This is a super exciting topic; I’ve been obsessed with this since I was a kid, and I used to cover up the calculator panel in math class and watch the screen fade out. Now, a lot has developed in the last 10 years. This equipment is more advanced, and it’s a lot more affordable. The problem is there are some challenges when you’re talking about sizing and sorting through all of the different gear that’s available on the market. I’m going to make this easier for you today. We’re going to make this beginner-friendly and cover all of these topics in great detail, so let’s be patient and stay tuned.
The equipment we need to charge our camper from the sun is obviously a solar panel, and we obviously need a battery on the camper, but we’re also going to need a charge controller. This is the brains of the operation. This is what takes the energy from a solar panel and converts it into a charging profile that can be used for a battery. A lot of beginners just starting need to learn about charge controllers. I find questions all the time on the internet about plugging solar panels into an RV. This is an essential component; otherwise, a solar panel would overcharge or damage the battery.
When we’re first getting started, the most essential part of this equation is actually the battery on our RV. This is the bottleneck; this is the weak link in the equation. When I see people just getting started off asking questions about solar, a lot of people come in and start talking about different types of panels and the charge controller. This is where you have to start. Now, what I’m concerned with is the capacity of your RV battery. This is an AGM battery, and it has 100 amp hours. That means we can use 50 amp hours. So, whether you have a 50 amp-hour lithium or 100 amp-hour AGM, you have the same capacity.
I want you to realize that this is like a rain barrel. If you have a small rain barrel and it’s raining out, by about 9 a.m., the barrel is going to start to overflow. That energy is wasted. It’s the same with your battery. If your RV came with a 50 amp-hour AGM or a type of car battery, you’re not going to be able to store the energy that you’re creating from solar panels. So, everything upstream of the battery is wasted. We have to start here.
Now, unfortunately, I’m not able to tell you what capacity battery you need without a bunch of questions and a lot of consultations, but I can give you a tip here. You’re going to want to be able to go for about three days unplugged with no solar panels and without running your battery down to low voltage. This is a significant number. If you can go on Friday, Saturday, and Sunday on just your battery, then we know once we go to solar, we can handle a rainy day or a day that we don’t have to set our solar equipment out. If your battery is so tiny that you deplete it after one-night camping, you’re going to run into the same issues even if you spend a lot of money on solar.
Now, these numbers will be different whether you live in San Diego or Seattle, but what I’m getting at is that if you don’t have enough capacity to bridge some periods of time without your solar hooked up, you’re not going anywhere anyway. So, let’s start with that capacity: a three-day capacity.
Once our battery is sized properly, we can start thinking about solar panels. Now, there are a million and one different types of solar panels out there, so I’m going to narrow this down, make a couple of recommendations, and then break things into categories to compare the pros and cons for you. For starters, panels can come in monocrystalline or polycrystalline form.
Now, monocrystalline panels give you more bang for your buck. The panels work better and use more advanced technology. My recommendation is not even to consider anything but monocrystalline panels. Luckily, most reputable distributors and vendors only sell monocrystalline panels, but you can still find polycrystalline panels on Amazon or online. These less efficient panels are really not worth your time.
Once we’ve decided to go with monocrystalline, there are a few more things to consider. The two categories for installation are fixed panels and portable panels, each with its pros and cons. A fixed panel might look like a style of panel that can be attached to a roof rack or come with hardware to be lagged down to the roof of your camper. For these installations, you’ll need waterproofing sealant. Alternatively, a fixed panel might be a thin, flexible panel taped down with double-sided VHB tape. However, these panels are notoriously fragile and need to be installed right away, as storing or handling them can lead to breakage. Whether you’re going with VHB-taped flexible panels or bolt-on panels, these are fixed solar applications.
