Requirements for rechargeable airplane batteries

A review is given of the major requirements of airplane secondary batte ries, with emphasis on commercial airplane batteries. Secondary batteries are required for emergencies and APU starting. APU starting imposes a particularly difficult requirement, for the batteries must provide current in excess of 1000 amperes over a wide temperature range. Since the batteries commonly used are vented, electrolyte loss is an important cause of the need for periodic maintenance. Reduced maintenance, high reliability and low cost of ownership are the main objectives of future aircraft batteries.