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Dual purpose "portable" solar setup for home and RV

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  • Dual purpose "portable" solar setup for home and RV

    I currently have a grid tie system that has worked beautifully for more than 4 years so I began to consider solar for my 5th wheel as well. We are not full timers, more like frequent weekend warriors who are considering a 1-2 month trip in it later this year. But I am a believer in the technology and I began to look into the possibility of adding it to our trailer mostly out of curiosity. I know the owner of the company who installed my grid-tie system and asked him how much he would charge to install solar in my 5er and he politely declined the project. However, he did offer to get me anything I needed at his cost and even offered me some used 165w panels relatively cheap which he took off another client's house who recently upgraded to newer panels. At this point the idea became a real possibility especially if I could double the system as a supplemental setup for my home. I can't tie them into the grid like my existing home system but if I could find a way to utilize the setup with a battery bank at home when I am not using my RV I could justify a much larger price tag for my RV system.

    Anyone have any experience utilizing a PV system for more than one designated purpose? According to my grid tie contractor it is doable if I was willing to do all the transfer of equipment each time I needed it and he mentioned something about quick disconnects so I could more easily move the inverter and charge controller(s) to my home so I wouldn't have to duplicate those costs. I wouldn't have to move the panels because I could get them cheap enough to just buy more, and I doubt I would want to move the battery bank so I would probably buy a duplicate GC2 setup, but the supporting equipment adds several thousand dollars that would kill this project if I can't find a way to use it the other 300+ days a year when I am not camping.

    The RV system would include somewhere between 6-9 panels, an 80amp MPPT controller (or two 40a, or possibly even three 30a Kid controllers), an inverter or maybe an inverter/charger and monitoring displays. The home system could be as large as 12 panels.

    How realistic is it to think the inverter and charge controllers could be setup in a way that it could be reasonably moved between my house and my trailer? Anyone ever thought about something like this? I can't imagine I am the first part time camper to want solar but who needs to cost justify it with a duplicate purpose?

    Without trying to complicate this scenario any more I should add that I have also considered setting it up as an isolated 24v system, separate from my12v RV batteries, but I am concerned that might add too much complexity to an already unique setup. Although that would certainly make it easier to run as a home system if I can find a way to make it work in the RV.

    Is this just a pipe dream? Any thoughts are appreciated.

  • #2
    Why so big? It seems like most RV owners are happy with 300-600 W of panels, and around 400 Ah. A system like that would cost well under $1000.
    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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    • #3
      Depending on where you keep the RV parked you should be able to run a heavy gauge extension cord or possibly some underground conduit from your inverter to your loads without having to remove any equipment. Then again if you don't keep your RV at home, obviously this won't work.
      As your guy said, anything is possible but it would be expensive and unless you could find another way to keep your RV batteries on a float charge you would need to continuously move this equipment back and forth. Sounds like a whole lot of work for a couple bucks worth of additional electricity.
      2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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      • #4
        Originally posted by sensij View Post
        Why so big? It seems like most RV owners are happy with 300-600 W of panels, and around 400 Ah. A system like that would cost well under $1000.
        Agreed, my RV experience is with 280 watts of panels and 200 Ah of battery and we don't worry about running out of power. We're long weekend warrior types, not full timers. I use my camper's PV system at home to plug various battery chargers into the inverter.
        I'm an RV camper, mine has 280 watts of solar

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        • #5
          Thank you guys for your responses...

          Originally posted by sensij View Post
          Why so big? It seems like most RV owners are happy with 300-600 W of panels, and around 400 Ah. A system like that would cost well under $1000.
          It doesn't have to be that big for the RV but in order for the system to be reasonably functional at home I would need a large inverter and charge controller(s) so I guess the RV system size was merely a function of sunk cost in all the rest of the equipment, especially since I can get the panels for $40 each. One added note, the original owners of our 5th wheel replaced the refrigerator with a household unit - all electric, no propane - so I have 290 continuous watts and 690 peak that would always be on the system when we are in transit or boondocking.

          Additionally, many of the places we camp are 95+ degrees in the summer (last weekend it was 106 at our campsite but fortunately we were staying at an RV park) so it would have to be big enough to run our portable 10,000 BTU air conditioner. I'm not sure 300-600w of power would be sufficient to keep the batteries charged for a long weekend in that environment. My 6-9 panel guesstimate was to make sure we had enough power for everything else after fridge and A/C were satisfied. Also, the used panels are now more than 8 years old so they are not putting out 165w anymore. The controllers would need to handle the original open current specs but real life output I'm sure will be down about 10%.


