One of the major challenges with the implementation of lithium-ion batteries in electric and hybrid vehicles (EVs and HEVs) is effective thermal management. Inherently, lithium-ion batteries are thermally sensitive which causes a reduction in vehicle performance and thermal degradation when operated outside of the recommended temperature range. However, the lithium-ion battery thermal management can be difficult in full-vehicle systems, due to the highly transient conditions demanded by the driver. Therefore, accurate full-vehicle and battery thermal models are required in order to predict the battery temperature throughout various driving conditions. This thesis begins with the development of a plug-in hybrid vehicle (PHEV) full-vehicle transient thermal model in Virtual Time-Temperature Analysis software in order to predict the battery surface temperature.