Build your Victron system
Four questions → a complete, honestly-sized kit list: lithium battery, solar, MPPT, engine charging, inverter and monitoring — with buy links for every part, or one button to have it designed and fitted by the people who run it daily.
★ Rated 4.9 on GoogleFamily-run since 1995No fix, no fee
1 · How much energy do you use per day?
2 · Biggest mains (230V) appliance you’ll run?
3 · Charge from the engine while driving?
4 · Monitoring?
⚡ The kit
Price guides are typical UK retail as of mid-2026 — a planning aid, not a quote. The live links always show today’s real price, and sales happen.
🔌 Cables, lugs & fuses — per circuit
Sized for short runs (≤3m one way) at 12V — longer runs need upsizing for voltage drop. Use tinned (marine) cable and adhesive-lined heatshrink on every lug. A fuse protects its cable — never fit a bigger fuse than the cable is rated for.
💰 On a budget? Buy it in this order
You don’t need it all on day one. This is the order that keeps you safe and useful at every stage — each phase works on its own.
🛠️ Tools for the job
Essential
Nice to have
💡 Golden rules (read before you build)
- Fuse every positive as close to the battery as practical — the fuse is there to protect the cable, not the gadget.
- Fat and short beats long and thin. Keep inverter cables as short as possible, and if you parallel batteries, keep the pair’s leads equal length.
- Crimp, don’t solder. Soldered joints crack with vehicle vibration; a properly crimped lug with adhesive heatshrink lasts decades.
- Put a battery isolator switch on the main positive — one twist to make the whole system safe to work on.
- Everything negative goes through the shunt. One cable from the battery negative to the shunt, and every load’s negative on the far side — or your state-of-charge reading is fiction.
- Torque terminals to the manual’s spec and re-check them after your first weekend away — connections bed in.
- Ventilate and protect from temperature. Lithium won’t charge below 0°C (the SuperPack protects itself) — inside the living space beats an unheated garage box.
- Know where DIY ends. 12V is friendly; the 230V side (hook-up, sockets, RCDs) is qualified-electrician territory, and gas is Gas Safe territory. No exceptions.
Indicative starter build, not a full design — battery bank size, alternator limits, run lengths and ventilation all change the answer, and every van, boat and building is different. We check everything before we fit anything.
Or skip the spanner: we design, supply & fit
This is exactly the kit we install — our own support van runs on it, streaming live on this website right now. Designed properly, fitted safely, monitored remotely, and one local number when you want a hand.
Also: See Our Van Live
// GOOD QUESTIONS
Frequently asked
How is the kit sized?
From your daily energy use: watts × hours plus 15% real-world losses, a 1.5-day battery buffer at lithium’s ~90% usable capacity, solar sized for UK spring/autumn sun (~2.5 peak hours), and the matching Victron MPPT from the official controller limits. It’s an honest starter spec — a real design also covers cable sizing, fusing and alternator limits.
Are the shop links affiliate links?
The Amazon buttons are — since September 2026 they carry our Amazon Associates tag, so we may earn a small commission if you buy through one, at no extra cost to you, and the note beside the buttons says so. Bimble Solar links are plain searches. We recommend this kit because we install it and run it ourselves; the links change nothing about what we pick.
How accurate are the price guides?
They’re typical UK retail ranges (as of mid-2026) meant for planning a budget, not quoting a job — Victron prices move with sales and stock, so the live links always show today’s real price. Expect the truth to land inside the range most of the time, and add the 10–15% cabling allowance on top.
Why Victron?
It’s the kit we trust with our own van: everything talks to everything (one app for the lot), the build quality is superb, warranties are long, and the remote-monitoring platform (VRM) is genuinely brilliant — you can watch our own system streaming live on this website.
Can I fit it myself?
Plenty of people do — 12V systems are DIY-friendly if you’re careful, and the SuperPack batteries with built-in protection make it safer. The parts that deserve respect are fusing, cable sizing and anything near the alternator or mains. We’re happy to fit kit you’ve bought, check over a DIY install, or do the whole job.
Will you price-match or supply the kit?
We’ll quote for supply-and-fit with warranty and remote monitoring set up — and we’ll tell you honestly if buying parts yourself and having us fit them works out better for you. No games; just ask.
What about winter?
UK winter gives roughly one hour of usable sun a day — an eighth of summer — so winter systems lean on engine charging (the Orion B2B) or hook-up. The builder already assumes that; don’t let anyone sell you a roof full of panels as a winter solution.
Where do the cable and fuse sizes come from?
From Victron’s own manuals and wiring guidance, stated for short runs (≤3m one way) at 12V. Two rules matter above all: the fuse protects the cable (never fit a bigger fuse than the cable’s rating), and longer runs need thicker cable to beat voltage drop. Our design service calculates exact runs for your layout.
