Last Updated on 22 July, 2026 by Robyn Dockendorf

Vanbuilds are exciting but daunting, especially the electrical wiring component. Before we built our van, we had no idea what a DC to DC charger was or what it was used for. After traveling on the road for a few years, we’re here to explain what it is and why you need it in your van build!

A DC to DC charger utilizes your van’s car battery to charge your house batteries. It takes the inconsistent energy generated from the alternator and manages it into the correct voltage and amperage to deliver to the house batteries.

So, do you need it? Like your van, this article will take you on an adventure, but instead of a cool destination, we’ll be discussing all there is to know about a DC-DC charger and whether you need it for your van build.

Disclaimer: I’m not a professional electrician or certified installer. The information in this article is based solely on my personal experience installing a DC to DC charger in my own van and the research I did along the way. Every van build is different, so please double‑check specifications for your components and consult a qualified professional if you’re unsure about any part of your electrical system.

Our Tool List:

• Renogy 12V 40A DC to DC Charger
• Renogy 12V 200Ah LiFePO4 Batteries w/ Low-Temperature Protection
• THHN wire, various sizes
• Wire crimpers and strippers
• Fuses, various sizes
• Lugs, various sizes
• WAGO connector
• Wire cutters
• Phillips and flathead screwdrivers
• Multimeter

This post includes affiliate links, but rest assured that we only recommend items we would use ourselves. If you choose to make a purchase, we receive a small commission at no extra charge to you. There are no sponsorships; this is just the truth about our favorite finds.

How Does A DC To DC Charger Work?

Let’s start with the most fundamental information: How does a DC-DC charger work? As I said, we had no idea what a DC to DC charger was before building our van. In fact, we didn’t know a lot about electrical wiring, voltage, amperage, or DC versus AC.

After dozens of hours of watching YouTube videos, reading blogs, and reaching out to professional engineers and welders, we feel we’ve got the scoop!

Before we start, know that DC stands for direct current. This means that energy only flows one way. AC stands for alternating current, which switches direction back and forth.

Step 1: Vehicle Batteries Obtain Power From The Alternator

The name ‘charger’ gives you a hint at the purpose of a DC to DC charger…it charges your battery banks! However, to charge something, it needs to obtain energy from somewhere.

When you turn your campervan on (or whichever vehicle you have!), a few things happen to generate this power:

• The engine belt spins
• The spinning creates a magnetic field
• The magnetic field creates electricity
• The electricity is AC at first
• A rectifier converts AC to DC
• Energy (in the form of electricity) is transferred from the alternator to the vehicle’s battery via a heavy-gauge wire.

There are, of course, a lot more components to generating this power, but this is a simplified explanation for people (like me!) who don’t have advanced knowledge of how an engine or alternator works.

A DC to DC charger will work when the vehicle is turned off, but it can quickly drain the vehicle batteries. For this reason, a DC charger should only be used when the vehicle is turned on.

By the way, installing a DC charger was just one of many things that made vanlife easier for us. Check out our article on 57 vanlife hacks to make life easier!

Step 2: Power Is Transferred From The Vehicle Batteries To the DC Charger

The next step involves a power transfer from the vehicle batteries to the DC-DC charger. When the charger is turned on, power is pulled from the vehicle batteries into the DC charger via a wire (more on wiring later!).

If the DC to DC charger is off, power will not be pulled from the vehicle batteries. 

Step 3: The DC Charger Stabilizes The Power

We’ve talked a little about DC current, but let’s break it down further.

Watts = Volts x Amps

Watts are a measure of power and relate to the rate of energy transfer. In simple terms, it tells you how much work an electrical device can do. For example, most cell phone chargers have a wattage range between 5 and 20, while an electric clothes dryer draws 1,800 to 5,000 watts.

Volts are like the pressure pushing through the electrical line. The higher the volts, the harder electricity is being pushed through the wire.

Amps are the flow pushing through an electrical line. Think of it like the amount of water flowing through a water hose.

So, how does this all relate to stabilizing the power? The voltage from an alternator fluctuates depending on the needs of a vehicle, typically floating between 13.5 and 14.7 volts, depending on the type of alternator.

A DC-to-DC charger stabilizes this voltage, outputting a specific voltage that is safe for the house batteries (whether they be deep-cycle lithium, AGM, etc.). This prevents under- and over-charging and prevents damage to the house batteries.

As for amperage, the DC to DC charger stabilizes that as well. Depending on the size of your DC charger, it will only output the specified amperage. For example, a 40-amp DC to DC charger may take in 45 to 50 amps from the vehicle batteries, but it will only ever output 40 amps of ‘flow’ through the electrical line. And really, the output is typically a little less than it’s rated for.

