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12V Electric Guide for Camper Vans & RVs (With Wiring Diagrams)

Building an electric system in a camper van is one of the most daunting projects when converting a van. There is a mind-boggling amount of products, components, and wires to piece together.

What products do you need, and in which order do you assemble them?

This post is a step-by-step installation guide and will specifically focus on how to build a 12v system in a camper van. We will specifically discuss:

  • Products you’ll need
  • Required tools
  • Installation order

We also provide many intuitive 12V wiring diagrams throughout this post to help you. Download our free electrical wiring diagrams ebook for offline reading.

So, if you’re ready, let’s dive into it.

12V System Wiring Overview

This post will show you how to build the same system as the diagram below. It can seem daunting at first, but we are taking a step-by-step approach to each section and introducing each of the products we use here and their purpose.

Complete camper van 12V wiring diagram connecting leisure batteries to 12V devices
Complete 12V wiring diagram for camper vans

If you are concerned about wire gauge, fuse sizing, breaker sizing, and general electrical safety, we will cover these throughout our post.

Just need the product list? Jump to our 12V parts list for a full itemization of everything we use and recommend.

Step 1: Select Your Batteries

The batteries are the heart of your 12V system and provide power to all your electrical devices. Selecting your batteries is the ideal first step when building your system.

But when browsing online, you’ll come across many types of batteries of varying chemistries, voltages, and Amp-hours (Ah). Which is best for you? We simplify the process for you here:

  • Type: Look for “deep cycle” batteries and avoid regular automotive “starter” batteries.
  • Chemistry: Get lithium (LiFePO4) batteries. They’re better in every way compared to AGMs, and prices have decreased substantially in recent years.
  • Voltage (V): For 1st time builders, buy a 12V (or 12.8V) battery. Avoid 24V/48V batteries.
  • Amp-hours (Ah): Keep it simple, look for either 100Ah or 200Ah batteries.

To learn more, read our camper van leisure battery guide.

If you’re not into learning about the tiny details of leisure batteries, use our recommendation below for a solid, budget-friendly lithium battery. After comparing two budget lithium batteries, we came away feeling that Li Time’s “TM” battery was a real winner in terms of value.

Best Budget LiFePO4
Li Time | Lithium Battery (100Ah)

Our top lithium battery recommendation! The Li Time "TM" packs a serious punch in a compact enclosure. Wide-ranging BMS with low-temperature protection. And superior shock resistance.

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What size batteries? Read our battery calculator post to help you determine how much battery power you need for your camper van.

Step 2: Wiring Multiple 12V Batteries Together

In this step, we’ll show you what you need (wires, components, & tools) to connect multiple batteries. If you are only using one battery, you can skip this step.

Don’t want to deal with multiple batteries? Li Time also sells single 200Ah and 300Ah batteries, double and triple the capacity of the 100Ah batteries we recommended in Step 1. This may help you eliminate the need for multiple batteries so that you can skip this step.

Wiring Diagram

If you are specifically building a 12V system using 12V batteries and want to wire multiple batteries together, you must wire your batteries in parallel (and NOT series). Parallel wiring will increase your battery capacity while keeping the overall voltage at 12V.

Three Redodo lithium batteries wired in parallel.
Three lithium batteries wired in parallel

The wiring diagram above shows how to connect multiple 12V batteries using electrical wire and copper lugs. The following section will show you precisely what you’ll need to complete this step.

Products List

To complete this first step, you’ll need these two items.

 
 
Description:

Rated for over 300A, this 2/0 wire will keep your 12V system safe—pairs with up to a 2000W inverter.

Description:

Crimps onto 2/0 AWG wire and connect to terminal posts on the battery.

Description:

Rated for over 300A, this 2/0 wire will keep your 12V system safe—pairs with up to a 2000W inverter.

Description:

Crimps onto 2/0 AWG wire and connect to terminal posts on the battery.

We recommend thick 2/0 AWG wire because these wires will experience the most current in your electrical system. These cables must support your inverter and 12V system simultaneously, potentially requiring a LOT of amps. We recommend 2/0 AWG wire with a 2,000W inverter to prevent your system from overheating. In the below video, we review the EWCS-branded 2/0 wires, but the Windynation-branded cables in the above table are the exact same quality (we tried them) but at a much better value.

EWCS 2/0 AWG Wire Review - Welding & Battery Cable

If going with a 3,000W inverter, we recommend going with 4/0 AWG cables.

Tools List

Below are the four tools you’ll need to complete this step. Many of these tools will be used throughout your electrical system build.

