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Electrical System: The Most Difficult Part of Van Builds

Electrical System: The Most Difficult Part of Van Builds

At first, building our own electrical system in our felt like we jumped off of a cliff and landed in glacial melt water. 

We decided to plunge in head first.

I generally order parts and components very carefully. 

I hardly ever return things unless they show up broken or the wrong item. 

However, I felt like I was ordering more and different terminal lugs every other day and returning half of them. 

A lot of the electrical system did not fully make sense for me until I had all the parts laid out in front of me.

In this post, I outline the steps YOU need to know to build your own DIY electrical system in your camper van. It will save you many headaches if you read on…

Full Disclosure: I am NOT an electrician and follow this post at your own risk.  I did do an obscene amount of research, but this was still my first time wiring a van electrical system

Also, this post contains affiliate links.

Electrical System Diagram

Before we bought most of the components, wires, and lugs, we made a diagram.  The absolute biggest help were the electrical diagrams from Far Out Ride.  We purchased their bundle, and it was a life saver!

WHATEVER YOU DO, make sure you adjust any diagrams you find on the internet to your own needs.

Why you may ask? Because, your fridge might have a wire that needs to run five feet longer than the diagram you’re copying. That five feet may result in a different wire size.

From the Far Out Ride Diagram, we changed it based on our needs.  While the changeable PDF worked, I did have a little trouble with it when I modified it a lot.  After a while, I found it stopped allowing me to change things.  So, when this happened, I pulled up a fresh one and started again.

Once I had appliances and main components set in the diagram, I moved them to my own diagram on graph paper.  Writing it out on my own helped me wrap my mind around the electrical system.

A few times, I would add something into the diagram, and it told me to manually calculate the wire and fuse sizes.  For this I used two electrical wire gauge and fuse calculators.  I used both Far Out Ride’s electrical calculator and the Explorist Life one. 

The Far Out Ride Bundle also came with an electrical system tutorial.  This was well written and helped immensely.  I found the terminal lug hole size particularly helpful.

Designing the Electrical System Box

We had to bring in our main components to design and organize our electrical system box.  Just like our water system box and our propane system locker, our electrical system would likewise have its own box. 

We planned on having the electrical system on the same side as the propane system under the bed.  This meant that we had to figure out how to place it all to use as little space as possible.

Remember: inches matter in a van. 

The space we allotted for the electrical system had the wheel well.  This made planning a little tricky.  We moved the batteries around and around. 

We held up the inverter and the charge controller in multiple places. 

What we continually had trouble with was planning for four circuit breakers and the bus bars.  They never seemed to have enough space.

Eventually, after about a week, we came up with our idea.  First, our design allowed us to make the electrical system box the same width as the propane box.  This allowed us the maximum possible under-the-bed storage.  Second, it allowed space for a third battery should we decide we want or need more than 200Ah.  This means our system could be adaptable if need be.

Sitting in the van looking at the electrical system, needing tea.

Building the Electrical Box

While the design took most of the time, we built the box itself in a piecemeal fashion.  We started by securing the batteries with some 1.25-inch metal-by-the-piece angle iron with screw holes.  This held the batteries in place to properly measure the height and width of the main side of the box.  The propane box would act as one wall and the bed/kitchen dividing wall would act as the other.

We did manage to make it so the propane locker could still be removed.  While we don’t expect to need to remove the propane locker, we like having the possibility.

On the other side, the wall that divides the kitchen and bed acts as the electrical system wall there. 

We decided to not build a wooden box over the wheel well like we did in the water box.  This provided us a few extra inches to run wires.  We had previously added the hard plastic wheel well cover over some wool.  This insulated the bare metal wheel well and gave us extra space.

For the top of the box, we made a specialized top after we wired the whole system.  Using a jigsaw, we cut very specific curves to allow for wire passage up to the charge controller, battery-to-battery charger, and inverter. 

Toward the very end of the build, we added magnetic covers over the charge controller, battery-to-battery charger, and the inverter.  One fits snuggly over the inverter with the top and side open for ventilation.  We also added extra ventilation slots on the front. 

A second magnetic wooden cover fits over the charge controller and battery-to-battery charger.  This, too, has an open top for ventilation.  Both provide protection for garage gear hitting them while allowing them to breathe.

Ordering Marine Grade Battery Cables and Terminal Lugs

While we already had all our 12v wires in place, I had none of the thicker battery cables.  All the 12v wires ended in terminal lugs near where we would have the 12v fuse block.  I held them in place with a hair tie in the meantime. 

When we had our electrical system layout design figured out, we could measure distances for wires.  I had loosely guessed in the diagram, but this allowed us more precision. 

After totaling up the feet of wire by gauge, I placed a few orders.  From ordering the smaller wires, I knew ordering directly from TemCo was cheaper than ordering through Amazon.  The TemCo customer service was also pretty stellar for the one order that had an issue.  I also found Greg’s Marine Wire Supply Store very helpful for many of the quick disconnects. I attempted to also order all the terminal lugs for the battery cables at the same time.  However, this I did not understand as well until I had all the pieces in my hands.  I made many terminal lug orders over the course of putting the electrical system together.

