Dynamic modeling approaches are presented for a battery electric vehicle (BEV) transcritical thermal management system. In BEVs thermal management comprises of both temperature regulation of the passenger cabin and the battery pack. This work proposes that a single vapor compression system may provide efficient and effective means to manage the temperature constraints on both systems. However, the transcritical vapor compression system, battery pack, and cabin are complex systems with coupled behavior among electrical and thermal domains. Dynamic and scalable models provide valuable insight to the coupling among systems, and allow for rapid thermal management architecture and control design. This potential is demonstrated with a simulation comparison of an air-cooled battery pack with recirculated and exhausted return air and examples of parameter variation analysis important for controller robustness.