could anybody help me,when i am on mains the battery tends to leak electrolyte out of the vent tube at the top of the battery as it is being charged,i don't think i have over-filled it as the fluid level is just above the plates,my understanding is that if one of the cells is u/s the charger will boil the battery dry which at the mo appears to be showing these symptons,it is a proper leisure battery less than 3yrs old,would be grateful for any advise on this matter.