Caravan Solar Setup Checklist

Three charging paths, one battery

A caravan house battery refills from three sources. The vehicle alternator through a DC-DC charger while driving. A roof or portable solar panel through a regulator while parked. And a shore-power or generator charger at a caravan park.

The alternator is the workhorse. On a long driving day it delivers more energy than the solar panel will in a week. The panel handles the overnight fridge drain at a quiet site without running the vehicle.

Shore power is the reset. After a cloudy week or a heavy usage weekend, the park's 230V hook-up fills the bank in a few hours. The three paths are complementary and no one alone covers every scenario.

The wiring between these three sources must not fight each other. A combiner or priority switch prevents the solar regulator and the DC-DC charger from competing at the same battery terminal.

Anderson plug is the single point of failure: If the plug corrodes, overheats or the crimp fails, the caravan loses its primary charge source. Inspect it before every trip and carry a spare set of pins.

The DC-DC charger handles distance, solar handles overnight quiet, and shore power handles recovery. Three paths, one battery, never in conflict.

The fridge is the boss load

A compressor fridge runs for eight to twelve hours a day in warm weather, cycling every twenty to forty minutes. On a hot afternoon it can pull fifty amp-hours from a 100Ah battery. That number sets every other decision.

Start-up current is the hidden challenge. A compressor can surge to three to seven times its running draw for a fraction of a second. Cable, fuse and battery must all handle that without voltage dropping enough to reset electronics.

The efficient solution is not a bigger battery. It is a well-insulated box, a good door seal, a shade position in camp, and a thermostat that avoids short-cycling in heat. Reducing the fridge's duty cycle is cheaper than doubling capacity.

Duty cycle, not watts: A 60-watt average fridge running 12 hours costs 720 watt-hours per night. Shade and a good seal cut the run-time and save more than a 200-watt panel.

The fridge sets the bank size, the cable gauge and the fuse rating. Optimise the fridge's duty cycle before sizing everything else up.

Vibration is the fixed-system problem nobody warns about

A static array bolts once and sits. A caravan array sees continuous low-frequency vibration on corrugated roads, wind buffeting at highway speed, and thermal flex from roof temperature swings.

Screws back out. Solder joints crack. Cable insulation chafes against an edge it touched only when the vehicle moved. Every mechanical connection needs a lock washer, thread-lock or anti-vibration isolator, and a seasonal torque check.

The panel itself has a rated maximum static load. Driving wind load can exceed that at highway speed, and a rigid panel on an unbraced frame at the wrong angle becomes a sail. Low-profile mounts with adequate fasteners prevent this.

The annual torque round: Set a calendar reminder before the first trip of the season. Every bolt, every terminal, every Anderson crimp. Ten minutes that prevents a weekend stranded on the side of a road.

Vibration undoes everything over a season. Torque-check terminals annually, isolate mechanically, and mount panels low to reduce wind load at speed.

12 volts means current, and current means cable

At 12 volts, a 60-watt load draws five amps. A 120-watt compressor starting draws fifty. Voltage is fixed and low, so current climbs fast. Cable gauge and length are the difference between a working system and one with dim lights and a hot insulation smell.

The rule: size cable for the worst-case current at the fuse rating, not at the nominal load. A 40-amp fuse means the cable must carry 40 amps without a dangerous temperature rise. Voltage drop over the run should stay under five percent.

Cable quality matters. Copper-clad aluminium is cheaper and works fine for a signal wire. On a 40-amp feed it drops twice the voltage of oxygen-free copper and heats at the terminals. Spend on proper cable for the high-current runs.

The three-foot rule: On a caravan, most cable runs are under three metres. At 12 volts that is already long enough to lose real current in undersized wire. Use the gauge calculator, not the roll from the hardware store.

At 12 volts, current is always higher than intuition says. Size cable for the fuse rating, keep voltage drop under five percent, and use real copper for high-current runs.

Roof versus portable: the placement trade

A roof panel charges while the caravan is parked in shade under a tree. A portable panel on the ground in full sun charges far more, but you have to set it up, cable it in, and collect it before moving.

The practical answer for most caravanners is both: a permanent roof panel for maintenance trickle during the day, and a foldable portable for campsites where the vehicle parks in shade. The roof panel never reaches its rating under a canopy.

The portable layer adds a cable run through a window or gland. Keep that cable organised and the Anderson or MC4 connectors accessible. A portable panel that is a hassle to deploy gets used half as often as intended.

The shade reality: A 200-watt roof panel under a gum tree produces maybe 30 watts. The same panel on the ground in full sun produces 160. Placement beats size every time.

Roof panel for trickle while driving and parked. Portable panel for serious sun harvest at camp. Both, with a simple deployment routine.

DC-first: skip the inverter if you can

Every conversion costs energy. An inverter converting 12V DC to 230V AC loses ten to fifteen percent in the process, and sips power at idle even with nothing plugged in.

A fridge, lights, phone chargers, a water pump and a fan all exist as native 12V products. Designing the caravan's load list around DC appliances means the battery lasts longer and the system is simpler.

If 230V is genuinely needed for a laptop or a CPAP machine, a small 300-watt pure-sine inverter is fine. Switch it off when not in use and count its idle draw. A shore-power connection at a caravan park eliminates the need for an inverter entirely.

The idle draw math: A 300-watt inverter at idle sips two to three amps continuously. Over a night that is 24 to 36 amp-hours: a quarter of a 100Ah battery for nothing.

Run everything possible at 12V DC natively. If an inverter is needed, choose a small pure-sine unit and switch it off between uses to stop the idle drain.

Maintenance that prevents roadside faults

A fixed installation can run five years between inspections. A caravan should get a quick check before every trip and a thorough one every season. The road does not forgive a loose connection the way a roof does.

The five-minute pre-trip: glance at the Anderson plug for heat discolouration, check the battery terminals for corrosion, confirm the solar disconnect switch is in the right position, and listen for a fan noise from the DC-DC charger.

The seasonal deep check: torque every bolt and terminal, clean and re-grease the plug contacts, inspect cable routing for chafe against frame edges, verify the regulator's charge profile still matches the chemistry, and measure actual overnight draw against the expected budget.

The logbook: A small notebook in the glovebox: date, overnight draw, any changed behaviour, any new device added. Three entries a season tells you if something is drifting wrong.

Pre-trip takes five minutes and prevents most failures. Seasonal takes an hour and prevents the other half. Vibration does not forgive a loose connection.