A passive thermal management system is examined for an electric vehicle battery pack. Phase change material (PCM) is infused in foam layers separating the lithium-ion (Li-ion) cells. Known operating conditions lead to selecting a suitable PCM for the application, n-octadecane wax. Suitable porous foam for infusion is decided on through experimentation. Finite volume based simulations are conducted to study the thermal behavior of a 4 cell sub-module. The effect of different discharge rates are compared for this sub-module, with and without the PCM's presence. The results show that the maximum temperature in the system is decreased up to 73 K by replacing dry foam with PCM-soaked "wet foam". The addition of PCM also makes the temperature distribution more uniform across the cells. The modeling results give indication of the quantity of PCM required, show the influence of the transient melt behavior under dynamic operating conditions, and examine design constraints associated with this approach. (C) 2014 Elsevier Ltd. All rights reserved.