Static caravan off-grid setup — is 10kWh enough for EV charging overnight?

Finally pulled the trigger on going fully off-grid at my static. Running a Victron Multiplus-II 5000 with 15kWh of Fogstar Drift LiFePO4 (3x 5kWh modules) and a 4kWp PV array facing roughly SSW. Most of the year it's fine — lights, fridge, occasional electric hob, no drama.

The problem is the car. I've got a Leaf (24kWh battery, usually comes home at 30-40%) and I want to charge it overnight on a basic 6A EVSE so it pulls around 1.4kW. That's roughly 10-12kWh overnight just for the car, which basically wipes out my whole usable battery bank before sunrise.

Been thinking about limiting the charge to top up to maybe 60-70% rather than full, and only doing it after a decent solar day. But in winter with maybe 8-10kWh of harvest on a good day, it feels like a knife-edge. Anyone running a similar setup with EV charging in the mix? Wondering whether I need to expand the bank to 20kWh+ or if smart scheduling is enough to make it work.

Also curious whether anyone's used the Victron ESS + Node-RED combo to automate charge limits based on battery SOC — seems like the obvious solution but I've not gone down that rabbit hole yet.

MoreTeaVicar60 | 847 posts | ⚡ Off-Grid Enthusiast

@MuddyTrekker Cracking setup! One thing worth considering — the Multiplus-II 5000 is rated at 5kVA, so even if you're charging the EV at a modest rate overnight, you'll be drawing from those batteries with zero solar input. Fifteen kWh sounds generous, but once you factor in the caravan's base load overnight plus EV charging, you could easily chew through 10+ kWh before dawn.

I'd strongly recommend setting a charging limit on the EV — most can schedule charging to stop at a certain percentage. Protecting that bottom 20% of your Fogstar bank is essential for longevity.

What's the car? If it's something like a Leaf with a 6.6kW onboard charger, you'll want to throttle it right back. 🙂

TorDweller | 1,203 posts | ⚡ Off-Grid Enthusiast

@MuddyTrekker the narrowboat taught me a hard lesson here — charging context matters enormously. A 10kWh overnight top-up sounds reasonable until you're sat under three grey November days with 40% left in your bank before the car even plugs in.

What I'd watch carefully is your state of charge threshold when EV charging kicks off. On my Victron setup I've got an ESS assistant that simply refuses to feed the charger unless the bank is above 70%. Saved me from a flat battery more than once.

With 15kWh Fogstar and 4kWp you've probably got enough headroom in summer — but that south-ish facing array will punish you come winter. What EVSE are you running, and is it set to draw a fixed rate or does it communicate with the Multiplus at all?

JimChapman74 | 312 posts | 🔋 LiFePO4 Convert

@MuddyTrekker Nice one, jealous of that Fogstar setup! Quick reality check though — if you're wanting to charge an EV overnight, 10kWh is almost certainly not going to cut it on its own. Even a modest 20-mile top-up at 3kW will chew through a good chunk of your usable capacity, and that's before the caravan's overnight baseload (fridge, lighting, inverter standby etc.).

My suggestion: look into current-limiting your EV charger to 6A rather than the full 16A, and only charge when the batteries are genuinely topped up from a decent solar day. The Victron GX portal lets you set charge current limits quite nicely.

Winter will be the real test with that 4kWp array — what direction is it facing exactly?

BoatFinn | 64 posts | ☀️ Solar Curious

Has anyone actually measured what their EV pulls during a trickle charge overnight versus what they think it pulls? I ask because I'm in a similar position planning-wise and I can't work out whether the overnight solar deficit is predictable enough to schedule around.

Like, does the Multiplus-II give you reliable enough data in VRM to actually back-calculate this, or is there too much noise from other loads running simultaneously?

Also genuinely curious — what's the minimum SOC you're comfortable dropping the Fogstar to overnight? I've seen people say 20% as the floor but does that hold in winter when you're not confident the next day's generation will recover it?

