More and more RVers are considering adding solar power to their rigs.
Maybe it’s the result of a cultural shift toward green energy or simply the convenience of having enough power to camp outside of comfortable but confining RV parks.
Whatever the reason, it’s clear that RV solar power systems are here to stay.
In this article, we’ll introduce you to the basic parts of an RV solar system, and talk a little about why you might consider adding such a unit to your rig.
RV Solar Power Basics
RVers install solar panels for two main reasons:
- to trickle charge house batteries
- as a source of primary electrical power
Solar Power Trickle Charging
When your RV sits for a prolonged period of time, your house batteries begin to lose power – regardless if they’re used or not.
For car owners this is the reason a battery dies after the car sits idle for too long.
The same principle applies to your RV. It’s also important not to leave the batteries dead for long periods of time as this could cause permanent battery damage – and leave them unable to hold a charge ever again.
All that’s needed to avoid much of the pain associated with a dead battery is a solar trickle charger. This charger will also keep your batteries fully charged and ready to go when the time comes to use them.
A solar trickle charger is usually a stand alone device that creates several watts of power for charging and maintaining RV house batteries.
These chargers are usually made of durable plastic and amorphous solar cells (more on that below), and are molded into a weatherproof unit that’s about a foot and a half square.
Installation is simple and straightforward.
Just take the small panel, usually no larger than a dinner plate, and connect the wires and battery clips.
Place the panel in the sun and voilà!
There is a chance that if you have a late-model RV you’ll already have one of these units installed directly by the manufacturer.
Here’s an example of what a solar trickle charger looks like:
Using Solar Panels For Primary Electrical Power
The second use of solar panels is to provide primary power to RV house systems.
This involves the installation of several solar panels and other gear, together sometimes called a solar kit, to create and regulate enough power for routine operation of your RV’s house systems.
For anyone new to RV solar, it’s easiest to think of an RV solar system as more or less a big, expensive battery charger.
Anything that can run off your batteries can be run from an RV solar system.
As you can imagine, RV solar systems are especially helpful for boondockers and dry campers.
An RV solar panel is much like a battery in that it supplies electricity at a certain voltage.
The major difference is that the panel itself needs the sunlight to make electricity while batteries require a chemical reaction to do the same.
How Much Solar Power Do You Need For Your RV?
When you wander around your local retailer looking for battery chargers, you may notice that many of them offer about ten amps of power.
The good news is that solar panels can also provide these ten amps of power, about what’s needed to charge a normal RV battery. You can expect a ten amp RV solar panel to offer a hundred watts in most cases.
Going lower than that will typically mean lackluster charging performance.
If you go higher, like with this 15 watt solar charging kit, you should be able to charge additional batteries or charge the existing batteries you have at a more rapid pace – you’ll probably also need a charge controller (more on that below).
Factor in energy losses from clouds, the angle of the sunlight onto the panel, the temperature of the panel itself, and other atmospheric and design factors, and the usable power from a solar panel is but a fraction of the energy that the sun deposits on the panel.
When all is said and done, modern solar panels provide about 60 watts per square meter – only 6% of the sun’s energy that hit the panel!
When you measure up the space you have available on your roof or elsewhere, you may find it difficult to capture the power required to run your RV’s house systems completely off of solar power.
For a large motorhome, you might need 500 to 800 watts of power. That’s about 10 to 15 square meters of real estate filled with solar panels.
If You Need RV Solar on Steroids
If you consider yourself a full-timer, boondocker, or dry camper, then chances are a standard trickle charger setup won’t get you excited.
You’re going to want to live fully ‘off the grid’.
You must realize you’re going to need a lot of solar panels if you want to make up for the power output of your generator.
As many RVers are quite frugal with their power needs, in some cases all that may be needed is 100 or so watts of solar panels and a few extra batteries to store the collected energy.
This should allow for moderate lighting, use of a TV and other basic electrical devices.
Some folks use propane to power the energy hungry appliances like the fridge, heater, and stove and save the solar for lighter-duty uses.
More Power, More Dollars
You may have seen RVs with multiple solar panels on their roof that produce upwards of 800 watts of power.
These systems, such as the 320 watt solar power system from Go Power! shown below, are built to capture huge amounts of power from the sun, store it, and then convert it as needed in order to run all the gadgets and appliances that make modern RVing fun and convenient.
Expect to pay around $200 for every 100 watts of solar power you’re looking to have. So for 800 watts of solar power, that’s an outlay of at least a couple of thousand dollars. This price is just for the panels though, and doesn’t include charge controllers or inverters.
