Vanlife on a Budget: DIY Solar System

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One of the most daunting parts of my van conversion was the electrical system. There seemed to be too many parts and I was for sure scared seeing as I, and my wonderfully helpful friends and family, had zero experience with any of it. I spent more time than I care to remember researching online, reading forums and blogs and watching hours of Youtube videos about circuits and fuses and amp-hours and waaaaaay too much math for my liking. I was learning a lot about all the individual pieces and about other people’s setups, but I was still totally unsure of how I could apply this new knowledge to my needs and most importantly, my budget.

Through what I see as one of my greatest moments of mental persistence, I was able to string all of it together and have been enjoying the illuminating fruits of my labor ever since! I made this post for anyone wondering how I did it (or just super interested in solar powering a van). It goes over exactly what I bought, exactly how I connected it all, and why.

Obligatory Disclaimer: This is what I did with my system based on research I did myself. I am definitely not an electrician and working with electricity can be dangerous. It’s always a good idea to be safe, not sorry, and consult with a licensed electrician beforehand.

Solar Power Components in a Nutshell

A solar system is a way to independently collect and convert the sun’s rays into electricity through the use of solar panels and batteries. However, because batteries can’t be trusted to take care of themselves, one needs a charge controller. A charge controller keeps the battery from soaking up more energy than it can handle. An inverter is also needed, this converts the voltage of a deep cycle battery (12V DC) into the voltage used by most of your at-home gadgets (110-220V AC).

How Much Do You Need?

Sizing your solar system is the first step and for me, it was by far the most complicated. The different things you want to power in your van and their electrical needs decide how big your batteries should be and how many solar panels you’ll need. That information will have a big effect on your budget so for me it was super important to figure out.

This part involves some math so stay with me!

First, you have to calculate the number of watts of electricity each item uses. (This can often be found in manuals or safety stickers on your device.) Then multiply that number by the hours you expect to use that item to figure out the total watt-hours (Wh) of electricity.

Watts x Hours = Wh

For example, if you have lights that use 5 watts and you have them on for 6 hours every day, they would use 30 Wh per day.

Let’s pretend your electrical bits use a total of 1200 Wh a day. Since battery capacity is measured in amp-hours (ah) and not Wh you next have to convert this 1200 Wh of power consumption into ah by dividing the system voltage (V). Car and solar batteries are usually 12V.

1200 Wh / 12V = 100ah

But you cant just buy yourself a 100ah battery and call it a day. You never want to fully deplete your battery. You need to double the size because if your battery drops below about 50% there is a large chance that its lifespan will be shortened and/or it will be damaged. So you would want something more around 200ah.

Next, how many solar panels are needed to fully charge your battery each day?

Solar panels are measured in watts. So to find your solar panel size you would divide your Wh of power consumption by the average amount of full sunlight per day in your projected area. (There are plenty of online charts about this.) Remember though that there are always cloudy days or days where you may use more power than others.

(Personally, I bought one 100-watt solar panel before I did all the calculating for my battery sizing. I had a small amount of roof space to work with and I knew the 100wh panel was what I wanted for my budget.)

The last piece is a must-have component for any van solar system. A smart battery isolator. One of these bad boys allows your auxiliary batteries to be charged by your vehicle’s alternator while it’s running. This is perfect for those overcast days or forest campsites and has kept my batteries in the green. Mine also has a button that jump-starts my van battery using the auxiliary batteries just in case I ever find myself in a bind.

Specs On My System

I use a 195ah battery bank charged by a 100w solar panel and a smart battery isolator to comfortably power two strips of LED lights, a compressor fridge, 4-speed Maxxair Fan, and multiple personal electronics.

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The parts and prices:

• Renogy 100 Watt 12 Volt Monocrystalline Solar Panel – $120
• Universal Power Group 12V 100Ah Deep Cycle Battery – $180
• NAPA 12V 95ah Marine/RV Deep Cycle Battery – ~100?? (this was something my dad had laying around)
• WirthCo Battery Doctor 125 Amp/150 Amp Battery Isolator – $92
• JOYHO 6-Way Fuse Block W/Negative Bus – $14
• Cobra Portable Power Inverter – 800 Watt – $70
• ACOPOWER 20A MPPT Solar Charge Controller – $120
• Misc wire ranging from 4 gauge to 16 gauge
• BougeRV 10AWG Solar Extension Cable (10Ft 10AWG) – $20
• Link Solar Weatherproof Double Cable Entry Gland – $14
• Facon 12Volt DC Touch Double Dimmer Switch (Double) – $26
• InstallGear in-Line Fuse Holder with 150 Amp Fuse – $11
• Blue Sea Systems MEGA/AMG Fuse (100A) – $11

The How-To’s

Let’s start with a diagram of my system.

