This article describes the technical fundamentals of the reev EMS (Energy Management System) for dynamic load management, PV surplus charging, and grid-compatible control of charging infrastructures. It is intended for qualified electricians and operators who integrate, configure, or operate the system.
Meter and Protocol Compatibility
The reev EMS exclusively supports energy meters that communicate via Modbus TCP/IP. Meters that only operate via RS485/Modbus RTU (e.g. Carlo Gavazzi EM210) are not compatible.
The following meters are currently compatible:
TQ EM420 (also known as ABL/Kostal energy meters)
Janitza UMG604/512 PRO
Wöhner 3700
GEWISS GWD6809
Siemens PAC 2200
Topology and Integration
The reev EMS reads measurement data via Modbus TCP/IP. A Teltonika router is used as an IoT gateway for this purpose. The gateway reads phase currents and active power values directly from the energy meter.
The charging stations communicate independently via OCPP with the reev backend. There is no Modbus connection between the gateway and the charging stations.
When Is an IoT Gateway Required?
An IoT gateway is always required when dynamic load management or PV surplus charging is to be used. This applies even if the charging stations are already connected to reev via an integrated SIM card. The gateway must be on the same network as the energy meter. Merging the network with the charging stations is not necessary.
Recommended Hardware
The following Teltonika models are recommended:
Teltonika RUT241
Teltonika RUT240
Teltonika RUT300
Teltonika RUT956
Requirement: Modbus TCP and RMS support.
Note: When using a reev SIM card, no port forwarding is required. RMS should be activated with the default settings.
Import/Export and PV Surplus Charging
The reev EMS automatically detects import and export at the grid connection point. It evaluates the sign of the measured power values for this purpose. PV surplus is automatically detected and used for charging. The system accesses the phase-accurate current and power values from the energy meter.
Phase Imbalance Monitoring
A configurable phase imbalance monitor activates when loads are unevenly distributed across phases.
Germany: Up to 20 A difference permitted (default)
Austria and Switzerland: Up to 16 A difference permitted
Phase imbalance monitoring can be deactivated upon request.
PV Surplus Charging
PV surplus charging can be activated globally and responds immediately to changes in PV power. The following points should be noted:
There is currently no hysteresis. With strongly fluctuating PV power, more frequent charging interruptions may occur.
Group-based PV activation is currently not possible. The setting always applies globally to the entire infrastructure.
Note: A hysteresis function is planned for 2026.
Configuration and Operation
Grid structures can be flexibly defined in the reev EMS.
Grid Structure and Current Limits
The following configurations are possible:
Main distribution with a defined total current limit
Sub-distributions or charging groups below the main distribution
Current limits at group and charge point level
Prioritisation
Priorities can be assigned for:
Individual charge points
Users
User groups
Tip: You can configure the prioritisation of charge points, users, and user groups directly via the reev EMS dashboard in the reev Platform.
Behaviour in Case of Failure
If the energy meter stops measuring or the connection is interrupted, the TxDefaultProfile of the charging stations is automatically applied. This profile is sent via the reev EMS and determines the behaviour in case of failure:
Default for AC charge points: 6 A per charge point (charging continues at reduced current)
Alternatively, charging can be stopped completely
The default value can be adjusted upon request via reev Support.
Note: Always keep the firmware of your charging stations up to date to ensure proper operation of the reev EMS.
Commissioning
The commissioning of the reev EMS is carried out in several steps.
Tasks for the Qualified Electrician
The qualified electrician performs the following steps on site:
Install the energy meter.
Install the IoT gateway (Teltonika router).
Establish the network connection between the gateway and the energy meter.
Activate RMS on the gateway.
Tasks for reev Support
The final steps are carried out by reev Support:
Configure the gateway.
Activate dynamic load management.
Assign the energy meter in the system.
Optional: Enable the PV surplus function.
Troubleshooting
Problem | Possible Cause | Solution |
Energy meter delivers no measurement data | Network connection between gateway and meter interrupted | Check whether the gateway and meter are on the same network and the connection is active. |
Charging stations only charge at minimum current | TxDefaultProfile active (fallback mode) | Check the connection of the energy meter and the reachability of the gateway. |
PV surplus is not detected | Sign of power values incorrect | Contact reev Support to review the meter configuration. |
Frequent charging interruptions during PV surplus charging | Strongly fluctuating PV power without hysteresis | Expected behaviour. A hysteresis function is planned for 2026. |
Note: For further issues, contact reev Support.
Frequently Asked Questions
Which energy meters are compatible with the reev EMS?
The reev EMS exclusively supports energy meters with Modbus TCP/IP. You can find an up-to-date list on the reev website. Additional meters can be integrated upon request.
Do I need an IoT gateway if my charging stations already have a SIM card?
Yes. The IoT gateway is always required when dynamic load management or PV surplus charging is to be used. It reads the measurement data from the energy meter. The SIM card in the charging station is only used for OCPP communication with the reev backend.
What happens if the energy meter fails?
In case of failure, the TxDefaultProfile is automatically applied. For AC charge points, this means charging continues at a reduced current of 6 A per charge point by default. The value can be adjusted upon request.
Can I activate PV surplus charging for specific charging groups only?
No. PV surplus charging currently applies globally to the entire infrastructure. Group-based activation is not possible at this time.
Does the reev EMS also support DC charging stations?
Yes. The reev EMS is also compatible with DC charging stations. DC charging stations are controlled on a power basis (in kW) rather than a current basis.
Do I need to set up port forwarding when using a reev SIM card?
No. When using a reev SIM card, no port forwarding is required.
Who configures the reev EMS?
The hardware installation is carried out by the qualified electrician. The final system configuration (gateway, load management, meter assignment) is carried out by reev Support.