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A Step-by-Step Guide to Wiring a DC to DC Charger in Your Campervan

Big Red at Stumpy Point

Dreaming about vanlife is one thing, but getting down to it and building your own home is a whole different story. A little gadget called a DC to DC charger is one of the crucial components that can make this dream a reality

This nifty piece of equipment quietly ensures your house batteries stay charged and ready to power your off-grid lifestyle. This charger uses your vehicle’s alternator – that’s right, the same one that keeps your vehicle’s battery topped up – to charge your house batteries.

This guide will walk you through wiring a DC to DC charger. We’re diving into the nitty-gritty of setting up your DC to DC charger. Imagine the satisfaction of doing it yourself and the bragging rights when you tell your buddies about your latest DIY achievement. Plus, it’s not as complicated as it sounds, we promise.

This post includes affiliate links but rest assured that we only recommend items we would use ourselves. And if you choose to make a purchase, we receive a small commission. No sponsorships, just the truth about our favorite finds.

Understanding the Basics of a DC to DC Charger

Alright, folks, gather ’round. We’re about to journey into the heart of your campervan’s power system. Don’t worry, though; we won’t let you get lost. Our destination? The DC to DC charger.

So, what’s this DC to DC battery charger thing all about? Picture it as a bridge that connects your vehicle’s alternator to your house batteries. It’s like a power highway, allowing energy to flow from the alternator, which is hooked up to your engine, right into your house batteries.

Let’s break it down a bit further. The alternator in your vehicle is like a mini power plant. When your engine is running, the alternator spins and generates electrical power. This power typically charges your vehicle’s battery. But when you’re wiring a DC to DC charger into the mix, you create a new route for this power to travel.

Why You Need a DC to DC Charger

You might wonder, “Why do I need a DC to DC charger? Can’t I just connect my house batteries directly to the alternator?” You technically could, but trust us, you wouldn’t want to. 

Here’s why:

  1. Better Battery Health: With a DC to DC charger, your house batteries receive a steadycontrolled charge. It’s like a personal trainer for your batteries, ensuring they get exactly the right workout, no more, no less. This helps extend their lifespan and keeps them in peak condition.
  2. More Efficient Power Management: A DC to DC charger manages power flow efficiently. It ensures your house batteries get the necessary juice without draining your vehicle’s battery. So, even after a long night of stargazing with all your van lights on, you can still start your engine in the morning!

The Role of the Alternator

Now, let’s revisit the alternator. This little dynamo is the heart of your vehicle’s electrical system. It provides power to your vehicle’s battery and, when you’re on the move, to your DC to DC charger.

Remember, the alternator only works when your engine is running. So, if you’re parked for several days without driving, your house batteries won’t get charged. That’s why balancing your adventurous spirit with some practical driving time is essential to keep those batteries topped off.

Wiring a DC to DC charger is more manageable than some make it out to be. By now, you should understand how this essential gadget fits into your campervan setup. Next, we’ll review the tools you need to wire this baby up and start your adventure!

Gathering Your Tools: The Roadmap to Wiring a DC to DC Charger

Wiring a DC to DC charger is like embarking on a thrilling rock climb or a challenging hiking trail. To make it to the top, you need the right gear. And just like you wouldn’t head out for a climb without your harness and carabiners, you shouldn’t start wiring your DC to DC charger without the proper tools.

So, let’s get down to business. Here’s your packing list for this DIY expedition:

  1. Wire: Wire carries the power from your alternator to your charger and then to your house batteries. Make sure you have the correct wire size based on your charger’s manual and the amperage that will be traveling in the wire.
  2. Fuses and Circuit Breakers: Protect your setup from power surges and electrical shorts.
  3. DC to DC Charger: This is the star of our show. It’s like your compass, guiding the power to where it needs to go and controlling how much power goes where.
  4. Wire Strippers and Crimpers: These are your multi-tools. They help you prepare the wire and make secure connections.
  5. Lugs and Shrink Wrap: These ensure your wiring connections are secure and insulated.
  6. Heat Gun: This helps shrink your wrap snugly around your wire connections.
  7. Screwdriver or Drill with Bits: You’ll need these for the DC to DC charger installation on the wall and to install the circuit breakers. Make a note of your stud posts!
  8. Wire Holders (Saddle Clamps or Tape): I highly recommend having a system to keep your wires tidy. Trust me. It will be much easier if you need to go back and fix something later. I suggest labeling your wires so it’s easier to find.
  9. Washers, nuts, and screws: You’ll need these to connect your wires to the breakers and fuses. Some breakers will come with the correct-sized lugs, washers, and nuts, but others won’t.

