How Does Solar Power Work? A Guide for Purpose-Built Vehicles
Harnessing the power of solar energy produced by an incandescent star that over a million Earths can fit inside can seem quite overwhelming. Choosing your solar power setup requires more research than what SPF is most effective for not getting a sunburn.
We’re here to help alleviate the confusion and ensure you choose the perfect solar panels, solar batteries, and solar inverters for your needs.
Solar Panels Produce Electricity. So what?
Solar power for purpose-built vehicles is simply the process of absorbing power from the sun's energy alone, converting it into renewable energy, and then routing it into a battery bank for later use.
Simple, right? But how does solar power work to create electricity? Does my solar panel system really matter? Should I understand the ins and outs of how my solar panel system works?
That depends on what you’re using them for. If you need a portable solar charger for your phone when you go backpacking, you probably don't need to understand how that little rectangle battery pack works other than "put it in the sun to recharge it."
Suppose you plan on being in the backcountry in some form of a recreational vehicle for days off-grid and want electricity to power lights, a refrigerator, or anything else. In that case, you should probably read on to determine the best setup for you.
Photo-wha? What is Photovoltaics?
We know we can get energy from the sun. Absorbing energy seems simple enough, but how do we capture that energy into a battery bank so we can plug in and use that power whenever and wherever we want? That’s where photovoltaic cells come in.
The official definition of photovoltaics is; the production of electric current at the junction of two substances.
The little grid sections on your solar panels are photovoltaic cells that make up your solar panel and work hard to produce electrical energy. Each solar cell has multiple layers, the most important being the positive and negative semiconductors (material that conducts current). Each layer plays a part in creating and directing the electrical energy absorbed.
When sunlight hits the top negative semiconductor layer, loose electrons (the negative charge of electricity) start warming up and moving around inside the cell. They become drawn to the bottom positive semiconductor layer as they move around. The more prolonged sunlight is in contact with the cell, the faster the electrons move around. The electrons quickly hit a speed that forces them out of the cell as an electrical current into your battery bank, creating an electrical load for you to store.
Each cell produces and sends an amount of electricity to your battery to store energy. More cells equal more solar energy sent at a time. This is why you see different-sized solar panels to meet everyone’s needs.
The process repeats as long as your solar panels can absorb sunlight or until your batteries are fully charged.
What are the 5 Components of a Solar Power System?
You get it. You need a battery. And, of course, you need the solar panel to charge the battery. But what the heck is a charge controller or a solar inverter? Why do you need those? What does each piece of a power system do, and what are your options?
We've outlined the five components of a solar system to help you understand how solar power works.
1. Solar panels
Solar panels come in two main types: rigid and flexible. Besides the obvious: rigid vs. flexible, what's the difference? Does one type of solar panel work better than the other? We’ll get to size and watt generation later, but let’s focus on the technology for now.
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Rigid solar panels are heavier due to being housed in an aluminum casing and having tempered glass covering the cells. These are durable, heavy, and not very portable unless they are anchored to the roof of your overland vehicle or RV.
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Flexible solar panels, or thin film solar cells, are… well… thin and flexible. They don’t need a flat base or brackets to be mounted on and can be installed on various surfaces. Some come with adhesive (literally peel and stick); for others, you can use silicone or even Velcro to mount. They are lightweight, easy to install, and can be portable if needed.
Flexible solar cells are also often twice the cost of rigid solar panels.
So why would you go with flexible vs. rigid panels? If you’re concerned about weight, don’t want to drill bracket holes, or if the shape of what you’re trying to mount them on is not flat, flexible solar panels will be perfect. If you have a solid flat space to mount them and weight isn’t a concern, rigid panels will be fine. Both panel types have about the same power output capability and are durable (depending on the brand).
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Did you think you just had to consider flexible solar panels vs. rigid ones? Dig a little deeper, and you’ll see even more options available.
CIGS solar panels
CIGS = (Copper-Indium-Gallium-Selenide). Don’t worry; that doesn’t mean much to most other people, either. Think of CIGS solar panels as the blue-eyed cousin to silicon panels. CIGS panels are more light-sensitive and produce up to 15% more power over a year. This isn’t because they produce more power over the same amount of time. It means due to them being more sensitive to light, they will produce power more often than a silicon panel.
CIGS solar panels work better if it’s cloudy or smoky and will still produce some power during twilight hours. They are more expensive than silicon solar panels because they are more challenging to create due to combining the four elements in a lab before manufacturing.
Even with the added manufacturing challenge, the process is more efficient since less material is needed and glass isn’t used in the final product.
Silicon rigid solar panels
Silicon is the second-most abundant material on Earth, next to oxygen. So, silicon is pretty darn popular and widely used globally in solar technologies. Silicon panels are tried and true in the solar industry, lasting 25 years or more.
Although they are not as efficient as CIGS panels in low-light conditions, they are more efficient under direct sunlight because the silicon atom cells are connected like a grid. This helps the current exit each cell and enter your battery bank faster.
