Abstract: Cover for electrolytic batteries, comprising a primary cover adapted to be fixed on a container of electrolytic cells and provided with a plurality of openings for filling with electrolyte for respective electrolytic cells of the container, the walls of the openings being crossed transversely by a common gas collection channel, the cover comprising at least one secondary cover which can be fixed on the upper face of the primary cover to cover the openings, the secondary cover comprising a plurality of caps, each one of the caps being provided with a radial expansion adapted to engage in a gas-tight manner on the wall of the respective opening between the common gas collection channel and the upper face of the primary cover, the caps being not accessible when the secondary cover is fixed on the upper face of the primary cover.