Epic Guide to DIY Van Build Electrical: Wiring and Installation

DIY Van Build Electrical Solar Wiring

When we first started thinking about our electrical system and buying our components, we had a lot of questions. We researched online, read other van build blogs and forum posts, and watched Youtube videos. Some were very helpful, but many left us with a swirl of even more questions.

What gauge wiring do we need? How do we go about grounding everything to the van? What exactly do we need to ground? What kind of fuses should we get? Do we need a fuse here? Do we need a switch there? How do we crimp battery cable? Where do we even get all this stuff?

We were learning a lot about circuits and electrical systems, but we were also overwhelmed by all the new knowledge coming at us from all directions. Electrical is such a vital part of any van build, and we wanted to get it right.

We longed for a resource that told us: Buy this. Connect it like this. Here’s a diagram.

This post is an attempt to make such a resource. We go over exactly what we bought, exactly how we connected everything, and we even have pictures and diagrams (yay)!

For those of you interested in further reading, we also include links to blog posts and other resources that helped us out.

We want this post to be as accurate and helpful as possible, so if we get something wrong or you want us to clear something up, let us know in the comments.

Obligatory Disclaimer: This post describes what we did with our own system based on our own research, and we hope you’ll find it helpful. That said, we are NOT ELECTRICIANS. Working with electricity in any form can be dangerous and lead to electric shock (or even explosion if you really screw up). It’s always a good idea to read the manuals for all of your components and consult with a licensed electrician before performing any electrical work.

Mega List of Everything We Used in Our Electrical Install

all the electrical components for our van build

What Does All This Stuff Do?

That’s a pretty intense list. But don’t worry, it’s really not all that complicated. Let’s break it down from a bird’s eye view.

how solar power works for van life

The Sun
It all starts with the sun. The sun not only gives us life, it also constantly beams electricity to us here on Earth. Using science, we can harness this electricity to power Van Life!

Solar Panels
Solar panels absorb light from the sun, convert it into electricity, and send it on to the charge controller.

Charge Controller
The charge controller regulates the flow of electricity from the solar panels and uses it to charge your batteries.

Batteries
The batteries we use store electricity at 12-Volt DC (direct current), which can power your lights, exhaust fan, fridge, USB/cigarette lighter outlets, and anything else that runs on DC. In our system, the electricity is fed from the batteries back to the charge controller, which then distributes it outward.

Inverter
If you want to power something like a computer or other complex electronics that require a 3-pronged wall outlet, you’ll also need an inverter, which converts 12-Volt DC to 110-Volt AC (alternating current). This is connected directly to the battery.

That’s basically what’s going on in a 12-Volt van solar power electrical system. Everything else just connects the dots.

How Much Electricity Do You Need? Choosing Solar Panels and Batteries

It’s a good idea to think about how much electricity you’ll use when deciding how many solar panels you need and how big your batteries should be.

We didn’t really do that.

Well, we tried, but it quickly got too complex, and there’s a lot you just don’t know about your usage if you’ve never lived in a van before. We spent way too much time entering numbers into a spreadsheet, only to come away more confused than before.

But, if you have the knowledge and desire to really dig into your electrical usage and size your system to your exact needs, then it’s a great thing to do.

How to Size Your System

First, calculate the number of watts of electricity you use, then multiply it by the number of hours you use that electricity to figure out how many watt-hours (Wh) of electricity you use.

Watts x Hours = Wh

So, if your lights use 5 watts and you have them on for 5 hours each day, their power consumption is 25 Wh per day.

For this example, let’s pretend all your electrical components use 1200 Wh each day.

Battery capacity is measured in amp-hours (ah), so to figure out how big your battery needs to be, convert the 1200 Wh of power consumption into ah by dividing by the system voltage (12V).

1200 Wh / 12V = 100ah.

If you ran that calculation and think you need a 100ah battery, well then...you’d be wrong.

See, you never want to fully deplete your battery. If your battery drops below about 50% you risk shortening its lifespan and/or damaging it, so in this example you would need at least a 200ah battery to accommodate 100ah of power consumption per day.

You then need to figure out how many solar panels you need to fully charge your batteries each day. Solar panels are in watts, so we’ll again use our 1200 watts of power consumption. Let’s divide that by the average amount of full sunlight per day (say, 5 hours) to get our solar panel size.

1200 Wh / 5 hours = 240 watts. So, a 240-watt solar panel should, in theory, fully charge your battery each day and accommodate your power consumption.

