Van electrical and power

This hub is for you if you're designing, installing or upgrading the house power in a camper van. It covers how the parts fit together, how to wire the alternator charger that most builds rely on, and how to keep a lithium battery healthy in winter. Electrical work in a van carries real fire risk, so the emphasis throughout is on correct fusing and cable sizing rather than brand choice.

How a van system fits together

A typical system is a lithium iron phosphate (LiFePO4) battery bank charged three ways: solar through an MPPT controller, the engine alternator through a DC-DC charger, and shore power through a mains charger. 12V loads run straight off the battery; 120V loads run through an inverter. The van electrical system guide explains each component, compares LiFePO4 with AGM, and shows how to size the bank and solar from an energy audit of your own loads. Most full-time van dwellers land somewhere between 100Ah of lithium with 200 to 300 watts of solar and 300Ah or more with 400 to 600 watts, but your own loads decide.

The key decisions

• Battery capacity: sized from your daily watt-hours plus the days you want to go without sun or driving.
• Charging mix: how much comes from solar versus driving. If you drive most days, a DC-DC charger does a lot of the work.
• Inverter size: only as big as your real AC loads. A pure sine wave inverter is the safe choice for electronics.
• Battery location: inside the heated living space if you camp in freezing weather.

A sensible order

Step	What to do	Guide
1	List your loads, size the battery and solar, and draw the system with every fuse and cable size	Electrical system guide
2	Wire alternator charging with correct fuses at both batteries	DC-DC charger wiring
3	Plan for cold-weather charging before your first winter trip	Lithium below freezing

DC-DC charging

The DC-DC charger wiring guide uses the Victron Orion XS 12/12-50A as a worked example. Victron's manual calls for a 60 to 70 A fuse at each battery and at least 6 AWG cable for runs under 5 m, and the Orion XS usually doesn't need an ignition wire because it detects a running engine from alternator voltage. Other chargers follow the same logic with different numbers, so size from your own unit's manual.

Lithium in the cold

LiFePO4 batteries can discharge in the cold but must not be charged while the cells are below the maker's minimum. Victron's Smart lithium batteries charge only from +5 °C (41 °F); Battle Born lists 25 °F. The cold-weather charging guide compares self-heating batteries, thermostat-controlled DIY warming and simply keeping the battery in the heated cabin.

When to use a qualified professional

A competent DIYer can build a van system, but high-current DC wiring is unforgiving. Bring in a qualified 12V installer or auto electrician when:

• You aren't confident with high-current DC work, or want your finished system checked before the first trip.
• Your van has a factory auxiliary battery, battery isolator or upfitter interface and you're not sure where a charger may connect.
• You need to tap a CAN-bus signal or integrate a battery management system.
• You're adding shore power or any 120V wiring and aren't sure how to do it safely.

Whatever you install, mount the main fuse as close to the battery positive terminal as practical, fuse both ends of any cable that has a source at each end, size each fuse to protect its cable, and use a fuse with an adequate interrupt rating at the lithium battery.