Still, these expensive systems will enable you to spend days without the need for power hookups or a generator.
Typical Solar Power System Components
Below is a run down of the basic components of an RV solar power system.
Solar Panel Basics
You may have heard that there are three types of solar panels, categorized by how each individual cell on the solar panel is constructed.
The three types are:
- monocrystalline – each cell is a thin wafer of a pure silicon crystal
- polycrystalline – each cell is made of silicon that’s melted and then poured into a mold
- amorphous – each cell is made of a thin layer of silicon attached to a backing material (think of a sticker on it’s backing)
Most of the trickle chargers we talked about earlier are made of amorphous cells. Amorphous cells are the cheapest of the three types, and are better at collecting power from the sun on cloudy days. But they’re not as efficient at collecting energy as the mono and poly cells.
Most solar panels made for powering and charging – as opposed to trickle charging (maintaining charge) – are made of either mono or poly cells.
The 320 watt Go Power! kit above, for example, is made of monocrystalline cells.
Flexible or Rigid?
While the actual solar panel cells are monocrystalline, polycrystalline or amorphous, the entire panel can be either rigid or flexible.
The mono and poly cells are usually part of rigid frames, while the less efficient amorphous cells can be molded into flexible panels that can bend up to about 30 degrees.
Recently though, Go Power! has introduced a new flexible panel with mono cells, called the Solar Flex.
Another manufacturer, Renogy, also has their own flexible mono cell panel on the market.
These flexible mono panels are a bit more expensive than their rigid counterparts, however.
Solar Charge Controller Basics
The charge controller, sometimes called a charge regulator, is the command center for your RV solar system.
It regulates the power (both current and voltage) coming from the solar panels to prevent your batteries from becoming overcharged. The solar powered trickle chargers we talked about earlier generally don’t come (or need) a charge controller.
And interesting fact about solar panels is that while they’re usually rated at 12 V, they often put out about 16-20 V.
You might wonder why the panels put out more voltage than the batteries they’re charging are rated for.
The answer is that if the panels were designed to only output 12 V, they wouldn’t produce nearly enough power during less than perfect conditions and full sun. So the engineers design the panels to output more voltage than rated during optimal conditions, so that when the clouds come in or the panel heats up (solar panels work better when they’re cool) you’ll still be able to get 12 V out of them.
Solar charge controllers can read and adjust battery voltage, optimize power flow, figure solar panel production, and keep the RV solar system running efficiently and your batteries from overcharging.
What Is Maximum Power Point Tracking?
Maximum power point tracking (MPPT) has improved the way charge controllers interact with the different RV solar components.
An MPPT controller is an electronic DC to DC converter that converts the higher DC output from the solar panels to a lower DC voltage needed to charge your RV’s batteries.
If you use a regular charge controller, you’ll lose a lot of power if there is a poor match between the output on the solar panel and the current charge on your battery.
The MPPT charge controller on the other hand, will constantly compare the output on the panel with the battery charge state, optimizing the voltage to get the most amps into the battery. You can read more about MPPT charge controllers here.
You should consider an MPPT charge controller if you’re serious about building a quality RV solar setup.
Digital Monitoring Unit
Who doesn’t like to know what’s going on?
The ability to monitor your RV solar system varies widely with the quality and cost of the setup. Some systems use indicator lights, others simply list the voltage.
By using a digital monitoring unit, such as the Xantrex CM/R-50, you’ll be able to read the volts, amps, and cumulative amp hours of your solar array.
Wiring is the backbone of your RV solar system. Just don’t get tricked though, as there’s no special wire made exclusively for solar panels.
It goes without saying that mounting your RV solar panels should be done with the highest quality hardware so that they are absolutely secure.
You can mount your panels either flat or on some tilt brackets.
Some RVers believe that tilt brackets can be troublesome. If you mount your panels permanently, be sure to consider the loss of efficiency if the panels don’t face directly toward the sun.
This RV solar guide is meant for the solar power beginner. While we’ve introduced the basic components and talked a little about how they work with each other, you’ll want to do more research before you make your final purchase decision.
If you want to continue your research we encourage you to visit the links below to learn more.
- Trailer Life – RV Solar Power
- GoneWithTheWynns.com – What Can Solar Power Do For an RV?
- MarxRV.com – The 12 volt Side of Life
- MacSlab.com – Optimum Tilt of Solar Panels
- Good Sam Club – Do-It-Yourself RV Solar: What you need to know.
- JackDanMayer.com – RV Electrical and Solar
- Northern Arizona Wind and Sun – Solar Power Equipment Dealer
Where to find RV solar panels, controllers, parts and accessories: