The battery cover comprises a cover having a floor and ceiling forming an interior area, and a bottom adjacent the housing sealably engaging the housing and partition walls. Several cell vents, in and extending through the bottom of the cover, communicate gases within the corresponding cells of the battery to the interior area of the cover. An atmospheric vent on the cover communicates gases from within the interior area of the cover to atmosphere. A labyrinth system, between the floor and ceiling in the interior area of the cover, is formed of several passages (26) forming several convoluted paths to communicate each cell vent to the atmospheric vent where each the cell vent communicates immediately with one passage of the labyrinth.; Several cell drains (24), on the floor and extending through the bottom of the cover, communicate with the passages and communicate liquid in the passages to respective cells. The passages of the labyrinth are arranged so that each of the paths has a branch above the electrolyte level for the corresponding cell when the battery is rotated as much as ninety degrees from an upright position.