Updated for March 2018. We originally wrote this post way back in February 2017. After nearly a year on the road, that seems like a lifetime ago. We've learned a lot about how our electrical system functions in the real world, so we decided to update and enhance this post based on our experience actually using our system full time. We hope you find it helpful!
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 along the way.
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!
Table of Contents
- >Mega List of Everything We Used in Our Electrical Install
- >What Does All This Stuff Do?
- >How Much Electricity Do You Need?
- >Budget-Based System Sizing
- >Choosing Solar Panels and Batteries
- >Basic Circuitry: What You Need to Know
- >Designing Our System (with an awesome wiring diagram!)
- >Making Sure You Have the Right Size Wires and Fuses
- >Connecting the Dots: Step-by-Step Installation of Our Electrical System
- >Awesome Resources for Further Reading
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
Lights, Dimmers, and Outlets
Wiring and Connectors
Fuses and Cutoff Switches
Update From the Road:
Why You Need a Smart Battery Isolator
There's one more component that we've discovered is vital to have on the road: a smart battery isolator.
A smart battery isolator allows you to charge your auxiliary batteries from your vehicle's alternator while driving. This is a great supplement to solar panels, especially if you're spending time in overcast or heavily forested environments where you don't get as much sun.
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.
It all starts with the sun. The sun not only gives us life, it also constantly beams energy to us here on Earth. Using science, we can convert this energy into electricity to power vanlife!
Solar panels absorb light from the sun, convert it into electricity, and send it on to the charge controller.
The charge controller regulates the flow of electricity from the solar panels and uses it to charge your 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.
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?
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. This can get a bit complicated, especially since there’s a lot you just don’t know about your usage if you’ve never lived in a van before.
But, if you want to make sure you have enough electricity to meet your daily usage while also not paying for more than you need, then going through the exercise of sizing your system is the best 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.
Rules of Thumb on System Sizing
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.
According to this awesome page, 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
A good rule-of-thumb is to match your solar panel wattage to your battery Ah capacity. So, you would want at least 200 watts of solar panels for 200Ah of battery capacity.
Budget-Based System Sizing
Sizing your system appropriately can be challenging, especially if you've never lived in a van before. There's just a lot you won't know about your real-world usage, and a lot you won't be able to foresee before you hit the road.
Another method is taking a budget-based approach to your electrical system, and adding capacity as-needed.
If you have a barebones budget, you don't need a huge, expensive solar setup. But if you can afford it, having a large system will make your life easier and means fewer compromises in your electrical usage.
Here are the main components we recommend for different budget levels:
If you have a tight budget, starting off with a good inverter, a battery, and a battery isolator should meet very basic electrical needs (charging phones/computers, some lights). You can always add on solar capabilities later if you need to.
This midrange setup gets your started on the right foot, with more battery capacity and 200-watts of solar. This setup is completely expandable, so you can add more panels later if you need to.
If your budget allows, a system this size should cover most electrical needs (unless you're trying to run an AC or electric heater). Over 300Ah of battery capacity, a smart isolator, and 400-watts of solar mean you'll never have to worry about plugging in!
Choosing Solar Panels and Batteries
What We Went With: 400-Watt Renogy Starter Kit with MPPT Charge Controller and Two VMAX 155ah AGM Batteries
Since we didn't know enough about what our electricity needs would be, we had a tough time calculating the exact size that 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.
We built a foldout PVC frame for this "extra" panel so we can prop it up and plug it in when needed. This lets us park in the shade on really hot days while still charging our batteries from the sun.
Is our system too big? We don't think so.
Having this much solar allows us to be 100% off-grid, and we rarely have to worry too much about our power consumption. We've met people on the road with smaller systems that regularly worry about making sure they have enough juice to keep their fridge running.
And even with a system this big, we have run low on juice in certain scenarios. If we're in overcast climates or heavily forested areas (or both) for more than five days or so, and if we're staying in one place and not driving much, then our batteries start to get down to the 12.0V-12.2V range in the morning. But because of our system size, we can boondock longer in the same spot, in all weather and environments, and still do everything we need to do.
Can you get by with less? Absolutely.
Whatever you go with, we recommend getting an MPPT charge controller instead of a 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 more expensive up front, but they’ll allow you to stretch your system much further.
(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:
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.
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.
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.
Making Sure You Have the Right Size Wires and Fuses
This can be a bit confusing if you're new to electrical work. But it's important to get it right if you don't want to deal with any electrical or safety issues down the road.
Below, we break down exactly how to calculate the wire sizes you need, and give you some tips on selecting the right fuses for your circuits.
