It is the purpose of this Aerospace Standard to provide for the definition of the requirements of vented type, rechargeable, Nickel-Cadmium batteries of the form generally used in aircraft. These batteries serve as power sources for engine starting and also function to provide a source of emergency back-up electrical energy for essential loads. This Aerospace Standard establishes minimum standards for those functional characteristics of the battery which are required to enhance the safety of both personnel and aircraft, insofar as it is dependent on the battery. It is the further purpose of this Aerospace Standard to delineate those characteristics which are utilized in the normal, non-emergency functions of the battery.