The world of EV charging infrastructure often feels like an alphabet soup; OCPP, OCPI, ISO 15118, OSCP. They sound more like sci-fi droids than anything to do with parking basements or power bills. But these acronyms matter. They are the invisible communication layer that determines whether a charger works reliably, whether a driver can pay smoothly, whether roaming is possible, and whether your building's power supply stays stable at 7pm. If charging hardware is the muscle of the EV transition, then communication protocols are the nervous system.

This guide breaks down the key EV infrastructure communication protocols with a focus on what they mean in practice for Singapore's built environment.

TL;DR - the cheat sheet of the EV ecosystem

• ISO 15118 - The car talking to the charger
• OCPP - The charger talking to the management software
• OCPI - One charging network talking to another
• OSCP / OpenADR - Charging systems talking to the power grid

Together, these protocols make charging smart, scalable, and interoperable. When an EV plugs in, behind the scenes, several conversations occur almost instantly: Is this car allowed to charge? How much power is available right now? How much should this session cost? Who records the data? Who gets paid? Each of these questions is handled by a different protocol.

1. ISO 15118: the digital handshake (Vehicle to Charger)

Traditionally, EVs and chargers communicated using very basic signals. ISO 15118 changes that by enabling a secure, digital conversation between the vehicle and the charger. This is what makes Plug and Charge possible - where the charger recognizes the car, validates the payment contract, and starts the session automatically.

As EV adoption scales in high-density environments like condominiums, offices, and malls, simplicity matters. Reducing user friction reduces support tickets, queueing, and misuse. The latest standard, ISO 15118-20, also enables Vehicle-to-Grid (V2G), allowing EVs to discharge energy back to the grid or building, turning parked cars into flexible energy assets during peak demand periods.

2. OCPP: the command centre (Charger to Management Software)

The Open Charge Point Protocol (OCPP) connects each physical charger to a central Charging Station Management System (CSMS). Through OCPP, operators can see whether a charger is online or offline, monitor faults and session status in real time, push firmware updates remotely, and restart or reconfigure chargers without site visits. In practice, OCPP is what separates managed infrastructure from expensive hardware sitting in the dark.

OCPP 1.6J is still the most widely deployed today. OCPP 2.0.1 and 2.1 offer stronger security, richer data, and native support for advanced features like Plug and Charge.

3. OCPI: the roaming bridge (Network to Network)

OCPI (Open Charge Point Interface) allows different charging networks to talk to each other. If you are a subscriber to Network A but find yourself in a parking lot owned by Network B, OCPI is what allows Network B to recognize you, authorize the session, and send the bill back to your home provider. Without OCPI, drivers would need a different app for every network. Singapore's charging ecosystem is multi-operator by design. Roaming reduces app clutter, increases charger utilisation, and supports a more unified national charging experience.

4. OSCP and OpenADR: grid guardians (Charging Systems to Power Grid)

When dozens of EVs plug in after work, the local electrical infrastructure feels it - especially in mixed-use developments where air-conditioning, lifts, and lighting are already drawing power. OSCP (Open Smart Charging Protocol) and OpenADR allow charging systems to communicate with grid or building energy systems. This enables dynamic load management, throttling charging speeds when the grid is stressed, and shifting charging to off-peak hours automatically. Instead of triggering costly upgrades or risking outages, charging becomes grid-aware.

How These Protocols Work Together

A modern charging session often looks like this: ISO 15118 authenticates the vehicle; OCPP reports charger status and controls the session; OCPI enables access through a third-party app; OSCP adjusts power draw based on site capacity. Each protocol has a specific role. Together, they create a system that is flexible, secure, and future-ready.

FAQ

Q: Do I need all these protocols? Not always. But most public or semi-public deployments will require at least OCPP, and increasingly OCPI. ISO 15118 becomes important for premium user experience and future energy services.

Q: Can one charger support multiple protocols at the same time? Yes. A modern smart charger typically uses ISO 15118 to talk to the car and OCPP to talk to the backend simultaneously.

Q: What is the risk of ignoring protocols? Vendor lock-in, limited roaming, poor scalability, and expensive retrofits later.

EV infrastructure is no longer just about hardware. It's about how well your systems communicate with vehicles, with users, with other networks, and with the grid. Eigen Digital helps operators navigate this protocol landscape by building software that is standards-based, interoperable, and designed for real-world constraints in markets. If you're planning your next EV charging project and want confidence that your infrastructure will still work five years from now, understanding the communication layer is the right place to start.