What is the difference between OCPP and OCPI?

Open Charge Point Protocol (OCPP) and Open Charge Point Interface (OCPI) are two widely used protocols in the electric vehicle (EV) charging industry. While both aim to facilitate interoperability and communication between charging stations, they have distinct differences in terms of their scope, architecture, and functionalities. In this article, we will delve into the in-depth technical details of OCPP and OCPI to understand these differences.

OCPP: Enabling Communication Between Charging Stations and Point-of-Access Systems

OCPP is a widely adopted protocol that allows charging stations and backend systems, commonly known as Charge Point Operators (CPOs), to communicate with each other. It defines a standard set of messages and procedures for exchanging information related to charging sessions, authentication, monitoring, and diagnostics. This standardized communication helps ensure compatibility and interoperability between different charging station models and backend systems from various vendors.

OCPI: Enabling Communication Across Different Charging Networks

In contrast, OCPI focuses on enabling communication between different charging networks or CPOs. Its primary goal is to establish a common framework for sharing essential information, such as charging tariffs, availability, and capacity of charging stations, across different networks. OCPI facilitates the roaming capability, allowing EV drivers to access charging stations connected to networks other than their home network. This interoperability promotes the growth of EV adoption by providing a seamless charging experience irrespective of the charging network being used.

Differences in Architecture and Functionality

The architecture of OCPP is typically client-server based, where charging stations act as clients and the backend systems function as servers. The protocol supports both SOAP and JSON over HTTP/S as transport mechanisms for message exchange. OCPP provides functionalities like start/stop charging, authorize users, retrieve charging history, and configure charging station settings. It offers flexibility through optional features and support for custom vendor-specific extensions.

On the other hand, OCPI follows a peer-to-peer architecture between different CPOs, allowing direct communication without being dependent on a centralized server. The OCPI messages are exchanged using Representational State Transfer (REST) via HTTP/S. OCPI primarily focuses on essential functionalities like retrieving availability information, reserving charging sessions, initiating payments, and accessing charging station details across multiple networks. It emphasizes simplicity and ease of implementation.

In conclusion, while both OCPP and OCPI serve as important protocols in the EV charging ecosystem, they address different aspects of interoperability. OCPP primarily focuses on communication between charging stations and backend systems within a network, whereas OCPI enables communication between different charging networks or CPOs. Understanding these differences is crucial for industry stakeholders to choose the appropriate protocol based on their specific requirements and goals.