Choosing the Correct Wire Sizes
Choosing proper wire sizes is an important step in any electrical install. If your wires are too thin, it can be a significant safety hazard. If your wires are too thick, you'll be spending more than you need and your wiring will be harder to work with.
Note: In the United States, wire size is measured in American Wire Gauge (or AWG). AWG gauges may be different than wire gauges used in other countries. Since we are in the US, we used wires measures in AWG for our electrical install.
The size wire that you choose should be based on the amount of current going through the wire and the length of the wire run. You want to use a wire size that's thick enough to safely handle the electrical current without experiencing too much voltage drop.
How do you figure out the max current that will be going through your wires?
Your lights, appliances, and other electronics should have their max current available in their technical specifications.
For DC appliances this should be listed in amps (max amperage). If for some reason your component specs lists this in watts, divide that number by the system voltage (so divide by 12 for a 12V DC system).
How do you figure out the length of your wire run?
First, you'll need to measure the distance the wiring is going to travel. Then double it.
What?! Double it?! Yup. When calculating wire sizing for DC systems, the wire length refers to the total length of both the positive and negative wire.
So, if you're wiring an outlet that will be 5 feet from your fuse box, your wire length is actually 10 feet - 5 for the positive wire, and another 5 for the negative wire to complete the circuit.
Okay, so now that I know my max current and wire length, how do I figure out what wire size I need?
Blue Sea Systems has an awesome "Circuit Wizard" calculator on their website that can help you determine the proper wire size for what you need.
Simply enter the system voltage, the max current, and the total wire length. The calculator will spit out the recommended wire gauge for you:
We also found this helpful automotive wire sizing calculator from Wire Barn that shows you more detail on what gauges will or won't work, as well as other pieces of information like voltage drop for each.
Here's an example using our Acegoo 12V LED lights:
System voltage = 12V
Per the tech specs on our Acegoo 12V recessed LED lights, they have a max current of 3W per light. To convert that to amperage, we divide by the system volume (3W / 12V = 0.25A).
Each light is wired individually to the switch, so we need wire that can handle 0.25A of current.
Max current = 0.25A
We planned on installing each light no more than 6-10 feet from the switch (we'll assume 10 feet to be on the safe side). To get our total wire length, we'll multiple 10 feet by 2 to account for both the positive and negative wire.
Wire length = 20 feet
Plugging all these numbers into the Circuit Wizard spits out a recommend wire thickness of 22 AWG. (We ended up using 18 AWG to be extra safe).
But that's not all. We also need to wire the dimmer switch down to the fuse box. Since we have sic LED lights wired to one dimmer, we need to multiply the light current by 6 to get our max current:
Max current = 1.5A
The distance between the dimmer and fuze box is about 4 feet. Double that to get the total wire length:
Wire length = 8 feet
Plugging these numbers into the Circuit Wizard gives us a recommended wire gauge of 18 AWG. (We ended up using 14 AWG here, again to be safe, and so we could use the same wiring for our dimmer switches and outlets).
You'll want to run this same calculation to get the proper wire sizes for all your components. In general, the wiring for things like lights, outlets, fan, fridge, and other DC components will be probably between 12 AWG and 18 AWG.
You'll need much thicker wiring for your batteries, inverter, and ground cables. Again, you'll want to calculate this yourself based on max current, length, and manufacturer recommendations. We used mostly 4 AWG battery cable for the batteries, and thicker 2 AWG cable for the inverter and ground connections.
Choosing the Correct Fuse Sizes
Choosing the right fuse sizes for your circuits is very important for safety. A fuse is an intentional weak point in a circuit. If the current in the circuit ever gets dangerously high, the fuse will "blow," breaking the circuit and saving you from some major electrical problems.
As a general rule, choose fuses that are above the max current of your circuit load, but below the amperage rating of your wiring.
Going back to our LED light example - the total max current of our light circuit is 1.5A. So, we fused this circuit with a 2A fuse. This is above the max current of our lights, but well below the amperage rating of the 14 AWG wiring we used.
For larger items like your batteries and inverter, you'll want to use a different type of fuse. We used ANL fuse holders with the proper fuses for our batteries and inverter, and an inline Maxi fuse holder to fuse our solar panels.
Make sure to check the manuals for your solar charge controller, inverter, and batteries for manufacturer-recommended fuse sizes.
Cutting and Crimping Wires
Crimping terminals onto thicker battery cable is a little more difficult, so we mostly bought 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
Important: DO NOT hook up your solar panels to the charge controller until the batteries are connected. It could literally explode (according to Renogy).
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 hook up the three panels on our roof and 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.
Mount the Charge Controller
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
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.
How to Properly Wire Your Batteries
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.
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
For this step, we used the leftover 8 AWG wire that came with Renogy's kit, crimping on ring terminals as needed. First, we ran 8 AWG 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 to the battery if we ever need to.
