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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
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).
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Lithium LiFePO4
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