ISO 15118


ISO 15118 Road vehicles -- Vehicle to grid communication interface is a proposed international standard defining a vehicle to grid communication interface for bi-directional charging/discharging of electric vehicles. The standard provides multiple use cases like secure communication, smart charging and the Plug & Charge feature used by some electric vehicle networks.

Overview

ISO 15118 is one of the International Electrotechnical Commission's group of standards for electric road vehicles and electric industrial trucks, and is the responsibility of Joint Working Group 1 of IEC Technical Committee 69 together with subcommittee 31 of the International Organization for Standardization's Technical Committee 22 on road vehicles.
ISO and IEC began working together on the standard in 2010, and a Plug & Charge section was released in 2014. No automakers had a productive implementation of the standard by 2018.

Plug & Charge

The Plug & Charge feature envisioned by ISO 15118 enables an electric vehicle to automatically identify and authorize itself to a compatible charging station. This makes it convenient for the driver, to receive energy for recharging the vehicle's battery. The only action required by the driver is to plug the charging cable into the EV and/or charging station, because the car and the station identify each other by exchanging public key certificates to facilitate payment.
An open test system accessible through the internet was launched in November 2021. The proposed standard can be used for both wired and wireless charging for electric vehicles.
Some 2021 model year EVs support the Plug & Charge standard, including the Porsche Taycan, Mercedes-Benz EQS, Lucid Air, and Ford Mustang Mach-E. Model year 2024 EVs include BMW i4, BMW i5, BMW i7, BMW iX, Hyundai Ioniq 5 and Hyundai Ioniq 6.
Other manufacturers such as Volkswagen updated their ID family vehicles to support Plug & Charge. Some cars need hardware updates.
All Tesla vehicles since 2012 have a proprietary version of Plug & Charge. Other proprietary solutions exist, such as those developed by Paua.
Besides Tesla, alternatives to Plug & Charge exist including "Autocharge", which is based on DIN Spec 70121 using the car's fixed MAC address. For the end-user, the functionality is similar but tied to the specific operator and their charging rates. Autocharge has been used for many years i.e. at the charging stations of Fastned and lately of Voltrelli. In the market, Autocharge is considered a less secure mechanism than Plug & Charge because of the missing certificate chain. Cars from the Volkswagen Group even have had a software update to 'break' this functionality. While Autocharge worked flawlessly at the launch of the ID.3 model, Volkswagen switched to variable MAC addresses and therefore these cars no longer be used with Autocharge. Some say this is for commercial reasons because the Volkswagen Group heavily invested in Plug & Charge. If Autocharge would become a big success then the need for the development of Plug & Charge would be minimized.

Secure communications and public key infrastructure

ISO 15118 communication between an electric vehicle and the electric vehicle supply equipment can be made secure with a connection using Transport Layer Security. This is mandatory for Plug & Charge applications. The standard describes how "V2G-PKI" needs to be set up to support this. The company Hubject provided the first working V2G-PKI in 2018 and the related ecosystem for the European Union and the United States. Several other companies were working on V2G-PKI solutions among which CharIn and Gireve. Nevertheless, charge station operators and automakers can also handle the certificates if they are based on the ISO 15118 standard.
and 2020, several Public Key Infrastructure issues remained unsolved for using the standard as proposed.

Standard documents

ISO 15118 consists of the following parts, detailed in separate standard documents:
  • ISO 15118-1: General information and use-case definition
  • ISO 15118-2: Network and application protocol requirements
  • ISO 15118-3: Physical and data link layer requirements
  • ISO 15118-4: Network and application protocol conformance test
  • ISO 15118-5: Physical and data link layer conformance test
  • ISO 15118-6: General information and use-case definition for wireless communication
  • ISO 15118-7: Network and application protocol requirements for wireless communication
  • ISO 15118-8: Physical layer and data link layer requirements for wireless communication
  • ISO 15118-9: Physical and data link layer conformance test for wireless communication
  • ISO 15118-10: Physical layer and data link layer requirements for single-pair Ethernet
  • ISO 15118-11: Physical layer and data link layer requirements for single-pair conformance test plan
  • ISO 15118-12: Requirements of message exchange for value-added service-based battery information between EVCC and SECC
  • ISO 15118-20: 2nd generation network layer and application layer requirements
  • ISO 15118-21: Common 2nd generation network layer and application layer requirements conformance test plan

    Heavy duty vehicles

ISO 15118 is also used as communication protocol for charging of heavy duty vehicles such as:
When using the ISO 15118 in a commercial operation the use of WLAN must be considered carefully since there is no way to guarantee operation uptime when using wireless communication based on WLAN. For these situations the same protocol as for passenger car charging can be used.