Version 1, 2024-02-06
Author: Klaudia Kostogłód

Introduction
With the rapid growth of the electric car market, power management issues at chargers are becoming
increasingly important. The efficiency of the charging process, the optimal use of the available power
and the speed at which the vehicle is charged are key issues that affect the user experience and the
development of the charging infrastructure. This document shows how to manage the available
charging current remotely based on the load value of the connection.

The issue and Enelion solutions
Enelion Lumina does not send information about the total load of the power connection in its
messages. Such a measurement for Lumina chargers is able to be made by the Enelion Energy Guard,
which measures the total current and voltage for each phase. The EEG sends these messages to the
Lumina over the mesh network or via the CAN bus, depending on the configuration.
OCPP 1.6 allows the sending of MeterValues messages, containing measurements of values such as
available power, voltage, or current, for a selected connector. The MeterValues for connector 0
(hereafter referred to as MeterValues(0)) represents the measurement for the entire connection and
is sent from the EEG. In the case of the Enelion Energy Guard, only two values can be sent via
connector 0. These are CURRENT.IMPORT and VOLTAGE.

With Enelion Energy Guarda, the Enelion Lumina station, and the OCPP backend, you can measure and
send connection data to the system using cloud-based power management. The communication
follows the diagram below :

1. The EEG measures the current at the main connection, so it has information on VOLTAGE and CURRENT.IMPORT.

2. CURRENT.IMPORT and VOLTAGE values are transmitted by the EEG to the Enelion Lumina station.

3. Lumina sends these values to the backend via OCPP MeterValues messages.

4. The backend system, knowing how much current is available, can limit the current to the charging stations via

cloud-based load management, e.g. using the OCPP SmartCharging module's SetChargingProfile

and ClearChargingProfile messages.

Fig. 1: Schematic of the communication between Enelion devices and the OCPP backend.

Technical implementation of the solution

The MeterValues(0) message is sent in two cases :

1. If the OCPP backend sends a TriggerMessage(MeterValues) without specifying a particular connector.

2. Cyclically, according to the OCPP ClockAlignedDataInterval key, which specifies every how
many seconds such a message should be sent. Sending zero will result in MeterValues
messages not being sent at all.

MeterValues will be sent provided the EEG is visible on the network - if it is not, or if 10 minutes have
passed since it was disconnected, the message will not be sent.

What do I need to configure in OCPP to get this message?
Apart from physically connecting the EEG, you need to make sure that the ClockAlignedDataInterval
key is different from zero and set it to the interval you want this message to be sent. The MeterValues
for each connected connector will also be sent during the same interval, but only connector 0 has
messages from the EEG. The others are measurements directly from the Lumina.
In addition, make sure that the MeterValuesAlignedData key contains the measured values
CURRENT.IMPORT and/or VOLTAGE. These are the only measured values that the EEG can measure
and if they are missing from the key, the MeterValues(0) message will not be sent.

What is the de facto value that MeterValues(0) measures?
The Lumina records the last measurement it got from the EEG and this is the measurement that is sent.
This means that in case of interference or loss of connection, the measurement value may be
overdone. The Enelion Energy Guard sends its measurement every 1 second, but in a congested
network some packets may arrive with a delay of several seconds. Setting the
MeterValuesAlignedData key to a low value will cause all chargers to send this message at the same
time, which can lead to further network congestion. In the event of an EEG failure, the Lumina will only
recognise that it has lost connection to the EEG after 10 minutes, meaning that it will transmit
MeterValues(0) with the value of the last recorded measurement for 10 minutes.