12 & 24V in the Vehicle

Distribute power, switch appliances and charge your devices on the road: here you’ll find components for the 12 V or 24 V electrical system in your camper van or motorhome. From fuses and distribution blocks to sockets and USB charging points, the voltage ratings, current capacity and connections need to suit your installation.

Which components do you need for your 12 V or 24 V electrical system?

To supply your appliances reliably, power from the leisure battery needs to be distributed, protected by suitable fuses and switched where required. The components you need depend on the number of circuits, the connected devices and how you want to control them.

Our subcategories help you start with the task at hand:

• Circuit protection: Choose fuses and fuse holders to protect your circuits.
• Switches & controls: Switch individual appliances or sections of your power supply on and off.
• Plugs & sockets: Connect appliances and install suitable charging points in your vehicle.
• Power distribution: Organise the supply to multiple appliances using distribution blocks and busbars.
• Wireless charging: Charge a compatible smartphone without plugging in a cable.

12 V or 24 V: What voltage is present at the connection?

What matters is the voltage of the circuit you intend to connect the component to. The vehicle and living area do not necessarily use the same voltage: a vehicle with a 24 V starter battery system may, for example, have a separate 12 V habitation system.

Check the permitted input voltage range of every device. A “12/24 V” label may mean that a product supports both systems, while other listings offer separate versions to choose from. Actual battery voltage is not constant either: it changes with factors such as state of charge and charging conditions. A suitable device must tolerate the voltage range it will encounter during operation.

Circuit protection: Which fuse suits your circuit?

A fuse is designed to interrupt a faulty circuit before excessive current causes damage. Its selection therefore depends not only on the connected appliance, but also on the cable, other components and the device’s installation requirements.

Check the fuse type, current rating and DC voltage rating. Its breaking capacity must also suit the system: this specifies the fault current the fuse can safely interrupt. It is a particularly important consideration with powerful battery banks.

The fuse and holder must be compatible. Fitting a higher-rated fuse because the existing one keeps blowing is not a solution to an overloaded or faulty circuit.

Power distribution: How many connections and how much total current do you need?

A fuse block distributes power to several individually fused circuits. A busbar provides shared connection points for positive or negative cables, but does not automatically include circuit protection. Always check which functions a distribution component actually provides.

Start by counting your planned circuits and allow spare capacity for future additions. Then compare the permitted current per output with the unit’s total current rating. Several individually rated outputs do not mean you can use all of them at their maximum current simultaneously.

For a new conversion, a central electrical distribution unit combining several distribution and protection functions may be useful. If you only need one extra circuit, a smaller addition to your existing installation may be enough. Your current setup and the functions you actually need should guide the choice.

Switch, relay or battery isolator: What do you want to control?

A switch for a small appliance performs a different job from a battery isolator. Choose according to the intended function and permitted DC load. An AC current rating cannot simply be applied to your 12 V or 24 V DC system.

A relay is useful when a low-current control circuit needs to switch a higher-current load. Both the coil voltage and the contact ratings must be suitable. Also account for possible startup currents from appliances containing motors or electronics.

When choosing a battery isolator, consider which circuits should be disconnected and which may need a permanent supply. Devices with a controlled shutdown or run-on cycle, such as a diesel heater, must not simply have their power cut during that process.

Plugs and sockets: The right connection for your appliance

Choose a connection that matches your appliance’s plug and required current. A conventional cigarette-lighter-style socket, a smaller DIN accessory socket and a dedicated high-current connector are not freely interchangeable.

Alongside the electrical rating, consider the location: will the connection be protected inside the vehicle, or exposed to moisture and dirt? Will a cable be plugged in frequently, or does it need to remain securely connected? For covered outdoor connections, check the conditions under which the stated ingress protection rating applies.

Also check mounting depth, cut-out dimensions and what is included. With modular switches and sockets, the insert, frame and any cover must be compatible with the same range.

USB charging sockets: Is there enough power for your laptop?

A USB-C socket alone does not tell you how quickly it will charge your device. The supported charging protocols, available output voltages and power per port are what matter. Many laptops, for example, require USB Power Delivery with a suitable power profile. The cable must support it too.

Also check the output the charging socket can actually provide at your vehicle’s system voltage. Some models only deliver their maximum output at a higher input voltage. Devices with suitable buck-boost technology can increase or decrease voltage, allowing them to provide higher USB charging voltages even from a 12 V electrical system.

If there are several USB ports, check whether they share the total power available. The advertised maximum is not necessarily available from every port at the same time. A suitable USB charging point lets you charge compatible devices directly from your vehicle’s electrical system without switching on a 230 V inverter.

Wireless charging: convenient when your phone and installation are compatible

For wireless charging, the smartphone and charger must support a common charging standard. Compare the charging power available for your phone and check whether its case is suitable.

Secure positioning matters while driving: the phone needs to stay on the charging surface and remain aligned with the charging coils. Choose a design that suits the installation location and your device’s dimensions. If your priority is fast charging with low energy losses, a suitable wired connection is often the better choice.

12 V appliances in a 24 V system: When do you need a voltage converter?

An appliance designed exclusively for 12 V must not be connected directly to a 24 V system. A suitable DC-DC converter provides the required supply voltage. Choose it according to its input range, output voltage and the combined power demand of all appliances that will run simultaneously. Startup surges and conditions at the installation location also need to be taken into account.

A voltage converter designed to power appliances is not automatically a battery charger. If you want to charge a second battery, you need a device approved for that purpose. You can find suitable options in our Alternator charging category.

What to compare before buying

• Purpose: Do you want to protect a circuit, distribute power, switch a load or connect and charge a device?
• Voltage: Is the component suitable for the actual operating voltage range of the intended circuit?
• Current capacity: Are the current ratings per connection and for the complete component sufficient?
• Compatibility: Does the fuse type, connector system, charging protocol or modular switch range match the other components?
• Installation location: Are the dimensions, mounting method and protection against moisture and dirt suitable?
• Installation: Are cables, connections and circuit protection correctly matched, with room for future expansion?