After all of my research, what I was really missing was a clear image of what my personalized system would look like. I highly suggest making your own diagram so that you can clearly see exactly how each piece connects to the next.

I took a lot of inspiration and based much of my system on “The Minimalist” set up put together by Will on www.mobile-solarpower.com.

Wire Charge Controller and Inverter to Fuse Box

My first hands-on step was to wire both my inverter and charge controller to my fuse box. This method keeps everything organized and allows me to easily fuse my charge controller for safety.

I connected the negative wire from my MPPT charge controller’s battery input to a negative fuse terminal on the fuse box. Then I did the same with the positive wire and added a 20amp fuse for my 20amp controller.

I recommend getting an MPPT charge controller instead of a PWM controller because they are around 25% more efficient at squeezing the energy out of your solar panels. This can be really helpful in a small system like mine. They are more expensive upfront but I decided it was worth the cost.

For my inverter, I did things a bit differently. There’s no need for a fuse here so I just connected the negatives/positives of my inverter and fuse box and that was that.

Wire Exhaust Fan, Lights, Dimmer Switch and Fridge

Next, I connected my two strips of LED lights, dimmer switch, exhaust fan and DC car outlet to the system. I used 16AWG wire left over from the demo of my conversion van for everything in this step.

Wire size is based on the length of the wire and the amount of current going through the wire. You need a size that’s thick enough to handle the electrical current without frying the wire or dropping the voltage so make sure to check any manuals or instructions included for sizing. 

Before I finished off the ceiling and a few other areas of my build I ran any wires that I wanted hidden and made sure to label the ends so I wouldn’t confuse the negatives and positives. 

The fan, lights and dimmer switch had very similar connection instructions. I used an electrical crimp set to connect each negative wire to a negative terminal on the fuse box and did the same with the positive. I also paired the positive and negative wires of my lights and dimmer switch (as per the instructions that were included).

Wire crimping set and hammer crimper similar to the ones my dad owns.

My fridge has a DC plug but I didn’t want to run that all the way up to the dashboard so I installed a DC outlet behind where the fridge sits. This was super easy, I just connected two more wires (-/+) to an open terminal on the fuse box.

This can all sound very confusing if you don’t have any electrical experience but it’s very important to get right and really isn’t as hard as it may seem!

Insert Fuses into Fuse Box

The right fuse size is important for safety. A fuse is an intentional weak point in a circuit so that if the current ever gets dangerously high, the fuse will “blow” which breaks the circuit and saves you from major electrical problems.

Generally you want to choose fuses that are above the max current of the load but below the amperage of the wiring. My blade fuse sizes were determined by instructions/manuals or by a quick google of the product.

Make sure to check all manuals for manufacturer-recommended fuse sizes.

Wire Batteries Together in Parallel

A parallel connection increases your total amp-hour rating but keeps the voltage the same. 

First, I connected the positive terminals on each battery together and then did the same to the negative terminals. Then I connected the negative of one battery to the load (my fuse box) and the positive of the other battery to the load.

Remember that high ah connections need larger wiring to keep the wires from burning out. I used 4AWG wires for this step and also made sure to include a 100amp bolt-on fuse for protection. 

Installing Smart Battery Isolator

The isolator I bought came with very specific installation instructions that also included wire and inline fuse sizes. I mounted the isolator under the hood near the main battery and then connected the positives, grounded the isolator to the metal, and ran a second positive wire underneath and up into the van through a hole I drilled so that it could be connected to the auxiliary batteries.

Mount and Wire the Solar Panel

My solar panel is attached to the roof using a custom made roof rack created by my dad from an old pop up camper aluminum bed frame. Creative isn’t he?

The panel is screwed into the aluminum and that is held on to the rain gutter of the van by some bolts and separate strips of metal. 

The cable connecting the panel to the charge controller runs inside the van through a hole on the roof covered by a weatherproof cable entry gland and sealed with Butyl Tape.

Wire Solar Panel to Charge Controller

The very last step was connecting the solar panel to the system. I took the wires from the solar panel that were already hanging inside the van and connected the negative/positive to their label spots on the controller, and that was it!

That’s All Folks!

That’s basically everything I did to complete my electrical install! It really was the most difficult and stressful part of my whole conversion, but I also consider it the best part. I learned a lot about a subject that I never expected to and I did the whole thing on my own and it actually works!

I tried to think of all the questions I had trouble answering during my experience and I hope this helps anyone out there struggling to make their own budget solar system. If there’s something I didn’t explain well enough or you have questions please let me know in the comments!