Step 4: Charger Delivers Energy With The Correct Charging Profile

Once the volts and amps are stabilized, the charger then delivers the energy to the house batteries using the correct charging stages required by your house batteries (if any…lithium batteries, for example, do not require a float charge).

These stages include:

• Bulk charging (think of a lightning cable for your cell phone – it’s fast charging!)
• Absorption (Think of topping off the gas tank)
• Float (depending on battery type)

How does it know? Depending on the model, these settings can be applied in an app via Bluetooth or may be changed by physically configuring DIP switches on the side of the charger.

Step 5: House Batteries Get Charged

Once the energy from the DC charger is stabilized, it gets delivered to the house batteries (or to a bus bar). The house batteries get charged, giving you more power to travel off-grid for longer.

Here’s Why You Might Need A DC To DC Charger

Not every van build requires a DC to DC charger. If you’re a weekend warrior or live in a really sunny state (looking at you, Arizona!), then you may not need a DC charger. Our guide on the 6 Things To Know Before You Start Vanlife has a section on electrical components that might be helpful before starting your build!

Here are a few situations where a DC to DC charger should absolutely be installed in your campervan build:

Cloudy Weather

Basically, all travel on the eastern side of the United States experiences cloudy weather at frequent intervals. If you have solar panels installed, that’s an excellent source of energy, but you kind of need the sun for it to work.

A DC charger is the perfect backup on those cloudy, dreary days.

Forested Areas

If you commonly find yourself parked in heavily forested areas, a DC to DC charger should be installed as a secondary power source. Solar panels need sunlight to work, and if the panels are covered in shade from trees, they won’t charge your house batteries as effectively.

Winter

Yuck. Most vanlifers dread the W-word, but the truth is, it’s inevitable. During the winter, there are fewer daylight hours and the sun sits at a lower angle, reducing solar panel efficiency. Additionally, cold weather means that the house batteries run less efficiently.

A DC-DC charger can fill the gap so you don’t run out of power while traveling in the winter.

Frequent Travelers

Every vanlife adventure is unique, as are the travelers! When we travel, we rarely stay in the same spot for more than 2 or 3 days. Others like to sit back and relax in the same spot for weeks at a time.

If you frequently travel in your adventures, a DC to DC charger becomes a reliable, predictable source of power each time you pack up and hit the road.

Lithium Battery Users

Today’s lithium batteries require very precise charging voltages and stages. A DC to DC charger for the alternator and an MPPT solar charger for solar panels are required to deliver energy safely and at the right voltage to lithium batteries.

You should never connect the alternator directly to the house batteries without a charger to safely convert the energy.

Boondockers And Off-Grid Travel

For those who boondock for long periods, a DC to DC charger can help keep your van’s house batteries fueled without the need to hook into the grid. It’s one of the best ways to keep traveling off the beaten path without having to stop to plug into shore power at a campground.

What Size DC to DC Charger Do You Need?

Now for the big question: What size charger do you need for your van build? The size of the DC charger will determine how fast your house batteries get charged and how much load you can place on the vehicle’s alternator.

You’ll want to hit a sweet spot between:

• What your alternator can safely provide
• What your house batteries can safely accept
• How fast you want to recharge while driving.

So, how do you figure this out? There are three main things you want to consider: your vehicle’s alternator size, the charging limits of your house batteries, and what other sources of power you’ll use to charge the house batteries. 

I’ll break it down below!

Check Your Vehicle’s Alternator Size

DC to DC chargers pull power from the alternator, so it’s important to choose a charger size that won’t pull too much power. Pulling too little is less of a problem, but it means your house batteries will charge very slowly.

A good rule of thumb for van builds is to keep the DC to DC charger size at least 50% below the output of your alternator. For example, if the alternator puts out 100 amps, you would need a charger that is 50A or less.

Not sure what size your alternator is? Here are some reliable ways to find out:

• Check the label or stamping on the alternator itself
• Use the VIN and an online VIN lookup or decoder
• Check the service manual for ‘alternator output.’
• Ask the dealership where you bought the car (if applicable)

Check Your House Battery Type, Connection Type, And Charging Limits

The two most common types of house batteries for vanlifers are lithium and AGM (Absorbed Glass Mat). Each battery comes with pros and cons, but no matter which one you choose, they can both be damaged by overcharging.

Finding the charging limit can be a bit tricky, but if you sift through the owner’s manual enough, you’ll eventually find something like “Maximum Continuous Charge Current.” This number is the maximum amount of amps the battery can safely accept non-stop without overheating, degrading, or being damaged.

The number is usually found under the technical specifications in the manual.

