Design of lithium-ion battery packs for two-wheeled electric vehicles

The design of lithium-ion battery pack to meet the power requirements of two-wheeled electric bikes for Indian conditions is studied here. Theoretical calculations are performed based on the technical data collected from various resources in India. In particular, the two-wheeled "Activa 6G " vehicle is considered for the analysis. Based on the numerical analysis, a relation between cell parameters such as: C-rate, voltage, capacity, pack configuration, and vehicle dynamics parameters like: weight of the vehicle, payload, travel range per charge, and energy consumption, has been established. Commercial cylindrical cells, namely: 18650, 21 700, and 26 650 are used in all the calculations. The corresponding battery packs are designed considering a range of 100 km. Furthermore, simulations are performed to understand the voltage-discharge characteristics, state of charge and variation of cell concentration with respect to time as the battery discharges. The studies are extended to analyze the battery thermal management to estimate the degradation and heat generation rate, and hence, the optimum operating parameters, that is, optimal electrode thicknesses and particle size to enhance the endurance. Based on the degradation and heat generation profiles, the life of the battery pack made of 26 650 cells is found to be better as compared to the battery packs made of 18 650 and 21 700 cells. Furthermore, the analysis is extended for battery packs made of 26 650 cells in four different configurations, considering air and mineral oil as the cooling fluids to estimate the maximum temperature and hence degradation characteristics. Tapered configuration is found to be the best configuration among the four, yielding lowest maximum temperature and capacity fading. On the other hand, when mineral oil is used as the cooling fluid in rectangular configuration, the maximum operating temperature is found to be reduced by 4.49 K. However, usage of mineral oil adds to the periodic maintenance and replacement costs.