Vibration Durability Testing of Nickel Manganese Cobalt Oxide (NMC) Lithium Ion 18,650 Battery Cells
Electric vehicle (EV) manufacturers are employing cylindrical format cells in the construction of the vehicles' battery systems. There is evidence to suggest that both the academic and industrial communities have evaluated cell degradation due to vibration and other forms of mechanical loading. The primary motivation is often the need to satisfy the minimum requirements for safety certification. However, there is limited research that quantifies the durability of the battery and in particular, how the cells will be affected by vibration that is representative of a typical automotive service life (e.g. 100,000 miles) This paper presents a study to determine the durability of commercially available 18,650 cells and quantifies both the electrical and mechanical vibration induced degradation through measuring changes in cell capacity, impedance and natural frequency. The impact of the cell state of charge (SOC) and in pack orientation is also evaluated. Experimental results are presented which clearly show that the performance of 18,650 cells can be affected by vibration profiles which are representative of a typical vehicle life. Consequently, it is recommended that EV manufacturers undertake vibration testing, as part of their technology selection and development activities to enhance the quality of EVs and to minimize the risk of in service warranty claims.