          Originally posted by littleharbor View Post
          Depending on where you keep the RV parked you should be able to run a heavy gauge extension cord or possibly some underground conduit from your inverter to your loads without having to remove any equipment. Then again if you don't keep your RV at home, obviously this won't work.
          As your guy said, anything is possible but it would be expensive and unless you could find another way to keep your RV batteries on a float charge you would need to continuously move this equipment back and forth. Sounds like a whole lot of work for a couple bucks worth of additional electricity.
          I am unable to keep the RV at my home and store it at a facility about 1 mile from my house. I would have no problem buying a secondary, inexpensive PWM controller which I could quick connect to keep the batteries topped off in the RV since I would not be transferring the panels. I guess I could always transfer the batteries to the home with the other equipment instead of buying a second battery bank - which would be very economically friendly - but I fear I would lose interest in transferring the system if it involved that much work.

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          • #6
            Any battery bank sized to run on this size system isn't something you want to be moving around . There is always the inherent danger involved with spilling acid and accidently shorting out batteries.

            Some people don't realize the cost of removing a RV refer till they go to replace it. I would never give up the propane option.
            2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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            • #7
              Originally posted by littleharbor View Post
              Any battery bank sized to run on this size system isn't something you want to be moving around . There is always the inherent danger involved with spilling acid and accidently shorting out batteries.

              Some people don't realize the cost of removing a RV refer till they go to replace it. I would never give up the propane option.
              If I were to choose the option to move the batteries I would buy AGM for that very reason - plus the fact I could spend more on the batt bank if I didn't have to duplicate it. But moving six batteries weighing 75lbs each does not sound like a lot of fun.

              Regarding the refrigerator, I completely agree and it was one of several things I used to negotiate hard in my purchase since I bought from a private party. Now I need to find a solution for it which could involve ~$1500 to replace it or $2000 in solar to overcome it and have a nice setup that provides dry camping power as well.

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              • #8
                Using Midnite Solar's sizing tool with the specs of these panels I could get away with one Classic 150 if I run 9 panels using 3 in series with 3 parallel. If I go with only 8 panels using 4 in series I exceed the limit of the Classic 200 by a small margin and can't use the 150 or 250 at all. So unless I step down to 6 panels - which may not be enough to charge my batteries based on my usage needs - it seems my only choice is to go with a 9 panel system unless I buy an additional charge controller only to end up with fewer watts, which would be counter productive on both fronts.

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                • #9
                  Originally posted by Tap2112 View Post
                  I currently have a grid tie system that has worked beautifully for more than 4 years so I began to consider solar for my 5th wheel as well. We are not full timers, more like frequent weekend warriors who are considering a 1-2 month trip in it later this year. .
                  I am not going to answer or help you unless you can answer 1 question I need to know to help you..

                  During this 1 to 2 month trips, how many days will you be parked without starting the RV engine.
                  MSEE, PE

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                  • #10
                    Originally posted by Sunking View Post
                    I am not going to answer or help you unless you can answer 1 question I need to know to help you..

                    During this 1 to 2 month trips, how many days will you be parked without starting the RV engine.
                    Just to be clear it is a 5th wheel, not a motor-home, but in effect it does get charged when I drive and plug in the 7-pin wire connector.

                    I cannot tell you how often we would be moving from place to place as we have not mapped out our travel plans yet. I would imagine there will be days when we change locations every 2 days and others where it may be 3-6 days. A good example might be what we are doing this coming weekend for the July 4th holiday. We will be in one place for 6 days. We are obviously staying at an RV park since I currently don't have solar, but this would be a prime example of how we might dry camp instead if we had our own power. I hope that helps.

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                    • #11
                      I guess my question is how will you mount those 9 panels on a 5th wheel. Most of the ones I have seen have a lot of stuff on the roof which will make it difficult to get that many panels on without anything putting some shade. Remember any panel that has shade will affect all of the panels in the same string reducing the total output.

                      You will also have to park in the sun which for many is not comfortable during the summer months or is even available considering the number of trees I see at most of the RV parks.

                      Just something to consider when you combine solar and RVing.

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                      • #12
                        SunEagle Honestly, I have not plotted them on my roof yet so I don't know how many it will hold. These are 72 cell panels (which is why they would be ideal for a 24v setup) and the dimensions of them are 62.01" x 32.52" so they are approx 3 inches shorter and 5.5 inches narrower than my residential panels. Additionally, my solar buddy suggested I keep at least some of them unmounted to set out away from the RV in case we do park in the shade. If I did 3 strings of 3 in series (with say 6 on the roof and 3 mobile panels - or possibly 3 mounted and 6 mobile) I could at least have use of part of the system while I was parked beneath any shade.

                        Again, this is all new to me. I don't claim to be coming in with all the answers so maybe there are holes in my plan that are too great to overcome. But, that is why I am inquiring now prior to purchasing any equipment. I have read numerous threads from others who already purchased their equipment - or worse, already installed all their equipment - before coming on here to ask necessary questions. I am trying to do all my due diligence in advance.

