Would an Expandable Master/Extender Charging Station Structure Make Sense?

[Tobias9876]

Hi,

We are using an ABL eM4 charging system consisting of one master and seven extenders.
This results in 8 physical charging stations with 2 EVSEs each, providing a total of 16 charging points.
Due to the master/extender architecture, all eight physical charging stations are connected to EVtivity through a single OCPP endpoint managed by the master.
Currently, EVtivity does not provide a way to represent these physical charging stations individually.

I was wondering whether it would make sense to introduce an expandable tree structure for such configurations.
The idea would be to allow operators to mark an OCPP charging station as a master and assign its EVSEs to the master itself or to individual extenders.

Example Structure

▼ ABL eM4 Master (OCPP Endpoint)
  ├── Master Station
  │   ├── EVSE 1
  │   └── EVSE 2
  ├── Extender 1
  │   ├── EVSE 3
  │   └── EVSE 4
  ├── Extender 2
  │   ├── EVSE 5
  │   └── EVSE 6
  ├── ...
  └── Extender 7
      ├── EVSE 15
      └── EVSE 16

The master would remain the only OCPP communication endpoint, while the individual physical stations would be represented as child devices.

In the operator portal, the master could be expanded or collapsed to show or hide its associated physical stations and EVSEs.

Ideally, the individual physical stations could also be displayed separately in the driver portal, allowing drivers to easily identify the correct charging station and charging point.

This would be a feature for logical grouping and visualization, designed to support such configurations.

Would this approach make sense within EVtivity's architecture, and do you think it would be a useful addition?
If so, I'd be happy to create a feature request.

Thanks in advance!

[evtivity-admin]

Thanks @Tobias9876, this makes sense, and we would like to support it. Here is what we propose.

Physical units under one station. Each physical box, the master and every extender, becomes a unit with its own name and an optional serial number. The operator assigns each EVSE to the box it is in. Units are optional: a station without them stays as it is.

The Structure

Today EVtivity sees one station with 16 EVSEs and nothing about the boxes:

flowchart LR
  S["Station ABL-01<br/>one OCPP connection"] --> E["EVSE 1, 2, 3 ... 16<br/>(flat list)"]

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With units, the same station and the same EVSE numbers, grouped by box:

flowchart LR
  S["Station ABL-01<br/>one OCPP connection"]
  S --> M["Master"] --> M1["EVSE 1, 2"]
  S --> X1["Extender 1"] --> X1E["EVSE 3, 4"]
  S --> X2["Extender 2"] --> X2E["EVSE 5, 6"]
  S --> X3["..."]
  S --> X7["Extender 7"] --> X7E["EVSE 15, 16"]

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What It Changes

• OCPP stays as it is. The master is still one station with one connection. Sessions, billing, tariffs, commands, logs and QR codes work as today.
• CSMS. The master stays one row in the Stations list, showing how many units it has. The station's Connectors tab becomes a tree: station, then each unit, then that unit's EVSEs. Session and EVSE views name the unit, so you know which box to go to.
• Driver portal and app. Each unit shows as its own charger, with its name, EVSEs and availability. Favorites and Notify Me When Free work per unit.
• Site layout. The 3D and 2D layout draw each unit as its own charger in its own spot.
• Roaming. OCPI partners get the unit name as each EVSE's physical reference.
• Stations without units are not affected at all.

Questions

A few questions so we get your setup right:

1. How does the eM4 group appear to the backend: one charge point ID with connectors 1 to 16, or a separate charge point ID per extender relayed by the master?
2. Which OCPP version does the master use, 1.6 or 2.0.1?
3. Do the extenders share one electrical feed managed by the eM4's own load management, or does each one (or a group of them) sit on its own breaker? Our first version would limit power per station, not per unit, so this tells us whether per-unit limits are needed.
4. What label or number is printed on each box for drivers? OCPI allows 16 characters for that reference.
5. Are all eight boxes at one site?

No need to open a feature request; this discussion is enough for now.

[Tobias9876]

Thanks for the detailed proposal. This is exactly the kind of solution I had in mind. The proposed structure with physical units under one OCPP station would fit our setup perfectly.

Here are the details of our installation:

1. Charge Point ID / Connectors

The eM4 system consists of one master wallbox and seven extenders.

There is only one Charge Point ID. The master handles the OCPP connection and contains all the configuration for the OCPP backend. The extenders are essentially "dumb" devices and do not establish their own OCPP connections. They are connected to the master via our infrastructure WLAN/LAN network and are managed by it.

Currently, the backend sees one charging station with 16 connectors.

