I Need RV Solar Help!

:blush: OK, I freely admit that I am at a loss here.

I am very handy in almost everything that I have encountered from building my first car and motorcycle (back in the early 60's) to most things concerning a house refurbishing. But, that being said, electrics/electronics is my down fall.

Here's my dilemma... I have a travel trailer, it is a 1994 Casita 16'. I want to put the strongest solar panel (Watt wise) that I can on the top of the trailer. I also want to have more than the one 12 volt battery for a power supply/backup that I currently have.

I have approximately 40"x62" in free space that I can use on the top of my travel trailer for mounting one really good (most bang for the buck) solar panel. I want more power than I will ever normally use (because I always plan on the unexpected). Honestly guys, I don't have a clue on what all I need to do this or who makes the best products out there.

I'm no dummy, don't get me wrong, but I know when to ask for help. I asking!

Whom, amoung you have the desire or the time to lay out what is needed for me and where I can get it all from? I am open to all suggestions and will gladly post pics of the completed project when I finish putting it all together.

I will be taking the trailer to some pretty remote places and staying for extended periods of time, so let me know your best ideas and think of it as "what would you do/build" if it were your travel trailer project.

Yes, I know, it's going to be a chunk of change, but it will be worth it if it is constructed well in make up. And that's what I'm asking you all for. The best, strongest and most well constructed 12 volt Solar set up for my RV.

Thanks in advance for any and all suggestions.


  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: I Need RV Solar Help!

    Welcome to the forum.

    To start, an FYI. Contrary to popular notion, solar panels on an RV are somewhat problematic issue. The first is that most people over estimate the amount of real world power they can harvest, and at the same time under estimate the loads that they are routinely going to use.

    For example,, a 100 watt PV sounds pretty good, but lets look at the numbers. In the real world most Pv will only put out ~80% of name plate under any normal circumstance. But wait, it gets worst.

    The rule of thumb I like to use in the off grid world is this. Take the name plate rating of the PV, divide that by two to account for all system loses including wiring, pv loses/ basic battery chemistry that cost you ~ 20% right out the gate, more wiring loses, inverter loses etc. Then take that number and multiply it by 4 to represent the average number of hours one might reasonably expect per day over the course of a year. so our 100 watt panel might look like this: 100/2=50*4=200 watt/hours/day. It actually continues to get worse because as batteries get nearly full, the charge controller dials back the current so there is more harvest "left on the table" so to speak.

    The other thing that makes RV installations hard, is that they very seldom have ideal orientation relative to the sun, especially if they are mounted flat. (leaded to more loses). One other big unforeseen issue is that most people who are in an RV wish to park in the shade to reduce cooling, and that is an anathema to good solar harvest.

    So, while it is not impossible, and many here have done so, go into it with your eyes open, but don't think you can drive into the boonies, plug in the A/C and the wide screen and live happily ever after. Spend some time calculating your loads, and then figuring out how best to power them. You may find that for the price of a modest solar installation, you could by a good, quiet honda Eu generator that would provide more power with a lot more flexibility,,

    Keep in touch,, and don't hesitate to ask questions. I don't mean to scare you off, only to be realistic.

    About 100 watts is what you will be able to fit in your described space. You will then need a good charge controller. Morningstar makes a very nice series of small controllers, and of course you will need batteries and and inverter. Most RV inverters by the way are modified sine wave form, and are not known for their efficiency.

  • BB.BB. Super Moderators, Administrators Posts: 28,315 admin
    Re: I Need RV Solar Help!

    We have a thread here with a bunch of solar links--but this post has a good bunch for starting out:
    BB. wrote: »
    Our general suggestion for getting into solar PV electricity:
    1. Conservation--Reduce your power needs by changing to LED/CFL lighting, Energy Star Appliances (computer, TV, etc.), and just turning things off. For AC devices--get a Kill-A-Watt meter to measure their draw.
    2. Know your loads--You need to measure your loads... Watts*Hours (average power * time) or Amps*Hours (for 12 volt / DC loads). Average usage per day and by season (more sun in summer, less in winter -- same for PV power). This is where you set your expectations for your solar power system. Generating the solar power is expensive (~$1.00 TO $2.00+ per kWhr vs $0.10 per kWhr for utility power).
    3. Design the System--This part is pretty straight forward. Define your location, season(s) of use, mounting of panels (fixed, flat or tilt, how much space, etc.). Generator backup power, battery monitoring equipment, how much you want to spend (range of solar panels, charge controllers, inverter, battery types, battery monitor, etc.).
    Here are some frequently asked questions that will help you with the understanding the basic issues:

    All About Charge Controllers
    Read this page about power tracking controllers
    All About Inverters
    Choosing an inverter for water pumping
    Deep Cycle Battery FAQ
    Solar Radiation Tables for US
    PV Watts--Simple Solar Power Calculator Program (use Derating=0.52 for off-grid systems)
    For 12 Volt & RV Systems - HandyBob's long discussion and rant is about 99% right on how to make RV and similar 12 volt systems work correctly. One of the few "non NAWS" articles that we recommend.

    Here is a nice thread with video from Kevin in Calgary Canada that shows designing and installing solar PV in a small RV trailer.

    Our host is Northern Arizona Wind & Sun (Flagstaff Az) and they have a webstore with a good selection of components to build your own solar system. You do not have to purchase from them--but it is a handy place to find reliable products at reasonable prices to layout your system.

