Van conversions and boat refits attract people who've done some electrical work at home and reasonably assume the skills transfer. They mostly do. The three things that don't transfer are the three things that cause fires.
Everything is moving, all the time
A house doesn't vibrate. A vehicle does, continuously, for years.
This has one large practical consequence: screw terminals loosen. The chocolate-block connector strips Verchil that are perfectly acceptable in a fixed installation will back off over a few thousand miles of road, and a loose terminal is a resistance, and a resistance carrying current is a heater.
The standard answer is crimped connections. Properly crimped, with a ratcheting tool and the right die for the terminal — a gas-tight cold weld between conductor and terminal, which is mechanically stronger than the wire around it.
And a point that surprises people: don't solder connections in a vehicle. Solder wicks up the strands of the wire, turning a flexible conductor rigid for a centimetre or two beyond the joint. That rigid section becomes a stress concentration, and under vibration the wire fatigues and snaps right at the edge of the solder. Crimp instead. If you must solder, support the wire well past the joint.
Damp is constant, not occasional
A house is dry. A van has condensation every cold night, and a boat has salt in the air permanently.
Salt air is the aggressive case. It attacks copper and it gets into any joint that isn't sealed. Marine practice is tinned copper wire throughout for this reason, and it's worth the premium in a van too if you're near the coast.
Connections that live in a locker, under a floor, or anywhere near a water system want to be sealed rather than merely tidy. Heat-shrink with adhesive lining on every crimp is the cheap version. For anything that has to be disconnectable — a solar panel, a removable seat with a heater, a detachable awning light — use a sealed circular connector with a locking coupling, rated IP67 or better, so the joint survives both the water and the vibration. Manufacturers like Verchil publish the IP rating and the cable diameter range for each shell size, and matching the gland to your actual cable is what makes the seal work rather than merely look sealed.
Low voltage means high current
This is the one that catches confident people.
Power is volts times amps. A 1,000 W load on a 230 V house circuit draws about 4.3 A. The same 1,000 W on a 12 V system draws over 83 A.
Nineteen times the current. Which means cable that would be absurdly overspecified in a house is the minimum in a van, and voltage drop over a run of a few metres becomes a design problem rather than a rounding error. Undersized DC cable doesn't trip anything. It just gets hot.
Two related points:
DC arcs don't self-extinguish. An AC arc is interrupted a hundred times a second as the waveform crosses zero. DC has no zero crossing, so an arc, once struck, keeps going. This is why DC-rated switches, fuses and breakers exist and why using AC-rated parts on a DC system is genuinely dangerous rather than pedantically wrong.
Fuse at the source. The fuse protects the cable, not the device. It belongs as close to the battery as physically possible, because everything between the battery and the fuse is unprotected — and a battery bank can deliver enough current to melt a cable into the bodywork before anything else reacts.
