Overview of the State of the Art in Battery Packaging and Elaboration of a Safe Design Process for Battery Packs in Large Electric Aircraft

Kurzfassung

A part of the aviation industry is currently working on the transition to all-electric aircraft, which use battery systems for power supply, to further reduce pollutant emissions. While some manufacturers have already announced appropriate battery solutions, the energy density at battery cell level is only sufficient to power small electric aircraft for short range flights. Thus, there is currently no commercially available large aircraft powered solely by batteries. Moreover, the mass and volume overhead at pack level poses a challenge as well. Although a number of publications focus on the relationship between the core elements of a pack, namely the battery, the battery management system (BMS) and the battery thermal management system (BTMS), there is still potential for improvements of the battery pack design. In particular, due to advanced cell chemistries and BTMSs, the parameters influencing each other have changed in recent years. Hence, the purpose of this paper is to provide an overview of the state of the art in battery pack design in order to derive conclusions for future design concepts and to suggest design combinations for use in large electric aircraft. It starts with the description of the general requirements of the cell, module and pack according to current aviation standards. This is followed by a comparison of different cell types as well as cell chemistries and their applicability in an electric aircraft. Subsequently, the different types of BMSs and BTMSs are compared to highlight the systems, which are suitable for the selected cells and how their size and functionality would change and affect each other. In accordance with the VDI 2221 guideline, a design process for battery packs has been developed, which can be divided into four phases. These are the identification of the requirements for the specific task, the definition of the functions that the product must fulfil, the generation of solution concepts for a preliminary design and finally, the detailed elaboration of the overall design. In this work, the requirements are derived from the relevant standards. Based on that, the functions are defined in accordance with the most significant elements of the pack. The combinations demonstrate which solution concepts are viable and how the individual elements affect one another. Ultimately, the selected concepts must be evaluated once more in consideration of the requirements. In contrast to VDI 2221, an iteration step has only been considered at this point with regard to the linear process in the first three steps. If a further iteration step is no longer necessary, a detailed design for the final concept can be conducted afterwards. Based on that, the selection process will be further explained in detail and conducted to emphasize the most appropriate concepts. This will contribute to the reduction of the volume and mass overhead of the pack design and will increase the feasibility of battery-powered all-electric aircraft.