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How Do I Make Sure Serpentine Cooling Tubes Fit 18650 or 4680 Cells?
How I Choose the Right Serpentine Liquid Cooling Tube for Cylindrical Cell Size (18650, 4680, 4695)——A Guide Designing an electric vehicle (EV) battery pack is like orchestrating a carefully balanced symphony: the cells must deliver high power, long cycle life and safety, while the thermal management system must keep them within a narrow temperature band. One component at the heart of this thermal orchestra is the serpentine liquid cooling tube. These extruded metal channels snake through a module, hugging the curvature of cylindrical cells and carrying coolant that absorbs waste heat. In my engineering projects I’ve found that choosing the correct tube shape and size is critical; too small and the cells overheat, too large and you waste space, mass and cost. This guide explains how I match serpentine tubes to three cell sizes—18650, 4680 and 4695—by combining fundamental cell physics with real world manufacturing constraints. A serpentine cooling tube is a continuous ribbon of aluminium or copper alloy that weaves between cylindrical cells, providing a large contact area for coolant flow. Engineers select a tube’s width and height based on the diameter and heat output of the target cells. Smaller 18650 cells (18 mm × 65 mm) dissipate heat easily and use narrower tubes (≈48–50 mm wide and 2.2–3.2 mm high,bending radius with TIM around 9.75±0.2 mm),while larger 4680 (46 mm × 80 mm) and 4695 (46 mm × 95 mm) cells require wider, thicker tubes (65–75 mm or 75–85 mm wide). Material choice (high manganese aluminium or copper), microchannel design and connection geometry (C2P, C2M or tri-way) further tune the cooling capacity. By analysing a cell’s size and power demands and by running thermal simulations, we ensure the chosen serpentine tube maintains uniform temperatures and maximises pack efficiency. The overview above explains what a serpentine cooling tube is and hints at how sizing works. The rest of this article dives deeper: we…