The advantages of fixed panels are that they’re always set up and bolted to your roof, so there’s no setup when you get to camp. They’re also more challenging to steal, which is an essential consideration with expensive outdoor gear. However, the disadvantages include potential installation costs if you’re not comfortable with tasks like screwing into your roof and waterproofing. Another disadvantage is that fixed panels perform less well since you can’t angle them toward the sun. Additionally, park your camper in the shade, which reduces the panels’ effectiveness. These factors make portable panels a better option for harvesting more energy.
When working with portable panels, there are many options to consider. All of these are monocrystalline, but their features vary. Glass panels, designed for permanent outside installation, can be bolted to a roof and last many years. These are rugged and durable.
These panels offer superior performance compared to others. However, they can be cumbersome, which is why I recommend investing in hinge-equipped suitcase-style panels for easier handling. High-quality panels like these are worth the cost, though there are cheaper alternatives. If you’re looking for a top-notch setup, these are among the best options.
You can also get portable panels that are lightweight and foldable. For instance, some panels have a linear shape instead of a big square, yet they can provide the exact wattage and charge as their counterparts. These panels need to be hung up from hooks or leaned against something like a cooler, leading to lower performance compared to fixed glass panels. However, their advantage lies in being extremely lightweight and easy to store when folded.
Ultimately, the best system combines a bit of everything—fixed solar, portable solar, glass panels, and foldable ones. This adaptability ensures the best performance in any situation. One additional benefit of portable panels is that they often include a small charge controller for USB charging, allowing you to directly plug in devices like cell phones, headlamps, or camera gear. Most larger panels, however, require a separate charge controller for this functionality.
The last type of portable panel is a hybrid panel, which I’ve coined here. These panels blend features of fixed and portable panels. These panels are good but need to improve in either fixed or portable categories. They collect less sun than other panels, are less durable, and are not as flexible when packing away. They’re heavier and take up more space, so while there’s a panel for everyone, hybrid panels may not be the best choice for all users.
For this demonstration, we’ve selected a 100-watt glass panel with a suitcase-style folding design and a 100 amp-hour AGM battery. The next component we need is a charge controller.
Now, this is the brains of the operation. It is actually what charges the battery. It just harvests the energy that the panel is producing and converts it into a charge profile.
There are a lot of things to consider when you’re going with the charge controller, and a lot of the information that I’m finding on the internet is about very advanced systems—tons of wattage on the solar panels wired in series, multiple lithium iron phosphate batteries. It’s hard to sift through all of this information, which is really talking about Teslas when most of us are talking about Priuses. So, if 99% of the systems on the market are 100 watts or maybe 200 watts for an RV, we’re going to talk about a much more practical approach to selecting your charge controller.
A PWM charge controller is an older technology, but it does a really, really good job in a specific application. It just so happens that 90-some percent of RVers use that specific application when they go solar. Now, a lot of the content that I find online talks about MPPT charge controllers being the only option.
Now, this is usually specific to very advanced applications—larger solar arrays, arrays wired in series, and certain areas that get a lot of clouds, like the Pacific Northwest. It does better in all of those applications. But if you drive around the country and look at the type of solar that most people are using with their campers, it’s 100 or 200 watts wired in parallel. When I test PWM charge controllers against those situations, they perform almost as well.
This one was 50 bucks; this one was like 79 bucks, and it comes with all of the connectors needed to plug into the solar panels. The charge controllers are considerably more expensive, and you need help finding them waterproof. There are a few on the market that are big money, but most of them have to be installed inside your camper or an enclosure. These waterproof PWMs can go with a suction cup up against the camper. You can put a bungee cord around them, put them around your battery box—they’re made to be out in the weather. That’s a massive advantage for a lot of us.
So before you write to me with your complaints about this comparison, I realize that an is a superior charge controller. It’s what I use for more complex systems. But when you’re talking about these smaller systems, save your money and go with the PWM. You can actually buy a second one because these things don’t last forever. So this one was 50 bucks. I like to use one that’s about 70 to 100, but you can find ones that are even cheaper than this to have a backup when you’re camping. It’s a better option for most people.
