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E-Mobility Fundamentals — OCPP

Knowing the EV charging industry complexity, I thought it would be a good idea to launch a series of blog posts on e-mobility fundamentals. The articles are to shed light on some of the topics that may not necessarily be clear to EV geeks!

In the first post, I introduced eMSP and CPO and their functions in the e-Mobility ecosystem. Today I will introduce a communication protocol that solve an interoperability problem between the involved parties in the EV charging.

What is a protocol & Why we need one?

While you are reading this post, there are many communication protocols working behind the scene to deliver this content to your screen. There are at least 35 different standard protocols in use on a day-to-day basis to help manage traffic on the internet. HTTP, TCP, SSH and SMTP are some examples.

The electric charging industry is no different from networks and internet. We need to have standards and protocols to enhance the interoperability between the charging parties. let’s get to know a well established one. The open charge point protocol OCPP.

What is OCPP?

The Open Charge Point Protocol (OCPP) is an application protocol for communication between electric vehicle charging stations and a central management system. It is an international, open-source, vendor-independent standard which is available for free.

The protocol was developed by the Open Charge Alliance (OCA) for the EV infrastructure market, and is considered the de-facto standard for charging infrastructure interoperability among charging equipment manufacturers, software and systems providers, charging network operators and research organizations.

Here are some use cases the OCPP supports: Booting, configuration and resetting an EVSE; EV and EV driver authorization; Charging transaction management.

The latest version, OCPP 2.0.1, was released in April 2018.

Why to use OCPP?

As the EV charging market evolves and hardware and software technologies advance, connectivity is critical. OCPP compliant e-Mobility service providers (eMSPs) have the freedom to choose from a wide variety of charging hardware and software necessary (eliminates vendor lock-in) to serve different EV charging use-cases, allowing EV charging providers to be completely technology agnostic.

Furthermore, OCPP 2.0.1 support for vehicle-to-grid (V2G) communications increases the possibilities for and potential of two-way charging.

Technical Overview

In this section, we will dive into the system architecture and how OCPP can be used as a communication mean. OCPP protocol is about transferring specified messages between clients (Charging Station) and server (Central System) over WebSocket connection.

The data passing over WebSocket can be formatted in 2 formats: Simple Object Access Protocol (SOAP) or the JSON (JavaScript Object Notation. Architecture for a baseline OCPP system would look like this:

OCPP system where only Charging Stations and Central System can communicate with each other isn’t very practical. EV drivers need to be able to interact with Charging Stations e.g. to remotely start and stop a charging session. To facilitate this, we should add an interface that EV drivers can access (via mobile app) and which in turn will communicate with the backend system . Let’s say this interface is a REST API. Now our OCPP system architecture looks as follows:

I hope this brief introduction is enough to get to know OCPP and its importance. In the future posts, we will discuss more technical details about OCPP as well as other protocols in the market.



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