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  • Adding more panels to RV?

    First I would like to say that I have some experience with 12V battery solar installs in the 20-125 watt range over the last 10-15 years. (boats, remote wifi relays, remote security cameras, etc.)

    I bought a used motorhome last month where the previous owner had started upgrading the electrical system, so I have been handed a partially complete project, which I intend to continue and perhaps alter a bit.

    First let me describe my current situation which is basically as I bought it, but the addition of installing a 2000 watt pure sine wave inverter (Xantrex ProWatt SW which is a stand alone inverter along with its associated external 15 amp transfer switch and remote panel), Not my first pick of the way to do things, but the inverter came with the motorhome, just not installed.

    Back to the current setup, I have 4, 100 watt panels for a total of 400 watts worth of panels on the roof feeding into a Schiender C35 (35 amp which seems kind of marginal to me) PWM charge controller, which seems to be a nice variable set point PWM controller, which charges a pair of 12V deep cycle batteries.

    My goal is to aim for 800+ watts worth of panels on the roof if possible while mounting around various obstacles (vents, etc.), at a minimum I would like to get up to 600 watts worth of panels I would also like to switch to Lithium batteries (probably LiFePO4) when the current deep cells need to be replaced in a couple of years (they were installed in 2014). Ideally I would like to do this in stages as I get time and money for this project.

    The catch is I want to do this without removing the existing 4 100 watt panels, as the motorhome has an Aluminum roof and I want to minimize the number of roof penetrations and being an Aluminum roof it is hard to patch the screw holes from the existing mounting brackets.

    Now here is the question, what is the best way to achieve this, I know mixing and matching panels is usually a bad idea?

    Some thoughts I have so far:

    option A,
    Add 4 more panels to the roof and wire them series / parallel with the existing panels and feed them into a MPPT controller so that each old panel would be wired in series with 1 new panel then let the MPPT controller handle the voltage reduction.

    option B
    Keep everything as is, and add separate circuit with the new panels and another charge controller, then adjust the voltage on the current charge controller so that it only operates for the bulk charge range, then have the new panels and their controller handle more bulk charging in parallel then let the new panels handle topping charge until I convert to Lithium. I am still researching al the special lithium charge controller issues, with the hope that more and better options will be on the market in a year or three.

    option C ??????


    thanks for your thoughts
    Last edited by Isaac-1; 12-13-2016, 11:20 PM.

  • #2
    It has been almost a month, no one has any thoughts on this?

    Comment


    • #3
      The missing part of the equation is the size of the batteries.

      If the batteries are of the generic 75-100AH design then I would not recommend increasing the solar array until you can replace them. 400 watt array with a PWM controller is about the max limit you want to have.

      If they are a larger battery in the 150-200 AH range then either of your options is possible and workable.

      If you can find panels that match the existing panels I'd only look at adding 2 more and replacing the PWM with an MPPT controller. It's greater efficiency will offset the smaller array.

      I wouldn't add a second charge controller unless it's the same as the present one so as to minimize problems between them.

      WWW

      Comment


      • #4
        Originally posted by Isaac-1 View Post
        It has been almost a month, no one has any thoughts on this?

        I have some experience with Mobile Solar/ Battery Based systems.

        I have done two.

        The first was good and the second has been VERY VERY successful and VERY good.

        First let me state a few things I recommend as baseline thinking:
        1) I installed RAILS on the roof of my food truck. The same rails used for PV arrays used in residential market. They work better than anything else. It is also easy to screw and glue/seal the penetrations.
        2) Use as large a PV system as possible, and use large panels, not the 100 watter little guys
        3) Use a Lithium battery bank with as much storage as you can afford
        4) Use quality, robust charge controllers ( I swear by OUTBACK)
        5) If you cannot get enough panels on your roof consider an "awning" that can raise up when you park and fold flat against the side when you drive. (it is always picking up sun power by the way as long as it is day time and even when the panels are folded flat against the sides when driving especially when the sun is hitting it straight on or substantially so)


        Pi Truck Solar Awning.jpgPi Truck 1c.jpg
        Pi Truck Photo Two Goats Summer.jpgPi Truck 2016A.jpg
        Attached Files

        Comment


        • #5
          Originally posted by Zoar View Post


          I have some experience with Mobile Solar/ Battery Based systems.

          I have done two.

          The first was good and the second has been VERY VERY successful and VERY good.

