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How To Build A 12v System In A Camper Van (With Diagrams)

From batteries, to specific devices, and wiring diagrams, this post teaches you how to set up your own 12v system in a camper van.

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Building a 12v system is a critical part of a camper van’s comprehensive electrical system. This is because most of the deep-cycle batteries sold here in North America are 12-volt batteries. So installing an electrical system that can be run directly from the batteries is a big convenience.

Not from North America? If you happen to be located in Europe, Australia, or elsewhere, chances are you might be looking to build a 24v system instead of 12v. If so, this article is STILL helpful for you. The information provided here is the same, just replace 12v with 24v and you’ll be fine.

In this post, we will detail how to build a 12v system in your camper van. Along the way, we’ll talk about the different batteries and devices you can buy for your electrical system.

Lastly, we’ll provide several 12v wiring diagrams and discuss how to hook everything together to get your own 12v system up and running.

Choosing The Right Batteries For Your 12v System

At the heart of any 12v system are the batteries. They provide the power required to run all the devices that you’ll eventually install in your camper, such as your lights, fan, fridge, etc.

(But we’ll talk more about popular 12v devices further below in this post).

When looking online, you’ll notice lots of different types of batteries. Different chemistries (lead acid vs lithium) and different capacities. It can be a bit confusing if you’re just starting out!

Let’s quickly talk about two of the important aspects of ‘deep-cycle batteries’ that are commonly used for camper van builds.

Battery Chemistry

AGM vs Lithium-Ion Batteries
Lithium vs AGM Batteries

One of the biggest questions you may have when choosing your house batteries is which ‘type’ of battery to select: AGM (Lead-Acid) or Lithium-Ion?

Unfortunately batteries are not all the same and each type has their own benefits, drawbacks, and even their own unique charging quirks.

If you’re not sure about which battery type to go with, we recommend opening a new tab and reading this post first: AGM vs Lithium: Which Battery Is Best For Your Camper?

Battery Storage Capacity

After battery chemistry, the next most important aspect of a 12v battery is the amount of energy it can store, which is typically rated in Amp-hours (Ah).

Most 12v batteries typically come rated at 100Ah, but you can also find batteries that are rated for 200-300Ah.

You can also hook up multiple batteries in parallel to increase the overall energy capacity, thus creating a ‘battery bank’.

For Example: In our camper van, we have three 100Ah lithium (LiFePO4) batteries. Therefore, our battery bank capacity is 300Ah.

What Is An Ideal 12v Battery Bank Capacity?

The ‘ideal’ battery bank capacity depends entirely on what electronic devices you plan to run in your camper van. And since everyone’s list of devices is different, it means everyone’s ‘ideal’ battery capacity is also different.

To calculate your own ideal battery capacity, we recommend reading this post: How To Calculate Your Ideal Battery Bank Size

Selecting The Right Devices For Your 12v System

Which 12v devices you want to put into your camper is entirely up to you. Below we list the six most popular 12v device groups for camper van builds.

Lights

Installing lights that run on 12v is a great way to brighten up your van’s interior when natural sunlight isn’t sufficient. We recommend getting a pack of LED Puck Lights to install in your camper’s ceiling. They’re bright, provide warm colored light, and draw only a tiny amount of power from your batteries.

Puck Light Stats:
Usefulness 9.5/10
Energy Draw 0.17ah per puck light

LED Puck Lights

To learn more about how to install LED puck lights, head over to our other post: How To Install A Beautiful Cedar Plank Ceiling.

Puck lights not what you’re looking for? Check out these two other popular alternatives.

LED Strip Lights

12v Reading Lights

Ventilation Fan

A roof vent fan is practically a must when living and traveling in a camper van. Vent fans not only help to bring in cool, fresh air and expel stale air, but they also help to regulate the internal temperature of your van and get rid of greasy smells when cooking.

We leave our vent fan on 90% of the time while we’re in the van.

Best of all, if you choose the MaxxFan, the product comes with a built-in rain cover so you can even use the fan when it’s raining. In our experience, a rain cover is critical.

Vent Fan Stats:
Usefulness 10/10
Energy Draw 0.25ah when on low

MaxxFan Vent Fan

Maxxair Maxxfan - Best RV Vent Fan
Maxxair 5100 MaxxFan

Want to learn more about our 12v vent fan? Check out our MaxxFan Product Review

12v Sockets & USB Ports

Having at least one pair of USB & 12v sockets is invaluable for van life. With sockets like these, there are so many different electrical devices that you can power. From your smartphones, to desktop fans, 12v fridges, USB propane detectors, cameras, portable inverters, and even aromatherapy diffusers. The list is endless.

