EV charger without internet: M2M SIM card

Why a charger needs internet

A charger communicates with the management system via the OCPP protocol (the open communication standard for chargers). Thanks to this link:

• users can start and stop charging in the app, and the property manager can grant or revoke access remotely,
• energy readings from every session reach the system and are assigned to a specific user and unit,
• the property manager can see charger status, session history and billing reports,
• dynamic load management works, as do remote diagnostics and charger restarts without a service visit.

Three ways to connect a charger

• Network cable (Ethernet) — the most stable connection, if the site’s network is nearby. In an underground garage, however, it means running a cable, often across several floors.
• Wi‑Fi — convenient at home, but in a garage concrete slabs and walls usually dampen the signal, and the connection can be unstable.
• M2M SIM card (LTE) — the charger connects via the mobile network, independently of the building’s internet. There is no need to run cables or use the housing community’s network.

How an M2M SIM card works

M2M (machine-to-machine) is a SIM card designed for communication between devices rather than phones. It is fitted in a charger with an LTE module or in a router to which the chargers are connected. The card transmits only the data the system needs to operate, so it uses very little data.

Connectivity via an M2M card is separated from the building’s network. The housing community does not need to share its internet or passwords, and a network outage in the building does not affect charging or billing.

LTE coverage in an underground garage

Mobile coverage in an underground garage can be weaker than outside. Before installation, we check the signal at the installation site. If it is too weak, a router is used with an antenna routed to a spot with better reception, and the chargers are connected to it by cable.

Charger groups and SIM card costs

In the Domena Power system, the subscription is billed per group of chargers. A group consists of chargers operating at the same address and connected to the same internet network, or chargers at the same site connected via M2M IT Easy cards.

• The first M2M SIM card is included in the subscription.
• Each additional card costs 10 zł net (12.30 zł gross) per month.
• System subscription: 30 zł net (36.90 zł gross) for the first charger in a group and 10 zł net (12.30 zł gross) for each additional one, with no commission on energy.

The number of cards needed depends on the site layout and whether the chargers can share a router. We confirm the final number when preparing the quote — you can calculate the cost in the calculator below.

What happens when the connection drops

A temporary loss of connection does not have to interrupt charging. Many OCPP-compliant chargers complete the ongoing session and store the readings, then send them to the system once the connection is restored. Starting a new session via the app does, however, require a connection — which is why in a garage it is worth ensuring stable connectivity from the start rather than relying on weak Wi‑Fi.

How a charger behaves without connectivity depends on the model and its configuration. We check this before the rollout.