The EV Charging Ecosystem

The Electric Vehicle (EV) charging ecosystem is a complex network of hardware, software, and stakeholders. As a developer, understanding these relationships is crucial for building effective solutions.

Key Players

1. EV Driver

The end-user who wants to charge their vehicle. They interact with the charging station physically and often use a mobile app to find stations and pay.

2. CPO (Charge Point Operator)

The company that operates and maintains the physical charging infrastructure. They are responsible for ensuring the chargers are online and functioning.

• Examples: EVgo, Electrify America, Ionity.

3. eMSP (e-Mobility Service Provider)

The company that has the relationship with the driver. They provide the mobile app, RFID card, and billing services.

• Examples: ChargePoint (App), PlugSurfing, Shell Recharge.

Note: A company can be both a CPO and an eMSP.

4. CSMS (Charging Station Management System)

The software backend used by the CPO to manage their chargers. This is where OCPP lives.

• Role: Connects to chargers, monitors status, handles firmware updates, and manages transactions.

5. DSO (Distribution System Operator)

The utility company that manages the power grid. They need to know how much load the chargers are pulling to prevent grid failure.

The Protocol Alphabet Soup

OCPP (Open Charge Point Protocol)

• Link: Charging Station ↔ CSMS
• Purpose: Device management and transaction handling.
• Analogy: The "USB driver" for the charging station.

OCPI (Open Charge Point Interface)

• Link: CPO (CSMS) ↔ eMSP
• Purpose: Roaming. Allows a driver from one network (e.g., Shell) to charge at another network's station (e.g., Ionity).
• Key Features: Syncing station location data (CDR), sharing tariff information, and handling cross-network payment sessions.

ISO 15118 (Plug & Charge)

• Link: EV ↔ Charging Station
• Purpose: Advanced communication between the car and the charger.
• Key Feature: Plug & Charge. The car identifies itself securely via certificates, eliminating the need for an RFID card or app.

OSCP (Open Smart Charging Protocol)

• Link: CSMS ↔ DSO
• Purpose: Grid management. The DSO tells the CSMS how much power is available in a specific area (capacity forecast).

Where ocpp-ws-io Fits

ocpp-ws-io is a library specifically for building the OCPP link.

• If you are building a CSMS, you use OCPPServer to accept connections from stations.
• If you are building a Charging Station firmware or Simulator, you use OCPPClient to connect to a CSMS.

It handles the low-level WebSocket framing, JSON serialization, and message validation so you can focus on the business logic of managing sessions and chargers.