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  • Solar Basics , Who? What? When? Why?

    As the title suggest I have many questions on Solar. Throughout many threads here there is plenty of "large" systems that will power a complete RV. Reading through all of them there is little mention of the actual what and how and why? the systems are built the way they are. With respect to all of those threads the "why?" is generally to power the complete RV with battery power when there is no other power available. The "How" seems to be pretty self explanatory but with a few questions as well. The "what?" may have the most questions.

    My "Why?" is that I have recently added 2 Lion UT1300 batteries for a total of 210 ah. With this I would like to have the ability to use Solar to charge the batteries when convenient, sunshine is key this process from what I gather and sometimes we are in the woods with very little sunshine getting through the canopy. It is my understanding that one would want 2 times the Solar wattage than the battery bank so I would need at least 400 watts of Solar, here comes the first question, If 400 watts is required then would 1200 watts be better? I can fit 6 - 215 watt Solar panels on my roof so should I do all 6 or will 2 be sufficient? Is the extra cost of the 6 worth it as far as gain in charging? A Solar panel is only about 17% to 20% efficient, What does this mean? Will a 200 watt panel only produce 40 watts? Will the cost of the 6 panels and a different charge produce faster charging that would override the cost of the setup or will 2 panels and a smaller charger do just as good? Maybe that is some of the "what?" part as well.

    The "How?" seems to me to be How do I not fall down the "rabbit hole" that leads to thousands of dollars spent when really at this time is unneeded. The system that I am thinking of , either 2,4, or 6 panels, will be set up to upgrade at a later point if I wish to go full blown inverter and all that jazz. An Inverter is not in the works at all at this time.

    The "What" part may be the worse thing. I have been reading and trying to comprehend the whole Solar systems, haha, but there is so many panels , controllers , wiring , and so on that it just seems to get more confusing each time I think I have it worked out I find something else or get another suggestion from someone.

    This may seem kind of jumbled as my brain is jumbled with all of this as well, but here is my basic needs as I like to keep things basic and easy for just about anyone to do on their own.

    Having the 2 batteries I would like to get a Solar system that would keep them charged or charge them when in sunshine while camped or traveling, I know the DC - DC charger will help with this while traveling and I may do that as well but this is about Solar.

    So , all of the Solar guru's out there let me have it, be kind , and help a basic owner out, as well as others who may be pondering a similar setup.

    Brian


    Brian & Michelle
    2018 Reflection 29RS Oct.2017 build date, EMS-HW50C , Lippert Remote
    2015 Chevy 3500HD CC LB Duramax , Reese Elite 18K

  • #2
    Country Campers Brian, how timely is this? We were just discussing adding a second panel to our factory optioned solar system, and adding a DC-DC charger. I don't know much more about this than you do, so I will be tuned into this thread, too (the more, the merrier).

    What I do know, is that we have rooftop solar on our home, also powering a second home. It is a 13.86KW system, no backup battery. During optimum conditions, my power meter runs backwards. If usage exceeds available output, then the meter runs forward, offset by the volume of solar power being generated (obviously none at night). When I purchased the system, it was explained that the system capacity--in my case 13.86KW--would be produced every hour under ideal conditions. As you slip away from ideal (say early am/late pm, heavy clouds, etc) output declines. No mention was made of built in efficiency losses inherent to the system.

    Back to the Solitude, I too wish to keep this simple. But I don't think I have sufficient solar for my four 6 volt AGM batteries also in the low 200 amp/hour range, especially with the res fridge.

    Thanks for the post!!

    Dave
    Dave and Darren
    2015 Chevrolet 3500 CC duramax SB SRW, pullrite 2400, timbrens
    2021 Solitude 390 RK-R (3 A/C, solar, gen, 8K axles), comfort ride shocks, VIN 03584
    Max and Riley, our chihuahua/tasmanian devil furbabies

    Comment


    • #3
      Country Campers (Brian),

      For how the DW and I use our camper, the solar on our 315RLTS is the least beneficial addition made to our power setup. After real-world use, the largest battery bank of LifePO4s the checkbook will allow (and fit in a trailer), a 3000W Multiplus II inverter (along with a battery monitor, etc) and the DC-DC Charger are the best bang-for-the-buck for how we use our trailer. The solar is nice, but in reality it's only been used once where it was needed and this was only for one week (in fair weather). A small generator could have recharged the Battle Borns just fine if there wasn't solar power available.