Wire sizing can be tricky, and there needs to be more clarity about what size wire you need in campervans and RVs. Washington State University tells us a few things to keep in mind about wires:

  • Copper wire is better than aluminum
  • DC systems use lower voltage
  • Stranded wires are recommended for large wire sizes
  • The smaller the AWG number, the larger the wire (6AWG is larger than 10AWG) until you hit 1/0 or ‘one-aught.’

In our next section, we’ll take these tools and embark on our step-by-step guide to wiring a DC to DC charger. It’s going to be one heck of an adventure!

Step-by-Step Guide to Wiring a DC to DC Charger

Before we begin, I want to emphasize that we did this for our specific van setup. We have a Ram Promaster 2500, a 180 amp alternator, a Renogy 40 amp DC to DC charger, and two Renogy 200ah lithium house batteries (400ah of house batteries). 

Our setup may be different from yours, so make sure you use the correct wire size, fuses, and circuit breakers for your specific setup. 

For example, Renogy suggests these wire sizes when wiring a DC to DC charger, depending on the distance from the charger to the vehicle’s batteries:

Distance between vehicle battery and DC to DC charger
0-10 feet11-20 feet21-30 feet
Recommended Cable Size:6AWG4AWG4AWG

Now, onto the main star of this article: a step-by-step guide to wiring a DC to DC charger in your campervan or RV.

Step 1: Materials

The DC to DC charger is powered by the alternator, yes. But you’ll be wiring directly to your vehicle’s batteries, not the alternator. This is because the alternator powers the vehicle’s battery, thus providing access to the alternator’s power via the batteries.

Here’s what’s needed:

  • Wire: we used 6AWG, which can handle 55 amps. This is the size of wire recommended in the manual for our DC to DC charger.
  • 50A Fuse: This gets wired directly to the vehicle’s battery and then to the 6AWG wire.
  • 60A circuit breaker: this is a failsafe between the vehicle batteries and the DC to DC charger
  • 50A circuit breaker: this goes between the DC to DC charger and the bus bars (house batteries).
  • 12V DC to DC charger: we used a 40amp DC to DC charger. The size of the charger correlates with how fast it will charge your batteries. Because we also use solar, we decided on a smaller size charger in exchange for drawing less power from our vehicle’s batteries. Unless you plan to run a hair dryer and blender daily, this is an excellent size.
  • Tools: We previously mentioned the tools needed, so ensure you have these handy to complete the wiring.

And before we begin, here’s a simplified DC to DC charger wiring diagram. Just remember, this is a Renogy DC to DC charger wiring diagram, so it may be slightly different if you’re using Victron or another brand.

wiring a DC to DC charger - This is a simple diagram to assist you.

Step 2: Wiring The Vehicle Batteries (Positive Cable)

Now, it’s time to put those tools to use and wire the vehicle batteriesEnsure your vehicle is off and any other power source in your vehicle is turned OFF.

  1. Find a terminal: Find an open positive terminal on your vehicle’s battery. Avoid terminals that are already connected to other wires or those that already have fuses on them:
choosing-a-terminal wiring a DC to DC charger
  1. Connect the fuse: Use a washer and nut of the appropriate size to connect a 50a fuse directly to the terminal. We had to bend the fuse slightly to attach the wire – you may or may not have to do this, depending on your batterie’s setup and terminal placement.
Placing a fuse on the terminal, wiring a DC to DC charger in a converstion van
  1. Prepare the wire: Strip one end of your wire (we used 6awg) using wire strippers. Attach a 6awg lug onto the wire and use a shrink wrap sheet and heat gun to attach the lug securely to the wire. 

