RV solar systems can be designed many different ways to perform many different functions.  They can consist of one very small panel for battery maintenance (trickle charging) applications or many large panels together with charging devices and an Inverter which can provide most or all of an RV’s electrical needs. Many RV’s are currently produced with some amount of solar already installed. Determining which you have (or want to have) is simple. James Mannett, a former energy industry executive and current owner of CEA Solar www.rvsolarnow.com, answers questions from readers about the proper use of Solar Panels for RV use.

Dear James,

I have a 2004 Travel Supreme Motorhome. I looks like I have a 10 watt solar panel on the roof but I am really not sure what the size is. It looks broken and some if it’s circuits are exposed. What is it connected to and what is it for? Could you give me some information on how to replace it?  What procedure should I follow? I am new at this.  Thanks.  Signed:  Hanging Circuits.

Dear Circuits:

Your 10 watt panel is most likely a trickle charger A.K.A. a battery maintainer.  It is usually wired to the engine battery and is intended to keep it fully charged while in storage.  These small panels help compensate for the small 'parasitic' drain on motorhome engine batteries from various electronic devices and from the natural discharge rate of batteries when they sit unused. Many RV manufacturers install a small indicator light inside the passenger compartment which will light up when the sun is out indicating that the panel is connected and working. The most common panels are 5-10 watts and usually about the dimensions of a standard novel. To determine the actual wattage, you need to carefully remove the remains of the panel and look on the back.  There will usually be a label which will tell you the wattage, operating voltage and operating current (amps). When replacing it, find a replacement panel with the same or similar wattage and operating voltage. 

Replacement of your 10 watt panel is pretty simple but the removal procedure can vary depending on how the panel was originally mounted. (glued to the roof, screwed to the A/C housing, etc.)

1.  Start by disconnecting your engine battery.

2.  Remove the old panel along with all the broken parts and pieces and expose the two wires that were connected to the panel.

3.  Attach the + and - wires to a new panel. The panel connections will be marked accordingly. The wire colors can vary depending on the RV manufacturer. If possible, read the polarity from the connectors on the old panel before removal.

4.  Re-attach the new panel to the roof in the same manner as the old one. Be sure to seal any and all roof penetrations.  Also, be sure to seal the hole where the wire comes through the roof. DICOR is a typical RV roof sealant and is available at most RV supply stores. Use plenty of it.

5.  Re-connect your engine battery.

6.  Observe the charge indicator (A red or green LED sometimes mounted inside the RV). The sun must be on the panel.

1.  If you don't have a charge indicator, simply put a digital volt meter on the engine battery and observe the voltage for 20-30 min.  If the voltage climbs slowly, the panel is working. If you don't have a digital volt meter, they are less than $10 at any number retail outlets.
2. If you suspect the new panel is not working, check all fuse panels.  The solar panel is sometimes wired through a fuse that may have blown when the panel broke. 

Have questions about RV solar power?  You may write James Mannett at jmannett@rvsolarnow.com or visit his blog at http://blog.rvsolarnow.com where you may post your comments or suggestions about this article or others that appear there.  Meet and discuss RV solar power at the Quartzsite, AZ rally January 21-30 2011 booth #140.

Most any household appliance can be powered from an RV battery bank, and an RV solar system can be designed to produce enough energy to replace what is consumed during a typical day. The trick is to strike a balance between the size of the solar system necessary to satisfy the daily power demand, and the needs and expectations of the user.  James Mannett, a former energy industry executive and current owner of CEA Solar www.rvsolarnow.com, answers questions from readers about the proper use of Solar Panels for RV use.

Dear James,

I have a small travel trailer with basic amenities.  They include a propane/110V fridge, propane alarm, propane water heater, lighting, TV, and a Microwave Oven. When  my wife and I boondock, we have to start the generator to watch TV or run the microwave.  It seems like such a waste of fuel, not to mention the noise, for the short period of time we need to use regular household appliances.  Is there a way to use solar on the travel trailer to run these items without breaking the bank?  Signed: Jonathan Rogers.

Dear Jonathan:

The short answer is YES. The cost of the solar system will depend on how much energy the RV appliances consume and how long you run them.  First, lets talk about the appliances, accessories, and how you use them.

A typical 32” flat screen TV consumes about 200 watts of power.  More if it’s larger.  However, a 19” flat screen TV that has a 12V power option consumes only 50 watts or even less.  Now there are folks out there that will never give up their big screen TV’s, and I understand that.  For them, a larger and more costly solar system will be needed to keep up with the demand.  However, if size is not important, these smaller 12V TV’s cost less than $200, can plug directly into a cigarette lighter, and can be run for many hours without depleting an RV battery.  And because they run on 12V, there is no need for a costly Inverter.  I know many RV’ers that use their big screens when parked in a campground when shore power is available, but bring out the smaller 12V TV when boondocking. 

