12V, 24V or 48V
Choosing a caravan system voltage.
Almost every van runs at 12V, and for most buyers that is the end of it.
The big off-grid builds run 48V, because air conditioning and induction cooking pull too much current at 12V.
Changing your mind later means replacing the battery, both chargers, the solar controller and the inverter.
Updated . 11 min read • Technical Guide
12V suits almost every van. 48V is for vans built around air conditioning, induction cooking or a large battery bank.
You choose the voltage once. The battery, both chargers, the solar controller and the inverter are all built for one voltage, so changing it later means changing all of them.
- Current at the same power - a quarter at 48V (compared with 12V, because power is volts multiplied by amps)
- Copper for the same voltage drop - about a sixteenth at 48V (same load in watts, same length of run)
- Changing voltage later - a system rewire (the battery, charger, solar controller and inverter all change with it)
The 30-second version
What the system voltage actually decides
The system voltage is what the van's battery bank runs at. Almost every caravan built in Australia runs at 12V, which is why a caravan battery is normally quoted in amp-hours at 12V.
The most expensive parts in the van are each built for one voltage and will not run on another. Pick the voltage and you have picked the battery, both chargers, the solar controller and the inverter with it.
Decided by the voltage
- The battery bank itself
- The mains charger
- The DC-DC charger from the car
- The solar controller
- The inverter
- The size of every cable between them
Not decided by it
- How much energy you can store
- How much solar you can fit on the roof
- What the fridge, lights and pump are
- What you can run at once
How much energy you can store, and how much you can draw at once, are set by the battery, the solar and the inverter, whatever voltage they run at.
Same watts, less current, less cable
Power is volts multiplied by amps, so the same appliance at four times the voltage draws a quarter of the current.
Current decides how thick the cable has to be, how much of your battery turns into heat on the way to the appliance, and how big the lugs and fuses get. A quarter of the current is a quarter of the volts lost over the same cable.
Follow it through and the copper needed to hold the same percentage drop is about a sixteenth. That is how a 48V van runs a household air conditioner off its battery on cable a person can bend and route.
A worked example: 1,200W over 6 metres of 16mm² cable
Same appliance, same cable, same run. Only the system voltage changes.
- At 12V: 100A through the cable, 1.31V lost, which is 10.9% of the supply.
- At 48V: 25A through the same cable, 0.33V lost, which is 0.7% of the supply.
The 12V version of that circuit needs much heavier cable. That only matters once the loads get big, which is why most vans never meet the problem.
Put your own load and run into the calculator and it works this out at all three voltages.
Those figures use 0.0175 ohm mm² per metre for copper at 20 degrees, and count the cable run twice because the current returns down the negative. The calculator shows the same working.
The appliances stay 12V either way
Caravan gear is built around 12V. Compressor fridges, water pumps, LED lighting, roof fans, radios and most reversing cameras are 12V parts, and that is what the aftermarket and the repairer down the road stock.
A 24V or 48V system does not change that. It feeds those 12V parts through a converter that steps the voltage down, so the van still has a 12V side, with an extra piece of equipment in front of it.
The heavy current stays on the short runs between the battery and the inverter, and the converter feeds the fridge, the lights and the pump at 12V.
Which voltage suits which van
12V suits a van whose biggest draws are a fridge, lights, a pump and a modest inverter, which is most caravans. A higher voltage earns its place when the van is built around air conditioning, induction cooking or a large battery bank, because those are the loads that make 12V cable heavy.
24V sits between them and shows up mostly in self-built and heavily modified vans, where the builder is choosing every component anyway.
Starting a load is the hard part
Appliances do not draw their label number evenly. A compressor or a motor pulls several times its running draw for the first moment while it gets itself turning, and even a kettle asks for more at the instant it switches on than the box suggests.
An inverter carries two ratings for that reason. Continuous is what it can hold all day, and it decides what keeps running. Surge is what it can cover for a few seconds, and it decides what starts.
Plenty of off-grid setups run everything on board comfortably and still trip the moment the air conditioning compressor starts, because that first moment lands on the surge rating.
What to ask about an inverter
Ask for the inverter's continuous rating, its surge rating, and how long the surge holds. A brochure often prints the continuous figure on its own, and the surge rating is what decides whether the air conditioner or the kettle will start.
Surge is set by the inverter, and the system voltage does not change it. The vans built around big inverters are the same vans that have moved to 48V.
Changing the voltage later is a rebuild
Everything in the first list above changes together.
Going from 12V to 48V means a new battery bank, a new mains charger, a new DC-DC charger, a new solar controller and a new inverter, plus a converter to keep feeding the 12V side of the van. The cable can often stay, because the higher voltage asks less of it.
Settle the voltage before you buy any of those parts.