NOTE: If you’re unfamiliar with wiring (like I was), use the proper size lug. There are various 6awg lugs – 1/4 inch, 1/8 inch, etc. Get the correct size based on how large you want the hole to be in the lug (where the screw will go to attach it).

This was one of the mistakes we made while building our van. You can read the article to avoid more tiny mishaps like this!

wire, lug and shrink wrap on plug, wiring a DC to DC charger in a converstion van
  1. Attach wire to fuse: Use a screw, washer, and nut to attach the positive wire to the 50A fuse.
wire connected to the fuse, wiring a DC to DC charger in a converstion van

Step 3: Wiring The Vehicle Batteries (Negative Cable)

The negative wire is always easier to connect than the positive because there is no need for fuses or circuit breakers. The negative wire will connect the vehicle’s battery directly to the DC to DC charger. Let’s break it down!

  1. Find a terminal: just like the positive side, you’ll need to find an open negative (-) terminal on the battery.
Finding the negative terminal, wiring a DC to DC charger in a converstion van
  1. Prepare the wire: Strip the end of the negative wire with wire strippers and attach a lug using shrink wrap and a heat gun.
Attach wire to lug, wiring a DC to DC charger in a converstion van
  1. Attach wire to terminal: Use the appropriate-sized washer and nut to attach the lug to the negative terminal.
Attach lug to terminal, wiring a DC to DC charger in a converstion van

At this point, you should have something that looks like this:

Overall shot of postive and negative battery, wiring a DC to DC charger in a converstion van

Step 4: Wiring From Battery To Charger

The next step in our wiring adventure is to figure out a way to inconspicuously get the wires from the vehicle’s battery to the DC to DC charger. We snaked the wires beneath the floor mats and under the driver’s seat, but there are many ways to keep the wires out of the way and less visible.

The longer the route you take to get to your DC to DC charger, the larger your wire will need to be (refer to the above table for reference on wire sizes).

Once you have your wires in place, it’s time to connect them to the circuit breaker (positive wire) and onto the DC to DC charger.

Step 5: Connecting Positive Wire To The Circuit Breaker And Charger

A lot of wiring is just looking at manuals and measuring the distance of wires. But don’t worry, I’ve already read through them and can summarize them here! 

If you’re using a Renogy 40A DC to DC charger, use a 60A circuit breaker between the vehicle batteries and the charger. This is what Renogy recommends, and they know their stuff pretty well!

  1. Prepare the wire: Strip the end of the wire you will connect to the circuit breaker and attach your lug using the same steps as you did before (heat shrink + heat gun!).
Positive wire to breaker, wiring a DC to DC charger in a converstion van
  1. Attach wire to the input of the breaker: most breakers will have the input/output labeled. Or they may say ‘aux’ and ‘batt.’ The ‘batt’ refers to the input, and the ‘aux’ refers to the output. Attach the positive cable from the vehicle battery to the ‘batt’ or ‘input’ on the circuit breaker.
Input battery to circuit breaker, wiring a DC to DC charger in a converstion van
  1. Attach wire to the breaker’s output: Cut a section of wire that will fit between the breaker and the DC to DC charger. Ideally, the breaker will be close to the charger (within 1 foot).

Strip the wire and attach a lug as you did in the previous steps. Then, connect the lug to the circuit breaker using a washer and nut. A lot of times, the breaker will come with the correct-sized lugs, nuts, and washers.

Output breaker to charger, wiring a DC to DC charger in a converstion van
  1. Attach wire from breaker output to DC to DC charger: Strip the other end of the wire attached to the output or ‘aux’ of the circuit breaker and attach a lug. Attach the lug to the input positive terminal of the DC to DC Charger using a nut and washer. You’ll know it’s the input terminal because it will say the word ‘input.’ 
Positive breaker to charger, wiring a DC to DC charger in a converstion van

Step 6: Connecting Negative Wire To DC to DC Charger

Again, the negative wire is a lot simpler than the positive! Connect the negative wire from the vehicle’s battery directly to the DC to DC charger. Strip the wire, attach a lug, and connect. Easy peasy!

Negative to DC to DC charger

Step 7: Positive Wire Output To Breaker And House Batteries

The DC to DC charger’s job is to regulate the amount of electricity from the vehicle to your house batteries. In general, the electrical output after the DC to DC charger will be lower than what is going in.