We’ve installed 3 pairs of these USB & 12v combo sockets throughout our van and they are constantly in use.

USB & 12v Sockets Stats:
Usefulness 9.5/10
Energy Draw N/A (depends what is plugged in)

12v Socket & USB Ports

12v Fridge

Dometic 46L Electric Cooler - Camper Van Kitchen Essentials

A 12v fridge is an under-appreciated appliance in many camper builds. Good quality RV fridges aren’t cheap and can take up valuable space inside a van. But having a fridge is practically a necessity when planning to live and travel long term in a camper. Compared to cheaper coolers, having a proper 12v fridge keeps your food cool 24/7, eliminates the need to look for ice every 2-3 days, and allows you to boondock in the countryside for much longer periods of time.

We love our 12v Dometic fridge and wouldn’t go any other route to keep our food cool.

Fridge Stats:
Usefulness 9/10
Energy Draw 0.72ah

Diesel Heater

Van Life Heating - Fuel Operated Heaters
Espar D2 Diesel Heater

Installing a diesel heater in a van is a luxury item, but it’s amazing how well they work, how fuel efficient they are, and how comfortable they can make winter van life.

For two days we were stuck at a campsite in Grand Canyon National Park after 2 feet of snow fell all around us. Though temperatures dropped to 9F (-13C) at night, we were still warm & toasty inside. Our diesel heater has also made getting up in the mornings so much easier because with just a push of a button, our van heats up in minutes.

Diesel Heater Stats:
Usefulness 9/10 in the winter
Energy Draw 1.7ah

Water Pump

12v Water Pump For Camper Van Water System

A water pump is a convenient item to have when it comes to van life. We installed one because we wanted our camper van to feel more like a real home with instant running water with just  a flick of a switch. If we could build a second van conversion, we would 100% install a water pump again.

Check out our other post to learn more how to install a water & plumbing system in a camper.

Water Pump Stats:
Usefulness 4/10
Energy Draw 1.7ah

What Next?

Below, we delve into how to build your own 12v camper van system.

But to complete the installation below, we assume you’ve already planned the location of your batteries and 12v devices and already laid out your 14 AWG wire throughout the van. If you haven’t, check out our other post: How To Lay Out Electrical Wiring In A Camper

How To Install A 12v System (With 12v Wiring Diagrams)

How To Connect A 12v System In A Camper Van

Now that you’ve selected your batteries and 12v devices, it’s time to wire them all together to create a functioning 12v system in your camper van. To do this, we break down the installation process into four steps.

Warning: This section is quite long and detailed, but this step-by-step installation guide will get your 12v system up and running.

If you’re ready, let’s get to it!

Step 1: How To Wire Multiple 12v Batteries Together

If, like us, you will have more than one battery then you will first need to connect those batteries together.

First, it’s critical to remember these two things:

  1. Wiring batteries in series keeps the Amp-hours (Ah) the same (energy capacity), but combines the voltage.
  2. Wiring batteries in parallel keeps the voltage the same, but combines the Ah.

Therefore, if you’re trying to run a 12v system and your batteries are already 12v, then you SHOULD NOT wire them in series. 

Instead, wiring your batteries in parallel will increase your energy storage capacity and keep your voltage the same.

Fig 1.1: Connecting Deep Cycle Batteries In Parallel
Wiring Three Batteries In Parallel

To connect multiple batteries in parallel, simply combine all the positive terminals together (red wire) and all the negative terminals together (black wire) using 3/8″ wire lugs.

Crimp the wire lugs onto the wire ends with a hammer lug crimper.

For safety, we recommend going with a thicker 2/0 AWG wire. Thicker wires are able to handle greater amounts of current safely without overheating. This is especially good if you plan to be able to charge your batteries from shore power.

After adding shrink wrap, your wire ends should look something like this and are ready to connect to the battery terminals.

00 Wire End With 3/8" Ring Connector
2/0 wire end with attached 3/8" ring connector

Tools & Products Needed

Step 2: Connecting Batteries To Bus Bars

Fig 2.1: Connecting Batteries To Bus Bars
Connecting A Battery Bank To Bus Bars

Rather than wiring all your devices directly to your battery, it’s good practice to first connect your batteries to bus bars.

