If you are fitting a V2C Trydan charger with dynamic power control, you need a meter to tell it how much the house is drawing. And here is an answer that catches almost everyone out: the newer model does not work.
What to buy, briefly
| Model | Does it work? |
|---|---|
| Shelly EM (classic) | Yes — documented integration, single-phase |
| Shelly 3EM (classic) | Yes — for three-phase installations |
| Shelly EM Gen3 | No — outside the integration |
If you are about to buy, that is the summary. What follows explains why — worth understanding before somebody tells you “it’s newer, it must be better”.
Why the new one fails and the old one works
The key is something easily missed: the Trydan’s integration does not speak “Shelly” in the abstract. It is written to read one specific model, at its specific endpoint.
The classic EM and the Gen3 look alike in the box and do the same job, but inside they differ:
| Classic EM | EM Gen3 | |
|---|---|---|
| API | First generation | Second generation (RPC) |
| Web interface | 192.168.33.1 | Different |
| Configuration | Wi-Fi mode menu | Another structure |
The charger asks for an address that on the Gen3 no longer answers the same way. It is not that the Gen3 is worse: the integration was written against the other API.
This is exactly the kind of incompatibility you cannot spot on a product page, because on paper both “measure consumption over Wi-Fi”.
What about MQTT?
The Trydan also supports MQTT for dynamic control, and the EM Gen3 speaks MQTT. In theory an advanced user could publish the readings that way and make it work.
But that is building it yourself, not picking “Shelly meter” from a dropdown. If this is an installation for a client, think about who maintains it in two years.
Where the clamp goes
The minimum is one 50 A clamp on the main line, so the charger knows the household draw and can modulate without tripping the breaker.
The second clamp is optional, and it is the one that opens the interesting possibility: reading solar production and charging on surplus. With PV, that clamp is the difference between charging the car and charging it for nothing.
Where each one goes is in how to measure your solar self-consumption with the Shelly EM.
The network: where it fails in practice
Both units must sit on the same household Wi-Fi. Not on the charger’s isolated network: hang the Shelly off that and the Trydan will not find it.
Two recommendations that head off most of the follow-up calls:
- A fixed IP for the Shelly. The charger looks it up by address. If the router changes it after a power cut, dynamic charging stops working without a word — and nobody connects the two events.
- Avoid mesh systems and repeaters between them. An extra hop adds latency and dropouts, and dynamic control needs steady readings to modulate properly.
If the garage has poor coverage — as it usually does — sort that first: see extending Wi-Fi coverage and building a backup network.
From the console you can see the meter’s connection history, which is where you check whether dropouts are why dynamic charging behaves erratically.
Installation by a qualified person. An EV charger carries its own protection and its own cable sizing.
How to use both, section by section: mobile app manual and web console manual.