Hardware Subsystem Proposal of an Off-Vehicle Battery Analyzer from a Charging/Discharging Perspective

Abstract: Electric Vehicles (EVs) are seen as one of the solutions to some of the world’s global current problems, such as global warming and air pollution, due to non-existent operational emissions and increased efficiency. There are multiple types of EVs, one of them being Battery Electric Vehicles (BEVs) which in most cases utilizes a Li-Ion battery pack as energy storage. Li-Ion batteries for EV applications are deemed to have reached End of Life (EoL) at 80%-70% of the battery’s initial energy capacity, the degradation is caused by calendar and cycle aging. Calendar aging is dependent on storage temperature and State of Charge (SoC), controlling these factors are therefore of importance when storing battery packs to minimize aging. Diagnostics of battery packs is also useful for determining second-life applications, State of Health (SoH) or other future usage. AFRY has therefore an interest in developing a product that would enable diagnostics and charging/discharging of off-vehicle battery packs, as regular chargers and tools are not compatible with battery packs separated from its vehicle. This thesis is a part of a project to develop a product that enables diagnostics and charging/discharging for different types off-vehicle battery packs. Due to time limitation of the thesis work this report focuses on the hardware design of the Power Conversion Module (PCM) from a charging/discharging perspective. This thesis project will propose a theoretical PCM from received requirements and choose appropriate components for this subsystemfrom a charging/discharging perspective. The design requirements were gathered through interviews, archive analysis and literature studies and argued for. This to achieve an understanding of the requirements that the system design needs to fulfill. A system design proposal of the PCM was presented and a component analysis of the included components was conducted. The proposed solution should in theory enable charging/discharging of battery packs, but further work and studies needs to be performed to validate the results in practice. Some calculations and variables were inferredwith the help of discussions, due to lack of information and time. The goal of the thesis was fulfilled, and the wider project objective was partially fulfilled within the boundaries of this thesis project.