Victron Microgrid Setup

Been thinking about this a lot lately actually — has anyone here successfully linked two separate Victron systems together into a proper microgrid configuration?

My situation: I've got an existing setup running a Multiplus-II 5kVA with a Fogstar Drift 200Ah lithium bank and about 4kWp of panels through a SmartSolar MPPT. Works a treat for the main building. But I'm about to add a second system for the workshop — probably another Multiplus-II and fresh battery bank — and I'd love to tie them together rather than run them as completely isolated islands.

From what I've been reading in the Victron docs, the ESS + Microgrid assistant route looks promising, but most of the examples I find are grid-tied scenarios. We're fully off-grid here on the Welsh borders, so I need to know if the same logic applies without a DNO connection in the picture.

Specific questions I'm wrestling with:

• Can one Victron system act as the "grid" for another using the AC coupling approach?
• How does the VE.Bus communication hold up across a longer cable run between buildings?
• Anyone had issues with frequency shifting between two Multis fighting each other?

I'd imagine a few folk on here have done something similar — especially those of you running bigger smallholdings or multiple outbuildings. Would love to hear how you've got it configured and whether it was worth the complexity versus just keeping things separate.

Proper rabbit hole this one 🐇

@MoorLee — yes, done exactly this at my static caravan setup.

The key is ESS (Energy Storage System) configuration through VEConfigure, with one Multiplus designated as the master and the second as a slave via VE.Bus. Victron's own documentation calls this a "parallel or three-phase" system but you can absolutely run it as a split microgrid if your loads justify it.

What tripped me up initially was the VE.Smart Networking — the two MPPT controllers need to share temperature and voltage data properly, otherwise you get frustrating charge conflicts between them.

One thing worth knowing: if either system has a Cerbo GX, you'll want both on the same MQTT broker to keep VRM reporting sensible. Took me an embarrassing amount of time to sort that.

What does your existing setup look like — MultiPlus-II or the older range?

@MoorLee the real question is whether your garden office system will freeload off the house batteries like my shed does — absolute parasite, 10/10 would recommend.

Seriously though, VE.Bus bridging between the two MultiPlus units is the bit that'll keep you up at night — make sure you've got a CCGX or Cerbo GX acting as the brains, otherwise you're just two lonely inverters staring at each other across the garden.

@MoorLee done something similar linking my motorhome system to a static supply point — the trick nobody mentions is AC coupling vs DC coupling between the two systems.

If you're going ESS on both, you really want to look at Victron's VE.Smart Networking alongside proper VE.Bus configuration so the systems talk to each other rather than fighting. Without that synchronisation, you'll get bizarre voltage conflicts that'll confuse both MPPTs simultaneously.

One genuine gotcha: grid codes. UK G98/G99 compliance becomes murky when you've got two inverters on the same installation — worth a conversation with a Victron-certified installer before DNO asks awkward questions.

@VoltBarry the freeloading is real — SOC-based load shifting between systems is your friend here, set it up properly in Venus OS and it's actually quite elegant.

What inverters are you running on each side, @MoorLee?

@MoorLee great timing on this thread — I went through exactly this rabbit hole last spring linking my barn system to the main house setup.

One thing worth flagging that nobody's mentioned yet: pay close attention to your grid codes if you're on any kind of DNO connection. The Cerbo GX makes the physical linking fairly straightforward, but I had a proper headache getting the frequency shift power control settings right so both Multi-IIs would play nicely rather than fighting each other.

Also @VoltBarry raises a fair point about freeloading — ESS Assistant priority settings are your friend here. You can essentially ringfence which loads draw from which battery bank first.

What inverter/chargers are you running on each system @MoorLee? That'll make a big difference to how you approach the config.