Battery Vents and Vent Plugs

Vent plugs of various designs are used. Generally, the vent plugs are baffled so gas can escape, but electrolyte splashed into the vent will drain into the cell. The plugs may be screw type or push-in type. The push-in type may be a single plug or a gang vent plug (three-plug manifold). Most maintenance-free batteries do not vent plugs. Instead, the gas is vented through baffled passages and small vent holes in the cover. Most conventional batteries have flame arrestor vent plugs. In maintenance-free batteries, the flame arrestors are located at the exits of the baffled passages. Only distilled water should be added to the battery.