Bus bars are an electric power distribution block that helps to keep your wire connections neat and tidy. And while bus bars are not technically required for a fully functioning electrical system, they’re very much recommended.

Now we’ll discuss how to connect your batteries to those bus bars.

The Positive (+) Side Connections

1. Connect Battery Bank Positive Terminal to Master Switch

Master On/Off Switch For Camper Electrical System
Master On/Off Switch

Using the same 2/0 wire and 3/8″ ring connectors, connect one of your battery’s positive posts  to the master on/off switch.

A master switch is useful to turn off your van’s electrical system for when you need to safely work on your electrical system or when you want to store your camper van long term and want to disconnect parasitic loads.

2. Connect Master Switch To 300amp Fuse

Coming out of the master switch, take more 2/0 wire with ring connectors and connect to a 300amp fuse (with holder)

This fuse will protect your 2/0 wire and downstream devices from unexpected electrical surges.

3. 300A Fuse To Red Bus Bar

Red Bus Bar
Red (Positive) Bus Bar

From the 300A fuse, connect straight to the red (positive) bus bar.

This bus bar will become the positive current collection/distribution center for your van’s electrical system.

The Negative (-) Side Connections

4. Negative Terminal To Battery Monitor Shunt

Victron Battery Monitor - Proper Battery Maintenance
Battery Monitor - Display & Shunt

From one of the negative battery terminals take your black 2/0 wire and connect to your battery monitor shunt.

A battery monitor is an optional component, but highly recommended. The battery monitor serves two purposes.

1. Displays the remaining percentage charge of the battery bank.
2. Shows the instantaneous net flow of charge into, or out, of the batteries.

If you use the Victron battery monitor, like we do, you can connect the shunt to the circular user interface device with the supplied RJ12 cable to display the battery charge information.

5. Battery Monitor Shunt To Black Bus Bar

Black Bus Bar
Black Bus Bus

On the other side of the battery monitor shunt, take more black 2/0 wire and connect straight to the black (negative) bus bar.

This bus bar will become the negative current collection/distribution center for your van’s electrical system.

Tools & Products Needed

Step 3: Connecting The Bus Bars To The 12v Distribution Panel

To keep things even tidier, 12v distribution blocks exist to accept all 12v load connections and provide a slot to fuse each load separately.

Like the bus bars, while not ‘technically’ required, a 12v distribution block is really recommended for any camper 12v system.

In our van, we connect all our 12v loads to a Blue Sea Systems 12v Distribution Block.

12v System Installation - 12v Distribution Panel
12v Distribution Panel
Fig 3.1: Connecting The 12v Panel To The Bus Bars

From the positive bus bar, run a piece of red 2/0 wire to the positive terminal of the 12v distribution block. In-between this connection, you’ll want to install a 120amp circuit breaker.

(Refer to the above wiring diagram)

From the negative bus bar, run another piece of black 2/0 wire to the negative terminal of the 12v distribution block.

Tools & Products Needed

Step 4: Connecting The 12v Distribution Panel To All 12v Devices

Lastly, you can now connect all your 12v devices to the distribution block.

To do this, simply attach a #8 ring connector to the end of each red and black wire and connect each wire to the distribution panel. See the below 12v distribution wiring diagram below.

For all 12v device wiring, we recommend using 14 AWG wire.

Connecting 12v Loads To Distribution Panel

You will also need to insert a blade fuse into each slot (blade fuses sold separately).

Blade fuses are generally rated for every 5 amps. So you can find 1A, 3A, 5A, 10A, 15A, and 20A fuses.

To calculate which size fuse is needed for each device, simply take the total watts the device is rated for and divide by 12. Take the result and round up to the next size rated fuse.

Tools & Products Needed

Save This Info For Later!

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Setting Up A 12v System In A Camper Van Is Just The First Step

Great job! If you followed this post from beginning to end, you should have a solid understanding of what is needed to build your own 12v system in your camper.

As we mentioned above, the 12v system is the heart and soul of any camper electrical system. But it’s not the only part. There are other pieces to the overall electrical system puzzle as well.

For more, check out our solar panel series. It’s a 7-part series that will take you through the entire process to build a robust solar panel system for your camper.

Or…head back to our camper van electrical system homepage.

Happy Building!

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