Most van builds stall on the electrical system, not because it is hard, but because every forum thread assumes you already speak in amp-hours. Here is the plain version.

The four parts you actually need Your system is a battery (storage), a way to charge it, a fuse block (safety), and the loads (your fridge, lights, fan). Everything else is detail. Start by listing every device and how many hours a day it runs, then add up the watt-hours. A 12V fridge pulling 40W for 12 hours is about 480Wh. Do this for everything and you will know how big your battery needs to be.

Sizing the battery A single 100Ah lithium (LiFePO4) battery gives you roughly 1280 usable watt-hours. For most weekend and part-time builds that runs a fridge, lights, a fan, and phone charging comfortably. Lithium costs more upfront but lasts far longer and can be drained nearly empty without damage, unlike lead-acid.

Charging from three sources - Solar keeps you topped up when parked. 200W of panels is a sensible starting point. - Alternator charging through a DC-to-DC charger refills the battery as you drive. This is the workhorse most people underrate. - Shore power with a simple charger handles the rare campground night.

Do not skip fusing Every positive wire gets a fuse rated to protect the wire, not the device. Use a marine-grade fuse block, size your wire from a chart for the amperage and distance, and crimp connections properly. A loose connection is the number one cause of van electrical fires. Build it once, build it safe, and it will quietly power your home for years.