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  • New To Solar

    Hello everyone!

    My fiancee and I are currently in the process of converting a 2003 Thomas EF school bus into an RV for off grid living. I also convinced my buddy to go this route as well rather than buying a 35 year old RV. I have nearly everything I need to get figured out but I am at a loss with solar.

    Since this will be a full time off grid situation, I obviously want to ensure we have enough of everything so that we do not run out of power. So here we go...


    1. I was initially thinking 1 battery per 100watt panel but can I have more batteries per panel? I figure this way, it will take longer to charge, but also longer do discharge.
    2. Seems like most panels are 100watt. Since I am working with a somewhat small area (the front half of a buss roof) I would like some higher end panels. I came across a company called Sunpower and enquirer about their 350 watt panels and when they got back to me all they said was "we're not in your area." Any way I can get these panels, or even find out the cost of them?
    3. Since I am working with limited space, what is the best and smallest sized inverter and charge controllers I can get?
    4. Anything I am missing?

    Thanks for the help. If anyone is interested in checking out our progress you can find us on just about every social media site as "Sasquatters"


  • #2
    Sunpower panels are only installed by Sunpower dealers. They aren't available for sale to the public. You may find them for sale as a used system from a homeowner selling off their system for any number of reasons. They will give you more watts per square foot than other panels. With proper planning and equipment you should be able to assemble a fully functional system with other than Sunpower modules
    2.2kw Suntech mono, Classic 200, NEW Trace SW4024

    Comment


    • #3
      Originally posted by sasquatters View Post
      1. I was initially thinking 1 battery per 100watt panel but can I have more batteries per panel? I figure this way, it will take longer to charge, but also longer do discharge.
      2. Seems like most panels are 100watt. Since I am working with a somewhat small area (the front half of a buss roof) I would like some higher end panels. I came across a company called Sunpower and enquirer about their 350 watt panels and when they got back to me all they said was "we're not in your area." Any way I can get these panels, or even find out the cost of them?
      3. Since I am working with limited space, what is the best and smallest sized inverter and charge controllers I can get?
      4. Anything I am missing?

      Thanks for the help. If anyone is interested in checking out our progress you can find us on just about every social media site as "Sasquatters"
      Tap the breaks partner, you are heading over a cliff without a road map. None of your assumptions are correct To start the most Expensive panels you can buy are 100 watt battery panels. They are antiquated and history. Battery panels you are looking at cost 2 to 6 times more per watt that Grid Tied Panels. Grid Tied panels will be 200 watts and larger, battery panels are 190 watts and less. Easiest way to tell a battery panels is count the cells. 36 cells is a battery panel. . Never ever use Prime Number of panels like 1, 3, 5, 7.....

      I have no idea where you came up with 1 battery per 100 watts, but is plain silly. I bet you think batteries are 12 volts right. Wrong dead wrong. Battery size is determined by how many watt hours you will use in a day which you have not done yet. You have no road map and driving off a cliff of Oh Chit. If you use say 4 Kwh per day you will be using 4 or 6 volt batteries. Your battery operating voltage may be 12, 24, or 48 volts. Again you do not know because you have not determined your needs. You have not even taken the first step.

      So stop right now and plan your disaster first to see how much damage you are in for. Start by reading the Stickies below as they will tell you how to design a system and answer all your questions. Read them, then come back if you have any questions. I think once you realize what it takes will hurt deep in the wallet. The fun thing is the expense never ends replacing batteries every few years. Just for grins you can make a quick cash and weight estimate. For every 1 Kwh of energy you need in a day (10-cents worth from (POCO) will cost you roughly $2000 and weighs 300 pounds. If you live like a hermit with bare essentials of 2 Kwh per day is going to be $4000 and 600 pounds of weight to carry around. $2000 of that in batteries you replace every few years. So be careful what you ask for. The neighbor you talked into this may take it out of your hide.

      So for now forget 100 watt panels and 12 volt batteries. Time to get serious and do your homework. You will thank me later.

      Off-Grid Design
      Inverter and your Battery
      Battery Stuff
      How Much Battery
      Last edited by Sunking; 12-08-2016, 08:57 PM.
      MSEE, PE

      Comment


      • #4
        Originally posted by sasquatters

        You can get your points across without acting like a jerk. Like I said, I am new to this. You have been here for 7 years have have nearly a quarter of a million posts. Trying being a little nicer. You were new to this once as well. You attack me for assuming things about solar yet you personally attack me. Money is not a problem. I want a nice system that will give me no trouble.
        Well SK comes across like that sometimes hoping to convince people not to waste their money even if money isn't an issue by being as blunt as possible.

        Try not to get offended because he can provide good information concerning solar pv systems that will be "nice" and should give you little to "no" trouble.

        Comment


        • #5
          Don't buy anything! Until you do a realistic energy assessment, you are not ready to buy a single item for said project.

          Comment


          • #6
            Here is what I have found...

            TV 59kWh/Yr
            Fridge 475kWh/Yr

            We are going to also have a water pump that doesn't take much to run, and some lights. I hope this is what you were looking for.