They are less expensive since they are easier to mass-produce, but they require more energy since you must purify the silicon (heat). This means even though you're reducing your carbon footprint by using renewable energy once installed, they are not as environmentally friendly to produce as CIGS panels.
2. Charge controller
We can’t control the sunlight and have it supply solar electricity with the right amount of power to charge our batteries safely. Most solar panels generate more power than they are rated for when conditions are perfect.
A charge controller ensures that the volt output to your battery isn’t too high, so your batteries aren’t damaged by overcharging. Unless you have a small setup with a trickle charger or are using a panel that only generates a few watts per 50 amp hours, you will need a charge controller so your batteries will work. There are a wide variety of charge controllers available that will meet your specific needs.
3. Solar Inverter - AC vs. DC
AC/DC isn’t a rock band here. Regarding your solar setup, DC electricity refers to the direct current your solar panels generate. That electric current goes through an inverter and is converted to AC electricity, or alternating current, which is what you use to power your lights, refrigerator, or any other electrical appliance.
To know what type of inverter you should choose, you’ll need to understand how much direct current you’re getting from your solar panels and how much alternating current you’ll draw at a time.
Your solar battery, solar panels, and solar inverter should all have the same input voltage. The output would be determined by how much power you will use. If you have a low-watt inverter and try to run a high-watt appliance, you’ll blow a fuse (or worse, fry your inverter). So, going back to what’s right for you? You must determine how much power you will use at a time.
If you’re not needing all the comforts of home and plan on a simple setup, you might not even need an inverter. Your fuse box (which you need regardless) should ensure you’re safe if you’re only running a refrigerator and a few USB outlets.
4. Fuse block
The fuse block is a central hub that directs DC electricity from the battery to individual low-amperage items in your system, such as your refrigerator, lights, USB ports, etc. Fuses in your fuse block (sometimes called a distribution block) protect your wires and devices in case of a malfunction that results in an overcurrent.
If you’re running something that unknowingly draws too many amps through wires that can’t handle the load, your fuse will “blow” before any damage occurs to your device or your wires heat up and cause a fire.
You can utilize various fuses depending on your wire gauge, how much current is running through it, and how you will use your power. Your fuses should match your items’ needs, so research this in detail before installation.
5. Batteries
This is how you store your power for later use, so selecting the proper battery(ies) for your energy use need is very important. There’s nothing worse than wanting to make pancakes and coffee in the morning with your induction cooktop after three days in gloomy, cloudy weather and realizing your batteries are nearly dead from lack of charge.
Ok, there are plenty of worse things, but who doesn't want pancakes on a brisk autumn morning in the backwoods? So, are you a pancake and pour-over coffee person or an instant oatmeal and Starbucks Via person? Are you just running low-watt lights in the evening, or are you charging electronics, using power tools, and cooking with an air fryer?
In addition to battery capacity, it’s essential to look at other things like battery lifespan (warranty, longevity, charge/discharge cycles), what temperatures you will be in (some batteries don’t perform well in heat and/or cold temperatures), and battery type (lead-acid vs. lithium-ion).
Here’s a look into two main types of batteries. Lead acid and Lithium. These two have even more variations, but we will keep it simple.
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Lead-acid batteries are much less expensive than lithium-ion because they use more common materials and are easier to produce. They require little to no maintenance and work well in cold weather conditions.
Lead-acid batteries can’t “cycle” (the time it takes to get from 100% charge to 0%) below 50% of charge without damaging the battery and shortening its lifespan. So, if you have a 100AH battery, you only have 50AH of usable electricity before possibly damaging your battery.
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Lithium-ion batteries are significantly more expensive than lead-acid batteries due to the different materials and newer technology involved in producing them. Lithium-ion batteries outlast lead-acid batteries by up to six times longer. Some companies have a 10-year warranty on their lithium batteries, so although they are more expensive, the initial investment can be worth it if you’re planning long-term.
Lithium can cycle down to 0% (but preferably not completely dead often) and not cause significant damage. This means you can use nearly all your 100AH battery if needed, nearly doubling your battery bank capacity usage for the same amount of amp hours stored.
Lithium batteries are significantly lighter than lead-acid batteries. If you’re concerned about overall weight in your build, you can cut weight by more than half and have twice the power available by opting for lithium-ion instead of lead acid.
Battery capacity and output
Lithium batteries charge significantly faster than lead acid depending on your chosen brand. This can come in handy when the days are shorter, and you’re still using the same amount of power. Of course, the charge speed will depend on how many watts of solar you have and how many amp-hours of batteries you’re charging.
Since Lithium charges faster and you can use more of the battery’s capacity, we’ll talk about lead acid charge times and what you can use with its capacity. Keep in mind this is only referencing a few items you might use, and usage will vary greatly depending on what other appliances or items consuming power you have.
Even keeping an inverter on so you can charge your laptop will consume a tiny bit of power in addition to the laptop charging. It all adds up, and it’s important to understand and keep track of what you use daily.
