Wiring guide help

Been down this exact rabbit hole with my static caravan setup — bought all the "main" bits (Victron Multiplus-II 3kVA, Fogstar Drift 200Ah, 400W of panels off eBay) and then stood in the garage genuinely baffled about what connects what.

The wiring between the major components feels obvious until you actually have to spec the cables, fuses, and busbars — then suddenly you're drowning in cross-sectional area calculations at 11pm on a Tuesday.

Few things that caught me out that might help others in the same boat:

• DC cable sizing between battery and Multiplus matters massively — undersized = voltage drop = the inverter throwing a wobbly under load
• ANL fuse as close to the battery positive as physically possible, not an afterthought
• MPPT to battery run should be kept short — mine's embarrassingly long and I still haven't sorted it 😬
• Victron's own wiring diagram PDFs are genuinely decent, but they don't always show the busbar arrangement clearly when you're adding solar into the mix

Anyone got a solid UK-focused wiring schematic they'd recommend for a Multiplus + MPPT + lithium setup? The Victron community forum has some good stuff but half of it's aimed at boat/RV installs with completely different earthing arrangements to a static on a UK site.

Also keen to know what cable suppliers people are actually using — last lot I ordered from Amazon was... optimistic about its ratings, let's say.

@BorderVanLifer the accessories budget is basically a second build hidden inside your first build 🔧

@BorderVanLifer mate, the "hidden second build" is real — budget at least 20-30% on top for the stuff nobody puts in the YouTube thumbnail: proper ANL fuse (Victron's own or MRBF block), crimping tool that doesn't ruin your lugs, tinned marine cable (not the cheap automotive stuff that corrodes and burns), DIN rail breakers, busbar, and enough heat shrink to wrap the moon 🌕 — learned that the hard way on my shepherd's hut build where I went through three dodgy crimp tools before caving and buying a decent hydraulic one off Amazon.

@BoatPaddy is right but I'd push that figure higher honestly — my narrowboat refit, the "accessories" ended up closer to 40% on top once I'd accounted for proper DC fusing (MIDI fuse holders aren't cheap), decent crimped lugs, busbar, cable management, Victron SmartShunt, BMV cabling... the list genuinely doesn't end.

The bit that caught me out specifically was cable sizing. Bought everything then realised my 50mm² DC runs were going to cost more than I'd budgeted for the whole wiring job. Metric tinned marine grade from a UK supplier like Batt Cables adds up fast.

@BorderVanLifer — would strongly suggest drawing a full system schematic before buying anything else, then price up every single component including ferrules, heat shrink, cable ties. Boring but it stops the creeping surprise costs.

@PanelEwan same energy here — built my garden office system, thought I was done, then spent three weekends driving to TLC Electrical and screwfix buying cable lugs, DIN rail, 6mm² twin and earth, random fuses, a Victron SmartShunt I somehow forgot existed, and a partridge in a pear tree 🎄

@BorderVanLifer the hidden costs that really catch people out are the busbars, fuse holders, and proper cable lugs — not glamorous, but a 3kVA Multiplus needs seriously chunky cable (I'd spec 70mm² minimum on the battery side) and the connectors alone can run £40-60 if you're doing it properly.

Also factor in:

• DC fusing at the battery terminals (ANL fuse, not cheap)
• Lynx Distributor if you want it neat (Victron's own, worth every penny)
• DIN rail breakers for AC distribution
• Crimping tool hire or a decent set of ferrules

With a Fogstar Drift you'll also want a proper BMS communications cable to the Multiplus if you're going the VE.Can route — check compatibility first.

@PanelEwan is absolutely right that accessories creep up. My static caravan second-fix cost nearly £400 in "just connectors and cable management." Budget accordingly.

@BorderVanLifer been there. DC cable alone nearly floored me — people forget you need serious gauge stuff between the battery and Multiplus, not the thin roll from Screwfix.

Also: DC isolators, shunts, fuse blocks. None of it's glamorous but it all adds up fast.

One thing nobody mentioned yet — conduit and cable management. If you're doing a static install properly, you'll want it tidy and protected. That's another sneaky £40-60 gone.

Budget roughly 20-25% on top of your main component cost for all the bits. Sounds excessive but it's about right in my experience.