Except that it never works that way. There’s shade, and clouds, and less sun in winter, and days where you consume more power than others. Something like three 100-watt panels would be a much safer bet.

See how complicated this can get?

What We Went With: 400-Watt Renogy Starter Kit with MPPT Charge Controller and Two 155ah VMAX Batteries

We gave up on calculating exactly what size our system needed to be. From watching Youtube videos and reading blogs, it seemed like many vandwellers just barely scrape by with two 100-watt solar panels, so we decided to go with the biggest system we could afford.

We bought Renogy’s 400-watt starter kit with the 40A MPPT charge controller, and paired it with two VMAX 155ah batteries (for 310ah of total capacity). We were only able to fit three of the panels on our van’s roof, but we’ve got the fourth stashed under the bed and plan on propping it up when we’re stationary (or selling it if we don’t end up needing it).

Is our system too big? Maybe. We don’t know yet. Can you get by with less? Sure. If you’re tight on funds, Renogy’s 200-watt kit is a great place to start. You can always add more panels later.

Whatever you go with, we recommend getting the MPPT charge controller instead of the PWM controller. MPPT controllers are able to squeeze higher efficiency from your solar panels. They’re supposedly up to 25-30% more efficient than PWM controllers. MPPT controllers are a little more expensive up front, but they’ll allow you to stretch your system much further.

Note: We found some great information on system sizing after we bought all of our components (that’s always when you find the best info...after you need it). Here are some guidelines on what kind of usage you can expect:

  • 6ah = ultra conservative usage
  • 35ah = modest usage
  • 120ah = living like you do on the grid

To make sure you’re not draining your batteries too much, your battery capacity should be at least two times your power consumption. So, if you consume 100ah per day, you should have a minimum 200ah of battery capacity. More is better.

A good rule-of-thumb is to match your solar panel wattage to your battery ah capacity. So, you would want 200 watts of solar panels for 200ah of battery capacity.

(Very, Very, Very) Basic Circuitry: What You Need to Know

Going too deep into basic electronics is beyond the scope of this post, but it definitely helps to visualize how a simple circuit looks when designing your system.

Here’s a diagram of a very basic DC circuit:

DC circuit-diagram

Closing the switch completes the circuit and allows electricity to flow between the battery and the lights. One common analogy used here is that of a water pipe. If there’s a break in the pipe, water won’t be able to flow.

A fuse is an intentional weak point in a circuit. It’s there for safety. If too much current flows through the circuit, the fuse will “blow” and break the circuit.

“Grounding” in van life electrical is a connection to the vehicle’s chassis. In our install, we grounded the battery and the inverter.

For further reading about how electrical systems work in the context of a van, we highly recommend checking out Van Dog Traveler's ebook. It's packed with detailed information on electrical (and other aspects of a van build).

Designing Our System (With an Awesome Wiring Diagram!)

In designing our system, we leaned heavily on wiring diagrams we found on the internet, particularly the one in this post by Van Dog Traveller (his ebook has even more detailed diagrams. Seriously, get it).

But all the diagrams we found gave us a lot of partial information or only halfway applied to our system, and led to some confusion on our part.

Almost right up until the install, we were working under the assumption that we should connect the negative load terminal of our charge controller directly to the chassis and individually ground each of our loads to the van frame. But after thinking about it we weren’t sure that was correct, and we actually called Renogy’s tech support line to get it straight.

After all of our research, we couldn’t find an all-encompassing diagram that showed us exactly how everything in our system fit together. So we made one.

van life solar panel wiring diagram

We highly recommend diagramming your system so you know exactly how everything is supposed to connect. Just drawing it out really helps you think it through and get it straight in your head.

Choosing Wire Sizes

This was one of the most confusing parts for us. In theory, you would calculate the current going through each circuit and the length of the wire run to figure out the thinnest wire you can have without experiencing voltage drop. Thicker wires will have less resistance and less voltage drop, but there’s no reason to go thicker than necessary.

With our limited electrical knowledge we had no idea where to start, and going through all these equations was even worse than sizing our system. Trying to be on the safe side, we just went out and bought some 12 gauge wire.

