Solar Skoolie Conversion: Turning a Bus into a Home on Wheels
Converting an old school bus into a home-on-wheels might be one of the ultimate DIY projects. Imagine bringing new life to a classic vehicle with all of its history, its space, and its endless possibilities! As a blank canvas, the interior design can fully be your own and the electrical system can be a customizable work of art crafted by your own hands. But, a skoolie renovation can be as awesome as it is intimidating! Where to begin on such a complex project?
Do you simply put as many solar panels as will fit on top of the bus, or set up a portable solar panel to plug into a port on the side of the bus? You could just install what your fellow skoolie friend or favorite social media influencer put into their school bus conversion project. But how do you know that it's the right size for YOU and how you want to live off-grid in YOUR bus? This blog is designed to help you figure all of that out. And, if your “bus” happens to be a van build, this blog will guide you as well.
We’ve been living, traveling and working from the road with solar power for nearly 13 years now. We spent a weekend helping our friend Jacob with his skoolie project, and luckily for us, all the interior electrical, plumbing, cabinetry, insulation and floors were already done – and done beautifully I might add! Where they needed some help was appropriately sizing the solar components to be able to live off-grid while traveling.
They wanted a system large enough for their energy needs, with some extra cushion in the “solar budget” in case they ended up using more power down the road than what they originally planned. They also wanted to build in enough flexibility so that they could recharge in 3 different ways: solar power, engine power, with shore power as a backup. To see this process in action, check out our installation video!
What Appliances Can I Run in My Off-Grid Bus?
The short answer is...whatever you want to! But, let’s take a look at what they intend to use. Since this bus was going to be used on short camping trips and music festivals, the number of appliances were far fewer than someone using the bus for full-time living – though we built-in lots of room for expansion should they want to scale things up down the road. Determine your own energy needs and organize your solar build!
Which Solar Components Do I Need to Run My Appliances?
Average Daily Solar Hours: How to Choose the Right Solar Panel Wattage
Unless you’re on the equator, the amount of hours of sunlight varies throughout the seasons; we’ll be using an average of 5 hours of solar gain per day which is a conservative average for the southeastern USA from springtime through fall. Find your daily average in the USA, or in other countries.
Using our comprehensive Solar System Sizing Worksheet, it looks like just one Renogy 320W Solar Panel might be enough to power their needs. But they’re likely to see only about 85% of that power output under the best of conditions, so to power their daily energy needs, they’ll need more than one. They chose to install two 320W panels, but they could have gone with four 100W panels, or two 200W panels to reach their minimum solar array size wattage.
The two 320W panels connected in parallel provide a maximum of 640W – at 85% that means a reliable 544W of solar power (assuming 5 hours of good solar gain per day). Again, planning for potential future expansion is a good idea, or those rainy days when solar gain is hard to earn.
We chose a parallel connection for two main reasons:
1. The wire length between solar panels and the solar component cabinet is short, so we won’t have much transmission loss.
2. This bus is mostly going to be used on the east coast, and that means trees and trees mean shade.
Parallel connections tend to work better in shade because if one panel is shaded, the other can still produce power. In series connection, if one goes out because of shade, they all go out. Renogy offers other panel styles that are designed to handle shading conditions.
Each panel has an output of 37.9V and 8.5A -- with the two connected in parallel — we’ll see a maximum output of 37.9V and 17A. This information will help us size the charger controller.
Selecting a Charge Controller to Handle the Power Input
Based on the specs from the solar array (37.9V and 17A), they chose a charger controller that can handle the input parameters, but also fit into the space allocated for the solar components. The 50A DC to DC Charger with MPPT is a powerful space saver as it does double duty! It will regulate both the solar input as well as boost the battery bank up with an engine charge while driving – win win!
With a maximum input of 750W, this small yet powerful charge controller helps create greater flexibility within the system. If it’s been cloudy for a few days or they’re parked under trees, they can charge up their house batteries simply while driving from one place to the next. The MPPT technology will take advantage of the higher voltage of these 320W solar panels and give the charging current a good boost. Tip: It’s important to give this component a good deal of breathing room so it will function properly and won’t overheat!
Also, when the battery bank is full, the solar input will trickle charge the bus starting batteries, so that they’ll be ready to crank the engine whenever they need it. This is a great feature for being out there in a boondocking situation or if the bus is going to see some time in winter storage. No more jump starting dead batteries!
