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ISO 15118 and OCPP 2.0: The dream team for Smart Charging?


November 11, 2021

In the past months, Charge Point Operators (CPO), electric fleet managers, and electric utilities have been increasingly reading about ISO 15118, which specifies the communication between an electric vehicle charging station and an electric vehicle (EV). The energy market hopes that the industry-standard ISO 15118 will provide a bi-directional digital communication standard based on the internet protocol. has summarized essential applications of ISO 15118 and has analyzed the effect on Smart Charging use cases (V1G and V2G).

ISO 15118 is "more" than user authorization and a “security layer”

ISO 15118 provides a Plug & Charge mechanism that has already been well described by Hubject and has-to-be. It represents an identification and authorization mode, where the EV driver and user of the EV charging station can plug his electric vehicle into the charging station (EVSE) without any additional user authorization (RFID card or mobile app). Imagine a driver of a combustion car using the gas station without any credit card! Car manufacturers and charging station producers apply a similar concept of the World Wide Web called Public Key Infrastructures (PKI). Both sides are authenticating themselves through a Public Key Infrastructures (PKI) model. That's one significant advantage of ISO 15118.

However, ISO 15118 is not just limited to the authentication of users and to encrypt messages (although this is a significant improvement). Equally important is that ISO 15118 enables EV and charging stations to transfer energy data between each other. Accurate energy data from the EV allows the central software systems to make better decisions for concepts of load management (also called Smart Charging).

More data leads to better Smart Charging

Smart Charging describes different concepts of controlling the charging process of EVs. One significant technique is to reduce peaks for the charging networks to avoid high charging costs (demand charges).

ampcontrol smart charging electric vehicle

To control the amount of energy that an EV may draw from a charging station, it is necessary to have some form of vehicle to grid communication. With ISO 15118, the car sends the State of Charge of its battery (energy amount that is left in the battery) to the charging station. Energy Management Systems now  know the actual requested energy amount (kWh) of each vehicle and can specify the Smart Charging output. With this improvement, a Smart Charging system avoids three major mistakes:

  • Empty cars: Charge the vehicle with insufficient energy amount
  • Inefficient optimization: Plan too much energy for a car and block other charging eventsPlan too much energy for a car and block other charging events
  • Complicated workarounds: Use time-consuming alternatives to access the described information

ISO 15118 needs OCPP 2.0

However, once the vehicle sent the energy data to the charging station, the CPO still needs to get the data somehow to the central charging management system (CMS). The majority of charging stations nowadays support OCPP. Open Charge Point Protocol (OCPP) is a protocol for communication between an EV charging station and a central back-office system. Similar to many IoT protocols, OCPP describes the messages that charging stations and IT backend send to each other to authenticate new EV users, track energy meter values, or give charging commands.

Most charging systems either run on OCPP 1.5 or OCPP 1.6. Luckily, the newer version (1.6) already has major Smart Charging functionalities that allow the CPO to send charging schedules (load profiles) or charging limits from the backend to the charge point. OCPP 1.5, however, only allows us to start or stop a charging process.

Unfortunately, very few hardware manufacturers have provided updates on newer version OCPP 2.0 in the past. This new version has a significant improvement that allows sending the requested energy amount (= kWh that the vehicle wants to charge) from the charge point to the central charging system.

With ISO 15118 and OCPP 2.0, the vehicle sends the requested energy amount (=absolute state of charge in kWh) to the charge point, and the charge point forwards this information to the backend system. The Smart Charging functionality uses this precise and accurate information to plan the charging event correctly.

ISO 15118 and OCPP 2.0

No Smart Charging without OCPP 2.0 and ISO 15118?

Three techniques make it possible to implement Smart Charging without OCPP 2.0 and ISO 15118:

First - Although, OCPP 1.6 doesn't send the requested energy amount as an absolute value, it allows to send a State of Charge (SoC) that represents the current state of the vehicle's battery in percentage (State of Charge = 80% means that 20% of the battery needs to be charged with electric energy).

Second - It is often possible for vehicles to send data themselves to cloud-based systems. Either through APIs provided by OEMs or additional data logging hardware. Both are very useful for fleet managers that own vehicles (FedEx or USPS).

Third - Nearly every charging system has a user interface (mobile app) that allows the user to send information to the central charging management system. The CPO can easily add a few fields for the user to select, before starting the charging process.

Although, smart charging can already be accomplished without OCPP 2.0 and ISO 11158 for most scenarios, having both will take Smart Charging to a whole new level of intelligence. You can compare this with the invention of the World Wide Web when computers could suddenly exchange information. It's now time for CPOs, fleet managers, and utilities to implement Smart Charging with available infrastructure to reduce energy costs, avoid investments, and charge clean energy.

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