skip to Main Content
BUILDING A VAN? WE'VE BEEN THERE. PRODUCT RECOMMENDS

Solar Panel Basics

When it comes to powering your van, there is a lot more involved than just going to the store and buying panels. Before going into how many watts of solar you need to buy, let’s take a look at the different types of solar panels available.

Determining which type of panel is right for your lifestyle will help give you a better idea of how efficient the panels will be. This is usually determined in tandem with calculating how many watts of solar to buy.

Solar panels powering a van @aves_sin_rumbo

Solar Panel Types: Rigid vs Flexible

Rigid Solar Panels

Rigid panels are solar cells mounted under tempered glass. They range in sizes from huge residential panels to small 50W device chargers. Most panels are mounted in an aluminum frame and designed for extended outdoor use withstanding hail, sand and wind. Glass is resistant to scratches which allows for long term light efficiency. Basic rigid panels are cheaper per watt and generally come with a long warranty.

Flexible Solar Panels

Flexible panels are flat cells that are molded with a layer of protective plastic on top. Because they don’t have a frame, they are low profile and can bend to shallow curves such as a van roof. It also makes them lightweight. The softer plastic on these panels is more prone to getting scratches on the surface. However, they are also less likely to crack from an impact. Bending the panels tends to cause issues with cracking and even shorting out between the cells, but this is improving on a yearly basis in the industry. Because of this, the warranty on these panel tends to be significantly shorter.

Solar panels work best when the whole panel is getting consistent light. For flexible panels, the more you bend your panel, the less efficient it will be because part of the panel will be getting less direct light.

Solar Panel Placement

Fixed solar panels

Fixed solar panels are permanently mounted as part of the van build. Some people build angled mounts that they can manually adjust to get more direct sunlight.

Pros of fixed panels:

  • They are always collecting energy as long as the sun is out; whether you’re camping or at a laundromat
  • They don’t take up valuable interior real estate
  • They are less easy to steal
  • Better accommodates those who are power hungry and need more than 200W of solar.
  • Can double as a shade on your van to help with reducing heat

Cons of fixed panels:

  • They are harder to position to get optimum light. Mounts that you can angle help this.
  • More involved to plan an install
  • Raise your roofline
  • Most panels reduce “stealth” to varying degrees
  • Reduces your roof layout options (goodbye sunroof!)

Portable Solar Panels

Portable solar pnels are either standalone units or a “solar briefcase” that you store in your vehicle and then pull out while you’re at camp.

Pros of portable panels:

  • Easier and cheaper for those who don’t have the means to do more custom work.
  • Can position to get the best lighting, opening up options for where you park your van as well.
  • Less evidence of living in your vehicle when they are put away
  • Easier for a wide range of vehicles (small cars, VW bus, etc.)

Cons of portable panels:

  • Need to set up each time you’re at camp
  • Takes up space inside the van when traveling, especially anything above 200W
  • Won’t be able to charge with solar when running errands
  • Not great for city dwelling

Solar Panels Perform Best When Cool

When planning your solar, be aware that solar panels perform best when cool. For fixed panels it is best to design a gap between the panel and the roof for air movement. Mounting or gluing panels directly to the roof loses important cooling airflow from the underside.

The Stealth Factor (Mounting Fixed Panels)

Any panels mounted to your roof are going to be a giveaway that someone is living in the van. There are various ways disguise this with roof racks and flush-mounted flexible panels. When you’re living in a van, hiding yourself has as much to do with your location as it does how your van looks. In neighborhoods that are wary of the homeless, just having a vehicle above a certain height will get the cops called on you. Other areas of cities have full Class C RV’s parked in broad daylight and no one blinks an eye.

This is all to say that we don’t think that it’s worth sacrificing a lot of effort and resources trying to hide your solar as you may be thinking. If you have big panels, hiding them is a loosing battle

Solar panel efficiency

Now that you have a general idea of the types of solar panels out there, let’s look into how to get the most efficiency out of your setup. Once again, before going into how many watts you should purchase we are going to delve into the things that make some solar panels more efficient than others. These include:

  • Weather conditions
  • Angle of solar panels
  • Shade
  • Monocrystalline vs. polycrystalline vs amorphous technology

Weather conditions

Once you have installed a solar panel, weather is going to be the biggest concern (and major headache) when it comes to collecting power.

Cleaning your panels is important. Snow and dust can greatly reduce the amount of power that you gather.

In our post on calculating how much electricity you need to live in a van, we walked through step-by-step how to calculate how much energy was needed to charge various things. One of the major factors in picking out how many panels you need is how much sun you will get. Make sure to think about the weather conditions you expect to most often experience.

Angle of solar panels

tilt mount will allow you to adjust rigid solar panels to face the sun directly during sunrise, sundown, and when the winter sun is low in the sky. If you have the budget and space, tilt mounts can increase your solar power capacity by as much as 25%, as long as you adjust them properly. Portable solar panels are already tilt-mount by design!

Flexible solar panels cannot really be individually tilted unless you mount them to a frame- effectively making them a rigid panel.