This turned out to be WAY too thick for most vehicle applications, unless you’re powering something really heavy duty. It’s also pretty difficult to work with. So we went back to the drawing board, and here’s what we settled on:

  • LED lights have a very low power draw. 18 gauge wire works perfectly for these.
  • For our fridge, 12V outlets, and FanTastic Fan we went with thicker 14 gauge wire. You might even be fine with 16 gauge wire here.

Wiring the solar panels, batteries, and inverter is a different story. The Renogy kit comes with 8 gauge wire, and that’s the smallest you should go for connecting your solar panels, charge controller and batteries. We used 4 gauge wire to fill in the gaps, and 2 gauge wire for the ground connection.

Inverters need thicker cables. The manual for our inverter actually recommends 0 or 00 gauge cable, but we had trouble finding wire that thick with ring terminals already attached. We decided to use 2 gauge wire and fuse it at 100A instead of the recommended 150A.

Cutting and Crimping Wires

How do all these wires connect to each other? With crimp connectors!

We used two kinds of crimp connectors in our van build: ring terminals and 0.25" quick disconnects.

Pick up a basic wire cutter/crimper/stripper and you'll be crimping wires in no time. Check out this Instructables article for a tutorial on crimping wires.

Crimping terminals onto thicker battery cable is a little more difficult, so we decided to buy short lengths of cable with the ring terminals already attached. However, you could save some money if you can buy cable in bulk and crimp it yourself.

Connecting the Dots: Step-by-Step Installation of Our Electrical System

Here's the part where we go through how we installed all the pieces of our electrical system. Between cutting and crimping wires, arranging and organizing components, making mistakes and figuring things out as we went, this whole process took us a few days.

Mount and Wire the Solar Panels

solar-panels-mounted_800x450

The first thing we did was mount our solar panels to our van’s roof and wire them together in parallel using this wiring connector. For parallel wiring, all the positive wires go together and all the negative wires go together.

We decided to wire our panels in parallel for a few reasons:

  • Parallel allows us to have three panels hooked up, whereas with series you need an even number of panels. This also lets us connect our fourth panel whenever we want.
  • With panels wired in series, if some shade gets on one of the panels the electrical output of the entire system will be affected. With panels wired in parallel, shade will only affect that one panel.

There are advantages and disadvantages to both parallel and series. Renogy has an awesome guide on the differences.

After we mounted our panels, we fed the wires inside the van and ran them through some conduit down to where we planned to put all of our electrical components.

This conduit ended up being WAY too thick
This conduit ended up being WAY too thick

Important: DO NOT hook up your solar panels to the charge controller until the batteries are connected. It could literally explode (according to Renogy).

Mount the Charge Controller

mounted charge controller_800x500

Next, we mounted our charge controller to the wall inside our van. Renogy recommends leaving a few inches of space all around for ventilation.

Wire Batteries Together in Parallel

wiring batteries together in parallel

If you have more than one 12V battery, wiring them in parallel is the way to go for a van system. To do this, connect the positive terminals together, then connect the negative terminals. We used 4 gauge battery cable for this.

Next, we grounded our batteries to the vehicle chassis. We used 2 gauge wire for the ground connection. We screwed the ring terminal directly to the vehicle frame using 1-⅝” self-tapping screws and shake proof lock washers. The connection is rock solid.

grounding wires

When you connect everything to your batteries, make sure you do it on opposite sides of your battery bank. What does that mean exactly?

Attach all of your positive wires to the positive post of one battery, and connect all of your negative wires to the negative post of the other battery. This allows your batteries to charge and discharge at the same rate and will help keep them healthy.

wires on opposite battery terminals

Check out this page for helpful diagrams showing how to wire together different sized battery banks in both parallel and series.

Wire Charge Controller to Batteries

We used 4 gauge wire here. First, we ran wire from the positive battery terminal on the charge controller to one side of a heavy duty on/off switch. This will let us kill the connection the battery if we ever need to.

close up of battery switch mounted

Next, we ran wire from the other side of the switch and connected it to one side of an inline fuse holder. The fuse should match the current rating of the charge controller (i.e. a 20A fuse for a 20A charge controller. We used a 30A fuse). Then, we ran a wire from the other side of the fuse holder to the positive post on our battery.

anl fuse holder

Now that we had the positive connected, we ran a wire from the negative battery post and connected it to the negative battery terminal on the charge controller.

screwing batteries into charge controller

As soon as we made the connection, the charge controller turned on. Exciting!

Wire Solar Panels to Charge Controller

connecting solar panels to charge controller

This was simple enough. We inserted the positive wire from the solar panels into the positive solar terminal on the charge controller, then did the same with the negative wire. Now the solar panels were charging the batteries!

Note: Renogy recommends adding a 30A fuse between the positive solar wire and the charge controller. We have not done this yet because we didn’t have enough cable and we wanted to get our system up and running. But we plan on adding one down the line.

Wire the Load Terminals to the Charge Controller

charge controller wires

We ran 4 gauge wire from the positive load terminal on the charge controller to one terminal on our blade fuse box.

close up of grounding bus and fuse box

The negative wire goes from the negative load terminal on the charge controller and connects to the terminal on a negative bus bar. You don’t need a negative bus bar if your blade fuse box has both positive and negative terminals.

Wire Lights, Fridge, Fan, Etc.

Next, we connected the lights, FanTastic Fan, and outlets to the system. We used 18 gauge wire for the LED lights and 14 gauge wire for the outlets and fan.

Before we hung the ceiling we had attached wires to the lights and fan using twist connectors and electrical tape.

light hanging by wire

Then we labeled the wires and ran them through conduit down to the electrical area. So all we had to do now was connect everything together.

We hooked up the lights to a dimmer switch. The dimmer switch comes with three wires: a positive, a negative, and a ground.

front lights switch

Using a twist connector, we twisted together the positive light wires, the positive switch wire, and another wire that ran down to the blade fuse box. We then twisted together the negative light wires and the negative switch wire. The ground switch wire we connected to a separate wire and ran that to the negative bus bar.

Installing the outlets was much simpler. We first drilled holes and mounted them in place.

outlets in bench

Then we crimped quick disconnects onto both red and black wires and connected them to the back of the outlets.

fridge outlet from behind

The other side of the positive wire connected to the blade fuse box with a quick disconnect, while the negative wire attached to the negative bus with a ring terminal.

The fan was the simplest - we just crimped connectors onto the positive/negative wires, then hooked them onto the fuse box and negative bus.

Insert Blade Fuses into Fusebox

The connection isn’t complete without fuses. We used the following fuses for each  circuit:

Lights: 2A
FanTastic Fan: 5A
Outlets: 5A

fuse box - horizontal

Hit the Switch Aaaaannnndd……

This is when things should turn on. But for us, nothing happened. We tried turning on the fan, turning on the lights - nothing.

It turned out that we had our charge controller set to cut off power to the load. If you get to this point and nothing turns on, check your charge controller settings!

Once we got the settings correct everything worked beautifully. The lights dimmed on and off, the fan turned on, the outlets charged our phones.

lights and fan on

Wiring the Inverter

We mounted our inverter to the outside of the partition that separates the electrical enclosure from the storage area under the bench.

view from countertop with inverter

The inverter connects directly to the battery. First, we ran wire from the positive battery post to a heavy duty on/off switch so that we can cut the power to the inverter if needed.

inverter switch and fuses

Next, we ran wire from the switch to an inline fuse holder with 100A fuse. We used one of Renogy's ANL fuse holders and replaced the 30A fuse it came with. From there, we connected to the positive terminal on the back of the inverter.

behind inverter

The negative wire goes directly from the negative battery post to the negative terminal on the back of the inverter.

Finally, we grounded the inverter to the van's chassis using self-tapping screws and shake proof lock washers.

Tip: Keep Things Organized!

Trust us, your life will be so much easier (and safer) if there isn’t a jumble of live wires spewed all over the floor of your van.

We concealed all of our electrical components in a compartment under the seat of our flip top bench. We screwed our blade fuse box to the floor and screwed our switches, inline fuse holders, and inverter to the plywood walls of the enclosure.

van life electrical neat and tidy

We used ½” metal wire straps from Home Depot to organize the thick battery cables, and smaller wire clips to hold down the smaller wires. This keeps the wires out of the way, and also takes tension away from the electrical connections so they’re less likely to come loose while driving.

Awesome Resources for Further Reading

Conclusion

That’s just about everything we did for our electrical install. We tried to answer all the questions we had when we started out, and some questions that we had right up to the installation. If there's something we didn't cover, or you have a question, or we got something wrong, let us know in the comments!

We’re supremely pumped to have power in our van - it definitely makes those late night van build sessions a lot easier! Stay tuned for more build updates as we go into building our awesome furniture. And don’t forget to follow us on Instagram @gnomad_home and on Facebook at Gnomad Home.

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