Environmental and economical constraints lead to designing more and more complex systems. To face these issues, Model Based System Engineering proposes an approach based on an interconnected multi point of view system modeling. Each representation of the system has a different abstraction level that is valuable at different stages of the system design and suits its own objectives respectively: 1) purposes and global constraints definition, 2) architecture choices, components sizing and strategies testing, 3) accurate simulation results on various scenarios. Interconnections between the different levels have two objectives: on one hand be able to define the requirements of a lower level using higher level information and on the other hand send back simulation variables values from a lower level to evaluate the higher level requirements satisfaction. In this paper, this multi-level methodology is applied to the thermal system management of an electric vehicle in order to optimize its resource management. The different levels design and the development of their interconnections are detailed.