In this paper, we present a computational fluid dynamics (CFD)-based study on the optimization of a liquid-cooled battery module design, with the aim of supporting temperature sensing system design in battery packs. Efficient thermal management is essential not only for battery performance and longevity but also for maintaining stable and reliable temperature measurements in battery management systems. CFD simulations were conducted using COMSOL Multiphysics to analyze the thermal–fluid behavior of a liquid-cooled battery module under different operating conditions. The key parameters investigated include coolant types, cooling jacket configurations (counter-flow versus cross-flow), and coolant flow rates. Unlike previous studies that primarily evaluated individual cooling parameters or thermal performance, the novelty of this work lies in integrating coolant selection, flow configuration, flow rate optimization, and sensor-oriented thermal field analysis within a unified CFD framework. This approach improves battery cooling by simultaneously reducing the maximum cell temperature and temperature non-uniformity while providing physically meaningful temperature and flow distributions for sensing system design. The results show that an ethylene glycol–water mixture provides improved flow uniformity and heat transfer efficiency compared with pure water, resulting in a more uniform temperature distribution favorable for distributed temperature sensing. In addition, a counter-flow cooling configuration in stacked casing designs effectively reduces temperature gradients. An optimal coolant flow rate of 2 L/min was identified, maintaining the battery temperature at approximately 26.7 °C with reduced thermal fluctuations. Overall, we demonstrate that CFD simulations can serve as a virtual design support tool for temperature field characterization and sensor layout planning in liquid-cooled battery systems, providing practical guidance for sensor-informed thermal management in advanced battery technologies.