Shade

Another big thing to know about panels is that most solar tech is very sensitive to shade. Each of the little squares on your panels are wired in a way that if one of them is shaded, the whole row can’t produce energy. Because of this, you can reduce your energy produced by up to 90% if a certain 10% of the panel is covered.

This is important when placing the panels and critical when planning the roof layout of the van. If you have a roof rack, chimney or storage box covering your panels you are likely significantly reducing your energy.

Monocrystalline vs. Polycrystalline vs Amorphous solar panels

This is what the solar gathering part of the panel is actually made of.

You will hear that one type is more “efficient” than another, but that mostly determines the size of the panel. Once it is in your hands, 100W panel is 100W no matter the technology. Look at the dimensions of the specific panel make sure it will fit and forget about the efficiency.

Monocrystalline panels are little more efficient- meaning they take up less space-and usually a little more expensive.

Polycrystalline panels are a bit cheaper and bigger per watt, but still share most of the same longevity and durability attributes as monocrystalline panels. You really can’t go wrong with either option as long as you take measurements and make sure everything fits.

Amorphous panels are quite a bit different from the other two. They are significantly less efficient- taking up more weight and space- and are more expensive per watt. These panels are the best in cloudy weather and not as severely affected by partial shade as the other types. These panels are also quite durable, even when flexible, so you can often see them sewn into backpacks and cloth items.

How much solar power do you need?

To know this, you need to know your energy usage and battery bank size. We go over all that good stuff in our post on how to calculate energy needs for you van.

You might find that your solar panel needs are too big or too expensive once you run the numbers. This is much better to know in the planning stage than when you’re on the road! You can make adjustments to your expectations or usage until it fits within your goals.

Wiring in Parallel vs Series

As with batteries, panels can be wired in parallel or series! What does this mean? Panels wired in parallel run all of their (+) wires into one combinor that plugs into the charge controller. (-) wires also go into a separate combinor. This keeps the voltage the same but increases the amperage going into the charge controller. Wiring in series is where you plug the (+) of one panel into the (-) of another in a long string like christmas lights. This increases the voltage but keeps the amperage the same. So which way is better?

  • Wiring in Parallel:
    • Most PWM controllers need parallel wiring. These charge controllers are only rated to a slightly higher input voltage than the battery bank. So if you have two 18V panels and wire in series to put in 36V of power into a PWM controller, you’re loosing anything above the 13.8V that’s going into your batteries.
    • In certain shade conditions parallel is better. If one panel is shaded and the other isn’t, you aren’t loosing as much power because you’re still getting the full power from the panel in the sun.
    • Parallel solar needs bigger wiring, fuses, and combinors. Each panel must be fused at the combinor junction in case one shorts out. The wiring must be bigger as you are increasing amps.
  • Wiring in Series:
    • No need for fuses and wiring is simpler and cheaper.
    • Higher voltage rather than amperage means the system is a more efficient
    • In certain shade conditions, series is better. Overcast days or low light situations benefit from Series. If panels are only getting enough sun to output 13V, then two panels in parallel won’t be outputting enough voltage to properly charge the batteries at 13.8V. If you’re wiring in series, you’re getting 26V which can be stepped down for a proper charge.

In our opinion, wiring in series should be the go-to setup due to less complexity and higher efficiency. If you’ve got a small system and PWM controller then wiring in Parallel is fine, just make sure you fuse everything properly.

This Post Has 9 Comments
  1. Just a question. If you are driving down the road, do you need Solar Panels on top? I have a Class C and my alternator is charging the batteries when I’m driving down the road… I think

    1. Charging with alternator will give you more power than most solar setups. So, no, definitely not needed. When solar is great is if you’re stationary for a few days!

  2. Just a heads up, I think the last line of the first bullet point under “Wiring in Parallel” should be parallel not series, as you covered wiring in series prior.

    Thank you for the very informative article! Keep up the great work.

  3. Thank you so much to share with us so many interesting infos about solar cells on a camping car roof. Now I have to calculate how many watts are needed on my motorhome…not easy…

  4. Hi Kate & Ian, is this correct??? >> I saw a video where a solar guy said if you’re running 2 or 3 x 100 watt panels for example, and add one more smaller, say only a 50 watt panel, then ALL of the panels would only be able to output the lower amount (in this example they all become 50 W each). Is he correct and why? Or would that depend on whether they’re wired in series or parallel? Super article thanks!!

    1. Ryan,

      The youtube guy is partially correct for exactly the reason you suspected. If you’re wiring panels in parallel, then to get the maximum output they should all be the same voltage. If you’re wiring in series, then to get the maximum output they should all be the same amperage. So, if you have a whole bunch of different panels, but all at 12V, then you won’t get reduced output as long as you wire them in parallel. For instance, if you have a 60W, 12V panel and a 100W, 12V panel, you end up with a 160W, 12V input by wiring them in parallel. If you were to wire them in series, you’d end up with a 120W, 24V panel (because the 100W can only output 60W due to the reduced amperage from the 60W panel)

      Here is a more lengthy article on the topic:

      http://solarpanelsvenue.com/mixing-solar-panels/

Leave a Reply

Your email address will not be published. Required fields are marked *

Back To Top
Share
Pin
Tweet
+1
Reddit
1.5K Shares