          First let me state a few things I recommend as baseline thinking:
          1) I installed RAILS on the roof of my food truck. The same rails used for PV arrays used in residential market. They work better than anything else. It is also easy to screw and glue/seal the penetrations.
          2) Use as large a PV system as possible, and use large panels, not the 100 watter little guys
          3) Use a Lithium battery bank with as much storage as you can afford
          4) Use quality, robust charge controllers ( I swear by OUTBACK)
          5) If you cannot get enough panels on your roof consider an "awning" that can raise up when you park and fold flat against the side when you drive. (it is always picking up sun power by the way as long as it is day time and even when the panels are folded flat against the sides when driving especially when the sun is hitting it straight on or substantially so)


          Pi Truck Solar Awning.jpgPi Truck 1c.jpg
          Pi Truck Photo Two Goats Summer.jpgPi Truck 2016A.jpg
          The lower left photo - close to south end of Seneca or Cayuga lake ?

          Comment


          • #6
            I'm thinking along the same lines as White Wolf. With only a pair of batteries, I don't think you want to go with any more solar wattage as the batteries wouldn't want that much peak current anyway. Do you need more battery power to handle your usage? If not, then it seems like you're sitting pretty with 400 watts of solar matched to a pair of deep cycle batteries.

            I love the solar food truck, there is an example of usage that I could see warranting all that square footage of panels since your peak power needs probably coincide with peak solar harvest times. So you need excess solar to even get any recharging to happen.
            I'm an RV camper with 470 watts of solar

            Comment


            • #7
              Originally posted by ewarnerusa View Post
              I'm thinking along the same lines as White Wolf. With only a pair of batteries, I don't think you want to go with any more solar wattage as the batteries wouldn't want that much peak current anyway. Do you need more battery power to handle your usage? If not, then it seems like you're sitting pretty with 400 watts of solar matched to a pair of deep cycle batteries.

              I love the solar food truck, there is an example of usage that I could see warranting all that square footage of panels since your peak power needs probably coincide with peak solar harvest times. So you need excess solar to even get any recharging to happen.
              Actually I currently have the solar powered food truck parked in my driveway in the cold dark long winter months of Western NY State and I am exclusively using this to power my off the grid home! So the "assignment" of the system now for the Food Truck is substantially and totally different from its original mission. Yet it works perfectly for BOTH applications!!! Amazing stuff this solar PV / battery based systems.

              Comment


              • #8
                Originally posted by Zoar View Post

                Actually I currently have the solar powered food truck parked in my driveway in the cold dark long winter months of Western NY State and I am exclusively using this to power my off the grid home! So the "assignment" of the system now for the Food Truck is substantially and totally different from its original mission. Yet it works perfectly for BOTH applications!!! Amazing stuff this solar PV / battery based systems.
                Out of curiosity what was your investment cost for the solar/battery system on that truck and what is the daily watt hour usage?

                Comment


                • #9
                  Thanks for the replies, sorry about being a little slow responding, been busy the last week with one thing after another breaking around here. Since starting this thread my likely timeline to do the upgrade has been pushed back a bit due to other upgrades I want to do to the RV first. I do tend to agree that the current setup is well sized to the current battery bank size and I will likely try to time my upgrade with the need to replace the current pair of batteries which I hope will last another year or so given the continuing drop in lithium battery costs.

                  As to the reason that I desire more solar power, my wife has a health condition where she needs to avoid getting overheated, and I would like the ability to run an air conditioner for at least a couple of hours at a time off of the battery system. The motorhome is equipped with a 13,500 btu roof top air conditioner / heat pump, but I also own a 9,000 btu water cooled marine air conditioner (that has been sitting in my shed for a few years), which I intend to add to the motorhome connected to a radiator mounted under the coach to dump the heat. This 9,000 btu air conditioner draws about 890 watts while operating (not counting whatever power the radiator fan will need), which I hope will allow me to keep the motorhome somewhat cool during the day without running the generator when stopped at tourist attractions, etc. while traveling. Therefore any solar capacity I can add towards that circa 1000 watt air conditioning load will help extend battery run time, and of course the highest need for air conditioning will also be during periods of bright sunlight.

                  Comment


                  • #10
                    Originally posted by Isaac-1 View Post
                    As to the reason that I desire more solar power, my wife has a health condition where she needs to avoid getting overheated, and I would like the ability to run an air conditioner for at least a couple of hours at a time off of the battery system. The motorhome is equipped with a 13,500 btu roof top air conditioner / heat pump, .
                    Not going to happen. Only way you can do that is either with the engine alternator running or with a generator.

