Abstract: A storage battery provided with an inverted U-shaped cover located over the generally flat top wall of the battery casing. The ends of the cover are open so that the space between the cover and the top wall of the battery casing communicates with the atmosphere. The cover is sufficiently flexible so that a downward force on the cover, even when applied repeatedly, can substantially flatten the cover against the top wall of the casing without cracking the cover. The cover is also sufficiently resilient so that upon removal of the downward force, the cover can return to its original inverted U-shape even after being maintained in a flattened condition for a substantial period of time.