The electrical system is the heart of a van build, and it is the part most beginners get wrong. Lights that flicker, a fridge that dies overnight, a battery that never quite charges: almost every van electrical problem traces back to the same mistake, which is buying components before doing the maths. Build from the loads outward and the system almost designs itself.

List everything that will draw power: lights, fridge, fan, laptop, phone, water pump, heater controls. Multiply watts by hours per day to get watt-hours. A typical two-person van with a 12-volt compressor fridge, a roof fan, lights, and laptops lands somewhere around one to one and a half kilowatt-hours a day. That number is your anchor for every decision that follows.

Add a margin of about twenty percent for losses and for the days you use more than planned. A system sized to your average day will disappoint you on your busiest day, and busy days are the ones that matter.

Lithium iron phosphate, usually called LiFePO4, is the standard choice for van builds now. It is lighter than lead-acid, it can be discharged deeply without damage, and it lasts far longer. A two hundred amp-hour lithium battery at twelve volts stores roughly two and a half kilowatt-hours, which covers a typical day plus a buffer.

Charge it from three sources if you can. Solar on the roof is the workhorse: two to four hundred watts covers most daily use in decent weather. A DC-to-DC charger pulls power from the alternator while you drive, which fills the gap on cloudy days. Shore power through a small charger tops everything up when you are plugged in at a campsite. Each source is simple on its own; together they make the system resilient.

Size your wires to the current they carry and keep the runs short. Thick cable between the battery and the inverter, thinner cable for lights and fans. Fuse every circuit close to the battery, because a fuse is the cheapest insurance you will ever buy. A short circuit in an unfused wire can start a fire in seconds.

Use a bus bar to keep the wiring tidy and a battery monitor so you always know your state of charge. Guessing is how batteries die young. With honest load maths, a lithium battery, three charging sources, and fused wiring, a van electrical system becomes something you forget about, which is exactly what it should be.

When a van electrical system misbehaves, the fault is usually simple. A battery that will not charge is often a blown fuse, a loose connection, or a solar panel in shade rather than a dead battery. Check the fuses first, then the connections, then the charge controller display, which usually tells you exactly what is wrong. A multimeter is the most useful tool you can carry: it turns guessing into measuring in about thirty seconds.

Voltage drop is the other classic problem. If your lights dim when the fridge starts, the wires are probably too thin for the distance they run. Shorten the run or fit thicker cable, and keep the battery as close to the big loads as you can. Carry spares of the small things that fail: fuses, a spare length of cable, crimp connectors, and electrical tape. Most electrical problems on the road are fixed with a ten-minute repair and a part that costs almost nothing, as long as you have it with you. Label every wire and every fuse as you install it, because the person troubleshooting the system at midnight in the rain will be you, and future you will be grateful for the labels.