      Edit: Actually the solar came in handy twice. The second time was a week of storage in a field near a relative's house. The solar kept the batteries charged so the refrigerator kept running--no worries about the food.

      Don't get me wrong--it is nice to have the silent power station on the roof, but it doesn't (and won't) run my whole trailer.

      I am not sure the chart below will help but it does represent the actual power I get from my setup. What it shows is the amount of solar energy (PV) my system generated that could be used by my trailer. (Remember--if the batteries are charged and there's no demand for electricity, any PV generated is "wasted".) I may get more utilization of generated PV than most since a Victron setup allows the use of solar to generate 120vAC (inverted from PV DC) to supplement shore power. Most solar systems will only charge the batteries--once the batteries are full there is no where else for the generated PV to go.

      Click image for larger version  Name:	Solar Power.JPG Views:	6 Size:	70.5 KB ID:	67580
      Let's use today's yield as an example (overcast and rainy). 1.83kW = 1,830 watts (power). There's a lot of math we could do, but I'll skip that and say that represents a little over an hour running one air conditioner. Not a lot and that's OK.

      To further give some perspective of this number, a 100aH Battle Born (assuming a steady 13vDC) is capable of providing about 1300W of power (running it to 0% state of charge). So with 1830 watts of PV that could have charged about 1.5 batteries (assuming they started at 0).

      To further give some perspective, Gulf Power electricity costs ~.15 per kW. That means if at home and plugged in (running the camper) today's savings would have been 30 cents. (Whoopie!) Since the camper is at a campground with full hookups, the solar output is saving them money (sigh). The app says the system has generated 1304kW since install, so assuming the camper was plugged in at home for that whole time the gross savings (versus paying Gulf Power) is $195. It's gonna take a long time for the cost/benefit equation to turn in my favor (if saving money was the goal).

      IMHO the benefit of solar comes to those who camp off-grid or must rely on their onboard systems for an extended time in areas where sunlight is (relatively) abundant and they don't regularly use high wattage appliances.

      One more thought: any shadows or blocking of the solar panels (as I've shown in other threads) will greatly reduce their output. Under trees = little to no output. If you decide to get solar, my .02 is to get the most you can fit on your roof.

      Not sure I helped. Getting tired and this is getting wordy. I'm sure Jim will have a lot more to add.

      Howard
      Last edited by howson; 10-09-2021, 04:35 AM.
      Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

      Howard, 2017 Ford F-350 DRW, '19 315RLTSPlus

      Comment


      • #4
        Brian,

        For the sake of simplicity, lets use some standard numbers.

        A typical 100 watt solar panel can generate about 30 amp hours of power a day. With great sunshine and a long summer day, a little more. With shade or winter skies, a little less.

        So you have a 210 amp hour battery bank. To completely recharge 200+ amps, you'd need 200/30 = 6-2/3 panels, or 666 watts of solar. But these are just estimates. i have 300 amp hours of LiFePO4 batteries, and 800 watts of solar. When I go to Quartzsite in February, I typically consume about 150 amps from my batteries. And typically, I'm fully charged back up by 1-2PM.

        There are so many variables that go into these calculations. For your system, I'd shoot for 600 watts. But your results may vary over time and you may want to add more.

        Jim
        The moderators for this site are not GDRV employees, but we do own GDRV products.

        Jim and Ginnie
        2017 Reflection 297RSTS

        Comment


        • #5
          howson How many panels and what wattage do you have?

          Country Campers Our current setup (the what) is a single 300W panel with (2) AGM batteries (200AH total), an 30amp solar charger, and 1000W inverter. We also have an onboard 4000W generator.

          The 300W panel has worked perfect to keep the 2 batteries topped off. The batteries have never been below 75%, even after 5 days of dry camping. We are very conservative with out power usage which has helped.

          I am in the process of purchasing thousands of dollars of equipment to increase the solar capabilities of our small trailer. I am planning 1600W, 800AH battery bank, 3000W inverter.