Need more tools info? See our electrical tools list to know everything we use and recommend when building an electrical system.

Installation Instructions

Check out our instructional video below, where we use each of the above-recommended tools to crimp a copper lug onto a 2/0 AWG wire.

How To Crimp Lug Terminals Onto Electrical Wire

Below are step-by-step instructions to attach a 5/16″ lug to a 2/0 AWG wire.

  1. Cut 2/0 wire to the appropriate length with wire cutters.
  2. With a utility knife, strip away ~1″ of insulation to expose metal strands.
  3. Insert heat shrink over the 2/0 wire.
  4. Insert 2/0 wire strands into a 5/16″ lug and crimp the lug with the hydraulic crimper onto the wire.
  5. Place heat shrink over the lug and 2/0 wire and activate with a heat gun.
  6. Attach the lug to the appropriate battery terminal.
  7. Repeat for other battery terminals.
2/0 wire with lug terminal crimped on.
2/0 wire with lug crimped on

Step 3: Connect the 12V Batteries to the Bus Bars

Now that the batteries are wired together, you are ready to connect the batteries to the positive and negative bus bars. After completing this 3rd step, you will have a safe and solid foundation to build the rest of your electrical system.

What are bus bars? Bus bars are power distribution and collection centers. They allow you to connect other devices (e.g., 12V fuse panel) to your batteries. 

Bus Bars

Bus bars are power distribution centers that collect and distribute electricity to/from multiple sources. They simplify the wiring process and help keep electric wiring clean and orderly. Connects to batteries, solar charger, inverter, and DC-DC charger.

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In this step, we discuss what products you’ll need to:

  • Keep your system safe (fuse)
  • Disconnect your system during maintenance & storage (switch)
  • Monitor battery usage & charge levels (monitor)
  • Distribute power to all downstream devices (bus bars)

Wiring Diagram

Refer to the wiring diagram below to visualize how the products form a cohesive unit.

Good To Know: Pay close attention to the lug colors. The different colors represent different sizes.

Wiring diagram connecting 12V leisure batteries to bus bars
Wiring 12V batteries to bus bars

Products List

Below are the additional products you’ll need to complete this step. Since you already have the 2/0 wire and 5/16″ lugs, we’ll omit these from the list.

 
 
 
 
Description:

Prevents 2/0 wire from overheating.

Description:

Crimps onto 2/0 wire and attaches to switch & monitor.

Description:

Disconnects the batteries from the electric system.

Description:

Displays battey state-of-charge and usage statistics.

Description:

Prevents 2/0 wire from overheating.

Description:

Crimps onto 2/0 wire and attaches to switch & monitor.

Description:

Disconnects the batteries from the electric system.

Description:

Displays battey state-of-charge and usage statistics.

We recommend 2/0 AWG wire in this section because these wires will also transmit high amounts of current to support your inverter and 12V system. This wire size is appropriate for inverters up to 2000W, but we recommend upgrading to 4/0 wire with a 3000W inverter.

Tools List

If you followed Step 2, there are no additional tools that you’ll need to complete this step.

Installation Instructions

Once you have your materials & tools, below are the steps to connect your batteries to the bus bars.

  1. With a red 2/0 wire, connect one of the battery’s positive terminals to the 300A fuse holder with 5/16″ lugs.
  2. Connect the 300A fuse to the battery switch using 2/0 wire, 5/16″ lugs, and 3/8″ lugs.
  3. Connect the switch to the red bus bar with 2/0 wire and 3/8″ lugs.
  4. With a black 2/0 wire, connect one of the battery negative terminals to the battery monitor shunt using 5/16″ and 3/8″ lugs.
  5. Connect the shunt to the display with the included RJ12 cable.
  6. Connect the shun to the black bus bar with 2/0 wire and 3/8″ lugs.

Step 4: Connect Bus Bars to 12V Fuse Panel

To power all your 12V devices (e.g., lights, fan, fridge), you will first need to install a 12V panel to distribute the power from the batteries of each device.

This section will connect the bus bars to the 12V panel and detail all the necessary products and tools to complete this step.

Wiring Diagram

Refer to the wiring diagram below to see what you’ll need to connect the bus bars to the 12V panel.

Wiring diagram connecting bus bars to 12V fuse panel
Bus bars to 12V fuse panel

Product List

Below are the additional products you’ll need to complete this step.

 
 
 
 
 
Description:

Recommended wire size for 12V panel wiring. Watch YouTube review.

Description:

This lug set Includes the 3/8" and 1/4" lugs for 4 AWG wires. Watch YouTube review.