Next, we’ll discuss sizing the system. However, sizing the system is the most important thing. It’s what people pay someone like me to do for them, and it’s very, very simple. So, if you learn how to appropriately size your panels, you’ll be able to set up solar panels on any camper you’re working with or make changes or upgrade your current system.
There are a lot of different connectors out there, but they don’t have to confuse you. It really is simple stuff. In upcoming videos, when we start installing these, we’ll show you which plugs to use for which situations.
I saved it for the people with the attention span. To size solar setups for your camper, you need to start with your battery. We talked about having a three-day runtime when you’re not connected.
Now, once you have that, it’s helpful to understand how much solar you need. To be able to do this, you basically have to be able to do third-grade math. I’m going to show you the formula to make this really easy.
The math we need to know to size these systems is that watts equal volts times amps. Since we’re working with 12-volt systems on these RVs, we need to find out the amps to determine the watts, or we need to find out the watts to determine the amps. So, in the case of having a 100 amp-hour battery, we know that we have a 1200-watt reserve capacity. It’s as simple as this.
Because it’s lead acid, we know that it’s actually a 600-watt capacity because we can only use half of the battery’s capacity. So, this math will help us determine what we need to know. It also is true that if you rearrange this, amps equal watts divided by volts.
If you’re looking for the amperage of a 120-watt solar panel on a 12-volt system, we know that we need a 10-amp charge controller or that this setup is a 10-amp setup. So, whether we have advanced systems or simple systems, this simple math can be used to size these components together better.
For this demonstration, we used a 100-amp-hour AGM, which is a 1200-watt-hour AGM. Now we know that we can only use 50% of the capacity on lead acid, so we have a 600-watt working capacity. This is useful information when we’re talking about panels.
The thing about panels is that one of the secrets is you can multiply them by 3.5 to figure out the average amount of wattage you’ll get in a day. It’s an average. Sometimes it’s going to be more; sometimes, it’s going to be less. So it’s essential to realize that 100 times 3.5 is a 350-watt-per-day panel.
Now, the way we get this formula is that panels are about 70% efficient. They have to be rated that way because if I took this panel and brought it to the equator on a mountain, it might go to total rating. This 100-watt panel might get 100 watts. That’s how we have to engineer these. But if you live anywhere in the continental U.S., this 100-watt panel is going to get you less than 100 watts, and if it does, it’s very, very rare.
The more useful figure is 70 times 5 hours of average daylight, which is the same as multiplying it by 3.5. So we have a 100-watt panel that’s a 350-watt-per-day panel, and we have a 200-watt panel that’s a 700-watt-per-day panel.
If we have 600 usable watts in our battery, a 350-watt panel will probably recover us on most average days. Remember I told you you should be able to go for three days. So 600 watts for three days is 200 watts a day. So, a 350-watt panel is going to fill you back up.
Now, a 200-watt panel over here brings in 700 watts a day. Now, that’s an overkill panel that oversized to the battery. You still might take advantage of using a 200-watt panel, and the reason why is that in real-world situations, you might want to pack this up when you’re not around camp. You might have it out for a few hours in the morning before you take off to go sightseeing. It’s a valuable thing to have it oversized.
But I would only go as big as this because you’re going to come up against the limits of how much charge you can put into your lead acid battery anyway. So this is how we size things. We convert our battery to watts, and we take our panels and multiply them by 3.5, thinking of a daily charge. A 50-watt panel is going to get a 150-watt-per-day charge. That’s how we do the conversion.
Now, finding a charge controller is even easier. Just divide it by the 12 volts. So, if you have a 100-watt panel, you know that a 10-amp charge controller can handle 120 watts. If you have a 20-amp charge controller, it can handle 240 watts. So, that simple math is how you size these things together.
I hope this information was helpful. I know it’sn’t the most interesting information in the world, but if you learn this stuff, all of the future videos we’ll make about installing solar will make a lot more sense. If you want to modify, adjust, or improve your current solar system, this is the sort of math and industry secrets that allow you to do this.