Cutting Wires and Crimping Terminal Lugs

While we found a wire crimper for 10 AWG – 22 AWG in Karma’s Dad’s garage, we had to order a different crimper for 2/0 AWG – 8 AWG. 

At first, we tried to get one from Amazon because it was cheap.  This was a HORRIBLE move.  It had the hexagonal dice that supposedly give a very good crimp.  However, none of the dice were sized correctly at all.  The dice for 2/0 AWG were too big and did not crimp at all.  Then the ones for 1/0 were too small and produced dangerous wings on the lug.  We ruined quite a few lugs before we returned it. 


Starting to Build the van's electrical system.
Crimping Battery Cables

We went onto TemCo’s website and ordered their hydraulic die-less indent crimper.  This worked significantly better, however, the markings for wire gauges were also totally off.  The benefit here though was that you could adjust it extremely easily. 

With our main components in place, we measured wires and cut them to size.  The fatter the wire, the less flexible it was.  In some cases, we had to make them a little longer to achieve the bend we needed. We added one terminal lug at a time, double checking the gauge and bolt size.  Several times on the double check I had one bolt written down wrong and had to order more lugs.  By several times, I mean frequently.

Homemade battery cable with a terminal lug crimped and heat shrank,
2/0 Battery Cable, Terminal Lugs Crimped, and Heat Shrank.

Connecting All the Battery Cables

Once we sat down to wire everything together, it only took a day.  However, the prep time to make and label every cable took way longer than I’d like to admit. 

We sat down with the diagram and quadruple checked every wire.  We were extra careful making sure red wires went to positives and black wires to negatives.  Likewise, as we connected a positive wire, we made sure it went to the next positive connection. 

Despite being extremely careful, we still created one spark from an errant wire connected on one side and not the other while we paused.  It was a great wake up call to only pause when we had a wire connected on both sides. 

We wired the batteries together in parallel. 

On the battery POSITIVE side, we added a 250 Amp catastrophic fuse on its way to the main on/off switch.  The on/off switch is vital to have the ability to work on the system when needed. 

From the on/off switch, the positive battery cable went to the positive bus bar.  The bus bar went to circuit breakers or fuses onto the 12v fuse block, the inverter, the charge controller, and the battery-to-battery charger. 

From the NEGATIVE battery side, a battery cable went to a shunt for the battery monitor and onto the negative bus bar. 

From the negative bus bar, negative wires went to the 12v fuse block, the inverter, the charge controller, and the battery-to-battery charger. 

A 2/0 awg battery cable also extended from the negative bus bar to a piece of bare metal on the van as a ground for the system. 

By the time we were connecting the wires, most of the work had already been done.  The harder work was all the research, planning, sizing, and obtaining the parts of the system.

Connecting the 12v Appliances to the Electrical System

We connected the appliances piecemeal as we added them.  At the beginning, we only had the MaxxAir Fan totally ready to go.  So, it was a great test.  Since the Battle Born Batteries came with some charge, we could turn the system on for a quick test. 

The simple act of turning on a fan that we installed and wired WAS SO DAMN EXCITING.  It felt so good to know that we installed it correctly and it worked!  That also meant that the core of our electrical system worked as well.

We turned off the main switch and the 12v fuse block circuit breaker to continue working on the system.

As we installed the other 12v appliances in the upcoming posts, we turned off the system and added each onto the 12v fuse block, then tested them. 

The main switch and the circuit breakers allowed us to turn off the power to individual parts of the system and protected the system itself.

Connecting the Solar Power

After we added the New Powa 210W Monocrystalline solar panels to the roof rack in the next post, we connected the wires to the charge controller. 

In reviewing the install guide, we connected the charge controller to the batteries first, then to the solar panels. 

Each positive wire had a circuit breaker on it.  This allowed me to turn off the power into the charge controller and/or turn off the power to the batteries. 

The Victron Smart Solar MPPT Charge Controller with Bluetooth was relatively easy to install.  We followed this Explorist Life video to program it.  He laid out the steps well and used Battle Born lithium batteries also. 

I downloaded the Victron Connect App and followed along with the video.  I only had to adjust for the size of our battery bank.  For once, there were no “oh shit” moments.

Programing the Battery Monitor

When we connected the batteries into the electrical system, we added the shunt to the negative side of the battery bank.  To do so, we followed the instructions from the Far Out Ride diagram and the Victron BMV-712 Battery Monitor with Bluetooth install guide. 

This installation went smoothly.  With the Victron Connect App already downloaded, we searched for another device.  Once it paired, we adjusted for our battery bank. 

Knowing how much power is left in the battery bank is vital in deciding what power you can use. 

This is especially important on cloudy days when you may have to ration out power.  For example, before we turn on our hot water heater, we check the battery monitor to ensure we have 20-30% battery we can spare.


Do your research before wiring anything! Use this post, YouTube, and the internet at large. Get as much information as you can.

Lay all of your pieces out and see how they fit together.

Order extra terminal lugs. Inevitably, you will mess a few up.

Then, dive and and have a go at it.

Leave any questions in the comments 🙂

How will you supercharge your campervan electrical system?  Here's how I did it.  This post details how we made an electrical diagram, wired 12v appliances, added an inverter, and a battery to battery charger in our van build.  We used two 100Ah lithium Battle Born Batteries.