The different physical ETS system architectures are identified by the form of the energy that is transferred etween the EV and the EVSE, as shown in figure 2. It is possible for an EV and EVSE to support more than one architecture.
This document does not contain all requirements related to EV energy transfer, as there are many aspects of an EV and EVSE that do not affect their interoperability. specifically, this document does not deal with the characteristics of the interface between the EVSE and the Utility, except to acknowledge the Utility as the source of energy to be transferred to the EV.
The functional requirements for the ETS are described using a functional decomposition method. This is where requirements are successively broken down into simpler requirements and the relationships between requirements are captured in a graphic form. The requirements are written as the transformation of inputs into outputs, resulting in a model of the total system.