Harnessing the Sun

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DISCLAIMER:

Please note: we are not experts and claim NO expertise in building vans and working with electricity. The information below is solely from our own build experience. Use it only as reference; proceed with caution; double and triple check your work.

Prequel

Because we want to be 100% ready for the zombie apocalypse (jk), we decided early on we did not want to be dependent on shore power. We love our ability to get all of our electricity from the sun; it makes us feel like hobbits who harness Mother Nature for our own dubious schemes. That and for some unknown reason Meghan had developed an irrational fear of having propane in the van. Secretly, I’m happy that we only have a single fuel source to replenish (don’t tell her that). But at the time the boatload of extra money and skills required for a beefed up electric system stacked the odds against us: more panels (500W), larger inverter (2000W), big mother battery (400Ah lithium). I’d love to say we use our rooftop solar array as a barbecue deck. However, we needed to find a different solution due to two issues: weight and shade.

A Weight Problem

We discovered quite quickly after purchasing our beloved Ubu that he had a weight problem. I find this mildly ironic, because I too have a weight problem. It was actually a running joke during the entire build that I was putting myself on a diet to save weight for items that still needed to be added to the van. Simply said, we had a 3,000 pound payload. That includes the two of us, our build components, water, fuel and all our stuff. As we number crunched every pound of every item (not kidding — we had a running spreadsheet of every single component entering the van), we quickly found that using flexible panels would save us 20+ pounds per panel. And for us, the weight issue was more concerning than the flexible panels’ shorter lifespan (approximately 2-3 years). Decision. Made.

Solar Panels from China

After receiving a recommendation from Josh @gratefulpursuit (many thanks for that as well as for helpful guidance on several related questions), we worked with Jackson Fu at Shenzhen Sanyifeida Technology Co. to order our flexible solar panels. They cost approximately $.95/W at the time. Shipping for 6x100W monocrystalline panels (only ended up using 5) was $150 and handling was $32, bringing the grand total to $758. As with many things — you get what you pay for. Buying bargain basement solar panels will come back to bite you in the arse at some point. I’m glad we spent the money on our panels and did it right.

Looking back, I’m not sure if importing the panels from China was worth the savings… Our shipping was delayed due to some weird Customs snafu, and with the new tariffs on solar panels it might be an entirely different ball game now. Your mileage may vary.

PDF link to Solar Panel Specs

Solar Charge Controller

A what? I know right… I’d never heard of this before; mostly because when we started out we didn’t know a WATT from an OHM from a VOLT or an AMP. We only knew they were important and it really mattered to get them right. Consequently I ended up spending two weeks in the Delano Public Library learning Electricity for Dummies with Meghan.

After much research I honed in on Victron equipment for a couple of reasons:
  • It’s European made — the Euro camper vanlife scene is well established.
  • Victron came highly recommended by people in the marine industry. (We quickly learned that when it comes to building in tiny spaces, boat folks have all their ducks in a row; they’ve been doing it since the dawn of time).
  • A lot of the setup is plug and play — just the way I like it.
  • Victron equipment is easily scalable, they have integrated components that are able to see and communicate with one another.
  • Impeccable customer service. I spent hours on the phone with the Victron crew picking their brains and getting advice for our install. Special thanks to a fella named Rich that had what seemed to be unending patience — I’m sorry for the grief I caused you. But let me tell you — I’m an evangelist for your product now largely due to your care and patience with me.
  • Last, this is one part of the build I had no desire to cheap out on. If I knew more about electricity I would have been less averse to taking money-saving risks. But, because I was so completely clueless, I figured if I got the best it would serve me well for many years.

