Batteries don't leak.
Gary, Batteries can freeze, and crack, if in a low charge state with very cold temps, or they can crack through mechanical damage or abuse, thereby causing fluid loss. Other than that they don't lose the amount of fluid you are speaking of unless they are subjected to overcharging, the vent holes are plugged or it is subjected to very extremely hard usage. If you have been topping off the cell fluid levels to the upper limit of full, like maybe too full, that could also cause fluid loss. The proper level is between the top of the cell plates (lower level) and the cell cap lower ring (upper level). Or in simple words, fill it 1/8th to 1/4 inch above the cell plates. If the battery is in good shape, cap vents open, and not overly worked, I would look at the charging system. Both shore powered and onboard powered. Both a damaged and leaking battery, or a over charging system that causes the battery to expell gas and fluid are VERY DANGEROUS CONDITIONS. Hope this helps, Ray