The Microwave is another matter.  Most microwave ovens consume between 800-1200 watts of power.  But, because a Microwave only runs for a few minutes each day, it is really a small energy user and very efficient.  The trouble is getting it to operate from your battery bank.  Currently I am not aware of any 12V microwave ovens.  If the operation of a microwave is essential while boondocking, then I know of no other solution than to use an Inverter.  A simple ‘modified sine wave’ type would suffice, but for better operation, a ‘true sine wave’ type is best, but is 4X the cost.  Then there is the issue of installation.  An improperly installed inverter can cause more harm then good.  One RV’er, who I know personally, recently had to replace his $1,000 inverter along with the RV’s $2,500 energy management system because the first inverter was installed improperly.  Even worse, there is a real fire danger if the Inverter is installed improperly.  For a small travel trailer, the easiest way to avoid all of the cost and installation risk of an Inverter would be to seriously assess the need to run the Microwave in the first place.  For the sake of the following analysis, let’s assume you have decided the Microwave makes a much better bread box when dry camping than a cooking appliance.

To determine the size of the solar system, let’s examine the power demand from all of the electrical devices. (I threw in a laptop computer even though you didn’t mention one)  Also, you might be surprised to learn that even propane appliances consume some battery power, although small.  

Propane Fridge  .5 amps 24 hours/day 12 amp/hours

Propane water heater .25 amps 24 hours/day 6 amp/hours

Propane alarm (sniffer) .25 amps 24 hours/day 6 amp/hours

3 standard RV lights 4.5 amps 4 hours/day 18 amp/hours

12V TV 4 amps 4 hours/day 16 amp/hours

Laptop Computer (w/12v 4 amps 2 hours/day 8 amp/hours

adapter)

Total Power Demand: 66 amp/hours.

A typical 120W solar system will produce about 65 amp/hours of day of energy which, in your case, would be just enough to satisfy your energy demand. A smaller system could be used if you were to find ways to conserve.  A roof top system of this size would be comprised of just one solar panel.  Or, if you didn’t want holes in your roof, a portable system would work well also.  Either way, the cost would be somewhere in the $600-$800 range, or less than a typical generator.  And a whole lot quieter!    

Have questions about RV solar power?  Would you like James’ RV power calculator? You may write James Mannett at jmannett@rvsolarnow.com or visit his blog at http://blog.rvsolarnow.com where you may post your comments or suggestions about this article or others that appear there.  RV solar devices can be seen at www.rvsolarnow.com.  

12V Television

RV Microwave Oven

RV Inverter

Roof top RV Solar panels run household fridge.

Propane fridge fires in RV’s combined with a demand for more fridge space is driving more new RV buyers to purchase the ‘Household Fridge‘ option.  Tiffin motorhomes reports the household fridge option to be the most popular.  But, what happens when boondocking for extended periods? And, if solar power is to be used, how much is required to run these new refrigerators?  James Mannett, a former energy industry executive and current owner of CEA Solar www.rvsolarnow.com, answers questions from readers about the proper use of Solar Panels for RV use.

Dear James,

A great deal of attention is being paid lately to the propane fridge recalls and fires. A lot of other RV’ers I know are replacing or thinking about replacing their propane fridges with a household version.  At first glance, this seems to be a good idea.  But, how much power do they use? What electrical changes are necessary?  And, what impact would it have on my batteries and my solar system?  Signed: Steve Maynard.

Dear Steve:

Great Questions!  I have been seeing the same trend and several people have already asked the same questions.  So, here are some answers for all readers.

First, let’s look at the numbers.  A propane fridge consumes about 0.5 amps at 12VDC.  That’s about 6 watts and about 12 amp/hours per 24 hour day.  Compare that to a typical new, Energy Star, household fridge that consumes about 1 amp at 120VAC (much more on start up).  If powered through an Inverter, that converts to about 13 amps at 12VDC (adjusted for Inverter efficiency losses, etc.)  That’s about 156 watts and about 125 amp/hours per day (assuming 40% duty cycle).  In short, the household fridge uses 20X more electricity than the propane fridge.   This is just about 60% of the stored energy in two RV batteries in one 24 hour period.

Many new RV’s are being built with household fridges.  The ones I have seen are wired to a dedicated inverter and a dedicated battery pack.  Running the generator re-charges the battery pack while dry camping, the vehicles engine recharges the battery pack while driving, and park power runs the fridge while parked. The owners I have talked to say the system works pretty well.  But, they now have 8 batteries on board.  2 for the engine, 2 for the fridge, and 4 for the rest of the house.

