<p>A specific design for the coolant passage of a U-type air-cooled lithium-ion battery pack is introduced to enhance cooling performance. The inclined manifold is utilized for the inlet and outlet coolant passages, and the inclinations are varied to investigate their influence on cooling efficiency and power consumption. As the inlet manifold tapers toward the end, the coolant is distributed more uniformly to the gap between the battery modules, thereby improving the uniformity of the battery temperature. However, power consumption gradually increases because the tapered manifold impedes the inflow of the coolant, resulting in a rise in the pressure difference between the inlet and outlet. When the outlet manifold expands toward the end, cell temperature uniformity is improved 49% by reducing the blocking effect of the coolant that flows into the outlet manifold through the gaps between cells. Additionally, less power is needed to maintain a constant flow rate with the expanded manifold.</p>