          Why?

          After 5000+ miles and over 100 nights on the trailer, we have found we prefer boondocking and don't like using the generator as a main source of power. We also have had to avoid places that don't allow generator usage (in Texas it get's extra toasty and AC is a good thing). I also want to have a "power station" in the event we lose power (like the famous February 2021 Texas power outages that crippled so many things).

          The price the "new" system will be about $9000. That is a STEEP price to pay for little usage (maybe 120 days per year??). IF you do go down the rabbit hole, accept the high cost and don't think about it.

          My opinion is that a 400W panel will probably keep your batteries topped off (depending on light and your power usage). If you plan to expand in the future, these are some things you may want to consider:

          -Wiring. Calculate wiring size based on the largest system you might want - particularly with your solar array. You don't want to have to keep drilling hoes in the roof. (I do agree with Howard, more panels is not a bad thing here. Perhaps start with 600W or 800W. Big picture: panels are usually less than 25% of total cost. Batteries are the killers). Also look into parallel vs series vs parallel/series for your solar array. How you connect them will make a big difference on what size wires you will need.
          -Power usage. Start tracking your normal power usage. This is key to sizing your solar system. Once you know the power you need from the system, you work backwards to size battery bank, inverter, solar array, solar charge controller, wiring, fuses, breakers....
          -Space. Look for a space that will fit the inverter, solar chargers, shunt, distribution blocks, wiring, switches, batteries, etc. Make sure that space will be available.

          IF you're good with just topping off the batteries, I wouldn't spend the time or money on a large system. I would just get 400W-800W panels, make sure the solar charge controller will handle the volts/amps and you're good to go.

          My personal opinion is that if you don't think you'll use a large solar system often enough to justify it, don't do it and spend the money on something you will use and enjoy.
          Momentum 21G

          Comment


          • #6
            acoleman43 -- twelve 100w panels.
            Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

            Howard, 2017 Ford F-350 DRW, '19 315RLTSPlus

            Comment


            • #7
              Great discussion! Getting the basics and the knowledgeable perspectives into one (hopefully short) thread will be an excellent reference point for the many newbies (including me) contemplating this idea.

              Rob
              Cate & Rob
              (with Border Collies Molly & Angel and their kitty Gracie)
              2015 Reflection 303RLS
              2014 Ecoboost F150 with Heavy Duty Payload Package (retired)
              2022 F350 Diesel CC SB SRW Lariat
              Bayham, Ontario, Canada

              Comment


              • #8
                Country Campers For us - it boiled down to the type of camping we want to do and how many "comfort accessories" we want to use.

                We have 100Ah LiFePO4 and 200W solar (2 panels in series). We do not have an inverter. I sized the battery and panels based on expected power usage in a 24 hour period for those times when we camp without hookups (we aren't boondockers). For us, the largest draws are the furnace, water heater (on gas), fridge (on gas) and water pump. I figured we needed about 60-70 Ah per day (the furnace is power hog!).

                As Jim noted above - with 30Ah charging per day for a 100W panel (give or take) I needed 2 panels to roughly replace (or offset) the power usage (2 panels @ 100W = 60Ah a day). Over a longer period, this math would slowly deplete our battery. Plus if we don't get sunshine we wouldn't last a second night - so we also have a small generator (2500W) that we could use the charge the battery and potentially down the road run the A/C with an Easy Start installed. So far we haven't needed to use it.

                This setup has worked just fine for us based on our "style" and where we tend to camp. Also as noted above, it would be really simple to add a couple more panels if needed - my solar controller and cabling would support this. So far I have seen no need. Bottom line is I am with acoleman43 - I think you only need to have enough solar charging to replace the power you use - not necessarily to fully charge your 210Ah from zero.

                I would add that since you are thinking about an inverter down the road, you might consider sizing your battery cables, bus bars, switches to support that high amperage load so you don't have to replace them if/when the inverter comes. Adds a little cost now, but would save you some in the long run. I am somewhat regretting that I did not do that.
                Ken & Sandra
                2021 303RLS | 2020 F350 Lariat 6.7L 4x4 SB SRW

                Comment


                • #9
                  Demographics as well as an open sky is an important part of this decision. With our camping largely in wooded areas. Having an energy absorbing LiFePH04 battery, with an inverter generator works exceptionally well for us. I personally cannot justify the cost of a solar system while operating at low efficiency. For others it obviously works based on their usage.