                    MSEE, PE

                    Comment


                    • #11
                      I agree, the air conditioning idea is probably not going to happen. Although the idea of running the 9000 btu one is more realistic, I don't think even 4 burly batteries are going to get you much run time, much less be able to recover from that deep discharge in a reasonable amount of time with 800 watts solar.
                      This is an interesting website. I haven't watched much of their video and just power read the webpage, but you may find it interesting. Noteworthiness is they are recommending 900+ Ah of lithium batteries, 3000 watt inverter, and 1000+ watts of solar with tilt mounting. But they are also talking about running a 13.5 btu AC.
                      http://www.gonewiththewynns.com/off-...r-conditioning

                      I've been interested in the Micro Air products which is a system of minimizing the peak current draw from an AC compressor during startup. For me it would be a way to get some use out of our Yamaha 2400 generator which can barely run our 13.5 btu AC in ideal circumstances. It lets us down in scenarios where we actually want it, like camping at high elevation in summer heat, so I don't even bring it with anymore. But if this product could make it reliably work, then maybe we would. I'm sure this type of product could help an inverter cope as well.
                      http://www.microair.net/main/products/product.php?id=20
                      https://www.youtube.com/watch?v=soP0...ature=youtu.be
                      I'm an RV camper with 470 watts of solar

                      Comment


                      • #12
                        Originally posted by SunEagle View Post

                        Out of curiosity what was your investment cost for the solar/battery system on that truck and what is the daily watt hour usage?
                        The costs for aluminum brackets, design and fabricating a structure with pneumatic piston arms to assist with lifting and lowering the solar awning, and also 8 300 watt solar panels, outback controller, inverter, lithium batteries, battery case, all wiring and connectors, etc is about $18,000. Then subtract 30% for Federal credit on my tax return so out of pocket was about $12,000 yet compared to a good, fairly quiet GENERATOR which costs about $8,000, the additional cost works out to only about $4,000 above doing it conventionally. And I do not have any fuel costs as I would with a Generator. The costs in the US are $500 to $1,000 a month for fuel for generators on food trucks. Obviously in a mere 4 to 8 months I am in the BLACK then and the solar vs generator argument is mute. It is MAKING ME MONEY! Plus, with solar panels on my truck I have so many other benefits---no mess and pain in the ass of buying fuel, transporting fuel, refueling, no stink of the exhaust, no noise at all (even quiet generators make noise especially in a confined space... And I am a rolling POWER PLANT that is using the SUN to make all my electricity for all me electrical needs; that means self reliance and self sufficiency. And solar saves me TIME! No time loss for getting fuel, refueling, etc.. and on a food truck TIME IS MONEY.

                        In addition, having SOLAR on my food truck draws more customers! It is a TV and RADIO and MEDIA magnet! It is by far the best advertising you could ever get and it is very sound Public Relations. It makes everyone feel good! If I tried to put a price on the advertising and positive public relations that the Solar System adds to my truck I would have to pay a firm $20,000 to $30,000 a YEAR for what the solar panels do for the business. I did not pay this out yet I derive the benefits as if I did, so the solar system is actually saving me money and making me money.

                        So the solar panels are a NET positive in many ways, particularly when you add up the benefits and the costs I do not have by going with a solar system.

                        Finally, how does it make me feel? It makes me feel great! I absolutely love being self-reliant/self-sufficient and NOT having to worry about fuel or the mess and stink/fumes and the noise... I can set up in a field and do a multi day event / a festival for example and NOT be worrying about fossil fuels or plugging in AND I can charge everyone's cell phones and laptops---which is a service we offer FOR FREE from the SUN!... Putting a solar and battery based systems on my food truck is one of the best things I have ever done in my lifetime. Yes. In my lifetime. What is the cost benefit of that???

                        Secondly you asked me what is my Daily watt usage? It all depends. Daily watt usage is incredibly variable and inconsistent.

                        I do power a full sized restaurant refrigerator 24/7/365 and water pumps and appliances and lights and water heater and everything I need as I have needed them. Although the frig runs all the time the other power uses are entirely dependent on events and bookings for the truck and that varies more than the moods of a severe bi-polar person. So, I can not give you Daily watt usage unless I went to my Outback controller and did some analysis on the past year to come up with the average although quite frankly average is of NO real value (and why I have no done it). It may be nice but the important thing for me to know is when we are slamming out pizzas and we have had 8, 10, 12 hours of customers and we are using appliances and lights and we are working as fast as we can, on those days and nights --- we have POWER. and yes we have had POWER! That is what matters.
                        Last edited by Zoar; 01-24-2017, 01:59 PM.