The line where the electrician takes over
Battery systems, chargers and inverters get specified and installed by a qualified auto electrician. Sizing a cable on voltage drop, which is what our calculator does, is only half the question: a cable also has a current rating that depends on how it is built, bundled and run.
Use these numbers to check a quote and to ask the electrician better questions before the work starts.
How to read this on a spec sheet
Put every battery into watt-hours before you compare it with another one. Multiply the volts by the amp-hours.
Amp-hours alone are not comparable across voltages. An amp-hour at 48V carries four times the energy of an amp-hour at 12V, so a 100Ah figure means very different things on the two systems. A 48V pack is often quoted in kilowatt-hours instead, which is the same thing in bigger units.
Worth asking about
- The system voltage. Stated plainly, in writing.
- Battery capacity in watt-hours or kilowatt-hours. The one figure that compares across any two vans.
- What feeds the 12V side. On a higher-voltage van, ask what steps it down and what happens to the fridge and lights if that part fails.
- Who services it. Ask where the van goes for battery-system work, and how far away that is from where you travel.
Vans that describe a 48V system
Higher-voltage builds are usually sold as part of a bigger off-grid or gasless package. These are ranges whose own description names a 48 volt system.
- Arctic CampersFrost 13
- Arctic CampersFrost 15 Bunk
- Arctic CampersFrost 15 LK
- Arctic CampersFrost 15 S
- Arctic CampersFrost 18
- Arctic CampersGlacier 14
- Arctic CampersGlacier 14 TS
- Arctic CampersGlacier 16
- Arctic CampersPolar 15
- Arctic CampersPolar 18
- BruderEXP-10
- EzytrailCeduna 15 Quad MK4
- HarvokCoastalor 22FT
- HarvokDream Cruise 19.6FT
- HarvokIronBark 18FT
- HarvokOcean Breeze 18FT
- HarvokPowerBank 22 FT
- HarvokSuit of Armour 16FT
- HarvokSuit of Armour 19.6FT
- Jayco AustraliaAdventurer 48V
- Jayco AustraliaSilverline
- Legend CaravansGroundbreaker Ultimate Off-Road
- Legend CaravansLegend Hybrid (Trackline 48V Standard)
- Legend CaravansLegend Ultimate Hybrid ERV
- Legend CaravansTrackline Bunka Family Series
- Market Direct CampersXT15 POP MK4
- New Age CaravansNam8
- Nova CaravansBravo
- Nova CaravansPride Platinum
- Retreat CaravansERV
What a gasless van changes about cooking, hot water and servicing is covered in electric caravans.
System voltage questions, answered
Can I convert my 12V caravan to 48V?
It is a rebuild of the whole system. The battery, the charger, the DC-DC charger from the car, the solar controller and the inverter are each built for one voltage, so changing the system voltage means changing all of them, and the 12V appliances still need a converter feeding them afterwards. Settle the voltage before you buy any of those parts, and have the work done by a qualified auto electrician.
Why do caravan builders use 48V at all if appliances are 12V?
Because 48V draws about a quarter of the current that 12V does for the same watts. Power is volts multiplied by amps, and both voltage drop and heat in the cable follow the current. So once a van carries a large inverter, air conditioning or a big battery bank, the cable and connections a 12V version would need get heavy, expensive and awkward to route. The higher voltage takes that problem away.
Is 24V a sensible middle ground for a caravan?
It is a common choice in a self-built or heavily modified van, and much less common in a factory one. It halves the current compared with 12V, which quarters the copper needed for the same voltage drop, and it stays closer to the 12V parts most caravan gear is built around. The tradeoff is supply: more caravan-specific components are made for 12V than for 24V, so parts and repairs on the road can be harder to source.
Does a higher system voltage give me more power?
No. How much energy you have is set by the battery capacity in watt-hours and by how much your solar and charger put back. How much you can draw at once is set by the inverter and the battery's own limits. A higher voltage moves that same power through thinner cable with less of it lost as heat, which is a wiring advantage.
Why does my inverter cut out when the kettle or the aircon starts?
Because starting a load is harder than running it. Compressors and motors pull several times their running draw for the first moment, and even a kettle asks for more at switch-on than its label suggests. An inverter carries two ratings for exactly this: continuous, which decides what keeps running, and surge, which decides what starts. If the surge rating cannot cover that first moment, the inverter shuts down to protect itself, even though it could have run the load comfortably once started. Ask for both ratings, and for how long the surge holds.
How do I compare a 48V battery with a 12V one?
Convert both to watt-hours, by multiplying the volts by the amp-hours. Amp-hours on their own are not comparable across voltages, because an amp-hour at 48V carries four times the energy of an amp-hour at 12V. A 48V pack is often quoted in kilowatt-hours already, which is the same figure in bigger units. Compare the watt-hour figures and you can see which battery holds more.
Put your own numbers through it
The cable calculator works out the volts lost on your run, at all three system voltages, and the smallest size that meets your target.