So, what do you do if you don’t have a new rig and still want to replace your fridge? If you have an RV without an Inverter, you are best to forget the whole idea.  Unless, of course, you want to install an Inverter and additional batteries.  Without an Inverter, plan on being plugged into park power continuously or run your generator continuously when Boondocking. 

If your RV already has an Inverter and multiple batteries (preferably a minimum of four 6V in a series parallel configuration) you can power your household fridge from your existing inverter.  Just don’t forget to turn on the Inverter when you leave the park.  In fact, don’t ever shut it off!  And, keep an eye on the battery levels.  More frequent charging will be necessary.

And finally, what does this do to your solar requirement?  Here’s the math:  To generate 125 amp/hours per day to satisfy the household fridge demand, you will need about 260 watts of solar power. That’s about 2 average sized panels just to run the fridge.  More if you want to power the RV’s other systems at the same time. 

In short, if you plan on doing a lot of Boondocking, think a little harder about replacing that propane fridge. If the safety concerns are still first and foremost in your mind, plan on burning more fuel in your generator keeping your batteries charged or installing more solar panels to keep up with the battery drain. 

With the cost of fuel rising along with the campground fees, I’ll be doing more Boondocking this year than last.  I’m keeping my propane fridge. 

Have questions about RV solar power?  Would you like James’ RV solar power calculator? You may write James Mannett at jmannett@rvsolarnow.com or visit his blog at http://blog.rvsolarnow.com where you may post your comments or suggestions about this article or others that appear there.  RV solar devices can be seen at www.rvsolarnow.com.  

22 cu ft Whirlpool residential refrigerator with in-door ice maker and water dispenser. Courtesy Tiffin Motorhomes.

RV solar panels can provide some, and even all of your on-board electricity needs.  How well RV solar works for you, and how much it costs, is not necessarily a function of the size or type of RV you own.  Instead, the effectiveness and practicality of RV Solar depends mostly on the household equipment and systems aboard the RV and how (and also how often) they are being used.  James Mannett, a former energy industry executive and current owner of CEA Solar www.rvsolarnow.com, answers questions from readers about the proper use of Solar Panels for RV use. 

 

Dear James,

I am looking for a solar system for my travel trailer camper. My goal is to have the camper running completely off solar power. This includes all the 120VAC items being run in the camper, such as space heaters (only in the winter), television, microwave, fridge, water heater, a laptop, and other small plug-in items. According to the campground I am in, I used about 706KWh of energy the last month I was running the space heaters. I would like a battery bank that would allow for at least 2 days worth of energy storage in the winter months. Can this be done and what would it cost? Signed: Off Grid Dreamin’.

Dear ‘Off Grid’

If money is no object (and it usually is) it can be done, but it may not be practical. 705Kwh of electricity each month is a lot. If I run a quick calculation, you would need 40 solar panels (130 watts each) and, to store enough power for one 24 hour period, you would need 36 batteries. 72 batteries for two days.  The cost for such a system could be as much as $40,000-$50,000. Or about 50% less assuming government incentives and utility rebates would apply.  The batteries would need to be replaced about every 5 years.  And then there is the question of where to put all that equipment including the panels which would occupy an area of about 600 square feet. And finally the mounting hardware, wiring, combiner boxes, disconnects, fuses, etc.  Whew!

 

The hardest part with implementing your plan is the use of the electric space heaters, electric water heater, and electric fridge.  Electric space heaters, due to the fact that they are a 'resistive load', are HUGE energy hogs and very inefficient.  Air conditioner/heat pumps are more efficient, but still big energy users and don’t work well when the temperatures get really cold.

 

Here’s another way to go about it: Replace your heating requirement with propane by using your RV’s furnace.  If permitted by law you may even use something called a 'blue flame' heater which emits virtually no CO, and has no circulation fan thereby preserving battery power.  (Follow all precautions and directions carefully)  Now your energy demand is greatly reduced.  If you go further and rely on propane to heat your water and run your fridge, you electricity demand is now at a level that is much more manageable and where the addition of a few solar panels could provide all the electricity you need. And this is how most 'dry campers' or 'boon-dockers' do it.

 

In the absence of the exact power specifications of the appliances you mentioned and the number of hours each day you operate them, I can give you this example of what you might need assuming your heating, hot water, and fridge are powered from propane:

 

1.  Install a 12V-120V Inverter.  Preferably 2000 watts.  The cost, including a professional installation, wire, fuses, and remote control is around $2,200.00.  This is optional, but converts battery power (12V) to household power (120V) enabling you to use common household appliances on occasion.