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You can run a Dometic CFX3 35 Portable Cooler for three days, charge a 100w laptop for nine hours, and run 10 CFL lights for ten hours. Perfect for the weekend warrior.
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Your Dometic CFX3 35 Portable Cooler will run for six days, you’ll have 18 hours of laptop charge time, and your lights will still work up to 20 hours. Those are pretty good stats for longer weekend trips or someone who doesn’t use much power.
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Are you planning to spend weeks in the backcountry or live in your vehicle full-time? With 300 AH of AGM batteries, your Dometic CFX3 35 Portable Cooler will run for nine days straight, and you’ll have 27 hours of laptop charge time to edit all those amazing photos you’ll be taking. Wintertime? Are days getting shorter? Your lights will run for 30 hours.
How Do I Choose the Right Solar Power Setup for My Needs?
There’s a lot to consider when choosing your solar power setup. A quick Google search is overwhelming with the growing popularity of solar power. Everyone has an opinion about what’s right for them, but how do you know what’s right for you?
Ask yourself these four questions as you are researching your options:
1. What do I plan to power?
We take power and its availability for granted when living in a brick-and-mortar home. You probably won’t notice a difference in your power bill if you charge one or three laptops daily. You’ll definitely notice the additional power consumption if you’re parked on BLM land for five days and only using solar as your power source.
Will you have a refrigerator? What kind? Do you like to cook? Will you be using propane or an induction stove? Maybe you want to bring that air-fryer or Instant Pot? Do you want air conditioning in your rig?
Based on the questions above, you’ll also want to consider and research the differences between a 12-volt and a 24-volt system and "in series" vs. "in parallel" circuits (more info coming soon to a blog near you).
2. How long do I plan to stay off-grid?
Are you a weekend warrior? Full-time traveler? Do you stay mostly off-grid, or at campgrounds/RV parks with shore power? What’s the weather like where you travel most? Is your destination sunny or cloudy?
3. How much space do I have available for solar panels and a battery bank?
Consider the space available for your solar panels, as well as space for your battery bank. If you cover your roof with panels but only have room inside for one battery, you’ll charge that up quickly, but it won’t be much good if you have a few days of cloudy weather. Power input and power capacity should align.
4. Where and how will I mount the solar panels?
Once you decide if you want rigid or flexible solar panels, that will determine how to mount them. Rigid solar panels are typically mounted with brackets drilled into a solid surface like a roof. Not only do you need to know how much space you have to mount them on, but you also need to know where your mounting points are to ensure a safe, secure installation.
Flexible solar panels attach to your roof via some form of adhesive and can flex to the shape of what you’re mounting it to. They are lighter weight and typically can be installed by one person.
If you want an option to tilt your panels, you must have a movable mount to stick them to. But unless you’re a hard-core traveler and going to areas with consistently low sun (like Alaska), this isn’t necessary.
3 Things to Consider When Designing your Solar Power System
Sure, all this technical stuff sounds super cool. But what do you really need? As much fun as it is to build a tricked-out system and be able to boast about all the power you have, you may not need it. Or maybe you do? Here are a few things to consider when planning your power setup:
1. How long are you keeping your vehicle?
If you're setting up an old beater 4x4 for weekend overlanding trips, you probably aren't worried about a solar system that will last decades. But if you're adding solar to an RV you plan to travel extensively in or on a boat you live on half of the year, you might want to invest in a more robust solar energy system. Some things to consider are:
Do you need a 25-year warranty, or are you just using the system temporarily?
How long do you want your system to last?
If you’re not keeping your vehicle long-term, what do you want the resale value to be?
Are you savvy with electrical systems and able to fix things easily alone, or do you want this to be a one-and-done scenario?
2. Where are you going?
The difference between traveling in the Southwest and Alaska is literally night and day. Solar panels require sunlight, and not everywhere provides the same amount of solar power. Ask yourself these questions:
Do you plan to be in the desert in full sun most of the time, or do you head to the mountains and ski all winter?
Will you be in environments often that have clouds or a haze?
Clouds, shorter days, dust, and smoke are all things that affect your power absorption and capacity needs.
3. How much effort do you want to put in post-installation?
It's ok not to know everything. Not everyone is familiar with how solar panels generate electricity and the upkeep needed on solar energy systems. It might benefit you to use a reliable solar power system.
But maybe you are a quick study on how solar energy works or have a background in electrical systems. If so, you're probably more comfortable working with solar energy systems.
Do you plan on bringing tools? (You should regardless, even if minimal)
Are you building your system yourself, or is someone else?
Are you comfortable troubleshooting and fixing electrical systems?
XPLOR Power is Here to Help!
We hope this article has been helpful for you. There are so many things to consider when planning your solar power setup for your rig, regardless of your rig type, and we want to help make some sense of it all!
Be sure to subscribe to our email list and check back in on our website for more helpful resources. You can also reach us directly with questions about our product by visiting our contact page.