery pack without protruding from the corresponding side wall (22-1, 22-2) of this pack so that the upper end opens onto the upper wall of this pack and the lower end opens onto the lower wall of this pack; - a plurality of captive screws, each captive screw defining a threaded lower part, a cylindrical intermediate part and an upper clamping part, and being designed to be inserted into the through-hole of a reinforcement via the upper end, when this reinforcement is inserted into a groove of a battery pack, and, in a fixed position, to partially pass through this hole in order to secure this battery pack to a battery pack of a lower layer of battery packs or to the floor by engaging the lower threaded portion in a tapped hole formed in this battery pack of the bottom layer or in the floor., the system further comprising a plurality of threaded sleeves, each threaded sleeve being designed to be inserted into the through-hole of a reinforcement via the upper end, when this reinforcement is inserted into a groove of a battery pack and when a captive screw is in the fixed position in this hole; wherein at least one tapped hole of a battery pack being formed by a threaded sleeve inserted in the through-hole of a reinforcement inserted in a groove of this battery pack. each battery pack has a substantially parallelepipedal shape defining two side walls (22-1, 22-2), a proximal wall, a distal wall, an upper wall, and a bottom wall, while each side wall (22-1, 22-2) defines a plurality of grooves; the battery packs being designed to be placed in several layers on the floor of the battery room between its side walls (16, 17) and against the back wall, the battery packs of the same layer being designed to be placed next to each other adjacent to their side walls (22-1, 22-2) so that the grooves of these side walls (22-1, 22-2) face each other so that the distal walls of these packs are adjacent to the back wall; wherein the system comprises: - a plurality of reinforcements, each reinforcement defining a through-hole between an upper end and a lower end, each reinforcement being designed to be inserted into a groove of a battery pack without protruding from the corresponding side wall (22-1, 22-2) of this pack so that the upper end opens onto the upper wall of this pack and the lower end opens onto the lower wall of this pack; - a plurality of captive screws, each captive screw defining a threaded lower part, a cylindrical intermediate part and an upper clamping part, and being designed to be inserted into the through-hole of a reinforcement via the upper end, when this reinforcement is inserted into a groove of a battery pack, and, in a fixed position, to partially pass through this hole in order to secure this battery pack to a battery pack of a lower layer of battery packs or to the floor by engaging the lower threaded portion in a tapped hole formed in this battery pack of the bottom layer or in the floor., the system further comprising a plurality of threaded sleeves, each threaded sleeve being designed to be inserted into the through-hole of a reinforcement via the upper end, when this reinforcement is inserted into a groove of a battery pack and when a captive screw is in the fixed position in this hole; wherein at least one tapped hole of a battery pack being formed by a threaded sleeve inserted in the through-hole of a reinforcement inserted in a groove of this battery pack. - a plurality of reinforcements, each reinforcement defining a through-hole between an upper end and a lower end, each reinforcement being designed to be inserted into a groove of a battery pack without protruding from the corresponding side wall (22-1, 22-2) of this pack so that the upper end opens onto the upper wall of this pack and the lower end opens onto the lower wall of this pack; - a plurality of captive screws, each captive screw defining a threaded lower part, a cylindrical intermediate part and an upper clamping part, and being designed to be inserted into the through-hole of a reinforcement via the upper end, when this reinforcement is inserted into a groove of a battery pack, and, in a fixed position, to partially pass through this hole in order to secure this battery pack to a battery pack of a lower layer of battery packs or to the floor by engaging the lower threaded portion in a tapped hole formed in this battery pack of the bottom layer or in the floor.,