For this reason, you can usually use a smaller wire and circuit breaker size when going from the DC to DC charger to your bus bars (or house batteries). Here are the recommendations from Rengoy for a 40A DC to DC charger:

Distance between DC to DC charger and house batteries (or bus bars)
0-10 feet11-20 feet21-30 feet
Recommended Cable Size:8AWG8-6AWG4AWG
  1. Connect wire to output terminal of charger: Based on the above table, cut your chosen wire size on one end, strip it, and connect a lug. Then, connect the lug to the positive output terminal on the DC to DC charger.
Positive charger to circuit breaker
  1. Connect wire to circuit breaker’s input: Strip the positive wire’s other end and connect a lug and wire protection. Then, attach the lug to the ‘input’ or ‘batt’ side of the 50A circuit breaker.
Positive charger to breaker, DC to DC charger installation
  1. Cut a length of the chosen wire size that will reach from the circuit breaker to your bus bars (or house batteries). Strip one end and attach a lug. Then, attach that lug to the ‘output’ or ‘aux’ side of the 50A circuit breaker.
Positive breaker to bus bars, DC to DC charger installation
  1. Finally, snake the positive wire from the 50A circuit breaker to your positive bus bar or house batteries (depending on your setup). Strip that end of the wire, attach a lug, and connect the lug to the bus bars.
Positive breaker to bus bar, DC to DC charger installation

Step 8: Negative Wire Output To House Batteries

  1. Attach negative wire to output of charger: Cut a length of negative wire that will reach from the DC to DC charger to your bus bars (or house batteries). Strip one end of the wire, attach a lug and wire protection, and then attach the lug to the negative output terminal on the DC to DC charger.
Negative to DC to DC to house battery, DC to DC charger installation
  1. Connect wire to house batteries: Snake the wire to your bus bars, strip the wire, attach a lug, and connect it to one of the terminals of your negative bus bar.
Negative bus bar, DC to DC charger installation

Step 9: D+ Ignition Cable

We’re almost there! The next step is connecting the D+ ignition cable or the charge wire. The charger will not run without this connection, so don’t skip this step!

The D+ ignition cable is what tells the DC to DC charger that your vehicle is on and that it can start using the vehicle batteries to charge your house batteries. This prevents the DC to DC charger from draining your vehicle batteries while the vehicle is off.

Renogy recommends 16-18 AWG wire for the ignition cable, so it will be much easier to work with than the heavy 6 AWG cables we worked with earlier. Let’s get started!

  1. Loosen the wire connection point: Use a small flathead screwdriver to loosen the clamp on the D+ inlet on the side of the DC to DC charger. 
  2. Prepare the wire: Strip the end of a 16 or 18 AWG cable with wire strippers.
  3. Connect wire to charger: Insert the exposed wires into the green D+ inlet on the side of the DC to DC charger. Use the small flathead from earlier to tighten the clamp down onto the wire. Give the wire a tug to make sure it is connected properly.
  4. Run the wire: Snake the wire to the front of the cab so it’s inconspicuous and out of the way. We ran ours down behind our wall and underneath the seats, similar to how we ran the cables from the vehicle battery to the DC to DC charger
  5. Connect wire to ignition circuit: It’s recommended to connect the D+ ignition cable to the ignition circuit in your vehicle. So, what does that mean? You want to connect this ignition cable to something that only turns on when the vehicle is on.
D+ ignition cable, DC to DC charger installation

We wired our cable to the vehicle’s 12V cigarette lighter outlet, and it has worked great so far. Other folks connect it directly to the ignition circuit (what powers up when you turn the key in the ignition). Unfortunately, this is tricky and requires some research into your specific vehicle to find the best place to connect. 

A safe bet is always the cigarette lighter or USB/charging ports. Most of the time, the plastic covering on these areas can be popped off, exposing the wiring and allowing you to splice in your D+ ignition cable.

All in all, this is what your DC to DC charger should look like with all the wire connections:

Complete wiring picutres

Step 10: Adjusting The DIP Switches

If you’re using the Renogy DC to DC charger, five pins will be on the side of the unit next to where the D+ ignition cable connects. These are called DIP switches and are labeled S1 through S5. These need to be adjusted based on your specific electrical system.