            Thanks.

            Comment


            • #7
              I suspect that TV power rating is with no satellite or cable box running 2-3 hrs a day. The fridge looks about right for a not especially efficient house type with ice maker.judging by it's 1.3 kwh usage per day. Assuming it's not a high pressure water pump maybe 100 watts for 1 hr a day. All led lighting so 50 watts for 5 hrs/day = 250 wh/day. Total average daily usage 1.81 kwh which is very lite. Since money isn't an issue and just for fun I'm going to add 1 kwh so you can run a dishwasher or washing machine and perhaps a coffee maker occasionally. microwave anybody?
              Your defining load is that refrigerator because of the high amp draw when it starts up While hard to find in the US an inverter type refrigerator would allow for a smaller inverter.so something to consider.
              For a 2.8 kwh/day system here are the numbers.

              2800wh/day x 1/.52 (1,92) system end AC efficiency / 4.5 hrs of sun = 1194 watt solar array

              And if you aim for 2 days of storage and 50% maximum discharge (protects your expensive batteries) a 24v battery bank would be...
              2800wh/day x 1/.90 (1.11) inverter efficiency x 2 days storage x 1/.50 (2) max discharge /48v battery bank = 232 AH 24v battery bank

              And to double check I'd suggest a 5 - 13% rate of charge for your battery bank with 10-13% being desirable. a 5% rate of charge is more for a weekend only cabin with no heavy daytime loads.

              232amp/hr x 29v charging x 77% charging system efficiency (1.29) x .05 rate of charge + 433 watt minimum array

              232amp/hr x 29v charging x 77% charging system efficiency (1.29) x .10 rate of charge + 866 watt array

              232amp/hr x 29v charging x 77% charging system efficiency (1.29) x .13 rate of charge + 1128 watt array

              I suspect that you will find that you wish you had a bit more power, especially if it rains for a few days, little solar input and lots of time on the computer with the tv running. If it were me and money wasn't too tight I'd go with four 6v roughly 400 amp hr batteries, 6 250+ watt panels (which would take up about 16' of your roof) and a 24v 2000+ watt pure sine wave inverter.

              Keep in mind that with the solar panels laying flat on the roof they won't make as much power thus the 6th panel. You don't want 5 300 watt panels because depending on your charge controller you probably couldn't wire 5 panels.
              Last edited by John Galt 1; 12-11-2016, 06:58 PM.

              Comment


              • #8
                Originally posted by John Galt 1 View Post
                I suspect that TV power rating is with no satellite or cable box running 2-3 hrs a day. The fridge looks about right for a not especially efficient house type with ice maker.judging by it's 1.3 kwh usage per day. Assuming it's not a high pressure water pump maybe 100 watts for 1 hr a day. All led lighting so 50 watts for 5 hrs/day = 250 wh/day. Total average daily usage 1.81 kwh which is very lite. Since money isn't an issue and just for fun I'm going to add 1 kwh so you can run a dishwasher or washing machine and perhaps a coffee maker occasionally. microwave anybody?
                Your defining load is that refrigerator because of the high amp draw when it starts up While hard to find in the US an inverter type refrigerator would allow for a smaller inverter.so something to consider.
                For a 2.8 kwh/day system here are the numbers.

                2800wh/day x 1/.52 (1,92) system end AC efficiency / 4.5 hrs of sun = 1194 watt solar array

                And if you aim for 2 days of storage and 50% maximum discharge (protects your expensive batteries) a 48v battery bank would be...
                2800wh/day x 1/.90 (1.11) inverter efficiency x 2 days storage x 1/.50 (2) max discharge /48v battery bank = 232 AH 24v battery bank

                And to double check I'd suggest a 5 - 13% rate of charge for your battery bank with 10-13% being desirable. a 5% rate of charge is more for a weekend only cabin with no heavy daytime loads.

                232amp/hr x 29v charging x 77% charging system efficiency (1.29) x .05 rate of charge + 433 watt minimum array

                232amp/hr x 29v charging x 77% charging system efficiency (1.29) x .10 rate of charge + 866 watt array

                232amp/hr x 29v charging x 77% charging system efficiency (1.29) x .13 rate of charge + 1128 watt array

                I suspect that you will find that you wish you had a bit more power, especially if it rains for a few days, little solar input and lots of time on the computer with the tv running. If it were me and money wasn't too tight I'd go with four 6v roughly 400 amp hr batteries, 6 250+ watt panels (which would take up about 16' of your roof) and a 24v 2000+ watt pure sine wave inverter.

                Keep in mind that with the solar panels laying flat on the roof they won't make as much power thus the 6th panel. You don't want 5 300 watt panels because depending on your charge controller you probably couldn't wire 5 panels.
                Thank you for this information. I can easily put the panels on a tilt system. Looking for others input as well.

                Comment


                • #9
                  Originally posted by sasquatters View Post
                  Here is what I have found...

