Abstract: A vent cap for mounting in a fill opening of an electrochemical battery includes a hollow cap body with connected top and bottom walls and an inlet aperture adjacent one end of the bottom wall. The body forms a material holding chamber and has a vent hole spaced away from the inlet aperture. A connector is provided on the bottom wall for attachably mounting the cap body over a fill opening. Acid resisting material fills at least a substantial portion of the chamber and provides a substantial surface area on which vapors are able to condense as they cool. The cap body has a horizontal length at least three times the height that the body projects above the top surface of the battery and projects a greater distance on one side of the fill opening than on the other.