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Charge workflow

Chargeboxes that implement the OCPP protocol must follow a strict workflow to start and stopped charges. Charges can be started locally o remotely.

Local charges are initiated when the chargebox reads an RFID value and asks permission to the OCPP server.

Remote charges are initiated by the server that sends a request to the chargebox to enable a specific connector.

note

Every charge is associated with an ID tag, a string that is used by the chargebox to easily distinguish one charge from another. In local charges this ID tag is the RFID value read by the chargebox's reader. In remote charges the ID tag is generated by the server and sent to the chargebox in the first step of the remote workflow.

Local charges#

Here is described the workflow of a local charge:

  1. The user shows the RFID card to the chargebox's reader
  2. The chargebox sends a request to the server asking if the given RFID is valid for starting or stopping a charge
    • If the server replies negatively, the workflow stops
  3. The chargebox sends a message to the server notifying it that a new charge has started on a specific connector
  4. The server can reply to the chargebox with either an accepted or rejected response
    • If the server rejects the start charge message, the chargebox has to stop charging and the workflow stops
    • If the server accepts the start charge message, the chargebox will start sending periodically meter values
  5. When the user wants to stop the charge, it has to show the same RFID card used when the charge was started
  6. (Same as 2.) The chargebox sends a request to the server asking if the given RFID is valid for starting or stopping a charge
    • If the server replies negatively the workflow stops
  7. The chargebox stops charging and sends a message to the server notifying it that the charge has finished

Remote charges#

Here is described the workflow of a remote charge:

  1. The server sends a request to the chargebox asking if it can start a charge on the given connector
  2. The chargebox replies with an accepted or rejected message
    • If the chargebox reject the message, the workflow stops
  3. The chargebox starts charging
  4. The chargebox sends a message to the server notifying it that a new charge has started on a specific connector
  5. The server can reply to the chargebox with either an accepted or rejected response
    • If the server rejects the start charge message, the chargebox has to stop charging and the workflow stops
    • If the server accepts the start charge message, the chargebox will start sending periodically meter values
  6. When the server wants to stop a charge it sends a request to the chargebox asking if it can stop a charge on the given connector
  7. The chargebox replies with an accepted or rejected message
    • If the chargebox reject the message, the workflow stops
  8. The chargebox stops charging and sends a message to the server notifying it that the charge has finished

Remote reservation#

Here is described the workflow of a remote reservation:

  1. End user choose to reserve the chargebox to start the charge in second time.
  2. In the time of reservation the connector choosen on the chargebox can't be used. It seems occupied.
  3. End user can choose to start the charge, or to leave the reservation free or the last option the reservation expire.
  4. I the end user decide to start the charge the workflow is this one:
    1. The server sends a request to the chargebox asking if it can start a charge on the given connector
    2. The chargebox replies with an accepted or rejected message
      • If the chargebox reject the message, the workflow stops
    3. The chargebox starts charging
    4. The chargebox sends a message to the server notifying it that a new charge has started on a specific connector
    5. The server can reply to the chargebox with either an accepted or rejected response
      • If the server rejects the start charge message, the chargebox has to stop charging and the workflow stops
      • If the server accepts the start charge message, the chargebox will start sending periodically meter values
    6. When the server wants to stop a charge it sends a request to the chargebox asking if it can stop a charge on the given connector
    7. The chargebox replies with an accepted or rejected message
      • If the chargebox reject the message, the workflow stops
    8. The chargebox stops charging and sends a message to the server notifying it that the charge has finished

Conclusion#

Starting and stopping charges can take time, especially those made on a car because the chargebox tries to establish a communication with the veichle through the cable.

So when the server sends a remote start charge and the chargebox accepts it, it might take some seconds before the chargebox sends a start charge confirmation. The same goes in local charges after the user has shown the RFID card to the reader.