If you have dual battery systems, take into consideration whether your batteries are connected in series or parallel. Two 100Ah batteries connected in parallel can accept 200 amps, while two of the same batteries connected in series can only accept 100 amps.

Consider Other Charging Sources

Most vanlifers have more than one way to charge their house batteries. This might include a combination of solar (via an MPPT Solar Charge Controller), shore power, and a DC-DC charger. It’s important to take into consideration the total amperage of all charger devices.

For example, if your house batteries can accept a total of 100 amps of charging current and you have a 60-amp MPPT solar charger, you’ll want to make sure the DC to DC charger is 40amps or lower to avoid overcharging the house batteries. (100amps – 60amps = 40 amps).

Basically, you want all the sources that are charging the house batteries to be less than the maximum accepted charge current of the house batteries. Our Ultimate Wiring Guide goes over some of the most common electrical components installed in campervans and how to wire them.

During a van build, it’s likely you’ll be installing solar and DC to DC power at the same time. This can help you play around with different sizing options. Think about where you’ll be traveling and the type of traveling you’ll be doing. If it’s going to be super sunny, opt for a bigger solar system. If you plan to do a lot of driving, go with a bigger DC charger. If you’ll be doing a combination of both, keep the MPPT and DC to DC battery charger the same amps (that’s what we did!).

Some DC-DC chargers also have a built-in MPPT component, meaning you can hook everything up to one device as opposed to installing two separate devices.

DC to DC Charger Vs. Solar: Do You Need Both?

This section is for anyone who is embarking on their first vanbuild adventure. If you’re a little lost on where to begin with powering your van, you may be wondering if it’s really necessary to have both solar and a DC to DC charger.

In my opinion, it’s absolutely necessary to have both. Solar is dependent on the weather and, therefore, unreliable as a stable source of power. You really wouldn’t believe the difference in solar output in the summer versus the winter!

A DC charger offers a reliable source of energy (as long as your vehicle is on) that’s essential on cloudy days or during the winter when there are fewer hours of sunlight.

Installation Basics

I won’t cover exactly how to wire a DC to DC charger in this section, but I’ll go over some basics to know before you install your charger. For a complete wiring guide, head over to our Step-by-Step Guide to Wiring a DC to DC Charger.

For visual learners, check out our YouTube video on how to install a DC to DC charger! 

Here are a few basics to know about installing your DC to DC charger in the van:

Wiring Length

Choose the location of your DC to DC charger with wire length in mind. The gauge of the wire will depend on the length of wire between the vehicle batteries and the DC to DC charger, and the length of wire between the DC charger and the house batteries.

It’s recommended to install the DC charger as close to the auxiliary batteries (the house batteries) as possible. This means the wire length between the vehicle battery and the charger may be longer, requiring a higher gauge wire.

If you’re unfamiliar with wire gauges, here’s a quick breakdown:

• The lower the gauge number (AWG), the thicker the wire and the more amps it can handle.
• The higher the gauge number (AWG), the thinner the wire and the fewer amps it can handle.

Below is a simple table to give you an idea of what amperage each copper wire size can handle.

Fuse Size

Fuses must be installed along the positive wire connections. Fuses will be installed between the vehicle batteries and the input side of the DC charger, as well as between the DC charger’s output side and the house batteries.

Ideally, you want the fuse as close to the source of power as possible. So, the fuse between the vehicle batteries and the charger should be as close to the vehicle batteries as possible. The fuse between the charger and the house batteries should be as close to the charger as possible.

The user manual that comes with the DC to DC charger will tell you exactly which fuse sizes to use. It’s critical to install the correct size fuse to keep your electrical system safe and fire-free.

Why is fuse size important? Fuses protect the wire from overheating and will blow before the insulation around the wire begins to melt. 

• If the fuse is too big, the wire will overheat without the circuit being cut off.
• If the fuse is too small, it will break the circuit prematurely and prevent power from reaching the house batteries.

Fuses also prevent damage if there is a short. Shorts can cause massive current flow from the alternator. With the correctly sized fuse, it will break the circuit, preventing damage to the wires.

D+ Ignition Cable

Depending on the type of DC to DC charger you use, you may need to install what’s called a D+ ignition cable. This stumped us for a long time because there’s not much information out there about how to install this.

YouTube to the rescue! With a little help and a lot of cursing, we got it figured out… 

The D+ ignition cable must be connected from your DC charger to a circuit on your vehicle that only turns on when the vehicle is running. The size of the cable is typically 16-18 AWG, but the manual will specify.

There is a specific slot on the charger where one side of the cable goes in. The other end of the cable should be spliced with the wiring of an ignition circuit on the vehicle, which often requires removing the plastic coverings from the dashboard.