Each physical box has two charging points. The maximum charging power per box is 22 kW when only one charging point is used, or 11 kW per charging point when both are used simultaneously.

2. OCPP version

We currently use OCPP 1.6. The eM4 system supports OCPP 1.5 and 1.6, but not OCPP 2.0.1.

3. Electrical supply and circuit protection

Each physical box (master and extenders) has its own three-phase electrical connection, protected by three 32 A fuses (one per phase).

4. Physical labels / Names

All boxes are automatically numbered from 1 to 8 by the master box. Additional boxes can be added.

The master is always number 1, and new extenders are numbered consecutively when added.

For the driver portal and OCPI physical references, names such as "Box 1", "Box 2", etc. would work perfectly. These labels are well within the 16-character OCPI limit.

5. Location

Yes, all eight physical boxes are installed in the same parking lot and belong to the same site.

Thanks again for considering this feature. I think this would be a very useful addition, not just for the ABL eM4, but also for other modular charging systems using a master/extender architecture.

[evtivity-admin]

@Tobias9876 Station units are now in v0.1.52-beta.3 for testing.

What changed:

• A station can group its EVSEs into named units, one per physical box (a master and its extenders under one Charge Point ID).
• Drivers see each unit as its own charger in the portal and the app: search, the station page, favorites and Notify Me When Free.
• The 3D and 2D site layout draws each unit as its own charger, with a box number plate.
• OCPI sends the unit name as the EVSE physical_reference.
• OCPP, sessions, load management and billing stay at the station level.

The Stations list keeps one row per station and does not show the units as rows. It shows a unit count under the model. You set up and see the units on the station's EVSE & Connectors tab: Add Unit creates a unit, each unit shows as a card with its EVSEs, and Assign EVSE and Remove EVSE on the card move EVSEs in and out of it.

Please try it on your setup and share your feedback here. The stable release is planned for next week.

[Tobias9876]

Hi,

I've tested the new Station Units feature in v0.1.52-beta.3, and it looks really good!

The configuration is quick and straightforward, and assigning EVSEs to individual units works very well.
All eight physical charging stations now appear as separate chargers in the site layout, exactly as intended. The existing charging logic remains unchanged, which is great.

I have two small suggestions/questions for further improvements:
1. Additional Unit Information

It would be useful to have a few optional fields for each individual station unit in the admin interface:

• Serial Number: To uniquely identify each physical charging unit.
• IP Address: To document the network address of a unit, if applicable.

Since the master and extenders are physically separate devices, having this information available would make maintenance, troubleshooting, and asset management easier.

Both fields could be optional.
These would only be additional administrative metadata fields and wouldn't need to affect the existing OCPP communication or charging logic.

2. Dashboard Overview – Physical Charging Units

Would it make sense to also include the number of physical charging units in the main dashboard overview?
Currently, our setup of eight physical charging stations (one master and seven extenders) is still counted as just one station in the dashboard.
The number of EVSEs/charging points is already displayed correctly, so no changes would be needed there.
However, it might be useful to distinguish between OCPP stations and physical charging units in the dashboard statistics.

For example, our setup would show:

OCPP Stations: 1 (displayed correctly as Stations)
Physical Charging Units: 8
Charging Points / EVSEs: 16 (already displayed correctly)

This would provide a more accurate overview of the physical charging infrastructure without changing the existing OCPP station or EVSE counts.

What do you think about this approach?

Overall, great implementation, and thanks for adding this feature so quickly!

[evtivity-admin]

@Tobias9876 Thanks for testing and for the two suggestions. Both are in v0.1.52-beta.4, along with more unit improvements.

Your suggestions:

• Serial Number and IP Address: each unit has both as optional fields, set when you create or edit a unit. They are administrative data only and do not affect OCPP or charging.
• Charging Units on the dashboard: the dashboard shows a Charging Units count next to Stations and EVSEs while any station has units. Your setup shows 1 station, 8 charging units and 16 EVSEs.

Other unit changes since beta.3:

• CSMS: Add Unit is now Create Unit, and its dialog holds the name, serial number and IP address. Rename Unit is now Edit Unit. When you create an EVSE on a station with units, you can pick its unit in the same dialog.
• Portal and app location page: a station with units lists each unit as its own charger, so your site shows 8 chargers instead of 16 EVSEs.
• Portal and app search results: each unit row shows the box first, then the station and the location.
• Guest charging: pages show the box and port number and use the same port cards as signed-in drivers.
• Charge pages: each connector of an EVSE gets its own line.

Please give it a try and let us know how it works with your eight boxes. The stable release is still planned for next week.