12V System Parts List | What You’ll Need For Your Installation

In this post, you will find a parts list of what you will need to build a 12V system. This electrical system can be incorporated into a camper van, RV, tiny home, or even a boat to power all your 12V DC appliances.

We have used these exact same parts in our camper van conversion for the last five years to run our ceiling lights, ventilation fan, water pump, diesel heater, and more.

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First, Download Our Free Electrical Wiring Diagrams PDF

This 12V system parts list post is intended to be used in conjunction with our electrical ebook. You can download this ebook for free by visiting our electrical wiring diagrams page.

You’ll find a wiring diagram like the one below in our ebook. This post will introduce all the components in this diagram and describe their function within this system.

Leisure Battery

The leisure battery is the heart of your electrical system. It stores and provides power to all of your van’s electrical devices, including the lights, vent fan, smartphones, fridge, and so much more!

Read our leisure battery beginner’s guide to learn more about the nuances of selecting the best battery for your van conversion.

But if you just want to skip straight to the point, we recommend getting a good quality, budget lithium (LiFePO4) battery. Lithium batteries beat out traditional AGMs in virtually every category that matters. Lithium prices have also come down tremendously over the past few years, and these batteries are not nearly as expensive as conventional wisdom.

If money isn’t a concern, Battle Born Batteries are the industry standard for camper van lithium batteries. But if you’re on a budget, we think the Li Time ‘TM’ battery provides excellent value for its price point. At 1/3 the price of a Battle Born, a Li Time “TM” battery comes with a comparable battery monitoring system (BMS), high-quality build, and English-speaking support staff.

Read our Li Time “TM” battery review for more details.

How much battery do you need? Don’t run out of power! Most modern van conversions require more power than a single 100Ah (12V) battery can provide. Use our battery calculator to help you determine your ideal battery size.

2/0 AWG Wire

For most van conversions, we recommend using thick 2/0 AWG cables to connect the batteries to the bus bars and to the inverter. This is because the wires in these sections of the electrical system will experience the highest current flow. You want to have thick wires to transmit this high current electricity without overheating.

Accurately sizing your wires can be rather math intensive, which involves calculating your maximum wattage draw, determining length of wire, and referring to a wire size chart. But to keep things simple, we recommend the following wire sizes based on the wattage rating of your inverter. This will ensure you help keep you system safe from overheating.

• 1000W inveter: 1/0 AWG wire
• 2000W inverter: 2/0 AWG wire
• 3000W inverter: 4/0 AWG wire

We like Windynation’s thick electrical wires. They’re priced very competitively and are constructed using top quality components. The 2/0 AWG wires are comprised of 1255 individual strands of pure copper conductors for efficient power transmission and ultra-flexibility. This is perfect for wiring projects in tight spaces like vans and boats.

The wire’s EPDM rubber insulation also exceeds basic wire standards and allows the wire to transmit greater amounts of current than basic wire amperage charts indicate.

Windynation is also a California-based company that assembles their wires in-house.

For more information, watch our EWCS 2/0 AWG wire review below. The Windynation wires are EXACTLY The same as EWCS, but are sold at a significantly lower price point.

ANL Fuse

In virtually every case, you should install a fuse directly after the auxiliary battery on the positive (red) line. The size of the fuse you need depends on how much current you will draw from the batteries and the size of the battery wire.

To simplify the fuse size calculation, we recommend sizing the fuse to the watt-rating of your power inverter.

• 1000W inverter: 200A fuse
• 2000W inverter: 300A fuse
• 3000W inverter: 400A fuse

We like Windynation’s ANL fuses because they’re priced competitively but they’re a California-based company that assembles their own battery cables in-house.

For more information, watch our 300A ANL fuse review below.

Battery Switch

After the fuse, you’ll want to install a heavy-duty battery switch. When in the OFF position, this simple switch disconnects the battery from all the downstream loads.

The ability to disconnect & isolate your leisure batteries is important for two reasons.