When we installed ours, we used a multimeter to figure out which wires were active only when the vehicle was turned on. Turns out our 12V cigarette lighter charging port was only on when the vehicle was on, so we spliced the cable into this circuit using a WAGO connector.

Ventilation

Having proper ventilation for the DC charger is critical when installing and running it. The charger can easily overheat, which reduces the power output and shortens the lifespan of the charger.

When a DC-DC charger overheats, it cuts back its output to protect itself. This means a 40A charger may start dropping to 30A of output, then 20A, and may even shut down if the heat is too intense.

We installed our charger behind an access panel and drilled holes in the frame to allow for ventilation. However, this ended up being insufficient, and we had to keep the access door open while the charger was operating (while we drove) to keep it properly cooled.

DIP Switches

Depending on the model, it may or may not have DIP switches. These are used to tell the DC charger what kind of battery you have and the appropriate charging, absorption, and float charges your battery requires, if any.

Newer chargers and smart chargers will usually not have DIP switches. They use Bluetooth and an app for these settings.

If the model you choose has DIP switches, here’s what you’ll need to know to set them:

• Lead Acid Batteries:
  • Absorption charge voltage
  • Float charge voltage
• Lithium Batteries:
  • The lithium voltage of the battery

If you install the DC charger correctly but it doesn’t charge, the DIP switches may be the reason.

Common Mistakes To Avoid During Installation

We made a lot of mistakes during our van build, and I’m happy to share them with you so you don’t make the same ones! And just to give you a pep talk, I had zero electrical experience before installing my DC to DC charger, and it’s been chugging away for three years now without incident.

So, even if you have no experience, you can do it! 

Here are some common mistakes to avoid:

• Undersizing wires: Use the correct wire size according to the user manual.
• Lugs: Lugs are used to connect the wire to the component. Make sure to size the lugs correctly according to the fastener.
• Fuse size: If you don’t know anything about electricity (like I was when I first started this), fuses can be con-fuse-ing…get it? Make sure to choose the correct fuse size that makes sense with the maximum amperage flowing through it. (Again, I go over this in detail in the wiring guide!).
• Enclosed space: The DC charger needs a well-ventilated area to run properly. If you put it in an enclosed area, it will overheat (yes, it happened to us. Take this one seriously!).
• Dip switches: If everything seems to be installed correctly, but the DC charger still isn’t generating power, one likely issue is that the dip switches are incorrectly set. 

Our article on the 5 Mistakes We Made While Building Our Van can help you avoid other common mishaps during your build.

Top Choices For DC to DC Chargers

Finding a DC to DC charger is challenging because there are so many choices out there. When choosing which charger to go for, take into consideration the type of house batteries you have (lithium vs AGM), what type of electrical system you have (12V vs 24V), and the other components you’ll be using (MPPT and batteries).

When we did our van build, we opted for Renogy because we had already purchased Renogy lithium batteries, and it made sense to keep all our electrical components the same brand. There are pros and cons to Renogy, as with any other choice.

We went with the Renogy batteries because they were more affordable than other popular brands like Battle Born, but we weren’t opposed to trying other brands.

Here are the four top choices for DC chargers:

• Renogy: Renogy is budget-friendly and has options with built-in MPPT solar charge controllers, so you can do everything in one device. They also work with a wide range of battery types. Example: Renogy 12V 30A DC-DC Charger with MPPT
• Redarc: Redarc offers premium products for rugged conditions and is considered very reliable. Their DC chargers are durable and great for hot climates. Example: Redarc BCDC1240D 40A.
• Victron Energy: Victron features high-quality components with Bluetooth app control. They’re highly configurable to specific setups and integrate well with other Victron electrical components like inverters. Example: Victron Orion – TR Smart 12/12-50A.
• Vevor: A low-budget option that works with lithium and lead-acid batteries. Vevor is best for weekend warriors and budget builds, but may not be the best for full-time vanlifers. Example: VEVOR 12V 30A DC-DC Charger.

If you’re looking for information on MPPT solar chargers, head over to our Vanlifer’s Guide to MPPT Chargers.

DC to DC Charger: Wrap-Up Session

Vanlife is the adventure of a lifetime, and being able to stay off-grid for longer means more adventures, more awesome destinations, and more amazing sights. One way to stay off-grid longer is to install a DC to DC charger in your camper vehicle.

DC chargers use the power generated by the vehicle to charge the house batteries. And since vanlife is all about the mobile lifestyle, it’s a no-brainer to install one!

For more wiring guides and vanlife tips, check out the Dirtbags with Furbags Vanlife Blog! Until next time, give your furbags an extra pet from us and keep exploring this beautiful world.