                  TV 59kWh/Yr
                  Fridge 475kWh/Yr

                  We are going to also have a water pump that doesn't take much to run, and some lights. I hope this is what you were looking for.

                  Thanks.

                  Your loads are similar to my house.
                  I never run the central air; heat and hot water is gas.
                  Stove is electric , refrig is electric
                  42" flat panel TV.
                  2-3 computers on most of the time
                  Radio on mostly.
                  lights are mostly LED or CFL, only a few on at a time.

                  However, I am grid tied and have a small surplus at end of year.
                  So, I'm thinking you will need more panels than can fit on top of the bus.
                  I have 324 square feet of panels (285 watts SW285 solar ridge, 18 each)
                  A bus roof is what, 8*30=240 square feet.

                  And you cannot simply lay them flat, other buses use a mechanisim to raise them up (tilt) when parked.



                  Dennis
                  SE5000 18 each SW185

                  Comment


                  • #10
                    Originally posted by sasquatters

                    I know I don't know about solar... that's why I am here. Rather than continuing to tell everyone that they are wrong, why don't you just tell me what I need and move on?
                    I did, now move on. I gave you very specific instructions that answers all your questions. All you have to do is read and do HOMEWORK. Again try reading:

                    Off-Grid Design
                    Inverter and your Battery
                    Battery Stuff
                    How Much Battery

                    They will answer all your questions or at least allow you to ask good relevant questions. The very first thing you must do is determine your Daily Watt Hour usage. Otherwise you are just wasting everyone's time trying to figure out what you want.
                    Last edited by Sunking; 12-11-2016, 04:33 PM.
                    MSEE, PE

                    Comment


                    • #11
                      Originally posted by Sunking
                      My my aren't you a thin skinned wanting everything nice, warm, and fuzzy. I was not attacking you, I was showing you how much you do not know and trying to save you from yourself. Lighten up and laugh at yourself. Because if you keep going like you are, there are going to be a lot of tears in your future, and you will loose friends if they copy your model.

                      John you do not design an off grid solar system based on charge rates of 5, 10, or 13% charge rates. 5% does not even meet any manufactures minimum charge rates, Where the heck did this come from?



                      That is complete nonsense. You also do not design a system for 50% discharge per day period. One cloudy day and he goes dark and has to wait until after a full day of sun to recharge before the lights come back on. Where the Hell did 4.5 Sun Hours come from. It impossible to get 4.5 Sun Hours on a RV even in summer months. I have no clue how you have a 48 volt 24 volt battery.
                      Ahh,,, Mr. Positive Attitude has spoken. Obviously he didn't bother to read carefully about the 5% charge rate. And considering that it's an RV I didn't bother to ask about the OP's location for average sun hours, I assumed that was so obvious that even you would understand that. Here in N. GA we average 5 1/2 hrs of sunshine a day through out the year. I took a conservative approach and figured at 4 1/2 hrs. Hope this helps you to understand.

                      I would say have a nice day but considering the lack of reading skills you have demonstrated on this thread I'll just put it as a symbol.
                      Last edited by John Galt 1; 12-11-2016, 07:10 PM.

                      Comment


                      • #12
                        John, you mentioned previously that the fridge did not seem energy efficient. I have found one that is less kwh/yr but it may be too tall for inside the RV. I used this online tool to calculate the watts. Does this image make sense to you/ did I do this right?



                        Thanks

                        Comment


                        • #13
                          Originally posted by sasquatters

                          You can get your points across without acting like a jerk. Like I said, I am new to this. You have been here for 7 years have have nearly a quarter of a million posts. Trying being a little nicer. You were new to this once as well. You attack me for assuming things about solar yet you personally attack me. Money is not a problem. I want a nice system that will give me no trouble.
                          Having been the target of SunKing's no nonsense advice when I first posted on this forum, I was also offended by his very direct and somewhat condescending sarcasm.............until I realized that he was grabbing me by the lapels and shaking me so I would realize the mistaken paths I was taking. Get past his comments and pay attention to the links he posted for you to review. He's not going to spoon feed you, he expects that if you want to know, you need to do your homework. He was "right on" with every bit of advice he gave me. Get a thick skin and read up on the links. As the saying goes "he knows of what he speaks".

                          Comment


                          • #14
                            did you use an energy monitor to get these numbers? or are you using the amps and volt information printed on the Power supply of the device? Keep in mind if you use the label, you will never get accurate power usage numbers, as these are Max. power consumption for said device. Usually only seen upon cold start up. Your actual consumption numbers will be lower. How much lower? You will only know after you do a proper energy assessment. You can use a "Kill a watt" device or a shunt with a quality meter.

                            Comment


                            • #15
                              I have a kill-a-watt device but I do not own the fridge or tv yet to physically test them. I have not bought anything since I do not know what size solar setup to get. That fridge was one of the lowest kwh/yr I could find. I really need to get this process moving along. I am hoping to be full time in the RV by Spring. As soon as I know what size setup I need I can obviously start purchasing items.

                              Thanks.

                              Comment

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