A battery includes a battery can housing an cell that supplies electrical energy at terminals of the cell by an electro-chemical reaction with oxygen, the can including, a first member having at least one hole that is exposed to air; and a second member. The battery also includes a mechanism coupled to one of the first and second members to move the one of the first and second members such that when current is drawn from the battery, the opening in the member allows air to pass into the battery, and to move the one of the first and second members such that when current is not drawn from the battery, the opening in the member is not in registration to inhibit air to pass into the battery. The battery also includes a circuit to control the mechanism. In one embodiment the circuit monitors levels of O.sub.2 in a air plenum that surrounds the cell. The circuit to monitor levels of O.sub.2 in the air plenum includes a florescent detector/sensor that senses and responds to changes in O.sub.2 in the plenum by using the "quenching effect" of oxygen on a fluorescent material.