Victron smart meter with Fronius AC coupled system

Been thinking about this a lot lately as I'm planning an expansion to my shepherd's hut setup, so figured I'd start a discussion.

Anyone here running a Fronius Primo AC-coupled with a Victron Multiplus? I've been looking at adding a Fronius on the AC output side alongside my existing Victron MPPT, and the metering side of things is giving me a headache.

Specifically — does the Fronius Smart Meter TS 100A play nicely within the Victron ecosystem when you're not grid-tied in the traditional sense? I know Victron's own Energy Meter works natively with GX devices, but I've seen some builds using the Fronius meter and getting decent results pulling data through into VRM.

My current setup is a Multiplus-II 48V with Fogstar Drift lithium, and I want to add a Fronius Primo on the AC output for the extra generation capacity. The frequency shifting for charge control (the 50.2–51.8Hz method) seems straightforward enough, but I'm wondering:

• Does the Fronius Smart Meter cause any conflicts with how the Multiplus reads grid vs. load vs. generation?
• Would you bother with the Fronius meter at all, or just stick with a Victron-native meter?
• Anyone had issues with Fronius firmware updates breaking the Victron integration?

There seems to be precious little UK-specific experience documented on this. Most of the threads I find are Australian or German installs where the grid situation is quite different to what we're dealing with here.

Would be good to hear from anyone who's actually got this running — particularly off-grid or ESS setups rather than pure export-to-grid.

Running almost exactly this on my static caravan. Fronius Primo feeding back into a Victron Multiplus II, with the ET112 smart meter on the grid side doing the magic 🧙

The ET112 is honestly the bit everyone forgets about until nothing works properly. Without it the MPPT assistant on the Multi has no idea what Fronius is producing, so you end up with the batteries getting absolutely hammered for no reason.

One gotcha — make sure your VE.Bus System Configurator settings match your Fronius's frequency shift thresholds. Took me an embarrassing number of evenings to figure that one out.

@24VGeek what size Primo are you looking at? The 3.0 is a sweet spot for most hut setups without falling foul of the 1:1 rule drama.

@24VGeek worth being precise here — the ET112 is a single-phase meter, fine for most shepherd's hut setups, but if you're ever adding a second phase later, you'll want the ET340 from the off.

The key thing people miss with Fronius AC coupling is getting the frequency shift settings right in VenusOS. Victron's implementation uses frequency to throttle the Fronius when batteries are full — if that's not configured properly you'll either overcharge or waste solar.

Also make sure your Fronius firmware is current. Older versions had quirks with the frequency response that caused instability.

@DustyCaptain — does your ET112 sit on the grid side or between the Multiplus and Fronius? Placement genuinely matters for how the DVCC handles things.

Running a similar setup on my cabin, took me longer than I'd like to admit to get the meter placement sorted correctly.

Really important point that seems to get glossed over in these discussions — the frequency shifting relationship between the Fronius and Multiplus II is doing the heavy lifting here, not just the metering. The ET112 is telling Victron what's happening, but it's the 50-52Hz frequency signal that actually curtails the Fronius when batteries are full.

On my narrowboat setup I had endless grief until I properly configured the PowerControl settings in VEConfigure — specifically the AC input current limit interacting with the Fronius output. Worth checking your ESS Assistant version too, as older firmware had some quirky behaviour around grid setpoint with AC-coupled PV.

@DustyCaptain did you position your ET112 on the grid side or between the Fronius and the Multiplus? Placement genuinely changes how ESS calculates self-consumption, and I've seen people wire this incorrectly and wonder why their feed-in reporting looks wrong.

@ForestBoater is absolutely right to flag frequency shifting — that's the beating heart of the whole AC-coupled arrangement. Worth adding some practical detail though: the Fronius Primo needs to be configured with the correct MG50 or island mode firmware to respond properly to the Multiplus II's frequency signal. Without it, the Fronius won't curtail output when the batteries are full, and you'll get voltage rise issues that trip the whole system offline.

On my narrowboat I run a Multiplus-II 24/3000 and had to manually configure the Fronius frequency response curve in the inverter settings — the defaults aren't aggressive enough for a small battery bank. Also double-check your ET112 is on the AC-in side, not AC-out. Seen plenty of installs where that's wired wrong and VRM shows completely nonsensical data.