2.  Install 4-6 accessories batteries wired in a series/parallel configuration.  You can expect to pay about $500-$700.

3.  Install 450-600 watts of RV solar panels  on the roof atop tilt brackets facing south. This would be 4-6 panels depending on the wattage rating of each one. You can expect to pay about $3500-$5000 including wire, brackets, installation, and weatherproofing.

4.  Finally you will need a solar charge controller, wire, and monitor panel suitable to handle the load from all the panels. You can expect to pay about $500-$1200. 

5.  And finally, a back-up generator for those few times when mother nature just doesn't provide enough sunshine for a long enough period to fully charge your batteries.  Or when inclement weather or an equipment problem occurs.

 

The above is just an example based on your individual energy demand.  Depending on how conservative you can be with your energy demand, the RV solar system could be scaled down even further driving your actual cost much lower. I know of many RV Solar users that have just one RV solar panel and one or two batteries and still generate and store all the power they need. Some even prefer portable solar panels.

 

Have questions about RV solar power?  You may write James Mannett at jmannett@rvsolarnow.com or visit his blog at http://blog.rvsolarnow.com where you may post your comments or suggestions about this article or others that appear there.

The use of RV Solar systems continues to expand. From small teardrop trailers to A class motorhomes, portable RV Solar and roof-top RV solar is showing up in increasing numbers.<< MORE >>

The use of RV solar panels can create savings in more ways than just fuel. This article discusses how using Portable RV solar and Roof top RV solar can save money in ways you may not have thought of.<< MORE >>

An RV solar system requires the use of a charge controller. In this article, several different types are discussed along with the advanges of each.<< MORE >>

Solar power systems for Recreational Vehicles have traditionally been roof mounted. While this is a convenient location and makes efficient use of unused space, it may not be the most ideal location. Since optimal energy production is the ultimate goal, the position of the panel(s) is critical. A 120 watt solar panel may be very powerful , but pointed in the wrong direction, angled incorrectly, or in the shade of a tree can cut daily energy production by 50% or more, or worse, render your expensive investment in solar useless.

For optimum performance, solar panels must be facing directly south (called azimuth). In Arizona, solar panels should be angled at about 33 degrees (called tilt). A slightly steeper tilt in the winter (50-60 degrees) and lower tilt in the summer (8-15 degrees) further improves energy production. Ideal tilt angles change with latitude. Therefore, the further north you travel, the higher the ideal tilt angle becomes. A simple calculator will help you determine your ideal angle. It can be found at http://www.wattsun.com/misc/photovoltaic_tilt.html. To use this calculator, you will need to know your latitude which can be found on any common road atlas.

RV and Marine solar systems are simple and require three main components. The first is the Solar Panel itself. For this application the panel should produce 16v-21vdc. There are many different manufacturers of these panels including Sharp, Kyocera, Solarland, and dozens of others, and they come in many shapes and sizes. The second component is a simple charge controller  which prevents battery overcharging. The controller should be sized correctly for the type and number of solar panels. There are many different manufacturers of charge controllers including Morningstar, Blue Sky, Solarland, and many others. The third component is a suitable mounting system. Unirac is a very common manufacturer of solar mounting accessories. A mounting system that enables adjustable tilt is highly recommended. Drill some holes in your roof, add a few lengths of 10awg wire and a connection to the accessory batteries and you're in business. Or, avoid your drilling anxiety go portable.

Recently, portable solar power systems have appeared on the scene. These systems usually employ either Thin Film or Crystalline solar panel technology, are usually ground mounted, have adjustable tilt legs for optimum tilt angle, have a built in charge controller, gives you your choice of various battery connection accessories, and can be folded up and stored safely in a padded carrying bag. When you arrive at your destination the set up process takes less than 5 minutes. Unpack the bag, unfold the panels, adjust the tilt legs, set on the ground in a sunny location pointing south, and finally connect the wires to your battery. Thin Film systems are usually lighter and more flexible than Crystalline, but Crystalline systems are usually 4 times more powerful and take up much less space.

Currently the only portable, folding, Crystalline system being offered to the RV and Marine industry is by Solarland. The SLP80F-12 is an all-in-one 80 watt system that is easily expanded to meet your energy demands.  No matter where or how you park your RV, this system can be placed in just the right location for optimal performance.  The Solarland SLP80F-12 (also known as the PSS-80C) can be purchased from CEA Solar for $595.00.  The Solarland SLP120F-12 is a 120 watt portable system and can be purchased from CEA Solar for $845.00.

James is a solar energy specialist and RV owner located in Phoenix, Arizona. James has extensive experience in alternative energy systems and devices and regularly consults with various individuals and corporations on the implementation and use of solar energy and associated technology.  To subscribe to more articles from James, sign up for future e-mail messages above.  Have questions? James can be reached at jmannett@rvsolarnow.com. 

 

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