Victron’s Bluesolar Charge Controller MPPT 150/70 is what I settled on. The 150 represents the voltage that the controller can accept, which is more than we needed (nice to know if I wanted to add more panels to my system this will not be a limiting factor). The 70 represents current or amps that it can safely accept — far more than our “in series” system will ever need (possibly a reflection on how little I knew early on when I was purchasing our gear).

ubuthevan IMG_1968 Van Build
ubuthevan IMG_1911 Van Build

Victron’s Bluesolar Charge Controller MPPT 150/70 is what I settled on. The 150 represents the voltage that the controller can accept, which is more than we needed (nice to know if I wanted to add more panels to my system this will not be a limiting factor). The 70 represents current or amps that it can safely accept — far more than our “in series” system will ever need (possibly a reflection on how little I knew early on when I was purchasing our gear).

Our choice of charge controller influenced our decision to run our panels in series. There are MANY opinions on the internet about the use of parallel arrays vs. series. What it came down to for us was efficiency and leveraging the tech of our charge controller. MPPT charge controllers (as opposed to less savvy and considerably less expensive PWM controllers) prefer higher voltage arrays.

ubuthevan ubuthevan-solar-build Van Build

Solar portion of our electric schematic.

Paint by numbers

Ima throw some digits at you now. (Bear in mind they don’t mean as much to me as it may seem — I’m not a math guy, I’m a creative. Nonetheless it does make some sense, no?)

By running 5x100W panels at 17.6 Vmp (max power voltage) in series, the amperage of 5.68 Imp (max power current) per panel remains the same, but the voltage increases by the sum of Vmp of the panels, equaling roughly 88V. MPPT charge controllers love using higher voltages to boost efficiency, so we opted for that over running our panels in parallel. (note: the biggest argument for parallel array relates to shading. It’s argued that if just a single panel in your array becomes shaded, you can potentially lose all other panels’ ability to harvest energy from the sun even if they are not shaded. I was told by some very smart people there are diodes built into the circuits of most high-end panels that mitigate this effect. Instead of losing the entire array, you might only lose half of a single panel’s efficiency — pending amount of shade of course.)

Pro Tip:

  • A breaker in between your panels and charge controller is critical. If you ever need to service the charge controller or be sure that no current will be coming into your system, this is a great fail-safe to have. I had a hard time finding high-voltage breakers. Amazon did us well here: MidNite Solar Photovoltaic DC Circuit Breaker – 150V/20A
  • I spent a chunk of time making computer diagrams of how to get the most panels on the roof with the least amount of shade. In our solar research, we learned about the loss of efficiency to solar panels when they are shaded. Everyone thinks about parking under shady trees, but not everyone remembers how much shade is thrown from something as simple as a fan vent. Or an awning. Be sure to take note of that when designing your array and placing the panels. Shading from your vent or awning or a beefy antenna will cause you a lot of grief.
  • Keep the wire run between the charge controller and the negative and positive busbars connected to the battery as short as possible. Thicker wire gauge = less voltage drop = higher efficiency.
  • You want an appropriately sized fuse after the charge controller before the battery in case anything ever goes wrong with the charge controller. I used a Blue Sea Systems Outdoor Marine 7182 40 Amp Surface Mount 285 Series Circuit Breaker.

The first pro tip was courtesy of my electric engineer guardian angel friend Dick whom I met on the Sprinter Forum. Dick doesn’t feature as much in this article because by the time I met him our solar build was mostly complete. Suffice to say, this man helped me in ways I will never be able to quantify, let alone adequately thank or repay. He spent hours texting and emailing advice on electric know-how and very well saved us from some disastrous choices that could have led to horrible, fiery deaths. No joke you guys, Dick is awesome.

Also, please go check out FarOutRide’s write up about electricity and all the considerations that play into it. They have by far the most complete, accessible and helpful walkthrough I’ve come across. We referenced it a lot while building our own system. Thank you guys!

Our complete electric schematic. Click the image to download a PDF version.