                        Any RV solar system will have limitations and compromises. My hope is to find the sweet spot where it works well for my needs in the RV and yet has portability to transfer all the expensive electronics to my home as a back up (or even continual use) system for my home. If I can do that I can justify the budget for this project. If not, then I will either scale down my RV system significantly or scrap the entire idea and just swap my residential fridge for a Dometic.

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                        • #13
                          Originally posted by Tap2112 View Post
                          SunEagle Honestly, I have not plotted them on my roof yet so I don't know how many it will hold. These are 72 cell panels (which is why they would be ideal for a 24v setup) and the dimensions of them are 62.01" x 32.52" so they are approx 3 inches shorter and 5.5 inches narrower than my residential panels. Additionally, my solar buddy suggested I keep at least some of them unmounted to set out away from the RV in case we do park in the shade. If I did 3 strings of 3 in series (with say 6 on the roof and 3 mobile panels - or possibly 3 mounted and 6 mobile) I could at least have use of part of the system while I was parked beneath any shade.

                          Again, this is all new to me. I don't claim to be coming in with all the answers so maybe there are holes in my plan that are too great to overcome. But, that is why I am inquiring now prior to purchasing any equipment. I have read numerous threads from others who already purchased their equipment - or worse, already installed all their equipment - before coming on here to ask necessary questions. I am trying to do all my due diligence in advance.

                          Any RV solar system will have limitations and compromises. My hope is to find the sweet spot where it works well for my needs in the RV and yet has portability to transfer all the expensive electronics to my home as a back up (or even continual use) system for my home. If I can do that I can justify the budget for this project. If not, then I will either scale down my RV system significantly or scrap the entire idea and just swap my residential fridge for a Dometic.
                          Combining a fixed set of panels on your 5th wheel along with a ground mount set might work for you. The problem is getting each of the paralleled sets to produce very similar voltages going to the charge controller. You might need a much bigger wire from the ground mounted set so the voltage drop is insignificant compared to the other 2 sets.

                          I played with the idea of a roof mounted system for my RV but decided to go with a "portable" ground mount that can be stored inside one of the bays. Of course I messed up by going with 80w & 90w panels along with a PWM CC. Both made my system more costly then needed. But that was about 4 years ago so I learned a lesson.

                          Here are a couple of pictures of my panels along with a combiner box that I put together and the 30A PWM CC which basically loses about 33% of the panel wattage. I also threw in a couple pix of my RV which my wife would rather I not put holes in the roof.

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                          • #14
                            SunEagle Very cool! I love to see projects that others have done. I talked with my wife about building portable stands...do yours allow for tilting or are they fixed angle? I considered smaller panels and PWM originally, but after hearing I could get Sharp 165w panels for $40 it pushed me into the MPPT realm due to the higher voltage and the cost savings will pay for the MPPT controller anyway so it ends up being a better option for the same price tag.

                            In regards to creating similar voltage from the different strings, if that proves to be to challenging or costly due to wire size can I just use multiple, smaller controllers for each string? That's one reason I considered multiple Kid controllers instead of one large controller. Wouldn't that solve any dissimilar voltage problems? The downside to that option is wiring it up and the transferring of electronics to my home system becomes more complicated with a multiple controller setup.
                            Last edited by Tap2112; 06-28-2017, 02:18 PM.

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                            • #15
                              Originally posted by Tap2112 View Post
                              SunEagle Very cool! I love to see projects that others have done. I talked with my wife about building portable stands...do yours allow for tilting or are they fixed angle? I considered smaller panels and PWM originally, but after hearing I could get Sharp 165w panels for $40 it pushed me into the MPPT realm due to the higher voltage and the cost savings will pay for the MPPT controller anyway so it ends up being a better option for the same price tag.

                              In regards to creating similar voltage from the different strings, if that proves to be to challenging or costly due to wire size can I just use multiple, smaller controllers for each string? That's one reason I considered multiple Kid controllers instead of one large controller. Wouldn't that solve any dissimilar voltage problems? The downside to that option is wiring it up and the transferring of electronics to my home system becomes more complicated with a multiple controller setup.
                              Each panel is mounted to a set of brackets which can be adjust to 3 different angles. I think I got them from HF or Amazon. They are shown in the highest angle but I can lower them to about 28 degrees. The brackets are also screwed into wood bases for stability. I can lower each panel flat to the wood base for storage.

                              I also thought the smaller 36 cell panels would be easier to move around but then found out that at $2/watt I was wasting money because I could have found a couple of 200 watt panels that would still fit in my RV storage bay and only cost me ~ $1/watt. Live and learn.
                              Last edited by SunEagle; 06-28-2017, 02:32 PM.

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