12V, 24V or 48V: which system voltage for your camper van?

A 12V system is the standard for most camper van conversions. It is simple, affordable and compatible with virtually all camper van equipment.

Rule of thumb: with daily consumption up to about 1500 Wh and cable runs up to 5 metres, 12V works perfectly well. Most lighting, fridges, water pumps and USB chargers run on 12V.

The big advantage: you do not need a DC-DC converter for 12V appliances, and you can charge directly from your vehicle alternator.

With higher daily consumption (1500 to 4000 Wh) or longer cable runs, 24V becomes attractive. At the same wattage the current halves, allowing you to use thinner and cheaper cables.

At 24V you also have less voltage drop over longer distances. This is especially relevant in larger vans (6 metres and above) where cables from the battery to the dashboard are several metres long.

Note: most 12V equipment does not work at 24V. You need a DC-DC step-down converter (24V to 12V) for lighting, fridge and other 12V consumers. You also need a step-up B2B (battery to battery, a charger between the starter and house battery) charger (12V to 24V) because your alternator outputs 12V. This is an extra cost that many builders forget in their budget.

48V is the choice for professional or very intensive installations with daily consumption above 4000 Wh. Think of camper vans with air conditioning, large induction hobs or multiple workstations.

The advantages are similar to the step from 12V to 24V: even thinner cables, less voltage drop, smaller fuses. Additionally, 48V inverters are often more efficient than 12V variants at high power.

Downside: 48V components are more expensive and less widely available. The installation is more complex and at voltages above 50V, stricter safety requirements apply in some countries.

Power is voltage times current. The same power at a higher voltage means less current, and current is what makes your cables thick.

A 2,000 watt inverter draws about 196 amps from a 12 volt battery, with the 85 percent efficiency included. At 24 volts that is about 98 amps and at 48 volts about 49 amps. The cable that goes with it drops from 70 mm² to 16 mm² to 6 mm², and the fuse, the battery switch and the cable glands scale down with it. That saves money and space: a 70 mm² cable is barely bendable inside a cabinet.

Voltage drop works the same way. The same 3 percent loss buys you twice the cable length at 24 volts that it does at 12 volts. In a long van with the battery up front and the inverter at the back, that is the difference between a workable cable and an unaffordable one.

What does not scale is the 230 volt side. Beyond the inverter everything is the same, whatever sits on the battery side.

The main objection to 24 or 48 volts is not the batteries but the equipment. The camper world runs on 12 volts: compressor fridges, water pumps, diesel heaters, LED lighting, fans and car radios overwhelmingly come in that voltage only.

There are three answers to that:

• A step-down converter that turns 24 or 48 volts into a 12 volt circuit for all the small loads
• Equipment with a wide voltage range; many fridges and heaters run on both 12 and 24 volts
• Keeping everything large on the high voltage and only the small items on the converted circuit

The converter is an extra box with its own fuse and its own efficiency, usually 90 to 95 percent. It has to handle the simultaneous draw of all your 12 volt gear, so add that up before picking a size and leave margin for the fridge compressor's inrush current.

All three charging sources exist for 24 and 48 volts as well, but not in equal supply.

Solar is the easiest: an MPPT (maximum power point tracking, the technique that gets the most out of a panel) charge controller converts panel voltage to whatever the battery asks for, and at a higher battery voltage the same controller delivers more power for the same amperage. A 30 amp controller suits roughly 360 Wp (watt peak, the output under test conditions) of panels at 12 volts and roughly 720 Wp at 24 volts.

The alternator is harder. It produces 12 or sometimes 24 volts, and charging a 24 volt battery from it needs a charger that steps up, such as a 12 to 24 volt B2B charger. Watch what that asks of the alternator: on the input side it draws well over twice the current that comes out on the battery side.

Shore power chargers for 24 volts are widely available; for 48 volts the choice is thinner and dearer. That is usually the point where 48 volts falls away for an ordinary camper.

Overview of the three voltages with a 2000W inverter example:

12V: 196A current, 50 to 70mm2 cable, widely available, lowest component cost but most expensive cables24V: 98A current, 16mm2 cable, step-up B2B charger needed, mid-range cost48V: 49A current, 6mm2 cable, specialist, highest component cost but thinnest cables

Those currents include the inverter's efficiency, which sits around 85 percent. Work with power divided by voltage and you land on 167, 83 and 42 A, a quarter short every time.

Cable thickness directly affects the cost and weight of your installation. With a large inverter (2000W or more), the difference in cable costs alone can easily amount to hundreds of euros. Additionally, large inverters (3000W and above) operate more efficiently and run cooler at 48V than at 12V, which benefits their lifespan.

Start by calculating your daily consumption with the Super Wiring Wizard. That tool automatically recommends a system voltage based on your consumption and configuration.

Also consider: you can always create a 12V sub-system within a 24V or 48V installation using a DC-DC converter. This lets you combine a higher system voltage with your existing 12V equipment.

When in doubt, choose 12V. Switching to a higher voltage is a fundamental design decision that affects your entire wiring, battery bank and charging system.