YOUR ENERGY PROFILE.
This document contains the sizing of your future electrical installation, calculated based on your appliances.
Inventory:
Battery
To guarantee 0WH without damaging your bank (80% max discharge):
Solar
Minimum power required to recharge your consumption:
220V AC
Maximum power (with 25% safety margin).
12V Cable Sizing Guide
Use this professional reference table to select the correct gauge (mm²) for your cables. For 12V in a van, the maximum tolerated voltage drop is 3%. Always use multi-stranded flexible automotive wire.
| Current (A) | Round trip < 2m | Round trip 4m | Round trip 6m |
|---|---|---|---|
| 5A (LEDs, USB) | 1.5 mm² | 2.5 mm² | 4 mm² |
| 10A (Fridge, Pump) | 2.5 mm² | 4 mm² | 6 mm² |
| 20A (Heater) | 4 mm² | 10 mm² | 10 mm² |
| 50A (DC/DC Booster) | 10 mm² | 16 mm² | 25 mm² |
| 100A (Inverter) | 25 mm² | 35 mm² | 50 mm² |
Fuse Sizing
The fuse protects the wire, not the appliance. Always place it as close to the power source as possible (battery or busbar).
- Wire 1.5 mm² → Max fuse 10A
- Wire 2.5 mm² → Max fuse 20A
- Wire 4 mm² → Max fuse 30A
- Wire 6 mm² → Max fuse 40A
- Wire 10 mm² → Max fuse 60A
SCHÉMA ÉLECTRIQUE
PANNEAUX SOLAIRES
0W
REGULATEUR MPPT
BATTERIE AUXILIAIRE
0 Ah
Lithium LiFePO4
BOÎTE À FUSIBLES 12V
Pompe, Leds, Frigo...
CONVERTISSEUR 220V
NON REQUI
SHOPPING LIST
Where to find this equipment? Here is the community-approved selection.
12V 6-way Fuse Box
Mandatory protection
Digital Multimeter
Test your connections
Heavy Duty Crimping Tool
For perfect lugs
Heat Shrink Tubing
Insulation and safety
Comparison table
| Component | Entry budget | Mid budget | Premium budget |
|---|---|---|---|
| Battery 100-200Ah | $150-300 | $300-500 | $600-900 |
| Solar panel 100-200W | $60-100 | $100-180 | $200-350 |
| MPPT controller | $30-50 | $50-100 | $100-200 |
| Inverter 300-1000W | $40-100 | $100-180 | $200-350 |
| TOTAL | $280-550 | $550-960 | $1,100-1,800 |
About this tool
Van Build Electrical System: Beginner's Complete Guide
Building a van electrical system from scratch feels overwhelming, but it breaks down into 6 clearly defined components. Understand each one and you'll be able to design a system confidently before buying a single cable.
The 6 Core Components
1. Battery Bank — Stores your energy. LiFePO4 is the modern standard: 80% DoD, 10+ year lifespan, lightweight. Start with 100-200Ah for weekends, 200-400Ah for full-time.
2. Solar Panels — Your primary source of free energy. Budget 200-400W for weekends, 400-600W for full-time. Mounted flat or at 5-15° angle on the roof.
3. MPPT Regulator — Converts solar power efficiently into battery power. Always use MPPT (not PWM) above 200W. Victron SmartSolar is the benchmark. Sized by: (Solar watts ÷ Battery voltage) × 1.25.
4. DC-DC Charger (B2B) — Charges your leisure battery from the engine alternator while driving. Essential for winter or cloudy periods. A 30A unit provides 360Wh per hour of driving.
5. 230V Inverter/Charger — Converts 12V battery power to 230V for charging laptops, appliances. Also charges battery when connected to shore power. Pure sine wave only for sensitive electronics.
6. Wiring and Protection — The unsexy but mission-critical part. Correctly sized cables, fuses, and a negative busbars prevent fires. Under-sized cables can get hot enough to cause fires under sustained load.
Sizing Quick Reference
| Component | Entry Level | Full-Time |
|---|---|---|
| Battery | 100-150Ah LiFePO4 | 200-400Ah LiFePO4 |
| Solar | 200W | 400-600W |
| MPPT | 20-30A | 40-60A |
| DC-DC B2B | 20A | 30-40A |
| Inverter | 1,000W pure sine | 2,000-3,000W |
The Right Order to Wire Your System
Critical safety rule: Always connect batteries last and disconnect batteries first. Sequence for connecting: fuse holders → busbars → MPPT → inverter → B2B → solar panels → battery. Reverse for disconnection.
All positive cables need an appropriately sized fuse as close to the battery positive terminal as possible — this is your last line of defense against a wiring fire.
Biggest Beginner Mistakes
- Undersized cables — use AWG/mm² charts based on current AND cable length
- No BMS on LiFePO4 — even branded LiFePO4 batteries need BMS protection
- PWM instead of MPPT — you lose 15-30% of solar production
- Fridge running directly off alternator via split-charge relay — this drains the starter battery; always use a proper B2B charger
Expert tip: Draw your electrical diagram before buying anything. Even a rough hand-drawn schematic will save you from buying wrong cable lengths, wrong-sized components, and ensure you haven't missed a fuse location.