Attachment Issues

Since we decided to go with the flexible beauties, we needed a way to attach them. We also needed said attachment system to allow for easy installation of new panels when necessary. While we researched and found many people who attached them straight to their roof, we were nervous about a couple potential problems with this method:

  1. Cupping: We don’t mean the therapeutic kind, but same principle really. Due to Sprinters’ ribbed roofs, the flexible panels can indent, or “cup,” between the ridges; these cups collect water and dirt that eventually contribute to panels failing earlier than they should.
  2. Heat: Solar panels are happiest when they have a gap beneath them to help with air flow. When stuck directly to the metal roof without a way to allow the heat they absorb to dissipate, the panels can become extremely hot. Extreme heat is bad for the panels’ longevity as well as their efficiency (not to mention the paint job on the roof of your van).
  3. Attachment: We had heard (and seen pictures) of too many people who had lost their panels while driving down the highway — both flexible and rigid panels. Flexible panels obviously don’t have rigid attachment points, and we didn’t want to push our luck drilling seventy eleventy holes in our roof to attach them. Most people get around drilling by attaching their flexible panels straight to the roof using Sikaflex or 3M VHB tape. But, how do we do this without risking cupping and still allowing for airflow?
Quick Summary Thus Far
  • We didn’t want our panels to succumb to cupping.
  • We desired a method of installation that would require no drilling through our roof.
  • We needed said method to weigh “zero” pounds.
  • And cost “zero” dollars.
  • And not fly off the roof at 65 mph.
  • And allow for adequate airflow.
  • No problem.

The Answer Appears

It was Meghan, my amazingly incredible wife, who returned from her lonely research garret with the solution. This may have been one of the most important contributions to our entire build. Meghan had stumbled on an obscure forum post where someone had used corrugated polycarbonate sheeting to attach solar panels to the roof of their RV. This, we thought, would be the perfect solution: aerodynamic ✔ cheap✔ lightweight ✔ no holes in our roof ✔

She set about finding said product. The national distributor led her to a local distributor of greenhouse supplies. What? We had no idea; this stuff is used to make greenhouses. Thank you greenhouse people! The local retailer spent time with us brainstorming the best installation approaches, and estimating how much polycarb and accompanying aluminum framing we’d need. We left the premises with a couple sheets of 4’ x 8’ Twinwall Polycarbonate Sheeting (as its properly called), some aluminum framing, and a dream in our hearts. Let’s go!

But not yet…

Tightwire Act

It’s not just the shade you must consider, but also the length of your wire runs. Longer wire runs tend to have greater resistance, resulting in more voltage drop along the way. To counter this, you can use thicker gauge wire to allow for the highest possible transfer of energy.

This may have been “slight” overkill, but I ended up replacing all the MC4 connectors and cables that came with the panels; this bumped the wire gauge from 16 AWG to 8 AWG. It also involved sourcing appropriate new connectors that still fit in the junction box, yet handled the thicker wire gauge. Oh what fun! (Although… I actually did have fun, but maybe in a sadistic kind of way as it wasted time. And, because I’ve only done this once, I have no idea what kind of efficiency gains were truly made. In my defense — and it never ceases to amaze me — even on the most cloudy of days we’re still able to pull 3-4 amps.)

Framing (Pre-Installation)

Given the reports we’d read about flexible panel failure, we wanted them to be easy to replace, just in case those reports held true for us. So, we set about devising a system for easy replacement. Once we figured out our final MOST EFFICIENT configuration, we set about cutting our sheets of polycarbonate with a jigsaw, sizing each to be slightly larger than its mounted solar panel. Then we cut aluminum track to size. We used our jigsaw for this task. Meghan actually loved cutting and is exceptionally adept at using this tool.

Pro Tip:

  1. Read the instructions for your jigsaw. There are different settings that will work better when cutting aluminum.
  2. Same goes for type of blade. We were burning through blades like nobody’s business until we went to the hardware store and found blades that are specifically made to cut aluminum. Don’t be like us.
  3. File the ends of cut aluminum pieces. We remembered to do this after we ripped our clothing. Because, that’s how we roll. Cut aluminum = sharp.

