Energy-optimized microchannel liquid cooling for 21700 lithium-ion battery packs

• Battery surface temperature reduced by up to 21.5 °C using microchannel BTMS. • ΔTmax decreased from 3.0 °C to 1.7 °C as Re increased from 400 to 700. • Pumping power remained < 0.08% of total 180 W battery output. • Surface temp dropped by 4.8 °C at Tci = 20 °C when Re increased from 400 to 700. • Achieved 75% lower coolant flow rates vs. prior studies with equal or better cooling. Effective thermal management of high-power lithium-ion batteries is critical for safety, stable performance, and long service life in electric vehicles and large-scale energy storage systems. This study presents a novel microchannel liquid-cooling system for 21700-type cylindrical lithium-ion cells, integrating numerical simulations with experimental validation to achieve efficient thermal control. The system incorporates optimized microchannel geometry and low-flow cooling strategies to enhance convective heat transfer while minimizing energy consumption. Thermal performance was evaluated at Reynolds numbers from 400 to 700 and coolant inlet temperatures of 20–30°C. Increasing the Reynolds number improved heat dissipation by up to 15%, reducing the maximum temperature gradient from 2.45°C to 1.86°C while maintaining a uniform surface temperature as low as 27.3°C at a 20°C coolant inlet. Notably, the optimized configuration achieved up to 75% lower coolant flow rates than conventional designs, with a maximum pumping power of only 0.145 W, representing less than 0.1% of the 180 W battery output. These findings demonstrate that the proposed system delivers high thermal uniformity and significant energy efficiency, highlighting its strong potential for scalable integration into compact, thermally robust battery packs for electric mobility and grid-scale applications.