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Most aircraft in the U. S. Air Force inventory currently use vented nickel-cadmium (Ni-Cd) batteries for the main aircraft d.c. electrical power system and emergency power as well as other functions such as powering lights and instruments prior to engine starting/ignition. The major concerns of todays users are the high maintenance requirements, low reliability of vented NiCd battery systems and lack of a built-intest capability to check the battery state of health prior to flight. This paper will summarize efforts by the Wright Research and Development Center to develop maintenance free battery technologies for current and future aircraft applications.

EEI bipolar nickel metal hydride batteries and cells were tested under various conditions relevant to consumer and aerospace pulse power applications, with differing power and discharge pulse time requirements. A generic hybrid vehicle specification required that a full scale battery obtain 300,000 life cycles, while being able to deliver 25 kW discharge power after 18 seconds and 30 kW recharge power after 2 seconds. This corresponds to 15 years of normal use. Using this testing procedure, over 300,000 life cycles were obtained (using 25 Wh energy swings, scaled) on single full-capacity cells, with less than 10-15% pulse power capability loss measured. The projected full-sized battery mass was 40 kg and volume was 20 L. Testing of selected cells is continuing. Another test related to an automotive application demonstrated that a 6 Ah cell starting at 50% SOC was capable of being discharged at 200 A for 10 seconds (33C), with an end voltage of 0.945 V.

Energy storage devices are needed for applications requiring very high power over short periods of time. Such devices have various military (rail guns, electromagnetic launchers, and DEW) and commercial applications, such as hybrid electric vehicles, vehicle starting (SLI), and utility peak shaving. The storage and delivery of high levels of burst power can be achieved with a capacitor, flywheel, or rechargeable battery. In order to reduce the weight and volume of many systems they must contain advanced state-of-the-art electrochemical or electromechanical power sources. There is an opportunity and a need to develop energy storage devices that have improved high power characteristics compared to existing ultra capacitors, flywheels or rechargeable batteries. Electro Energy, Inc. has been engaged in the development of bipolar nickel metal hydride batteries which may fulfill the requirements of some of these applications. This paper describes a module rated at 300 V (255 cells) / 6 Ah.