For example, S5 is always switched to OFF when using lithium batteries. However, for lead acid batteries, S5 is always switched to ON. Check the manual to see how to properly set your DIP switches.

For our 12V system with lithium batteries, we configured ours as follows:

  • S1 – OFF
  • S2 – ON
  • S3 – ON
  • S4 – ON
  • S5 – OFF
DIP switches

Step 11: Test

The final step on this wiring adventure is to test out your electrician skills. Double-check your connections and ensure the DC to DC charger is not currently on. Now, go ahead and crank the vehicle on.

Does a green light come on? If so, the DC to DC charger is on! Now, that doesn’t mean it’s working, just that it senses power and that your wiring is most likely correct. Check your battery monitor (I highly recommend having one!) and see if you are pulling in about 20 extra amps. If so, the DC to DC charger is charging your house batteries, and you’re good to go!

Give yourself a pat on the back before moving on – that’s a serious victory! 

Navigating the Bumps In The Road: How to Troubleshoot Wiring a DC to DC Charger

You know that feeling when you’re deep into a hike and suddenly find yourself off the beaten track? That’s a bit like what wiring a DC to DC charger sometimes feels like. But we’re here to help troubleshoot your issues step by step.

Common Wiring Hiccups and Their Fixes

  1. No Light: If your charger doesn’t light up when you start the vehicle, don’t panic. Double-check your connections. Ensure your wires are snug in their lugs and that your fuse or circuit breaker isn’t tripped. 
  2. Hotter Than a Campfire: If your charger is getting hotter than marshmallows roasting on an open fire, it might be gasping for fresh air. Your charger needs good ventilation. Pay close attention to the mounting location for your charger, giving it plenty of space on all sides.
  3. Battery Blues: If your house batteries are acting like they’ve run a marathon without enough hydration, check your wire size. Skinny wires can cause voltage drops, leaving your batteries thirsty for more power.

When DIP Switches Play Tricky

Now, if you’ve double-checked your wiring but still face issues, it’s time to chat with those little DIP switches on your charger. 

These tiny guys control your charger’s settings, and if they’re not in sync with your battery type, they can be quite the pranksters. Flip open your charger’s manual and make sure your DIP switches align with your setup.

Maintenance Tips for the Long Haul

Just like we keep our hiking boots clean and our camping gear in top shape, it’s vital to take care of our DC to DC charger, too:

  1. Regular Check-ups: Make a habit of checking your charger’s wiring and connections. If anything seems loose, fix it as soon as possible.
  2. Keep it Clean: Dust and grime are as unwelcome on your charger as in your campervan. A swift wipe-down with a dry cloth can keep your charger looking and performing its best.
  3. Listen to Your Charger: Don’t ignore it if it’s making odd noises or getting unusually hot. These could be signs of a problem that needs your attention.

Wrapping Up the Adventure: Wiring A DC to DC Charger

We’ve reached the end of our DIY journey. Just like a good hike, it’s been challenging but rewarding. We’ve navigated the tricky terrain of common wiring issues, danced with DIP switches, and learned how to give our trusty DC to DC chargers the TLC they deserve.

Some of the most critical points in this article include:

  • Proper wiring
  • Correct wire and lug sizes 
  • Make sure all connections are secure.
  • Ensuring the DIP switches are correctly set for your battery type. 

So, are you ready to embark on this electrifying DIY adventure? No matter if you’re a tow vehicle, a trailer, a truck, or a campervan, we believe in you! And remember, every adventurer needs a support crew. So, don’t hesitate to share your experiences, triumphs, and tribulations in the comment section below. Your insights could be the guiding star for someone else on this journey.

And hey, if you found this guide helpful, why not share it with your fellow adventurers? Who knows, you might inspire a friend or family member to take on their own DIY project.

So, until our next adventure, stay safe, have fun, and keep exploring. Remember, life is an adventure, and we’re all in this together. Happy trails! For more vanlife tips and wiring guides, check out our vanlife blog! We have an excellent article on vanlife insulation and sound deadener mats.

How to start to start a campervan conversion. Living like a dirtbag and moving into a van.

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