For optimum performance of battery modules in electric vehicles (EVs), the temperature of the batteries must be well managed and maintained within a definite range. In this paper, a passive thermal management with phase change material (PCM) is evaluated for prismatic Li-ion battery modules under abusive conditions. The proposed model aims to analyse the thermal performance of battery modules in circumstances the PCM content is reduced due to a leakage and some part of the batteries are exposed to ambient. Two different configurations are considered: one with the top of the batteries exposed to open medium with free air convection, and the other with the top of the batteries exposed to close medium with no air circulation. Comparing the two configurations, the former decreases the maximum temperature in the module by 1.17 K, 1.39 K, 1.63 K and 1.86 K for 2, 4, 6 and 8 mm PCM shrink levels. The effects of aluminum sheet (Al) placed at the top of the battery modules and charge/discharge cycles were also studied.