ISO 15118 – the communication standard between bus and charger

ISO 15118 is a set of international standards that define how electric vehicles communicate with charging infrastructure. It simplifies daily operations, enhances safety, and enables smart fleet management as well as integration with the city’s energy grid. A shared “language” between the vehicle and the charging station improves efficiency and coordination.

Just like in a foreign language: to understand each other, you need to speak the same dialect and follow the same rules. Thanks to this, the entire charging process—from connection, through automatic authorization, to intelligent power control—can happen without any driver interaction. ISO 15118 defines what secure and automated “negotiation” between devices should look like.

Charging and communication

ISO 15118 standardizes communication between the vehicle and charging station using PLC (Power Line Communication) technology, which transmits data over the power line. While it’s commonly said that data is sent “through the same wire,” in reality, during DC charging, separate conductors are used for power (+ and -) and communication (CP, PP, PE). This physical connection allows the vehicle to “introduce” itself to the charger, and data is exchanged without additional cables or wireless networks.

What exactly does ISO 15118 define?

1. Handshake – initial exchange of information

Once connected, the bus and charger determine if they “speak the same language” and jointly define:

• charging mode (AC/DC),
• available power,
• operational parameters (battery level, desired charging end time, need for power limitation).

2. Plug & Charge – vehicle authorization
The bus can send a digital certificate—a kind of electronic ID key (known as Plug & Charge)—to the station. The charger verifies it against a list of trusted devices. If verified, charging begins automatically—no RFID cards, apps, or codes needed. The entire process is encrypted, much like online banking.
Note: Plug & Charge is a relatively new technology and not mandatory for ISO 15118 compliance. It is currently more common in passenger vehicles.

3. Smart control and management
Throughout the charging session, the vehicle and charger continue exchanging data:

• adjusting power output in real time,
• ending the session when target parameters are reached,
• reporting data to operator or depot systems.

4. Vehicle to Grid (V2G) – bidirectional energy flow
In the latest version of the standard (ISO 15118-20), a bus can not only charge but also return energy to the grid. This function supports grid stability and helps balance power demand, e.g. during peak hours.

Why does it matter?

ISO 15118 increases user convenience while standardizing and automating communication between bus and charger. It enables:

• precise and secure vehicle identification,
• interoperability between different vehicles and chargers, regardless of manufacturer,
• simplified daily operations in depots,
• integration with smart energy grids.

This is a standard that truly supports the development of modern public transport—automated, secure, and ready for the challenges of the future.