Choosing the Best Lithium Battery Technology in the Hybridization of Ultralight Aircraft

Many research centers and companies in general aviation have been devoting efforts to the electrification of propulsive plants to reduce environmental impact and/or increase safety. Even if the final goal is the elimination of fossil fuels, the limitations of today's battery in terms of energy and power densities suggest the adoption of hybrid-electric solutions that combine the advantages of conventional and electric propulsive systems, namely reduced fuel consumption, high peak power, and increased safety deriving from redundancy. Today, lithium batteries are the best commercial option for the electrification of all means of transportation. However, lithium batteries are a family of technologies that presents a variety of specifications in terms of gravimetric and volumetric energy density, discharge and charge currents, safety, and cost. This work presents a series/parallel hybrid electric powertrain derived from automotive applications (Honda i-MMD) and tailored to an ultralight aircraft and discusses the sizing of the battery according to a sample mission. Different lithium–battery technologies, specifically NCA (LiNiCoAlO2 – Graphite), NMC (LiNiMnCoO2 – Graphite), LFP (LiFePo4 – Graphite), LTO (various - Li4Ti15O12), and Lithium-Polymer are compared. The results show that in the application here analyzed, the most relevant performance indexes are the power density and the runaway temperature.