                  Jim.
                  2017 Imagine 2600RB
                  2015 GMC Sierra 4x4

                  Comment


                  • #10
                    Originally posted by Country Campers View Post
                    As the title suggest I have many questions on Solar. Throughout many threads here there is plenty of "large" systems that will power a complete RV. Reading through all of them there is little mention of the actual what and how and why? the systems are built the way they are. With respect to all of those threads the "why?" is generally to power the complete RV with battery power when there is no other power available. The "How" seems to be pretty self explanatory but with a few questions as well. The "what?" may have the most questions.

                    My "Why?" is that I have recently added 2 Lion UT1300 batteries for a total of 210 ah. With this I would like to have the ability to use Solar to charge the batteries when convenient, sunshine is key this process from what I gather and sometimes we are in the woods with very little sunshine getting through the canopy. It is my understanding that one would want 2 times the Solar wattage than the battery bank so I would need at least 400 watts of Solar, here comes the first question, If 400 watts is required then would 1200 watts be better? I can fit 6 - 215 watt Solar panels on my roof so should I do all 6 or will 2 be sufficient? Is the extra cost of the 6 worth it as far as gain in charging? A Solar panel is only about 17% to 20% efficient, What does this mean? Will a 200 watt panel only produce 40 watts? Will the cost of the 6 panels and a different charge produce faster charging that would override the cost of the setup or will 2 panels and a smaller charger do just as good? Maybe that is some of the "what?" part as well.

                    The "How?" seems to me to be How do I not fall down the "rabbit hole" that leads to thousands of dollars spent when really at this time is unneeded. The system that I am thinking of , either 2,4, or 6 panels, will be set up to upgrade at a later point if I wish to go full blown inverter and all that jazz. An Inverter is not in the works at all at this time.

                    The "What" part may be the worse thing. I have been reading and trying to comprehend the whole Solar systems, haha, but there is so many panels , controllers , wiring , and so on that it just seems to get more confusing each time I think I have it worked out I find something else or get another suggestion from someone.

                    This may seem kind of jumbled as my brain is jumbled with all of this as well, but here is my basic needs as I like to keep things basic and easy for just about anyone to do on their own.

                    Having the 2 batteries I would like to get a Solar system that would keep them charged or charge them when in sunshine while camped or traveling, I know the DC - DC charger will help with this while traveling and I may do that as well but this is about Solar.

                    So , all of the Solar guru's out there let me have it, be kind , and help a basic owner out, as well as others who may be pondering a similar setup.

                    Brian

                    Brian - loots of good advice above. Some things I learned the hard way - plan and be sure what you want to do - I switch up mid stream and it cost me. I was looking a t stand alone components Separate inverter. charger. transfer switch, etc. I still have the transfer switch left over. I discovered it was cheaper overall to go with the Multiplus - simplified a lot of things.

                    First - do you have a lithium compatible charger? If not you will not get your batterys fully charged.
                    Are you planning for a future inverter. If so I too recommend the Multiplus II for you 50A service as it can power both legs. This also will give you a good programmable battery charger for you lithium batterys.

                    Now solar - I have 540 watts on the roof going through two MPPT solar controllers (two different size panels). I am running 4 Crown CR260 6 volt batterys (520 AH - 260 usable) These are deep cycle golf cart flooded batterys. Right now the solar keeps them charged and will keep up with my typical night stay and CPAP use. However if I start running my inverter I may be pushing the battery limits.

                    Its important that you use a MPPT controller as they are more efficient. Victron has some excellent units and the are lithium capable - you can program the charge profile. I have a thread on my install that might help you plan.

                    Hope all the helps - good luck on your project.
                    2018 Reflection 150 Series 220RK 5th wheel. Reese R20 Titan hitch, Steadyfast system, 2004 F350 King Ranch dually

                    Comment

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