ISO 15118
ISO 15118 is about communication between a charging station and an electric vehicle. The international standard supports the Combined Charging System( CCS) for wired and wireless charging, both normal charging and fast charging of vehicle batteries. The official title of the ISO standard is: "Road Vehicles - Vehicle to Grid Communication Interface." In smart charging, the charging station communicates with the electric vehicle's charge controller.
ISO standard 15118 supports the concept of smart charging and plug-and-charge from the aspects of electronic energy billing, the charging profile taking into account the power connection, the required charging energy and, in the long term, also around the aspects of smart grids in which the electric vehicles are to be integrated as energy storage devices. In smart charging, a charging plan is applied from which the available energy of the smart grids and the probable mobility demand emerge. This allows the grid capacity to be adjusted to the power demand for charging.
ISO standard 15118 is about charging communication between charging station and charging controller. This standard is supported by the Europeans. In the USA, the standards of the Society of Automotive Engineers( SAE) are used, and in Japan those of the Chademo organization, which stands for Charge de Move.
ISO 15118 consists of three parts and defines the functions for the communication of the different layers according to the OSI reference model. Part 1, ISO 15118-1, deals with the application; Part 2, ISO 15118-2, deals with layers 3 through 7 and describes the technical protocols; and Part 3, ISO 15118-3, deals with the physical and connectivity requirements for the physical layer and the link layer. ISO 15118, which is adopted by DIN and DKE, is about active charging control, current consumption and spontaneous adaptation of the charging process to avoid overloading the power grid.
Communication between charging station and electric vehicle
In terms of communication, ISO 15118 relies on the IP protocol at the network layer, as well as Stateless Address Autoconfiguration( SLAAC) used in IPv6, Dynamic Host Configuration Protocol( DHCP) and Powerline Communication( PLC). At the transport layer, data is transported using the TCP protocol and, alternatively, the UDP protocol. Security is ensured by encrypting the data with Transport Layer Security( TLS), which uses the TCP protocol as a connection-oriented transport protocol.
With the TLS protocol, the electric vehicle must identify itself to the charging station as a trusted entity. A session key is then negotiated between the partners, via which secure communication is possible.
In addition to the communication options mentioned, there is also the Open Charge Point Protocol( OCPP) via which the charging station communicates with the central system. The Vehicle to Grid Transport Protocol( V2GTP) resides on the communication control layer for communication between the electric vehicle and the smart grid. It supports smart charging and sits on top of the underlying protocols. On the representation layer resides the minimalized and efficient data format Efficient XML Interchange( EXI) and on the application layer the V2G messages, Vehicle to Grid (V2G), are transmitted.