State of Health Recognition for Aircraft Batteries Dynamic Equivalent Schematic and First Principles Model Considerations

Aviation battery maintenance is trending toward maintenance on-condition. NiCd, VRLA, or prospective Li-ion batteries are used to start engines, provide emergency back-up power, and assure ground power capability for maintenance and pre-flight checkout. As these functions are mission essential, State of Health (SoH) recognition is critical. GEM Power has developed a technological approach for SoH recognition, based on a battery equivalent schematic. The schematic is derived from a Matrix of Parameters (MoP), which includes ohm resistance, chemical resistance, electrical double layer capacity (EDLC), and open circuit voltage (OCV) [1]. Based on the dynamic equivalent circuitry approach, this paper will analyze failure modes for different aircraft battery chemistries, in addition to the initial stage of development of the first principles model, where a battery is considered a physical object and its behavior (charge, mass, and heat transfers) is described in terms of mathematical and physics equations.