Effective thermal management constitutes a critical enabling technology for the safe, efficient, and durable operation of lithium-ion battery packs in electric vehicle applications. The present study presents a reduced-order, lumped thermal-network investigation comparing the thermal performance of staggered (zig-zag) and inline (aligned) cell arrangements in a 13S8P battery pack configuration employing commercial Panasonic NCR18650BD lithium-ion cells under passive natural convection cooling conditions. A reduced-order, node-per-cell thermal model incorporating temperature-dependent thermophysical properties, Arrhenius-type internal resistance behavior, and well-established Churchill-Chu natural convection heat transfer correlations is developed and systematically evaluated across eight discharge rates spanning from 0.20 °C to 1.97 °C, representing the full spectrum of electric vehicle operating conditions from auxiliary loads to peak acceleration demands. The results indicate a consistent but modest thermal benefit for the staggered arrangement. Evaluated at a common depth-of-discharge (15.01 Ah removed at every operating point), the staggered configuration attains an average maximum-temperature reduction of 1.3 °C, equivalent to 3.4% in absolute terms or 14.5% of the temperature rise above ambient, with the reduction increasing monotonically from 0.3 °C at 5A to 2.0 °C at 50A. The mean effective convective heat transfer coefficient is approximately 71% higher for the staggered arrangement, which directly reflects the array correction factors adopted from tube-bank correlations rather than an independently resolved flow field. The model-estimated intra-pack temperature non-uniformity is small for both arrangements (ΔT ≲ 0.35 °C) and is sensitive to the assumed air-mixing parameters; consequently only a weak, qualitative uniformity advantage is claimed, and a quantitative uniformity result would require CFD or experimental validation. Both arrangements maintain maximum cell temperatures below the 45 °C threshold up to 40A (1.57 °C) and become marginal at 50A (1.97 °C); within the range studied the staggered arrangement therefore provides additional thermal margin (approximately 1.9 °C at 40A) rather than an extended current limit. This additional margin is obtained purely through cell arrangement, without active cooling intervention. A paired comparison of the maximum-temperature difference across the eight operating points yields a mean difference of 1.3 °C (paired t-test p = 4.8 × 10−4, Cohen’s d = 2.2, 95% CI [0.81, 1.83] °C); because the comparison is across deterministic model outputs rather than experimental replicates, this is reported as a descriptive measure of the consistency of the advantage rather than inferential proof. Numerical solution convergence is established through a time-step refinement study, the maximum temperature changing by less than 10–3% between successive step halvings. These findings provide actionable design guidelines for passive battery thermal management systems, demonstrating that simple geometric modification through cell arrangement optimization can substantially enhance thermal performance without adding system complexity, weight, parasitic power consumption, or manufacturing cost. The comprehensive dataset and validated methodology presented herein provide a reproducible foundation for continued optimization of cylindrical cell battery pack designs for electric vehicle applications.