Multi rs et wallbox

Been mulling over a similar scenario for a while now, so thought I'd throw this out to the collective.

I'm running a Victron Multi-RS Solar (6kVA) feeding my garden office setup, with a reasonable PV array behind it. The question I keep coming back to is around EV charging — specifically whether it makes any practical sense to hang a 7.4kW AC wallbox off an inverter that peaks at roughly 5kW continuous output.

On paper it looks daft. The wallbox will immediately saturate the inverter and you're either throttling the car's onboard charger or tripping protections constantly. But in practice, I wonder if there's a workable middle ground:

• Type 2 EVSE with adjustable current output — something like an Ohme or a Zappi set down to 16A or even 10A keeps you within the inverter's comfort zone
• AC coupling with grid feedback — obviously not applicable in a pure off-grid context, but worth mentioning for hybrid setups
• SOC-based automation via Node-RED / VRM — only enable charging when battery is above, say, 80% and PV is producing surplus

My array is decent but UK cloud cover is a real constraint (Suffolk, so maritime weather — lots of grey days). On a dull January afternoon you might see 1–1.5kW from the panels, which makes 7.4kW wallbox talk fairly academic.

Curious whether anyone here has actually made this work long-term — particularly interested in experiences with Fogstar Drift or similar LiFePO4 banks where you've got the capacity to absorb overnight charging loads.

What's your real-world approach?

@SuffolkCruiser the Multi-RS is a cracking unit but the Wallbox integration side is where it gets interesting. I went down a similar rabbit hole for my shepherd's hut setup — ended up using the Victron GX + EVCS combo rather than the Wallbox route, mainly because the native integration just plays nicer with ESS.

Few things worth checking:

• Your grid code settings — crucial for UK DNO compliance
• Whether you're on single or three-phase (limits your Wallbox options considerably)
• The Multi-RS's AC-out current limits under inverter-only mode

The dynamic current limiting via Cerbo is genuinely useful if you want to prioritise battery over EV charging during low-sun periods. Took me ages to get the Node-RED flows right but worth it.

What's your battery capacity? That'll probably dictate whether the whole thing makes practical sense.

Ran a similar setup on the boat for a bit before I moved the EV charging ashore. The Multi-RS handles it reasonably well but I'd be cautious about assuming the dynamic current limiting will always play nicely with a Wallbox — in my experience there's a noticeable lag in the communication loop that can cause the inverter to briefly overcommit.

Worth checking your ESS assistant configuration carefully. A lot of people overlook the minimum SOC settings when EV charging is in the mix and then wonder why their batteries are hammered by morning.

What battery chemistry are you running? That'll change the conversation significantly. LiFePO4 with a decent Fogstar or similar bank gives you more headroom to play with than lead-acid, obviously, but the charge profile interaction with the wallbox protocol still needs watching.

Worth noting the Multi-RS and Wallbox will have a proper domestic marital dispute the moment your battery SOC dips — one wants to charge everything, the other wants to throttle back, and you're sat there in the garden office watching the MPPT throw a wobble on VRM like it's a drama series on BBC Four.

@OffGridGeek beat me to the marriage metaphor but mine's more like a divorce — the Multi-RS gets the house, the Wallbox gets absolutely nothing when my Fogstar 48V decides it's had enough around 4pm in February.

Curious whether anyone's actually mapped out the AC load priority order when this happens in practice — does the Multi-RS genuinely shed the Wallbox cleanly, or does it just throttle everything indiscriminately?

Running a similar arrangement on the boat and considering adding a garden office circuit, so this is directly relevant. My concern is whether the VRM portal gives you any useful real-time visibility of which load is being curtailed, or whether you're left guessing after the fact by staring at historic graphs.

Also — has anyone tried setting the Wallbox to a fixed 6A minimum as a floor to avoid the constant connect/disconnect cycling @OffGridGeek is hinting at? Wondering if that's a better compromise than letting it fight for headroom.