Loading...
YOUR ENERGY PROFILE.
This document contains the sizing of your future electrical installation, calculated based on your appliances.
Inventory:
To guarantee 0WH without damaging your bank (80% max discharge):
Minimum power required to recharge your consumption:
Maximum power (with 25% safety margin).
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 |
The fuse protects the wire, not the appliance. Always place it as close to the power source as possible (battery or busbar).
0W
0 Ah
Lithium LiFePO4
Pompe, Leds, Frigo...
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
If your van is Euro 6+ (most Sprinters, Transits, Ducatos post-2017), your alternator is "regulated" — it stops charging as soon as the starter battery hits 14.0V. With a simple voltage-sensitive relay, your leisure battery gets almost nothing. I learned this the hard way on my 2019 Transit build.
A DC-DC charger like the Victron Orion-Tr Smart 12/12-30 bypasses this entirely. It detects engine-on state via voltage signature, then charges at full 30A regardless of what the regulated alternator is doing. For LiFePO4 leisure batteries, this isn't optional — a voltage relay under-charges LFP chemistry and eventually kills the BMS.
With 30A output at 12V, you need 6mm² cable minimum between starter battery and Orion input, and 6mm² between Orion output and leisure battery. Add a 40A midi fuse on each side within 30cm of each battery post. Don't go thinner than 6mm² to save a few euros — undersized cables heat up at sustained 30A and the voltage drop eats 3-5% of your charging power.
Typical install time in a van: 2-3 hours if you can route cables through existing harness holes. The Orion itself mounts flat or upright, needs minimal ventilation (stays at 30°C ambient, rises to ~50°C under full load with the internal fan).
If you run a 300Ah+ LiFePO4 bank and drive daily (overlander, digital nomad), the 30A version caps you at ~12% state-of-charge per hour of driving. The Orion XS 50A jumps that to ~20%/hour. Costs 40% more (~€250 vs €180) but fills larger banks noticeably faster.
For a standard weekend van build (100-200Ah leisure), skip the XS. The 30A is plenty and half the price of the equivalent Renogy or Redarc DC-DC chargers with the same features.
On my 2023 Transit with a 230Ah Battle Born bank, the Orion 30A delivers a steady 28.5A at 14.2V while the engine runs (Bluetooth logs don't lie). After a 2-hour drive from full-flat, I'm back to 55% SOC. Over 3 summers in Europe (~40,000 km), zero faults, zero BMS disconnects, zero derating from heat.
One caveat: if your van has a very long run between batteries (aft installation in a Sprinter 170 extended), losses add up. Use 10mm² instead of 6mm² above 4m total cable run to keep voltage drop under 3%.
Results based on a typical use case
| Appliance | Power | Usage/day | Wh/day |
|---|---|---|---|
| Compression fridge | 45W | 24h | 1080 |
| LED lighting | 20W | 4h | 80 |
| Water pump | 30W | 0.5h | 15 |
| Phone charging | 15W | 2h | 30 |
| Daily consumption | 1205 Wh | ||
Adjust these values with the calculator below
Here's the scene that sold me on DC-DC for good. 2022, Transit Euro 6, 200Ah LiFePO4 house bank, cheap voltage-sensitive relay installed by a previous owner. After a 4-hour highway stretch in Portugal, house bank reads 76% SoC. Next morning, cranking battery at 12.0V. What went wrong? Euro 6 alternators flutter between 12.4V and 14.8V based on ECU demand — the VSR relay opens and closes like a strobe, the LiFePO4 never sees a proper charge cycle, and some days your starter takes the hit instead.
The Victron Orion-Tr Smart 12/12-30 solves this cleanly. Instead of a fixed threshold, it watches for "engine running" via rising input voltage above 13.1V (adjustable in VictronConnect), then pulls a steady 30A no matter what the alternator does next — the 10-17V input range absorbs the dips. Clean charging, cranking battery left alone.
Install matters more than most guides say. Mount the Orion within 1-2m of your house battery, not near the alternator — the output side is where the amps live, and that's where voltage drop hurts. Cable: 16mm² minimum (6 AWG) on BOTH input and output, with a 50A fuse on each side within 30cm of every battery terminal. Dropping to 10mm² because a pre-crimped kit is on sale costs you 4-5% voltage drop and triggers thermal derating when the unit heats up.
VictronConnect gives you three profiles: Normal runs 14.4V absorption (safe for any LFP), High pushes 14.6V for aggressive charging when your BMS is solid, Fixed 14.2V for mixed-chemistry edge cases. Real-world efficiency sits at 87-88%, giving ~430W usable on the output side. Pulling a 100Ah LiFePO4 from 50% to full takes roughly 2-2.5 hours of actual driving — great if you're stacking 30-min daily commutes plus a real drive on weekends.
Running a 200Ah+ bank or need 60A+ charging? Victron officially supports up to 4 units in parallel (120A total) since firmware v1.21. The Renogy DCC50S at ~$160-200 looks great on paper (50A plus built-in MPPT), but the Bluetooth polish and EU warranty support aren't in the same league. For a Euro 6 van with a 100-200Ah LiFePO4 house bank, the Orion-Tr 30A at €250-280 remains the right answer.
Links marked with * are affiliate links. If a purchase is made through them, I receive a commission at no extra cost to you. The editorial selection and product evaluation are not influenced by commission rates. Your click helps fund this free tool.