ISO 15118

What is ISO 15118?

ISO 15118 is an international communication standard for electric vehicles (EVs), charge points (CPs), and charge point management systems (CPMSs). It specifies a secure and reliable way for these devices to exchange authentication and authorization data, charging parameters, and billing information.

Applications of ISO 15118

Authentication, Authorization, and Plug & Charge

ISO 15118-enabled charge points (CPs) allow charge point operators (CPOs) to provide EV drivers with a more seamless and secure charging experience. The protocol makes this possible by establishing a reliable communication environment between the EV, the CP, and the charge point management system (CPMS)—a centralized backend software for managing chargers and charging networks.

In the typical scenario, EV drivers can initiate charging only after authenticating themselves and their car. Upon authenticating through an app, RFID card, or another method, the backend system authorizes or disallows charging depending on preset criteria. 

The purpose of this data exchange is for the CPMS to know who’s the driver charging which car, whether the driver is allowed to use this particular charger, and who needs to receive the bill for the session. While authentication and authorization happen in a matter of seconds, the need for drivers to physically authenticate is an added inconvenience.

ISO 15118 makes this process more accessible thanks to the Plug & Charge functionality. As the name implies, with Plug & Charge, EV drivers can simply plug into a CP, and authorization and authentication happen automatically. This works because after initial set-up, the EV stores information about the driver, which is then automatically shared with the CP so charging can begin immediately. 

Without bogging into too much detail, a Public Key Infrastructure system manages the information exchange. This secure public-key management system uses hardware, software, and procedural units to acquire, store, and manage sensitive data.

Smart Charging and V2G

In addition to already discussed functionalities, ISO 15118 enables enhanced charging features such as smart charging and vehicle-to-grid (V2G). The latter allows bi-directional energy exchange between the grid and V2G-compatible EVs. Normally, electricity flows unidirectionally—from the grid to the CP and then to the EV, whereas V2G allows electricity to flow both ways. 

When V2G-enabled EVs and CPs connect, the EV can send energy stored in its battery back to the charging station and the electricity grid. This way, the grid can handle higher energy consumption without needing peak demand generation. 

The latter refers to power generators that are intermittently activated during peak energy demand. The downside is that, on the one hand, this extra generation increases electricity prices, and on the other hand, it usually means involving unsustainable sources such as coal plants. Utilizing the energy stored in EV batteries lowers or outright eliminates this need and acts as energy storage for excess sustainable energy.

Where EV charging is concerned, smart charging establishes two-way communication between the EV and CP to set charging speeds and schedules. Put simply, the electric car sends data about how much electricity it needs to the CP and by what time. In turn, the CP calculates how much energy it needs to release to the EV to efficiently and effectively meet the required time and state of charge (SOC).

Data Security

Data security is an essential consideration in EV charging. Data exchange is protected within the EV ecosystem by using cryptographic layers added on top of hardware and software solutions. ISO 15118, on the other hand, has built-in security measures, meaning that ad-hoc data security is unnecessary when using this protocol. It handles data protection on several levels—through authentication, authorization, and data encryption.

Importance of ISO 15118

ISO 15118 is among the important standards for the ongoing development of the EV charging industry. This communication protocol is a secure, reliable, and internationally recognized instrument compatible with many EV hardware and software solutions and charging speeds. Adding to that is the role this protocol will play as grid-balancing technologies become more widespread.

Practical Examples of ISO 15118

Here are some practical examples of how ISO 15118 can be used:

• An EV arrives at a public charging station. The EV and the charging station communicate using ISO 15118. The EV sends the charging station its SOC, which is the percentage of battery power that is remaining. 

The charging station also communicates with a back-end system, which manages the charging infrastructure. The back-end system considers the current grid load and sets the optimal charging rate for the EV.

Based on this information, the charging station and the EV agree on a charging schedule. The charging station may start charging the EV immediately or delay it until the grid is under less utilization. The EV and the charging station continue to communicate throughout the charging process. This allows them to adjust the charging rate as needed, for example, if the grid load changes or the EV’s SOC reaches a certain level.

• Let’s continue the previous example, but look at what happens with Plug & Charge. The EV plugs into the charging station. 

The EV and the charging station communicate using ISO 15118. The EV sends the charging station its identity data for authorization. The charging station verifies the EV’s identity and approves it for charging. The charging station initiates the charging session without any user interaction. 

For this process to work, the EV driver needs to go through an initial set-up process, providing their personal and billing information. This information will then be used for each Plug & Charge-enabled session.

• Regarding V2G, energy providers can improve their electricity rates by using the battery capacity of EVs during periods of high demand instead of relying on additional energy sources. In certain instances, utility companies may even pay users for participating in V2G events. For example, when EV drivers supply electricity to the grid during peak demand or charge their vehicles during low energy demand.

Additional Information for ISO 15118

• ISO 15118 is developed by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). This means that the protocol is backed by the expertise of two of the world’s leading standards organizations.
• Because of its scalability and high potential for future growth, EV software and hardware providers are thus interested in making their solutions ISO 15118-compliant.
• The latest version of ISO 15118 is ISO 15118-20. This version includes several improvements, such as V2G support, improved security, and better interoperability.