Keeping your camper van cool can be the difference between an amazing off-grid experience and sweaty nights of frustration.
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A common solution to temperature management in campervans and RVs is the ever-popular 12v DC air conditioner. These compact, energy-efficient units are specifically designed to run on your van batteries 12V DC power.
In this guide, we’ll cover everything you need to know about choosing, placing, and wiring 12V air conditioners, along with key power considerations and helpful tips to get you going.
Let’s drive in.
12V battery-powered air conditioners are low-voltage cooling systems designed to work on the 12V DC system of your van’s leisure battery.
Unlike traditional high-voltage AC air conditioners, they can be run off-grid using standard electrical systems, making them perfect for enjoying a cool night out in the wild.
12V camper air conditioners are also designed for compactness and energy efficiency, making them ideal even for smaller campervans with tight spaces and smaller batteries.
As you might have guessed, they consume significantly less energy than their high-voltage counterparts, using small DC compressors to generate amazing cooling without needing shore power or dedicated generators.
To get the most out of a 12V air conditioner, you’ll need to take a few factors into consideration. Read on to learn more.
Common types include:
There’s no point splashing out on the best 12V air conditioner money can buy if your van isn’t properly insulated. Good insulation is crucial to keeping your camper van cool, and without it, much of the cold air generated by the unit will escape. This makes the unit work harder leading to increased power consumption, less running time off-grid, and increased wear.
Conversely, proper insulation in your walls, floors, and windows will reduce your cooling needs and extend the life of your battery.
Proper airflow throughout your van is also vital to effective cooling. Be sure to factor in venting to your build, ensuring the vents are strategically placed to let cool air circulate efficiently. Without this, pockets of hot air can form around the van, reducing the effectiveness of your air conditioner.
Once these challenges are tackled, it’s time to move on to the fun part: electrics!
Successfully wiring in your 12V air conditioner needs careful planning to ensure it works properly and compliant with wiring safety regs like BS Electrical standards.
Tools you’ll need:
Without further ado, here’s a step-by-step guide to wiring your system.
Before starting the wiring process, it’s important to assess the power draw of your air conditioner. The formula for this is A (Amps) = W (Watts) / V (Voltage).
You can use this to calculate current draw by dividing the watts drawn by 12 to work out the amperage of the system.
For example, a W 12V air conditioner will draw about 150A of power from the battery (W ÷ 12V = 150A).
It’s crucial to make sure that the battery, wires, and fuses in your circuit can safely handle this load.
Wires are rated based on how much current they can carry. This is calculated based on their cross-sectional diameter and the material they’re made of.
We’ll assume you’re using regular stranded copper wiring due to it being the most common type, both due to its low cost and flexibility (which makes it great for stuffing behind camper van interior panelling).
Be aware, getting this wrong and using too small of a wire can lead to significant safety concerns including overheating and fires.
For that reason, we don’t use the minimum possible sizes. Instead, we use thicker wires to increase the safety margin and avoid voltage drop.
For our example current of 150A, a standard gauge wire (SWG) of 8.mm is recommended for short distances of around 10 metres. For our transatlantic cousins who insist on the imperial system, that’s equivalent to 1/0 in American wire gauge (AWG).
In addition to the right wire gauge, fuses further prevent your electrical system from fires when the current exceeds a safe threshold.
That means the fuse needs to be rated lower than the power your wiring can carry, but higher than the draw of your air conditioner.
For example, for our 150A power draw, you should use a 200A fuse, with the wire being rated to around 250A to ensure safety.
These will be bigger than the standard blade fuses found in your glove box, which brings us to the next section.
Most campervans will use a regular 12V fuse box for regular appliances like LED lights and a minifridge, but your air conditioner will usually require its own circuit due to the higher current that is drawn.
For units pulling more than 100A, you’ll need dedicated mega or midi fuses in their own fuse holder sat in between the wiring from your AC unit to the battery.
Ensure this is easily accessible in case you need to replace the fuse in the event of a surge.
Here’s a simple 12V Campervan wiring diagram to help:
Bus bars distribute power evenly across multiple circuits. This is important as you’ll probably be powering more than one device from your 12V leisure battery.
Connect your air conditioners’ positive and negative wires to the right bus bars and install an appropriate breaker in the system for easy shut-off.
Logic would dictate that you need a 150A breaker for a 150A power draw, however, breakers can generally only handle around 80% of their actual rating.
That means a 200A breaker is actually more suitable for a 160A circuit, ideal for the 150A power draw of our example air conditioner.
Once you’ve got everything wired up, test your system using a multimeter to make sure the current readings are within safe limits.
Double-check for safety by ensuring there’s no excess heat coming from any of the connections or wiring after running the air conditioner for a few hours.
Once this is complete, you’re all set!
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In addition to choosing the right 12V air conditioner based on placement, there are a couple of other factors to consider. These include:
BTU rating. The cooling capacity of an air conditioning unit is measured in BTUs. This is essentially the amount of cooling power it can generate. The bigger your van’s interior, the more BTUs you’ll need. As a rough guide, small vans with a volume of 6 cubic metres might need a unit with 7,000 – 9,000 BTUs, while the biggest vans might need well over 10,000 BTUs.
Energy efficiency. Choose a unit that offers the highest energy efficiency available for your budget. This is measured in what’s called EER (Energy efficiency ratio). The higher the EER, the more efficient the 12V air conditioner, meaning it will draw less power from your battery
12V air conditioners. As we’ve discussed, these run straight from your van’s battery, making them perfect for off-grid camper van use. They’re also generally more energy efficient and use less power versus 230V units. However, there is a trade-off and 230V units are usually more powerful.
