Application Dependent End-of-Life Threshold Definition Methodology for Batteries in Electric Vehicles

Abstract

The end-of-life event of the battery system of an electric vehicle is defined by a fixed end-of-life threshold value. However, this kind of end-of-life threshold does not capture the application and battery characteristics and, consequently, it has a low accuracy in describing the real end-of-life event. This paper proposes a systematic methodology to determine the end-of-life threshold that describes accurately the end-of-life event. The proposed methodology can be divided into three phases. In the first phase, the health indicators that represent the aging behavior of the battery are defined. In the second phase, the application specifications and battery characteristics are evaluated to generate the end-of-life criteria. Finally, in the third phase, the simulation environment used to calculate the end-of-life threshold is designed. In this third phase, the electric-thermal behavior of the battery at different aging conditions is simulated using an electro-thermal equivalent circuit model. The proposed methodology is applied to a high-energy electric vehicle application and to a high-power electric vehicle application. The stated hypotheses and the calculated end-of-life threshold of the high-energy application are empirically validated. The study shows that commonly assumed 80 or 70% EOL thresholds could lead to mayor under or over lifespan estimations.

Design, build, test and flight of the world's fastest electric aircraft

“…[25] Whilst many other areas of the aircraft will incur significant capital expenditure, the ESS is likely to be considered as an operational expenditure, for example, a consumable and will regularly require refurbishment with new cells being installed as they reach EoL, typically deemed to be retaining 80% of their original energy. [28] A cell's lifespan is dictated by the stress applied to the internal chemistry under loads; however, certain conditions at which this occurs can expedite the ageing effects, particularly when this chemistry is heated above 50°C. [29] High ambient temperatures, high power loads at high SoC and high current loads at low SoC are cases where the limitations of charge transfer within the cell make it extremely susceptible to capacity degradation.…”

Estimation of electric vehicle battery capacity requirements based on synthetic cycles

“…Several authors have started to question this threshold, arguing that, in most cases, lower values of SoH could be reached without affecting the EV performance (Canals Casals et al, 2019;Saxena et al, 2015). Other authors, however, suggest that the 70-80 % threshold could be too optimistic in some cases (Arrinda et al, 2021). It is therefore clear, that the EoL criteria for EV batteries should be revised to guarantee that the safety and performance requirements are met, while ensuring that the batteries do not experience an early retirement from the vehicle.…”