Understanding the Meter Values Message in the OCPP Protocol

The Open Charge Point Protocol (OCPP) is an application protocol used for communication between electric vehicle chargers and a central back office system. One of the use cases of OCPP is the “Meter Values” message, which provides important information about the charging session.

In the context of OCPP, a typical “Meter Values” message would include the following data:

• connectorId: The ID of the charging point’s connector.
• transactionId: The ID of the current charging session.
• meterValue: An array of objects containing detailed information about each sample taken during the charging session.
• timestamp: The date and time when each sample was taken.
• sampledValue: An array of objects representing the sampled value, including the actual value, context, format, measurand, location, and unit.
• context: A string that describes when the measurement was sampled, such as periodic sampling, start of a new session, or end of a session.
• measurand: A string that represents the form of the measurement. For example, “Energy.Active.Import.Register” signifies total energy consumption.
• unit: The unit of the measurement. In the given example, the unit is Watt-hours (Wh).

By sending the “Meter Values” message to the central system, the charging station notifies the system of the relevant information about the charging session, including the energy consumption.

The “Meter Values” message is just one example of the data exchange that occurs between electric vehicle chargers and the central back office system using the OCPP. This protocol ensures seamless communication and management of charging sessions, enabling efficient monitoring and control of electric vehicle charging infrastructure.

A use case example of the “Meter Values” via OCPP could be something like this:

{
    "connectorId": 1,
    "transactionId": 7777,
    "meterValue": [
        {
            "timestamp": "2022-01-01T12:30:00Z",
            "sampledValue": [
                {
                    "value": "20.5",
                    "context": "Sample.Periodic",
                    "format": "Raw",
                    "measurand": "Energy.Active.Import.Register",
                    "location": "Outlet",
                    "unit": "Wh"
                }
            ]
        }
    ]
}