230V air conditioners. These units are generally more powerful and can cool bigger vans quicker. They need a 230V power supply to work which usually requires an inverter to convert the current from DC to AC. They’re more suitable for vans that can regularly recharge with shore power.
Your battery’s overall capacity is crucial when choosing a 12V air conditioner as it dictates how long the air conditioner can run when off-grid. For example, a 12V air conditioner drawing 100 amps can run for 4 hours on a 400Ah battery in eco mode. For higher power modes this runtime would be much shorter. This is why a high-capacity battery bank is essential for powering a 12V air conditioner off-grid for extended periods, such as overnight use.
Lithium Iron Phosphate (LiFePO4) batteries are usually the go-to due to their high efficiency, low weight, and better discharge capability compared to traditional AGM batteries.
You’ll want the highest Ah rating LiFePO4 battery that cost, space, and weight can allow for to provide the highest runtime possible, especially when running an air conditioner off-grid for extended periods.
You can also adjust the power settings on many modern 12V air conditioners to suit your recharging situation, with many offering eco and power modes. On the eco setting, some can draw as little as a quarter of the power as when they’re on power mode.
It’s important to match this power consumption to your battery’s capacity to avoid depleting your battery too quickly. Let’s look at some common scenarios to get a better understanding of how this looks in real-world terms.
Battery capacity: 200Ah
Usage: 1 hour/day
Off-grid time: 4-5 days
Battery capacity: 300Ah
Usage: 1 hour/day
Off-grid time: 3-4 days
Battery capacity: 400Ah
Usage: 1 hour/day
Off-grid time: 2-3 days.
It’s also worth considering how the battery will be charged. In general, there are three different methods to achieve this, which can be combined with one another:
Solar charging. With the cost of solar panels dropping in recent years, it’s common for camper vans to convert sunlight into electricity to recharge leisure batteries. MPPT controllers are better for this as they’re more efficient than PWM controllers.
Split charging. Split charging relays (SCRs) connect to your campervan’s alternator to charge the leisure battery while driving. There are also DC-DC chargers which are more efficient and ideal for newer vans with smart alternators. These can also cater to solar input to combine alternator charging with solar input.
Shore power. This uses an onboard mains charger to recharge your battery by connecting to electrical hookups, such as those found at campsites. Alternatively, portable generators can recharge your battery. These are great as a backup when you’re off-grid and there isn’t enough sunlight.
For off-grid charging, solar is ideal and you can be more lenient when making your power calculations as solar panels will help offset the air conditioner’s power consumption during the day.
The exact number and size of panels you’ll need will depend on your overall energy needs and the amount of available flat space on your van’s roof. You’ll also need to factor in the additional power systems required to integrate solar charging into your setup.
While 12V air conditioners are popular, there are alternatives available. These include:
Portable AC units. These run off a 110V or 230V power system and generally require an inverter to use. They’re not as efficient as 12V units but can be a good option if you normally stay at campsites where shore power is available.
Evaporative coolers. These consume less energy than traditional air conditioners and work by pulling in warm air and passing it over water-saturated pads to cool it before recirculating. This works best in dry environments and isn’t suitable for travel in humid regions.
Ventilation and fans. This also consumes much less energy than air conditioning units, relying on simple airflow increases through vents, windows, and fans. This method helps to exhaust hot air and bring in cooler air but won’t achieve anywhere near the same level of cooling as an air conditioning unit.
Pricing for 12V air conditioners depends on the type of unit, along with its size and the brand you choose. As a rough guide:
Portable 12V Air Conditioners. Typically cost between £400 – £ depending on capacity. Some are only suitable for small spaces and have limited power modes.
Roof-Mounted 12V Air Conditioners. The most common type of 12V air conditioner, these usually cost between £ and £, with large premium units coming in at well over £.
Evaporative Coolers. Generally more affordable, these cost anywhere between £500 – £ and are great for saving money in dry climates.
Installing a 12V air conditioner can drastically improve your comfort during hot weather adventures, and the wiring process can be a particularly rewarding introduction to electrical systems.
If you’re in the process of combing through forums and piecing together a shopping list of components, why not use Vunked’s simple builder to build the perfect kit for your project? You’ll receive full wiring diagrams and detailed installation instructions.
Take the stress out of camper van wiring with our online tool that helps you choose the right parts for your build. You’ll get every bit and piece you need, along with the peace of mind of knowing your system is up to professional wiring and safety standards.
Maintenance is key to keeping your 12V air conditioner working properly. Regularly clean the filters and inspect the wiring for any corrosion or damage and to check the refrigerant levels to keep your system running efficiently. You should also be sure to follow the manufacturer’s instructions when doing your annual checks.
Yes, you can run a 12V air conditioner off solar power. However, you need to make sure your solar system and battery capacity are in line with the energy requirements of the unit you choose.
Large solar setups of 500W-W combined with a high capacity LiFePO4 battery should be ample to run energy efficient units during the day time. Just be sure to calculate your overall daily energy consumption and balance it with the amount of input your solar set-up provides.
The lifespan of your 12V air conditioner will depend on the unit’s build quality and how often you use it. It’s also important to maintain it according to the manufacturer’s guidelines to get the most out of your purchase. High-end units from reputable brands can last up to 15 years.
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