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
| Charger | Output | Efficiency | App | Price |
|---|---|---|---|---|
| Victron Orion-Tr Smart 12/12-30 | 30A / 360W | 95% | VictronConnect | $160-200 |
| Victron Orion-Tr Smart 12/12-18 | 18A / 216W | 95% | VictronConnect | $120-150 |
| Renogy 40A DC-DC | 40A / 480W | 92% | Renogy BT | $120-160 |
| Sterling B2B 30A | 30A / 360W | 90% | — | $100-150 |
About this tool
The DC-DC charger (also called B2B charger or battery-to-battery charger) is the most misunderstood component in van electrical builds — and getting it wrong either destroys your lithium battery or leaves it perpetually undercharged.
The problem it solves: modern Euro 5/6 vans have "smart" alternators that actively vary output voltage to reduce engine load at highway speed (fuel economy mandate). A Transit Custom alternator can cycle between 11.8V and 14.6V during normal driving based on ECU load management. LiFePO4 batteries need a stable 14.2-14.4V absorption phase to fully charge — an unpredictable alternator can never provide this.
A DC-DC charger acts as an isolated DC-DC converter: it draws variable voltage from the starter battery (which the alternator does charge correctly, as it's the primary load the ECU manages), and outputs a clean, programmable multi-stage charge profile to the leisure battery. It's galvanically isolated, meaning ground faults on one side don't affect the other — important for steel van body integrity.
The Victron Orion-Tr Smart 12-12|30 is the van conversion standard for good reason: Bluetooth monitoring via VictronConnect app, adjustable absorption voltage (critical for matching your specific LiFePO4 BMS settings), separate inputs and outputs for proper isolation, and a 5-year track record of reliability in van builds.
Installation tips: always fuse within 50cm of the source battery (80A ANL fuse on input side, 40A blade fuse on output). Use 16mm² cable for runs up to 2 meters. Connect the ignition sense wire to a switched 12V source (cigarette lighter socket via relay) to ensure charging only occurs when engine is running — this prevents drain-down when parked with ignition off.
For maximum charging speed on long driving days: two Orion 12-12|30 units in parallel deliver 60A (720W) output, charging a 200Ah LiFePO4 from 20% to full in about 3.5 hours of driving. At €280 total for two units, it's the most cost-effective upgrade for urban van lifers with daily drives under 4 hours.
Sizing the DC-DC charger correctly: Rule of thumb is 30-40% of battery bank capacity in amps. A 100Ah LiFePO4: 30-40A DC-DC charger (Victron Orion Smart 30A = 360W @ 12V output). A 200Ah LiFePO4: 40-60A charger. Over-sizing the charger above 50% battery capacity rarely provides benefit since LiFePO4 bulk charge acceptance tapers off at higher SOC anyway. Under-sizing below 20% means very slow replenishment on driving days.
Vehicle alternator compatibility — the critical detail: Modern vehicles with smart alternators (variable voltage 13.2-14.7V, ECU-controlled) and start-stop systems require an isolated DC-DC charger, not a simple B2B connection. The non-isolated input of some budget chargers can cause ground loops between the starter battery and house battery — causing confusing charging behavior and potential ECU interference. The Victron Orion-Tr Smart (galvanically isolated) resolves this at €140-200.
Engine runtime for meaningful charging: A 40A DC-DC charger at 12V adds 480W to the battery. Driving 1 hour = 480Wh recovered. For a van depleted to 20% SOC (80% battery to recover = 160Ah for a 200Ah pack = 1920Wh): requires 4 hours of driving to fully charge. Practical for most travel days; insufficient for stationary days without solar.