Anyone else running EV charging from a garden office solar setup?

Got a static caravan on the plot and I'm planning a garden office build nearby. The idea is to run both from the same off-grid system — probably a Victron Multiplus-II 48v with a decent Fogstar battery bank, maybe 20kWh to start with.

The bit I'm stuck on is whether it's realistic to occasionally charge an EV from the same system. Not talking about rapid charging — just a slow 7kW or even a 3.5kW trickle via a Type 2 lead overnight when solar production has been good and the batteries are full. The caravan already pulls a fair bit in the evenings (fridge, lights, occasional heating boost).

Has anyone actually done this? Wondering if a Victron EVCS paired with something like a SmartSolar MPPT makes sense here, or if I'm just asking for the batteries to get hammered every time a cloud goes over mid-charge. What sort of array size would you realistically need to make this work without constantly running on empty?

@HMK_Sparks this is almost exactly my setup. Running a Multiplus-II 48/5000 with a 15kWh Fogstar Drift stack, and I tapped into it for EV charging about eight months ago.

The key lesson: don't underestimate the office load + EV simultaneously. My system looked perfectly sized on paper until a grey November fortnight where I was running monitors, heating, and trying to top up the car. The Multiplus handled it fine — the solar just couldn't keep pace.

I ended up adding grid-assist via an ESS configuration, which transformed reliability. Worth planning that conduit run to a DNO connection point before you pour any concrete, even if you intend to stay fully off-grid initially.

What battery capacity are you eyeing? With a caravan in the mix I'd argue 20kWh minimum is realistic for UK winters.

Hey @HMK_Sparks, great project! One thing worth flagging that I don't think's been mentioned yet — if you're planning EV charging from this setup, have a serious think about your DC bus voltage and cable runs before you commit to placement. The distance between your battery bank and the Multiplus really does matter when you're pulling big sustained loads.

Also worth considering a dedicated EVSE rather than just a socket — something like an Ohme or even a basic 7kW unit set to charge at a lower rate overnight when the batteries are topped up. That way you're not hammering the inverter with peak draw constantly.

What size solar array are you thinking? That'll largely dictate whether EV charging is genuinely viable day-to-day or just a nice occasional bonus. 🙂

@HMK_Sparks the EV charging side is where it gets interesting. I'd seriously look at a smart EVSE that can do load-aware charging — something like an Ohme or a Zappi wired back to the Victron via its assistants. You can set a minimum SoC threshold so the car only pulls power once the battery's topped up past, say, 80%.

The trap people fall into is underestimating the panel capacity needed. EV charging is hungry even at 6A minimum draw. Size your array for the office/van loads first, then treat the car as purely surplus-only.

Also worth checking your DNO situation — even off-grid installs can get complicated if you're exporting or using grid backup anywhere on the plot.

Really interesting thread this — I'm not doing EV charging yet but I'm watching this closely because it's on the horizon for me (currently split between a boat and a shepherd's hut, both off-grid).

One thing I'd add to what @MarshChild said about smart EVSEs — has anyone looked at the Ohme units specifically in an off-grid context? I know they're designed with grid tariffs in mind but I've seen people repurposing the logic for solar-surplus charging.

Also curious whether anyone's found a neat way to prioritise loads across a split site like yours — office vs. static caravan pulling from the same Multiplus-II. Does Victron's load shedding via the BMS handle that gracefully, or does it get messy?

Would love to hear how @Drift_Geek's 15kWh Fogstar stack holds up across winter — that's my real concern before committing to anything similar.

From my shepherd's hut setup I can say the battery sizing is where most people come unstuck. EV charging even at 7kW will hammer a modest pack overnight. I'm running Victron kit with Fogstar Drift cells and even for just the hut I went bigger than I thought I'd need — glad I did.

For a combo system like yours @HMK_Sparks I'd be thinking minimum 20kWh usable, probably more. Also worth factoring in winter solar yield — I'm in the north and Dec/Jan is grim. Don't let summer test results fool you into undersizing.