1. Eliminate parasitic loads: Even when unused, some devices still require trace amounts of power to function. This can include the battery monitor, USB ports, and diesel heater. Over time, these devices leach power and drain the battery during long-term storage. A switch prevents parasitic loads from slowly trickling power out of the battery.
2. Safety during electrical maintenance: When troubleshooting your electrical system, working with live circuits is dangerous. Touching the wrong parts of your system can damage electrical equipment and harm your body. A switch isolates the battery, ensuring your safety and protecting your equipment.

Blue Sea System’s battery switch is one of the best on the market. A solid, hard plastic switch with thick 3/8″ terminal posts. It handles up to 300 amps of continuous current without melting or degrading and works on 12V, 24V, and 48V systems.

Budget alternative: Nilight battery switch

For an in-depth look, check out our video review below.

Bus Bars

Bus bars are an intermediary between the batteries and every load/charging point in an electrical system. They collect/distribute DC power and help keep your wiring clean, simple, and organized.

When your electrical system is finished, these bus bars will connect to your batteries, 12V fuse panel, inverter, solar charge controller, and DC-DC charger.

Since these bus bars are placed at the nexus of all power flow, you want to get good quality bus bars that can handle high levels of current for prolonged periods of time. The bus bars that we recommend (and personally use) from R2X Racing are heavy-duty and can handle up to 250 amps of current.

For more information, watch our review of the R2X Racing bus bars.

Battery Monitor

It’s easy to know when your smartphone or laptop is running out of power because there’s usually an icon at the top of your screen that indicates the battery’s percentage charge. When it’s 100%, you know the battery is completely full, and when it’s below 20%, it’s time to charge it.

But leisure batteries don’t have a display to tell you what percentage state-of-charge (SOC) it’s at. Without an intermediary device, you don’t know if your battery is full or nearing empty. The budget method is to use a digital multimeter and refer to a voltage chart. However, if your budget can manage it, we recommend using a battery monitor.

A battery monitor is a device that is installed next to the battery and monitor’s the power that flows into and out of the battery. And based on the data, the monitor will display the battery’s estimated charge percentage. Victron’s battery monitor is the one we recommend because the device is Bluetooth-enabled and allows you to view all of your battery’s instantaneous stats on your smartphone. It’s an awesome, intuitive user experience that makes it easy to manage your batteries charge.

The utility of the Victron monitor is compounded when you also use Victron’s solar charge controller and DC-DC charger. These three devices all integrate in the VictronConnect App, which gives you a bird’s-eye-view of your electrical system in it’s entirety.

Budget alternative: AiLi battery monitor. This device does the some job as our Victron recommendation, but without the Bluetooth capability and at a cheaper price point.

For installation guidance, read our battery monitor install tutorial.

Terminal Lugs (2/0 x 3/8″) (M10)

Lugs are used to attach electrical wires to various devices like fuses, breakers, and bus bars. We use size ‘M10’ lugs wherever you see dark orange-colored lugs in our electrical wiring guide. These lugs are typically used to connect to the battery switch, bus bars, and battery monitor since they tend to have larger 3/8″ terminal posts.

Lug sizes are dependent on wire thickness, so these specific lugs require you to use 2/0 AWG wire, which we refer to in our guide.

We like using Wirefy lugs because they’re made from thick, solid copper. You want a high-quality, thick metal lug so that it can transmit large amounts of current (amps) without getting too hot and potentially melting. These lugs also come with pre-sized heat shrink sleeves to reinforce the lug-wire connection.

For more information, watch our Wirefy lug product review below.

Tool recommendation: To attach a lug onto a wire, you’ll need this hydraulic crimping tool. Follow the link to also watch our crimping tutorial.

Terminal Lugs (2/0 x 5/16″) (M8)

Lugs are used to attach electrical wires to various devices like fuses, breakers, and bus bars. We use size ‘M8’ lugs wherever you see pink-colored lugs in our electrical wiring guide. These lugs are typically used to connect to batteries, ANL fuses, and inverters, since they tend to have 5/16″ terminal posts.