Which Off-Grid Batteries Offer the Best Power for Their Size?
Based upon the initial energy use assessment of 1500 watt hours (WH) per day, they needed a battery bank that could deliver enough power without going below the safe depth of discharge (DOD). Using lead acid batteries (at a 50% DOD) would have required them to install 3000 WH of batteries because with this chemistry they could only safely use half of the battery capacity. But, with Lithium Iron Phosphate batteries (at an 80% DOD), they only needed 1875 WH. So, instead of 3 heavy and very large lead acid batteries, 2 small yet powerful LiFePO4 batteries did the trick!
They chose to install 3 DuoHeat 100Ah Mini-Core LiFePO4 Batteries to power the living area in the bus when off-grid. That extra battery is simply insurance for those days when the sun doesn’t shine for several days and they aren’t driving. These small, lightweight, and powerful batteries can handle a wide array of temperatures because they are self-heating. They can be installed inside the living area and won’t need to be removed from the bus during winter storage because they can handle some pretty cold temps (down to -4 degrees F in storage)!
With an 80% DOD, these batteries will safely deliver over 3kWh per cycle. Again, they’ve built enough flexibility into the battery bank that if they need to use more power, they can without dipping down too low. See our video review of the DuoHeat 100Ah Mini-Core LiFePO4 Battery for more details!
How Do I Run Household (AC) Appliances in My Off-Grid Bus?
Obviously, this bus didn’t come with a traditional RV converter that would allow them to charge up auxiliary batteries and run household appliances while plugged into shore power, so they chose to install Renogy’s 2000W Inverter Charger to do double duty! With this 2-in-1 component, they’ll be able to run household AC appliances while off-grid AND charge up the house batteries when plugged into shore power. Another win, win!
With the automatic transfer switch, this unit safely switches between power in and power out. And, if they ever want to run a coffee maker or instant pot or even a hairdryer occasionally, a 2000W inverter will do the job. However, it’s important to point out that the inverter can safely handle any one of these appliances alone, but not together. The great news is that if you overload an inverter, it will beep and simply turn itself off, rather than doing any damage to the component or your appliances.
What’s the Best Way to Monitor my Off-Grid Solar Powered System for My Bus Conversion?
To monitor the batteries, charging status, and the electrical load, we’ve installed the Battery Shunt 300 between the negative battery terminal and the negative busbar. The shunt will connect wirelessly to the Renogy ONE Core Monitor which will show them the status of all their components in the system with a convenient touch screen format! They mounted this just above the solar cabinet in an easy to read location.
Installation Considerations
Here are some things to keep in mind, in addition to what you’ll find in each of the component installation manuals:
Always disconnect any power supply from solar panels or shore power while installing solar components.
All of the components give off heat while doing their jobs, so be sure to plan out not only the size of the components, but also the free space they need around them for ventilation.
Fuses and breakers need to be appropriately sized and placed in between components, see wiring diagram.
Short wire runs increase efficiency. We were lucky that the location of the solar cabinet and the bus starting batteries were so close together. This saved money on the wire length and decreased transmission loss.
Grounding the DC to DC Charger. Experience has taught us that it’s best to ground the DC to DC Charger directly to the common ground on the starting battery, in addition to the common negative busbar.
The Inverter Charger needs to be grounded to the vehicle chassis in addition to the common negative busbar.
Many school buses have no AC power distribution panel. When installing the AC power output from the Inverter Charger, it’s recommended to install an AC power breaker panel to provide additional protection for the AC outlets.
It’s also a good idea to install a DC distribution panel for all DC appliances so that they will be protected with an appropriately sized fuse as well.
Ready to dive into your own project? With the right sized solar panels and components, you’ll be ready to power up your own skoolie adventures and hit the open road. The “Fest Bus" is already rolling along – and the Renogy solar powered system is providing all the power that they need to enjoy some summertime music festivals in the southeast!
This blog contains affiliate links. When you use our links and promo code to make a purchase at renogy.com, you get a sweet discount and we get a small commission. In addition to volunteering our time, we donate a portion of our affiliate proceeds to non-profit organizations that support youth education/development, sustainability, health, environmental education, and access to outdoor adventure. Discover more about us and how we've been traveling with solar power since 2012 -- all over the North American continent.
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