Description:

Protects 4AWG from overheating. Watch YouTube review.

Description:

Distributes 12V power from the leisure batteries to each end device. Watch YouTube review.

Description:

Insert these blade fuses into the appropriate slots in the 12V fuse panel.

Description:

Recommended wire size for 12V panel wiring. Watch YouTube review.

Description:

This lug set Includes the 3/8" and 1/4" lugs for 4 AWG wires. Watch YouTube review.

Description:

Protects 4AWG from overheating. Watch YouTube review.

Description:

Distributes 12V power from the leisure batteries to each end device. Watch YouTube review.

Description:

Insert these blade fuses into the appropriate slots in the 12V fuse panel.

We recommend 4 AWG wire to connect the 12V fuse panel to the bus bars. This is the wire size (150A rating) recommended by the 12V fuse panel manufacturer (rated for 100A).

How To Size Your Blade Fuses: You can generally find blade fuses rated for 1A, 3A, 5A, 10A, 15A, & 20A. To calculate which size fuse is needed for each device, divide the total watts the device is rated for by 12. Take the result and round up to the next size-rated fuse.

Tools List

If you already have the tools from the previous steps, you won’t need additional tools to complete this step.

Installation Instructions

Once you have your materials & tools, below are the steps to connect the bus bars to the 12V fuse panel.

  • Using red 4 AWG wire, 3/8″ lugs, and 1/4″ lugs, connect the red, positive bus bar to the 120A circuit breaker.
  • Connect the 120A breaker to the 12V fuse panel with 4 AWG wire and 1/4″ lugs.
  • Connect the fuse panel to the negative bus bar with 4 AWG wire, 1/4″, and 3/8″ lugs.
  • Insert the appropriate blade fuse into each slot in the fuse panel.

Step 5: Connect 12V Devices To Fuse Panel

This section discusses how to connect all the 12V devices in your camper van to the 12V fuse panel. Once these devices are connected, they’ll powered up and working.

Wiring Diagram

Refer to the below diagram to see how to make this connection and which products you’ll need. (We also include several popular camper van 12V devices for reference)

Wiring diagram connecting the 12V fuse panel to individual 12V devices
12V fuse panel to 12V devices

Products List

Below are the materials you will need to connect the 12V panel to all the 12V devices in your camper van.

 
 
 
Description:

Ideal wire gauge for virtually all standard 12V devices. Watch YouTube review.

Description:

Crimps onto 14-gauge wire and connects to the 12V fuse panel.

Description:

Extends the red & black wires from each 12V device to the fuse panel.

Description:

Ideal wire gauge for virtually all standard 12V devices. Watch YouTube review.

Description:

Crimps onto 14-gauge wire and connects to the 12V fuse panel.

Description:

Extends the red & black wires from each 12V device to the fuse panel.

We recommend 14 AWG wires for virtually all your 12V device wiring. This wire is suitable for up to 20 amps (or 240W at 12V). If you think you will be doing lots of long wire runs of over 20 feet, especially to your fridge, you may consider upgrading to 12 AWG wire instead to resist voltage drop.

14 AWG Wire Product Review - GS Power

Tools List

You will need a wire tool to cut, strip, and crimp the 14-gauge wire. This is a common tool you (or a friend) might already have. If not, here’s a link to the device we use.

Frequently Used Tool
Wire Cutter, Stripper, & Crimper (10-22 AWG)
$22.39

Great tool for quickly cutting, stripping, and crimping on terminals. This will be one of your most frequently used tools when building your van's electrical system.

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02/18/2024 05:12 am GMT

Popular 12V Devices

Below are four popular 12V devices used in camper van conversions. We use each of these products in our van and use these devices daily.

Installation Instructions

Once you have your materials & tools, below are the steps to connect each 12V device to the fuse panel.

  • With a wire stripper, strip away ~0.5″ of insulation from the 14-gauge wire to expose the bare wire strands.
  • Crimp the M8 ring terminals onto the metal strands.
  • With a heat gun, activate heat shrink over the wire.
  • Attach the ring connector to the appropriate terminal post on the fuse panel.
  • Attach 14 AWG wires to each 12V device with butt connectors.

Want more information? Check out our post teaching how to wire LED lights in a camper van.

Step 6: Grounding The 12V Electric System

To ground the 12V electrical system, you must wire the negative (black) bus bar to an appropriate ground point. This is usually somewhere along the vehicle’s metal chassis in a camper van.

What Size Ground Wire To Use? If you have been following our wiring diagram, you will need 4 AWG wire. If not, check out this ground wire chart from Learn Metrics.

