The world's leading electric vehicle international standard - ISO 15118 full series

The official title of ISO 15118 is "Road vehicles - Vehicle-to-grid communication interface". I may be a little biased as I am one of the co-authors of this international standard, but I firmly believe that ISO 15118 is one of the most important and future-proof standards available today.

Smart charging mechanisms built into ISO 15118 make it possible to perfectly match grid capacity to the energy demands of the increasing number of electric vehicles connected to the grid. ISO 15118 also supports bi-directional energy transfer for vehicle-to-grid applications by feeding energy from the EV back to the grid when needed. ISO 15118 allows for more grid-friendly, safe and convenient charging of electric vehicles.

In this article, we describe the main features of ISO 15118 and each part of the ISO 15118 document series. Let's start with the story behind the creation of this standard.

History of ISO 15118

In 2010, the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) joined forces to create a joint ISO/IEC 15118 working group. For the first time, experts from the automotive industry and the utility industry have collaborated to develop an international communication standard for electric vehicle charging. The joint working group succeeded in creating a widely adopted solution that is now the leading standard in major global regions including Europe, US, Central/South America and Korea. ISO 15118 is also rapidly being adopted in India and Australia. A note on the format: ISO has taken over publication of the standard, which is now simply called ISO 15118.

Vehicle-to-grid - integrating electric vehicles into the grid

ISO 15118 supports the integration of electric vehicles into smart grids (also known as vehicle-2-grid or vehicle-to-grid). A smart grid is an electrical grid that interconnects grid components such as energy producers, consumers, and transformers through information and communication technologies, as shown in the diagram below.

ISO 15118 allows the EV and charging station to dynamically exchange information, based on which an appropriate charging schedule can be (re)negotiated. It is important to ensure that electric vehicles operate in a grid-friendly manner. In this case, "grid friendly" means that the device supports charging multiple vehicles at the same time, while protecting the grid from overloading. The smart charging app will calculate an individual charging schedule for each EV, using available information about the state of the grid, each EV's energy demand, and each driver's mobility needs (departure time and distance traveled).

In this way, each charge perfectly matches the grid capacity with the electricity demand to simultaneously charge the EV. Charging when renewable energy is highly available and/or when overall electricity usage is low is one of the main use cases that ISO 15118 can enable.
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(Illustration of an interconnected smart grid)

Secure Communication Powered by Plug & Charge

The grid is a critical infrastructure that needs to be protected against potential attacks and drivers need to be properly charged for the energy provided to EVs. Without secure communication between the EV and the charging station, malicious third parties can intercept and modify messages and tamper with billing information. That's why ISO 15118 has a feature called Plug and Play. Plug & Charge employs a variety of encryption mechanisms to secure this communication and guarantee the confidentiality, integrity and authenticity of all data exchanged

User convenience is key to a seamless charging experience

The plug-and-play functionality of ISO 15118 also enables the EV to automatically identify itself to the charging station and gain access to the energy it needs to charge the battery. It's all based on digital certificates and public key infrastructure provided through plug-and-play functionality. the best part? The driver does not need to do anything other than plug the charging cable into the vehicle and the charging station (during wired charging) or park on top of the floor mat (during wireless charging). Using this technology, entering a credit card, opening an app to scan a QR code, or looking for an easily lost RFID card is a thing of the past.

ISO 15118 will significantly impact the future of EV charging globally due to three key factors:

Plug and play brings convenience to customers
Encryption mechanisms defined in ISO 15118 for enhanced data security
Grid-Friendly Smart Charging
With these basics in mind, let's dive into the nuts and bolts of the standard.

ISO 15118 family of documents

The standard itself is called "Road Vehicles - Vehicle-to-Grid Communication Interface" and consists of eight parts. A hyphen or dash and a number indicate the corresponding section. ISO 15118-1 refers to the first part and so on.

In the diagram below, you can see how each part of ISO 15118 relates to one or more of the seven layers of communication that define how information is handled in telecommunications networks. When an EV is plugged into a charging station, the EV's communication controller (called EVCC) and the charging station's communication controller (SECC) establish a communication network. The purpose of this network is to exchange messages and initiate accounting sessions. Both the EVCC and the SECC must provide these seven functional layers (as described in The complete ISO/OSI communication stack) in order to process the information they send and receive. Each layer builds on the functionality provided by the underlying layer, starting with the application layer on top and continuing to the physical layer.

For example: the physical and data link layers specify how EVs and charging stations use charging cables (powerline communication via Home Plug Green PHY modem described in ISO 15118-3) or Wi-Fi connections (IEEE 802.11n as referenced in ISO 15118-8 ) as the physical medium. Once the data link is properly set up, the network and transport layers above can rely on it to establish a so-called TCP/IP connection to properly route messages from the EVCC to the SECC (and back). The application layer on top uses the established communication paths to exchange any use case related messages, whether it is AC charging, DC charging or wireless charging.
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The eight parts of ISO 15118 and their
relationship

When discussing ISO 15118 as a whole, this encompasses the set of standards within this general title. The standard itself is divided into several parts. Each part goes through a set of predefined stages before being published as an International Standard (IS). That's why you can find information about the individual "status" of each section in the following sections. This status reflects the release date of IS, the final phase of the ISO standardization project timetable.

Let's dig into each documentation section individually.

Process and timeline for publication of ISO standards

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Stages in the timeline for publishing ISO standards (Source: VDA)
The figure above outlines the timeline for the ISO standardization process. The process starts with a New Work Item Proposal (NWIP or NP), which enters the Committee Draft (CD) stage after 12 months. Once the CD becomes available (only for technical experts who are members of standardization bodies), a three-month voting period will begin, during which these experts can provide editorial and technical comments. Once the comment period is over, the comments collected will be addressed in online webinars and face-to-face meetings.

As a result of this collaborative work, a Draft International Standard (DIS) was subsequently prepared and published. The joint working group may decide to draft a second CD in case the experts decide that the document is not yet ready to be considered a DIS. DIS is the first document to be publicly available and available for online purchase. Another comment and voting stage will follow the DIS release, similar to the CD stage process.

The final stage before an International Standard (IS) is the Final Draft International Standard (FDIS). This is an optional stage that can be skipped if the expert group working on the standard considers that the document has reached an adequate level of quality. The FDIS is a document that does not allow any additional technical changes. Therefore, only editorial comments are allowed at this comment stage. As can be seen from the figure, an ISO standardization process takes a total of 24 to 48 months.

In the case of ISO 15118-2, the standard has been in development for over four years and will continue to be developed as needed (see ISO 15118-20). This process ensures it stays up to date and adaptable to many unique use cases around the world.