Lug sizes are dependent on wire thickness, so these specific lugs require you to be using 2/0 AWG wire, which we refer to in our guide.

We like using Wirefy lugs because they’re made from thick, solid copper. You want a high-quality, thick metal lug so that they can transmit large amounts of current (amps) without getting too hot and potentially melting. These lugs also come with pre-sized heat shrink sleeves to reinforce the lug-wire connection.

For more information, scroll up to watch our Wirefy lug product review.

4 AWG Wires

We recommend 4-gauge wires when connecting the fuse panel to the bus bars because that is the maximum size recommended by the fuse panel manufacturer (Blue Sea Systems).

Windynation’s 4 AWG wires are constructed from 370 pure copper strands for ultra-flexibility, essential for wiring in tight spaces like a camper van or boat. The wire’s tough EPDM outer jacket better resists high temperatures and allows the conductors to transmit greater amounts of current than lower-grade 4-gauge wires.

We also like the Windynation brand because it is a California-based company that assembles its battery cables in-house. The wires come at a premium quality and are priced competitively.

For more information, watch our Windynation 4 AWG wire review below.

Circuit Breaker (120A)

The purpose of this circuit breaker is to protect the 4 AWG wires from overheating in case of an overcurrent situation. We recommend using a 120A breaker because this is the maximum size recommended by the fuse panel manufacturer (Blue Sea Systems). When paired with a 4-gauge wire, this breaker is designed to trip well before the wire would overheat.

We like Gloso’s circuit breakers because of their thick, heavy-duty design and solid terminal posts. Users report that the breaker trips as intended but experiences no melting when exposed to high current flows.

For more information, watch our Gloso 120A circuit breaker review below.

12V Fuse Panel

A fuse panel is essential if you plan to have numerous 12V devices running off the auxiliary battery. Theoretically, you COULD connect each device directly to the battery, but this is messy and a potential safety hazard.

Blue Sea System’s fuse panel allows you to connect up to twelve individual 12V devices. This can include the fan, fridge, water pump, multiple light circuits, and more. This panel also allows inserting blade fuses to protect each 12V circuit from overheating.

The panel can handle up to 100 amps of continuous current and 30 amps per branch circuit. You will need 1/4″ lugs for the feeder terminal posts and #8 ring connectors for the branch terminal posts.

Budget alternative: 6-circuit fuse panel

Note: We do not recommend using an off-brand fuse panel. Using thinner plastics and metals, these devices can melt and degrade if too much current is pushed through.

For more information, watch our Blue Sea Systems fuse panel review below.

Assorted Lug Set

This is an assorted set of lugs for different sized wires and terminal posts. It includes the lugs you will need to connect the 4 AWG wire to the fuse panel, circuit breaker, and bus bars.

If you are following our wiring diagrams, this lug set is a perfect pickup because it contains all the various lugs you’ll need to connect the 12V system, DC-DC charger, solar charge controller, and to ground your electrical system. This saves you money since you don’t have to buy individual lug sizes, which often contain many more units than you actually need for your build.

• Wire size range: 2 AWG to 8 AWG
• Ring sizes: 3/8″, 5/16″, 1/4″

This lug set also includes pre-sized red and black heat shrink sleeves. After you’ve crimped the lug onto the wire, slip on the sleeve and use a heat gun to activate the heat shrink to reinforce the lug/wire connection.

For more information, watch our Sanuke lug set product review below.

Tool recommendation: To attach these lugs onto the wires, you’ll need a hydraulic crimping tool. Follow the link for our tool description and to watch our crimping tutorial.

Ring Terminals (#8)

These size #8 ring terminals are essential if you are using our recommended fuse panel. These connectors crimp onto 14-16 AWG wires and connect directly to the panel.

We like these ring terminals because they also come with blue heat shrink tubing already attached. So all you need is a heat gun to activate the heat shrink over the wire once you’ve completed your crimp.