                        Comment


                        • #13
                          Originally posted by Zoar View Post

                          The costs for aluminum brackets, design and fabricating a structure with pneumatic piston arms to assist with lifting and lowering the solar awning, and also 8 300 watt solar panels, outback controller, inverter, lithium batteries, battery case, all wiring and connectors, etc is about $18,000. Then subtract 30% for Federal credit on my tax return so out of pocket was about $12,000 yet compared to a good, fairly quiet GENERATOR which costs about $8,000, the additional cost works out to only about $4,000 above doing it conventionally. And I do not have any fuel costs as I would with a Generator. The costs in the US are $500 to $1,000 a month for fuel for generators on food trucks. Obviously in a mere 4 to 8 months I am in the BLACK then and the solar vs generator argument is mute. It is MAKING ME MONEY! Plus, with solar panels on my truck I have so many other benefits---no mess and pain in the ass of buying fuel, transporting fuel, refueling, no stink of the exhaust, no noise at all (even quiet generators make noise especially in a confined space... And I am a rolling POWER PLANT that is using the SUN to make all my electricity for all me electrical needs; that means self reliance and self sufficiency. And solar saves me TIME! No time loss for getting fuel, refueling, etc.. and on a food truck TIME IS MONEY.

                          In addition, having SOLAR on my food truck draws more customers! It is a TV and RADIO and MEDIA magnet! It is by far the best advertising you could ever get and it is very sound Public Relations. It makes everyone feel good! If I tried to put a price on the advertising and positive public relations that the Solar System adds to me truck I would have to pay a firm $20,000 to $30,000 a YEAR for what the solar panels do for the business. I did not pay this out yet I derive the benefits as if I did, so the solar system is actually saving me money and making me money.

                          So the solar panels are a NET positive in many ways, particularly when you add up the benefits and the costs I do not have have by going with a solar system.

                          Finally, how does it make me feel? It makes me feel great! I absolutely love being self-reliant/self-sufficient and NOT having to worry about fuel or the mess and stink/fumes and the noise... I can set up in a field and do a multi day event / a festival for example and NOT be worrying about fossil fuels or plugging in AND I can charge everyone's cell phones and laptops---which is a service we offer FOR FREE from the SUN!... Putting a solar and battery based systems on my food truck is one of the best things I have ever done in my lifetime. Yes. In my lifetime. What is the cost benefit of that???

                          Secondly you asked me what is my Daily watt usage? It all depends. Daily watt usage is incredibly variable and inconsistent.

                          I do power a full sized restaurant refrigerator 24/7/365 and water pumps and appliances and lights and water heater and everything I need as I have needed them. Although the frig runs all the time the other power uses are entirely dependent on events and bookings for the truck and that varies more than the moods of a severe bi-polar person. So, I can not give you Daily watt usage unless I went to my Outback controller and did some analysis on the past year to come up with the average although quite frankly average is of NO real value (and why I have no done it). It may be nice but the important thing for me to know is when we are slamming out pizzas and we have had 8, 10, 12 hours of customers and we are using appliances and lights and we are working as fast as we can, on those days and nights --- we have POWER. and yes we have had POWER! That is what matters.
                          Impressive system. I am glad it is working out for you.

                          Although I am surprised at the lost cost considering you have lithium batteries. But then again if you work at putting the system together yourself you can find the parts for great prices.

                          For those that are reading, you can find some great quite generators in the 3000 watt area like the Yamaha or Honda that cost < $1/watt and way below that $8000. But to each their own on where they want to get their power from.

                          I appreciate you posting this information.

                          Comment


                          • #14
                            I know the short answer is always you can't run air conditioning on solar and the concern about battery recovery on solar. The difference here is that I am not really trying to "run" air conditioning full time on solar or depending on solar for battery recovery. I don't mind running my generator or plugging in at night to recharge the batteries, all I want from the solar is to cushion the drain on the batteries while they are supplying power to run the air conditioner. In this case an air conditioner that I have successfully ran (in water cooling mode) using a Honda EU-1000i.