 

Installation

VHB Tape

When using VHB tape — surface prep is EVERYTHING. I can’t stress this enough. Make sure your surfaces are clean, and free of moisture and dust. We used isopropyl alcohol found in Mac’s 7200 Thermo Aid — a  fuel additive available in most automotive stores. It contains 90% isopropyl alcohol. We doused rags with this stuff and cleaned every surface multiple times before putting down any tape.

Pro Tip:

  1. Make sure that each solar panel is in good working order. Put your multimeter to good use before gluing them down and installing them onto your roof. Aren’t we smart? Not always, but this time, yes…
  2. When doing the actual installation remember to cover your panels with cardboard or some sort of opaque covering so there won’t be any electric current to contend with. Getting electrocuted is not fun.

Laying track

We started with the two pieces that run the length of the roof. They were used as the base of the frame. Then we followed with the cross pieces on top of them, creating a giant grid of sorts.

We also built “VHB tape towers” to use in between the cross sections and the places where they didn’t quite reach the roof. We figured extra holding strength can’t do any harm.

Adhere panels and slide them in

With the framing in place, we used MORE VHB tape to adhere each solar panel to its polycarbonate mount. This step is pretty self-explanatory. See pictures in the gallery below for more details.

The basic idea is that we would cut the wires to an individual panel if it were to fail, slide the old piece of polycarbonate out, and slide a new one (with new panel) in. Easy right?

Quick video to show how the panels slide in and out.

Wiring

Remember how I had replaced all the wiring in the junction boxes earlier? At the time I wanted to keep the MC4 connectors for ease of use, but later learned that they are a possible point of failure. So, I decided to cut off all the MC4 connectors and use trusted butt joints with heat shrink tubing instead. All the panels were connected this way and only the final two cables entering the roof of the van retained their MC4 connectors. This allowed for all the cabling to be neatly tucked and clipped away. I used little VHB clips from Amazon to do this. After everything was wired and in place we used Dicor LAP self-leveling sealant over all of the junction boxes. (I had read that these boxes are prone to failure because the rubber gaskets inside them can degrade and let moisture in. My thinking was, in the event of failure I won’t be going into the junction box to repair it, I’ll just replace the panel.)

Double cable entry gland  

And just when you think you’re done – you have to find space for the entry gland box.

So, holes (but only two!) will be drilled, then sanded, and painted, and sealed. I used rubber grommets to protect the cables from the metal surface, and affixed the entry gland with, you guessed it – VHB tape.

We sealed it with “approximately 47” tubes of Sikaflex to manage our anxiety about water leakage and rust (note that this anxiety is OBVIOUSLY higher than the anxiety about ever having to replace a wire, because if that has to happen with this amount of Sikaflex… 🤷🏻‍♀️)

Pro Tip:

  • We Sikaflexed the sh*t out of each adhesion joint between the frame and the van. Because UV and sun don’t play nice with VHB tape. Again, probably a step born out of anxiety and needless fear, but I sleep better at night knowing that sucker isn’t going anywhere any time soon.

We test-drove the van to see if any of the panels would fly off (and consequently crash into our car’s windshield that we still need to sell when the van is done). Fun times! It was solid as a rock. We even attached our GoPro to the roof to make sure there wasn’t any play in the panels.

This was a massively rewarding day and felt as though all our planning and research was rewarded. Not to mention a little bit of luck from the VHB gods.

One year in

All the panels and framing are still holding strong exactly as they were the day we affixed them to the roof — zero play. I’m very thankful for that, especially considering how little we knew going into this part of the build.

ubuthevan Asset-13 Van Build

If you’re curious about the deep-dive into greenhouse twinwall polycarbonate features that translate to van building, check this list out from Interstate Plastics:

  • Highly Flexible, Virtually Unbreakable
  • Extreme Durability & Impact Resistance
  • UV Protected from the Elements
  • Wide temperature operating range (-40F to 280F)
  • Can be cut with standard jigsaw, or even a box cutter
  • Can be drilled with standard drill bits

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