Tool recommendation: You’ll need a wire crimping tool to connect the ring terminal onto the wire. This is also a multi-tool that also cuts and strips electrical wire.

14 AWG Twin Wire

In most cases, using a 14-gauge wire is sufficient to connect the fuse panel to all your downstream DC devices, like the lights, fan, water pump, and fridge. 14 AWG wire safely handles up to 15 amps of current (~180W @ 12V), which is more than enough for most devices.

We like this ‘twin’ wire from GS Power because the red and black wires are encased in a durable white outer jacket. Even with our blade knife, it was difficult to puncture this outer protective layer. This is an important feature for camper vans and boats because these wires will experience lots of vibrations while your vehicle is in motion, and this constant friction can damage the wires over time.

These wires aren’t the cheapest, but you get what you pay for. These wires are made from pure-copper conductors and the exterior is tinned to prevent corrosion. This wire also has a higher strand count than what you can get at most hardware stores, which is critical for ultra-flexiblity and vibration-resistance.

Need thicker wire? If you think your wire runs will be longer than 20 feet, consider upgrading to 12 AWG twin wire. This is to combat voltage drop and ensures your devices operate correctly.

For more information, watch our GS Power 14 AWG wire review below.

Butt Connectors

All of your DC electrical devices will come attached to a short amount of electrical wire. Unfortunately, these wires are usually only about 1-2 feet long and not nearly long enough to reach the fuse panel.

Butt connectors allow you to extend these short wires to additional wires so that each electrical device can reach the fuse panel. We like Wirefy’s connectors because they use thick metal crimp tubes, which create a solid hold on the electrical wire. Each connector also comes with heat shrink tubing already attached for convenience.

Ventilation Fan (Maxxfan Deluxe)

If you value fresh air inside your van, installing a ventilation fan is a must. Simply cracking the windows open isn’t enough. You need a fan to actively pull clean, outside air into the van and exhaust the stale, stuffy air out.

While there are several different vent fans to choose from, the Maxxfan Deluxe should be at the top of your list. This is because this is the only fan that comes with an adjustable rain hood that allows you to continue using the fan even when it’s raining. Most vent fans only have a simple lid that must be closed during rain, making the fan unusable. But the Maxxfan’s hood allows the fan to pull air from under the hood, so air can still enter the van while keeping rain water out.

We have been traveling with our Maxxfan for over 5 years and it’s worked non-stop virtually 24/7 without issues. We’ve also realized that when it’s raining outside is precisely when you NEED to have the fan running to vent out humidity and moisture that builds up inside the van.

For more information: Read our Maxxfan Deluxe review.

Ceiling Puck Lights

These are the lights we use in our van’s ceiling. At over 215 lumens, each light unit provides sufficient brightness and only consumes 3 watts of power. These lights are also only 1/2″ thick, meaning they don’t require much vertical space to install and easily fit into plywood and plank boards.

Specifically, we recommend the ones that give off a ‘warm white’ light. This really gives your van’s interior a warm, cozy aesthetic.

Need installation help? Read our LED light install guide.

12V Socket & USB

There are lots of different USB/12V socket outlets out there, but this compact unit from QIDOE is our recommended choice. It comes with both the newer USB C and the older USB A socket with ‘quick charge’ capabilities.

The USB C is great for charging modern smartphones, while the USB A is still useful for powering lower-tech devices, like small fans, electric toothbrushes, and speakers.

This unit also comes with a standard 12V DC socket, which comes in handy if you want to power a small, portable inverter, DC fridge, or charge a car vacuum.

Computer charging caveat: The USB C outlet can also be used to charge certain laptops, including Macbooks. However, this feature only works if your electrical system is operating at 24 volts.

Assorted Blade Fuse Set

If you are using a fuse panel, you will need to pick up a pack of assorted blade fuses. The panel is designed to accept these blade fuses to protect the 14 AWG wire – which connects the panel to each individual 12V device – from overheating.

This assorted pack comes with eight different fuse ratings, and you will need to insert the correct fuse into each slot in the panel.

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