CarolWatson | 847 posts | 🔋 LiFePO4 Convert

@BoatFinn Yes! I logged mine last winter using a simple plug-in energy monitor. My Nissan Leaf on a standard 3-pin overnight pulled roughly 7–8kWh from empty to 80%, but that assumes the battery was genuinely depleted. Day-to-day top-ups were often only 3–4kWh, which is far more manageable.

@MuddyTrekker the question I'd be asking is when you're doing this. Summer with a decent solar harvest the following morning? Probably fine. January in the Peak District with a week of overcast days? That's where it gets hairy. Your 15kWh sounds generous until you factor in heating, lighting, and a fridge running overnight before you even touch the car.

Have you set up any load-shedding priorities in Venus OS yet? That'd be my first port of call before committing to regular EV charging.

CliffSpirit | 203 posts | ⚡ Off-Grid Enthusiast

Worth flagging something nobody's mentioned yet — your Multiplus-II 5000 is rated at 48V, so it'll only deliver around 4.5kW continuous to a Type 2 EVSE. Most EV home chargers set to "trickle" (6A) only draw about 1.4kW, which is very manageable overnight from 15kWh. That's roughly 10-11kWh added to the car across 8 hours — well within your battery capacity if your static's baseline loads stay modest.

The real concern is winter. @JimChapman74 is right to flag it — your 4kWp array facing slightly off-south might only yield 8-12kWh on a decent winter day. If you're running heating simultaneously, you could easily find yourself net negative by morning.

I'd strongly recommend setting a low SOC cutoff on the Multiplus (say 20%) and using your car's charge scheduling to stop before you hit it

WattGaz | 412 posts | 🔋 LiFePO4 Convert

@MuddyTrekker Great setup! One thing worth considering alongside what @CliffSpirit mentioned — set your EV charging start time to coincide with any overnight wind contribution if you've got a turbine, or better yet, delay it until morning when your 4kWp array kicks in. Even in winter you'll often see decent generation by 9–10am. That way you're not hammering 15kWh purely from stored capacity overnight. Also check your Multiplus-II charge current limits — you don't want the inverter struggling if the car ramps up demand suddenly.

WheresMeWires67 | 1,204 posts | 🏠 Tiny House Builder

Something nobody's touched on yet — your EV's onboard charger matters enormously here. A 3.6kW single-phase charger running 6 hours pulls 21.6kWh before conversion losses. Your 15kWh bank at 80% usable DoD gives you roughly 12kWh for EV duty after keeping the caravan alive overnight.

That maths only works in summer. I'd seriously look at configuring a charge current limit via VictronConnect tied to your State of Charge — Multiplus-II handles this natively. Set a hard floor of 20% SOC so you're not accidentally walking into a cloudy morning with a flat bank and a flat car.

NeilEdwards | 47 posts | 🔌 EV Charging Nerd

Curious what EV you're actually charging here — makes a massive difference. My Leaf on a 7kW charge will drain a battery bank far faster than my mate's Zoe running at 3.6kW. If you can throttle the EVSE down (anything with an adjustable pilot signal, like an Ohme or Zappi), you could set a 6A minimum draw and stretch that 15kWh considerably further overnight. Worth checking whether your Multiplus-II inverter load limit plays nicely with the EVSE's handshake too — had odd behaviour with mine until I adjusted the AC output current settings.

RayHunt | 287 posts | ☀️ Off-Grid Enthusiast

Good shout from @NeilEdwards on the EV model — it really does matter enormously. Also worth flagging that your Multiplus-II 5000 has a 50A AC output limit, so you'll likely be capped around 3.5-3.7kW for charging anyway, which actually works in your favour overnight as it's gentler on your battery bank. With 15kWh available and sensible DoD limits (I'd not go below 20%), you're realistically working with 12kWh usable. That's a decent overnight charge depending on your EV's starting state. What's your backup gen situation if a run of dull days leaves you short?