What tools do I really need?
The one that matters most is a proper hydraulic lug crimper — a bad crimp on a 70mm² inverter cable is a fire risk, a good one lasts decades. The builder lists the essential kit and the nice-to-haves, with links. Or borrow ours: we fit customer-supplied kit too.
// FREE TOOLS
More free tools for life off-grid
No sign-up, no catch — free tools built by our techies. See all our free tools →
Free tool
Battery & Solar Calculator
Campervan, boat or off-grid? Tick what you run and get an honest battery & solar panel sizing.
Try it →Free tool
Live Broadband Speed Test
Measure your real download, upload and ping right now on a live animated gauge.
Try it →Free tool
Coverage Checker
Pop in your postcode to see if we cover your area for on-site visits.
Try it →The kit we’d buy. Because we did.
Our own support van runs on exactly this equipment — designed, fitted and monitored by us, streaming live on this website. Whether you buy the parts or we supply them, we’ll make sure it’s done right.
01202 775566 · help@365techies.co.uk · MON–FRI 9AM–5PM
// HOW IT WORKS
How to size Victron campervan cables and fuses
Answer four questions and this free builder returns a complete Victron campervan system with the exact cable, lug and fuse size for every circuit — sized for short runs (up to 3m one way) at 12V — following the golden rule that the fuse protects the cable, so you never fit a fuse rated higher than its cable.
Victron 12V cable & fuse guide — short runs (≤3m one way). Golden rule: the fuse protects the cable, never fit a fuse rated above its cable.
| Circuit | Cable | Fuse |
|---|---|---|
| Main battery (with ~800W inverter) | 25mm² | 100A MEGA |
| Main battery (2000W MultiPlus) | 70mm² | 300A MEGA |
| Main battery (3000W, kettle/induction) | 2×70mm² per pole | 400A Class-T (lithium) |
| Battery negative → SmartShunt | Same as main (M10 lugs at shunt) | — |
| Engine → battery (Orion XS 50A) | 16mm² (25mm² longer) | 60A MIDI at BOTH ends |
| Panels → MPPT controller | 6mm² solar cable + MC4 | — |
| 12V distribution feed | 10mm² | 40A MIDI feed fuse |
MPPT solar controller by array size: up to ~220W → SmartSolar 75/15 (6mm², 20A fuse); ~290W → 100/20 (6mm², 25A); ~440W → 100/30 (10mm², 40A); ~700W → 100/50 (16mm², 60A); ~1000W → 150/70 (25mm², 100A MEGA).
Step by step
- Set your daily energy — Pick a preset (weekender ~350Wh, regular ~800Wh, full-timer ~1500Wh) or fine-tune the Wh/day slider — this drives the battery, solar and cable sizing.
- Choose your biggest mains load — Say whether you run all 12V, a laptop/TV inverter, a microwave, or a kettle/induction — this sets the main battery cable and MEGA/Class-T fuse size.
- Add engine and monitoring — Choose whether you charge from the engine (adds an Orion B2B circuit) and your monitoring level, so every relevant circuit appears.
- Read the per-circuit table — Scroll to ‘Cables, lugs & fuses — per circuit’ for the cable mm², fuse and lug for the main battery, negative/shunt, solar, PV, engine and 12V distribution runs.
- Apply the golden rules — Fuse every positive close to the battery, keep inverter cable fat and short, crimp don’t solder, and upsize cable for runs longer than 3m to beat voltage drop.
Good to know
What size cable and fuse do I need for a campervan inverter?
It depends on the inverter: the builder specs 25mm² cable with a 100A MEGA fuse for an ~800W Phoenix, 70mm² with a 300A MEGA fuse for a 2000W MultiPlus, and twin 70mm² per pole with a 400A Class-T fuse for a 3000W kettle-capable unit. In every case the fuse protects the cable, so it is never rated above the cable’s capacity.
What fuse goes on a Victron Orion B2B engine-charging circuit?
For the Orion XS 12/12-50 the builder specifies 16mm² tinned cable for runs up to 3m (25mm² for longer) fused with a 60A MIDI fuse at BOTH ends — at the starter battery and the leisure battery — because that cable runs the length of the vehicle and must be protected at each end.
Do longer cable runs need a bigger cable in a 12V system?
Yes. The sizes shown are for short runs of up to 3m one way at 12V; longer runs need thicker cable to beat voltage drop, while the fuse stays matched to the cable it protects. Use tinned marine cable and adhesive-lined heatshrink on every lug; for exact runs on your layout our design service calculates them properly.