    If you have questions about those products, or others from different vendors--please ask. We are all volunteers here with no connection to NAWS (except for Windsun, the Admin from NAWS) and are happy to help.

    What would be very helpful is knowing how much power per day (AH at what voltage or Watt*Hours), where you want to camp (amount of sun), genset usage, etc...

    Also, can you make a "solar awning" or mount a couple of panels 50' from the RV in direct sun while the RV is in shading (reduce solar heating load), etc.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • WandermanWanderman Solar Expert Posts: 180 ✭✭✭
    Re: I Need RV Solar Help!

    I feel your pain! I am in the midst of an RV Solar power project right now and it has been an experience so far.

    I have a Very small, low profile Class A (Aero Cruiser 23'8") that had very few places to place panels. Most of the off the shelf versions were either too wide or too long for a given power in watts. Ultimately I had to have them custom made in China to fit the spaces.

    After a lot of calculations about what loads I was going to put on the system, how many batteries I could fit (and charge from a given wattage) I settled on a minimum of 270 watts at 17v (a 12 v panel) After additional research, there was no way that would be sufficient and have enough over head to make me feel secure.

    I settled for 450watts of custom panels. Unusually, they are only 3mm thick and will be mounted on the roof "flush" while keeping the weight way down.

    I will have 3 130a/hr lead acid batteries fed by a Morningstar TS-45 MPPT controller.

    The specs of the panels can be found in my "Balanced MPPT system?" at:
    [URL="http://forum.solar-electric.com/showthread.php t=10006"]http://forum.solar-electric.com/showthread.php?t=10006[/URL]

    Take a look at that one, it should help a bit.

    Here is a photo with measurements of the roof. Is is taken at roughly a 45 deg angle so the 42"x42" space in front of the forward roof vent isn't clear.

    I am familiar with the Casita as I was looking at them before I moved over to a Class A.

  • soleilsoleil Solar Expert Posts: 45
    Re: I Need RV Solar Help!

    What solar charge controller are you using? If you're not tied to a 12 volt panel, you could easily fit a 200+ watt panel (like this: http://www.solar-electric.com/kykd210waaop.html) in the space you describe.
  • CrotalusCrotalus Solar Expert Posts: 26
    Re: I Need RV Solar Help!


    I have a 17' Casita trailer that I have installed solar on. I have three small panels wired in parallel with two on the trailer and the third that I can move around with a detachable plug for a total of 150 watts. I was able to get, very cheap a Heliotrope HPV-22 solar controller from someone that was upgrading to a higher amp controller. I paid 1/3 the normal cost and I knew that it worked. My panels are from different manufactures with different watt ratings. Two are from BP and the other one is a Sharp. I chose them for the physical size and ratings. Two of the panels have a 17.3 Vmp and the other one has 17.2 Vmp, close for horseshoes. Everything does work, but it is a costly option. With sunlight we have been able to dry camp for a week at a time. And I say with sunlight. We have a Honda EU2000I generator for backup and I have always used the AC connected to the trailer converter to charge the battery. I also use the generator to run the microwave for short periods of time. If you have not changed your lights to LED's, do so as it saves a lot of battery power. I believe that you have the water heater and fridge that has the thermocouple for the gas. We have the electronic versions and need 12 volts to start and run them as they have solenoid gas valves. The furnace and the water pump are the big power hogs. Check out the following forums;


    Do a search on solar and will find a ton of information on what people have done to their trailers and how they have attached the panels. I like 3M (Very High Bond) VHB tape as it will not come off after it sets for about 10 minutes. Boat wire or welding wire is easy to use as the lower gauge, 10 to 6 is easy to work with. Drill a hole with a Forstner drill bit and use a Liquid Tight Wire Seal and you will have only one hole through the fiberglass.

  • mike95490mike95490 Solar Expert Posts: 8,068 ✭✭✭✭✭
    Re: I Need RV Solar Help!
    Crotalus wrote: »
    ..... With sunlight we have been able to dry camp for a week at a time. And I say with sunlight. .

    If you are running out of power after a week, you do not have a balanced system, and are deficit charging your batteries, which will destroy them much faster than normal. It's better to run your genset for 10 min to boost the batteries each AM, and let the solar top them off.

    Since you do have your panel voltages closely matched, are there loads you can reduce ?
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • CrotalusCrotalus Solar Expert Posts: 26
    Re: I Need RV Solar Help!


    I should qualify that a week is about the time the need for a long hot shower is in order. Also the water in the fresh water tank and holding tanks becomes an issue.

    My comment about sunlight relates to what Tony said about parking the thing where you can get 3 or 4 hours of direct sunlight on the panels every day. Add to that several heavy overcast and rainy days and no amount of solar panels would help much. The 50 watt movable is connected with a 25 foot 10 gauge extension cord that I can point directly at the sun and move it as need be. Sometimes it is the only one that produces enough to charge the battery. However that works when we are at the campsite, otherwise it would grow feet and walk away. I have it in a wood case for travel and storage. Any larger and the size and weight for travel could be a problem.

    We have had the generator for several years before the solar panels went up. The solar was a result of staying in a few national parks where generators were not allowed.

    As was stated before you have to understand what it can do and what it can't do. I have seen several installations on small trailers and even on truck campers that work.

    TRavel guy, don't give up on it as it will work but do your homework first.

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