Synergistic liquid cooling design and optimization for 18650 battery modules in electric bicycles

Thermal accumulation during charging of lithium-ion batteries in electric bicycles seriously endangers safe operation. To address the thermal management of 18650 cylindrical battery modules, a composite liquid cooling strategy with bottom-internal synergistic cooling is proposed. Among the three channels (A, B, and C), Type C has the best heat dissipation performance, reducing the maximum battery temperature to 58.016°C under 2C discharge conditions. Optimization via 16 orthogonal tests identifies the optimal parameters: channel height 3.2 mm, spacing 13.5 mm, and fillet radius 5 mm. This parameter combination further lowers the maximum battery temperature to 57.552°C, while reducing the coolant temperature difference by 2.089°C and the channel pressure drop by 131.5 Pa. The innovative internal symmetrical cooling layout solves the inadequacy of traditional cooling, suppressing the maximum battery temperature to 39.837°C, which is 30.78% lower than the optimized bottom cooling scheme. It also reduces the maximum temperature difference inside the module to 13.126°C and improves temperature uniformity by 40%. This synergistic cooling strategy significantly enhances thermal safety, offering a practical and efficient thermal management solution for electric bicycle battery modules.