Where On The Chassis Is The Ground Point? Every vehicle type has designated ground points in different locations. We found our ground points by referring to our Ford Transit’s handbook. (We grounded to point #30)

Ford Transit ground points on the chassis

Wiring Diagram

To ground the 12V system, use 4 AWG wire to connect the negative (black) bus bar to a designated ground point on the vehicle’s chassis. Refer to the below diagram to see how to do this.

Connecting the negative bus bar to a ground point on vehicle chassis with 4 gauge wire.
Grounding the 12V system with 4-gauge wire

Products List

If you have 4 AWG wire left over from Step 4, you can use that instead of buying additional wire. Use the lug terminal we recommended earlier.

Tools List

If you have the tools from our other steps, you won’t need to get any additional tools.

Conclusion: Add Solar Panels & An Inverter Next!

Congratulations on reaching this point and successfully finishing your 12V system installation! This is no small feat.

But there is more to build than just the 12V system. If you want to power standard household appliances, you must install a power inverter. Or, if you charge your leisure batteries, you’ll need solar panels and/or a DC-DC charger.

We recommend reading our guides below for the following steps to extend your electrical system’s functionality.

Or, if you’re looking to start from the beginning, visit our ultimate camper van electrical guide, where we take you from start to finish. And by the end, you’ll have a robust & multifaceted electrical system that resembles the diagram below.

Complete electrical wiring diagram connecting leisure batteries to 12V devices, solar panels, inverter, and DC charger
Complete camper van electrical wiring diagram

And that’s it for this post. You can continue reading below for additional 12V information, or if you have any questions, please post a comment in the below section.

Happy building!

Recommended 12V Devices

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.

LED Lights

Usefulness 9.5/10
Energy Draw 0.17ah per puck light

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 installing a pack of LED Puck Lights in your camper’s ceiling. They’re bright, provide warm colored light, and draw only a tiny amount of power from your batteries.

Top Recommendation
Acegoo | 12V LED Lights

We use 12 of these 12V puck lights in our camper van. They fill the van with bright, warm white light and only consume 3W per device. Slim profile means they take up minimal ceiling space. Easy to wire to batteries.

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To learn more about installing LED puck lights in a van ceiling, head 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.

Ventilation Fan

Usefulness 10/10
Energy Draw 0.25ah when on low

A roof vent fan is a must when living in a camper van. Vent fans not only help bring in cool, fresh air and expel stale air, but they also help regulate the internal temperature of your van and eliminate 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.

Maxxair | Maxxfan Deluxe

A high-quality vent fan is a top van life essential. It exhausts stale, greasy, & musty air and promotes fresh air flow into the van. The Maxxfan's unique rain cover allows you to continue operating the fan even when it's raining hard outside.

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

12V Sockets & USB Ports

Usefulness 9.5/10
Energy Draw N/A (depends on what is plugged in)

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 three pairs of these USB & 12V combo sockets throughout our van, which are constantly in use.

Qidoe | USB & 12V Sockets

Great charging outlet that supports standard 12V ports and USB A & C. Suitable for all iPhones and Android models and 'Quick Charge' ready.

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12V Fridge

Usefulness 9/10
Energy Draw 0.72ah

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. However, having a refrigerator is necessary 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 more extended periods.

We love our 12V Dometic fridge and wouldn’t go any other route to keep our food cool. To learn more, check out our Dometic Fridge review!

Top Fridge Recommendation
DOMETIC 45-Liter 12V Fridge

A 12V fridge is a top van life essential. It keeps food cold & fresh and allows us to wild camp for more days. We recommend getting a top quality fridge with a durable compressor, electric components, and frame. Our Dometic fridge has handled all the crappy roads we've driven on.

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Diesel Heater

Usefulness 9/10 in the winter
Energy Draw 1.7ah

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

We were stuck at a campsite in Grand Canyon National Park for two days 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.

Top Value Pick
12V Diesel Heater (Budget)

Keeping the camper van interior warm when it's cold out is a top priority. And this Chinese-made diesel heater can help you keep warm at an extremely affordable price. Comes with automatic high-altitude adjustment for up to 16,000 feet.

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To learn more, check out our post, How To Heat A Camper Van During Winter

Water Pump

Usefulness 4/10
Energy Draw 1.7ah

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 natural 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 about installing a water & plumbing system in a camper.

Top Pick
SHURFLO Water Pump

Compact electric water pump for camper vans & RVs. Can be installed in any direction and comes with attached wires to connect to the leisure batteries. Pair with filter, accumulator, and silencing kit to complete installation.

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