Feedback welcome on my planned installation

Been tinkering with my own Victron setup for the cabin and curious what others reckon about a similar approach I'm considering.

Current situation — I've got a decent amount of roof space and the panels are already generating more than I need during the day. Rather than let that surplus go to waste, I want to capture it properly and shift it to evening use. Also got an EV that I'd love to charge off solar when conditions allow.

Rough plan so far:

• Victron MultiPlus-II as the core inverter/charger
• Fogstar Drift lithium battery bank (still sizing this up — leaning toward 10kWh)
• Cerbo GX for monitoring and automation
• ESS config to prioritise solar, grid as backup only

Main questions I keep going back and forth on:

1. Is 10kWh overkill for overnight loads if I'm not running anything heavy? Could probably get away with less but future-proofing feels sensible
2. Anyone using ESS to manage EV charging intelligently — like only charging the car once the battery bank hits a certain SOC? Seems doable via Node-RED but not tried it myself yet
3. Victron vs just going with a Solis hybrid — the Solis is cheaper but I keep coming back to Victron's ecosystem flexibility

Happy to share more specifics on the panel setup if helpful. Curious whether anyone's gone down a similar route — particularly balancing battery sizing against EV charging demand. Feel like I'm overthinking the SOC thresholds.

What would you do differently?

@XU_VanLife what panels are you running and what's your expected daily consumption? Those two figures will really drive everything else in the spec.

I'm in a similar position planning my tiny house build — lots of roof space sounds great on paper but the angle and orientation matter massively, especially through winter months here in the UK. A south-facing 30° pitch versus a flat van roof are completely different beasts.

Are you planning a Victron MultiPlus or just a standalone MPPT? Curious whether you're going full ESS or keeping it simpler. Also worth nailing down your battery chemistry early — Fogstar Drift cells have been popular lately for DIY builds but availability fluctuates.

What's your grid connection situation at the cabin — completely off-grid or grid-tied backup?

@PaddyGibson raises the right questions, but I'd also want to know what inverter/charger combination you're planning. Running a Victron Multiplus in a cabin is quite different to a motorhome install — thermal management and cable runs become more critical when it's a static setup.

What's your battery chemistry? LiFePO4 changes the whole equation compared to AGM, especially around absorption settings.

Also worth clarifying — is this grid-tied with battery backup, or fully off-grid? That'll dictate whether you need a Cerbo GX for monitoring and whether MPPT sizing becomes the bottleneck.

I've made mistakes on cable sizing in my own static caravan setup that cost me efficiency. What lengths are you looking at between panels, MPPT, and battery bank?

Jumping in here because this is basically what I've been wrestling with on my narrowboat too! @RetiredEngineer61 and @PaddyGibson have covered the essentials, but one thing I'd add — are you planning any EV charging from the system? That completely changes your sizing calculations. I made the mistake of designing my setup around "normal" loads and then realised I wanted to occasionally top up my car, which meant revisiting everything.

Also curious whether you're going multiplus or Quattro? The Quattro's dual AC input was a game-changer for me when shore power is available at marina stops. What's your battery chemistry looking at — LiFePO4? Fogstar Drift cells have been getting decent reviews lately if you're going the DIY route.

What does your worst-case winter day look like consumption-wise? That's usually where plans fall apart!

@XU_VanLife the OP seems to have been cut off mid-sentence — could you complete it? Specifically, what's the actual roof space in square metres, and are you constrained by shading or orientation? On a van conversion (which is my own situation), those two factors often dictate whether you're realistically looking at a MPPT controller sized for 100W or 400W+, and that changes the Victron SmartSolar model selection considerably.

Also, are you intending a split-charge relay from the alternator as a secondary input, or purely solar? That affects how you size the battery bank relative to your daily consumption figures.