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  • Need advise on what to start with.

    Hello all, first off I want to thank in advance for sharing your experience and having patience for educating those with question.

    Probably, as most of you, I do not have a lump sum to put out for pre-wired power center, 20 300w panels and a 20kwh battery bank.

    According from above, I was thinking starting small, and with the time building a stable system.

    After some research and few quotes from solar installers I decided to do it on my own as I don't feel like overpaying for everything.

    My goal is 8Kw solar panel array with 48v 200-250Ah battery bank. I already have 12v 250Ah battery bank, when it will be finished it will be 48v. At the end it will be grid interactive system.

    I was thinking starting with 4 to 6 300w panels and getting 80amp cc. Should I go which 150v, 200, or 250v input? As I understand, a charge controller is one of the important parts in the system, that said, this controller should be able to handle 8Kw input in the future.

    For now I am planning to run lights, fridge and other non-sensitive electronics as I already have 2Kw modified wave inverter that I was using in the truck.

    Any suggestions are greatly appreciated.

  • #2
    Anything you take off-grid is going to cost you 5 to 10 times more for power the rest of your life. Forget the batteries.

    Anyway a 48 volt 250 AH must have at least 1200 watts of panels and no larger than 1600 watts and can only handle up to a 2000 watt Inverter. Then 3 to 5 years from now the batteries will need replaced and that will be the time to grow. Don not ever parallel batteries or mix old with new.

    You are in for a very expensive journey. If you are smart you will forget about batteries.
    MSEE, PE

    Comment


    • #3
      I did not want to go off grid, I would be grid-tied system with battery back up, I forgot to mention it is li-ion battery bank. You have said my system would be able to handle only 2000 watts, is it because of my starting panel array or because of the battery bank limitations, according to my math 48x250 would be 12000wh of back up power. I know there are inverters that can act as grid tied and off grid in case of power outage.
      So my question was - what type of charge controller should I start with since I already have a battery bank without upgrading it in the future.


      Thanks

      Comment


      • #4
        Since you're asking for suggestions and, pardon my assumption, perhaps comments:

        Suit yourself, but once you educate yourself, you may well find that battery backup for a grid tied system is more costly in terms of time/treasure/hassle than it's worth.

        To start/continue your education, download and read "Solar Power Your Home for Dummies", or get an updated version for ~ $25 at bookstores or Amazon.

        After the read, after determining your annual load, by month, and after learning how you're charged for electricity (a bit of a PITA but a very worthwhile experience), download and run something called PVWatts from the net. Read the help/info screens first and use a 10% system losses rather than the 14 % default value.

        Then, size the array using different sizes to see the possible effect those different sizes may have on your annual bill.

        Adding to PV systems incrementally is a better idea in theory than practice.

        Then, check with your local building authority to find what they require for permits, design and building requirements and don't be surprised if they require engineering work, calcs and drawings , some of it possibly done/reviewed by a P.E.

        If you have a tile roof, make sure you have enough spare tiles for what will get broken.

        Don't forget to inspect/repair the roof under where the array will be before you start. Solar PV can last a long time. Give the roof under it the best chance of lasting as long. Cheap insurance you will not regret.

        Welcome to the neighborhood and the land of few(er) illusions.

        Comment


        • #5
          The only reason I am looking for back up is we work from home and power outages are costly. The math was already done, we pull 1Megawatt/month, we are being charged 29c/kwh including delivery, but this is not the issue of the day.

          I was asking a simple question - what charge controller professionals like you would choose for 8kw solarpanel array and if would it make sense go with capable of handling such load in the future controller, spend $500 or start with $100 one and upgrade as I go?

          I believe I can get away with 20A mppt controller to keep my battery bank topped off and run some small appliances for starters just to keep battery cycling once in a while but everyone deviates from my simple question.

          Is worth buying a good cc with intention of scaling up the system in the future and whick one would you prefer?

          Comment


          • #6
            Will you be getting a Grid Tie agreement to sell excess power to the Grid, when you are not using backup ?
            Powerfab top of pole PV mount (2) | 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

            Comment


            • #7
              Battery backup is the last thing you want. Being Grid Tied if you want backup, use a Generator and an ATS. It is a lot less expensive, more reliable, and allows you to power everything in your house including Air Conditioning day and night.

              With a Hybrid battery backup you only get to power Emergency loads, very small loads like a fridge and a few lights. For extended outage requires a Generator. Either Way you will have a generator.
              MSEE, PE

              Comment


              • #8
                Hello Mike, eventually yes, excess power will be sold back to the grid, I just want to make sure if it is worth taking small steps towards it or taking a loan and get it done all at once, hoping to save a buck or two by buying everything on my own and just paying solar electrician for a hook up plus permits and other related fees.

                Comment


                • #9
                  Sunking, thanks for clearing batteries vs generator part, this is where I was in the clouds, I do understand that batteries need more tweaking than a generator and here is the scoop: I have access to the lithium ion batteries in bulk for about $1 per 6 batteries (2500mah 3.7v) and I am handy with soldering iron and I was wandering if it is worth doing it since each 1 kwh of back up will cost me roughly $80 including cell holders, soldering materials, fuses erc.

                  Thanks

                  Comment


                  • #10
                    1) The solar market has reached bottom, and as vendors go bankrupt, there will be some fire sales for a couple more months - 1 year. Then the incentives and rates start eroding and your installed cost will start going up.

                    2) With batteries and their eventual replacement, you will never break even, the battery replacement costs will sink you. For the price of 1 battery bank, you can get a deluxe generator. And with batteries, you still need a generator. (I have 3, 2 on-line, and 3rd mothballed.)

                    3) Building a battery out of little Li cells. Please don't. I'm sure it sounds like a clever idea, but if you start soldering to the tabs on cells, you WILL ruin the cell seals and then it all goes bad from there, ending in a blackout (best case) or fire (worst case).
                    Powerfab top of pole PV mount (2) | 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

                    Comment

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