Note: DO NOT disconnect the battery while the solar panels are hooked up to the charge controller. Whenever we need to cut off power to work on the system, we always make sure to disconnect our solar panels first.
Next, we ran 4 AWG wire from the other side of the switch and connected it to one side of an inline fuse holder (we switched to 4 AWG here, but you could keep using 8 AWG wire here without any problems). 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 4 AWG wire from the other side of the fuse holder to the positive post on our battery.
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.
As soon as we made the connection, the charge controller turned on. Exciting!
Note: Renogy recommends adding a fuse between the positive solar wire and the charge controller.
We didn't do this at first, mostly because we couldn't decide what type of fuse to use, and we were anxious to just hit the road.
But we finally fused our solar panels in our latest round of upgrades. Here's what we used:
- 8 AWG Maxi Fuse Holder. We spliced one end to the positive solar wire, and plugged the other end straight into the charge controller.
- 14-8 AWG Cable Splice Kit. We used this to form a secure, shrink-wrapped connected between the solar wire and the fuse wire.
- 40A Maxi Fuses.
Electrical safety is no joke, and we highly recommend following all fusing guidelines for your electrical components.
Wire 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!
Wire the Load Terminals to the Charge Controller
We ran 8 AWG wire from the positive load terminal on the charge controller to the terminal on our blade fuse box.
To get your 8 AWG wire, you can use leftover wiring from the solar panels and crimp a ring terminal onto one end.
Next, we ran another 8 AWG wire from the negative load terminal on the charge controller and connected it to the terminal on our Blue Sea Systems common bus bar.
Note: You don’t need a separate bus bar for the negative connections if your blade fuse box has both positive and negative terminals, like this one from Blue Sea Systems.
Note: Twist connectors are NOT designed for automotive use, and if not installed properly there is a chance that they can vibrate loose. To help prevent this, after forming your twist connection wrap the wires together with electrical tape just below the twist connector. This helps take pressure off the connection point and make it less vulnerable to coming loose.
Installing the outlets was much simpler.
We first drilled holes and mounted them in place.
Then we crimped quick disconnects onto both red and black wires and connected them to the back of the outlets.
We attached the other side of the positive wire to the blade fuse box using a quick disconnect, while the negative wire attached to the negative bus with a ring terminal.
The fan was the simplest.
Using butt connectors, we crimped additional wire onto the positive/negative wires coming to the fan. We then attached the positive wire to the fuse box using a quick disconnect, and attached the negative wire to the common bus bar using a ring terminal.
Wire Lights, Dimmer Switches, and Fan
Next, we connected our LED ceiling lights, vent fan, and outlets to the system. We used 18 AWG wire for the LED lights and 14 AWG wire for the outlets and fan.
Before we hung the ceiling we had attached wires to the lights and fan using twist connectors, and wrapped it with electrical tape to prevent the connection from vibrating loose.
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 dimmer switches.
We rigged up one dimmer switch in the front controlling a set of six lights, and another dimmer in the "bedroom" controlling two lights.
The awesome dimmer switch we used comes with three wires: a positive, a negative, and a ground.
Using a twist connector, we twisted together the positive light wires, the positive wire from the switch, and another wire that ran down to the blade fuse box.
We then twisted together the negative light wires and the negative switch wire.
We spliced the "ground" wire from the switch to a separate wire that connects to the negative bus bar.
Insert Blade Fuses into Fusebox
Without fuses, the circuit isn't complete. When designing your system, you'll want to base your fuse sizes on the max amperage of the circuit.
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.
Wiring the Inverter to the Battery
We mounted our inverter to the outside of the partition that separates the electrical enclosure from the storage area under the bench.
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.
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 a wire from the fuse holder to the positive terminal on the back of the 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.
The inverter has regular 3-pronged outlets on the front. You can plug your AC devices directly into these outlets, or run an extension cord to a power strip or AC outlet elsewhere.
We have two 3-outlet extension cords plugged into our inverter, and we mounted the outlets in a convenient location.
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.
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
- 12V electrics and wiring for my campervan conversion (Van Dog Traveller)
- From Van to Home ebook (Van Dog Traveller)
- Basics of Solar Power (CheapRVLiving)
- Road Less Traveled Solar Post
- Battery Wiring Diagrams
- Renogy's Resource Page (TONS of info and manuals)
- RV Solar Power Made Simple (Road Less Traveled)
- How to Crimp Cables and Wires (Instructables)
- Jack and Jill Travel Solar Post
- RV Electric Power for Dry Camping (system sizing)
- Youtube Video Showing Installed Components (Campervan Cory)
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!