                            Ideally I would like to get 3-4 hours of air conditioner run time, for the sake of easy math lets use some round numbers. Lets assume the battery draw to run the 9000 btu air conditioner is 100 amps per hour, so in theory a 200AH Lithium battery bank could then run said air conditioner for 2 hours ignoring depth of discharge issues, however if I had a solar array that produced 50 AH of electricity during peak mid day hours, in theory this could extend the run time of the above mentioned 200 AH battery bank to 4 hours. If the solar panels could generate 75 AH the run time would be extended to 6 hours, etc. Now I know I don't have enough roof top real estate for that last example, it was just meant as an illustration of concept. I am also not advocating a 200AH battery bank, again it was just used for an illustration.

                            My goal here is to keep the motorhome cool during mid day stops while on the road (stopping to eat, tourist stop, get supplies, etc.) , it is not to embrace solar as sole solution.

                            A typical day might go something like this, spend the night plugged into shore power at an RV park so starting off with fully charged batteries, plan to travel about 300 miles in the day, drive so a couple of hours, pull off to see the worlds largest ball of yarn or something, keep the motorhome cool while there for half an hour, get back on for another hour or so (running the generator to power the roof air conditioner and recharge some of the lost power from stop #1), See a sign for Bubba's Best BBQ and decide to stop for lunch, again keep the motorhome cool, then back on the road with the generator running for another hour or two, before stopping at the main planned attraction for the day, lets say 2.5 hours spent touring the museum of interesting rocks, again trying to keep the motorhome cool with a combination of battery and solar power. By now the batteries are fairly low, so another hour or so on the road with the generator running and we are at our stop for the night, the batteries can recharge on shore power, and we can be off again the next day.

                            Comment


                            • #15
                              Originally posted by Isaac-1 View Post
                              I know the short answer is always you can't run air conditioning on solar and the concern about battery recovery on solar. The difference here is that I am not really trying to "run" air conditioning full time on solar or depending on solar for battery recovery. I don't mind running my generator or plugging in at night to recharge the batteries, all I want from the solar is to cushion the drain on the batteries while they are supplying power to run the air conditioner. In this case an air conditioner that I have successfully ran (in water cooling mode) using a Honda EU-1000i.

                              Ideally I would like to get 3-4 hours of air conditioner run time, for the sake of easy math lets use some round numbers. Lets assume the battery draw to run the 9000 btu air conditioner is 100 amps per hour, so in theory a 200AH Lithium battery bank could then run said air conditioner for 2 hours ignoring depth of discharge issues, however if I had a solar array that produced 50 AH of electricity during peak mid day hours, in theory this could extend the run time of the above mentioned 200 AH battery bank to 4 hours. If the solar panels could generate 75 AH the run time would be extended to 6 hours, etc. Now I know I don't have enough roof top real estate for that last example, it was just meant as an illustration of concept. I am also not advocating a 200AH battery bank, again it was just used for an illustration.

                              My goal here is to keep the motorhome cool during mid day stops while on the road (stopping to eat, tourist stop, get supplies, etc.) , it is not to embrace solar as sole solution.

                              A typical day might go something like this, spend the night plugged into shore power at an RV park so starting off with fully charged batteries, plan to travel about 300 miles in the day, drive so a couple of hours, pull off to see the worlds largest ball of yarn or something, keep the motorhome cool while there for half an hour, get back on for another hour or so (running the generator to power the roof air conditioner and recharge some of the lost power from stop #1), See a sign for Bubba's Best BBQ and decide to stop for lunch, again keep the motorhome cool, then back on the road with the generator running for another hour or two, before stopping at the main planned attraction for the day, lets say 2.5 hours spent touring the museum of interesting rocks, again trying to keep the motorhome cool with a combination of battery and solar power. By now the batteries are fairly low, so another hour or so on the road with the generator running and we are at our stop for the night, the batteries can recharge on shore power, and we can be off again the next day.
                              What you suggest is very doable. As long as you understand that you will not get the same amount of usable sunlight every day and that you may not get any sunlight when you park your RV while you go to get something to eat or to visit a museum. If you need to figure extra battery into those times the costs start to go up very quickly.

                              So you might be able to build a system to run that AC unit most days but unless you over size your battery / pv system there will be days your RV will become hot until you get back on the road and run your generator. Maybe those days your go out to start up the cooling system before your wife enters the RV.

                              I use to do that in the Winter when it got real cold or icy outside so I would "warm up" the car before my wife and I took off.

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