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  • My 13.7kWp grid tied as battery charging station

    We've got a ground mount 13.7kWp grid tied system, with SolarEdge SE11400H - US inverter, no batteries. If the grid goes down, as a community service, we would like to be able to charge as many "large" batteries during the day as possible. By large I mean RV or heavy equipment types of batteries or the occasional car battery for a family with a small inverter to get through the night. Right now we average about 90kWh/day production. 300+ days of sun. We have a sufficient solar generator to get us through night-to-night so "lighting the house" is not the goal.

    The array has a quick disconnect along with the inverter and it's about 130' to the house load center & meter and additional disconnect, if that matters.

    We don't want to make the investment in batteries for the house alone for the unlikely need and would like as flexible system as possible if the need arises. We are looking for recommendations on charge controller and how "easy" it would be to accomplish our goals with our existing setup.

    Curious about your thoughts.

  • #2
    How frequently does the power grid in your area normally go down?

    Weekly? Monthly? yearly?

    Here where I live on the East Coast, after 15 years we have never witnessed any 30-day period where the power grid has not gone down.

    I totally understand planning for grid down when it happens so frequently. But there are other posters here who can go for years without power outages.


    4400w, Midnite Classic 150 charge-controller.

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    • #3
      Right!, OrganicFarmer. Power goes out very infrequently and that's why we don't want to invest in a big battery array that will sit but would like a flexible way to use the asset if the grid does go down.

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      • #4
        Around here nearly every house has at least one generator.

        We don't have a generator, often when the grid is down a few days and we have no idea how many more days it will be. I watch the battery charge. if we began the outage with a fullcharge it is much less stressful. But often the grid goes down when we only have a partial charge on the battery. So then we must go onto more extreme austerity measures.
        4400w, Midnite Classic 150 charge-controller.

        Comment


        • #5
          Originally posted by Wolfeie View Post
          We've got a ground mount 13.7kWp grid tied system, with SolarEdge SE11400H - US inverter, no batteries. .........
          So, what you want first, is a high voltage Battery Charge Controller. They accept up to 600VDC from the solar and down-convert it to 48V ( or a more wasteful 12 v ) for battery charging

          RV's have their own charging system built in - their engine. Someone pulling a car battery out, charging it, is not going to run their house. They will have a couple lights and maybe charge a cell phone. That''s all there is in a car battery.

          Folks would be better off getting their own automotive jumpstart pack for themselves, and use that.

          Something to consider - does the power go off in clear sunny weather, or in storms ? How much sun will you have the next day ?

          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


          • #6
            Originally posted by Mike90250 View Post
            ... Folks would be better off getting their own automotive jumpstart pack for themselves, and use that.

            Something to consider - does the power go off in clear sunny weather, or in storms ? How much sun will you have the next day ?
            Thank you, sir.

            Living on solar power is shifting to an entirely different lifestyle. You must be aware of the storm fronts and likely power outages, of how many days do we expect to go before the next sunny day.

            Once I am on batteries, I have to keep an eye on my wife, she likes having a coffee pot turned on all day [and most of the night] with hot coffee. But one coffee pot left on will drain our battery bank in a couple of hours.

            There is a lot to keep in your mind, to be aware of when doing this lifestyle.

            When we go onto battery, laundry must stop. One of the biggest things here was showering. My wife was still working, when we made the shift to solar power. She would come home after work, and she wanted to sit and relax with a beer for an hour and then have supper. Only after all of that, then she wanted to have a long shower. I have nothing against long showers. But not when we are on battery. We have a well pump, an electric water heater, and a sewage pump. All to bring in that water inside, to heat it, and to remove it. Our battery bank would go dead about halfway through her showers.

            Until she retired, I was never able to convince her that she needed to take her showers first thing when she got home, while the sun was still in the sky. And not after it had become dark.
            4400w, Midnite Classic 150 charge-controller.

            Comment


            • #7
              Originally posted by Mike90250 View Post

              So, what you want first, is a high voltage Battery Charge Controller. They accept up to 600VDC from the solar and down-convert it to 48V ( or a more wasteful 12 v ) for battery charging...
              Thanks, Mike. That was what I was thinking, too. I have seen a few BCC's that have the ability to charge two separate banks simultaneously and auto-switch between 12/24/48V. How do I calculate the necessary Amps for the BCC? I presume that the Charge Controller gets wired in at (parallel), or prior to (series), the inverter.

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              • #8
                Most of the 600V controllers, are rigged for 24 or 48V, and are either 60A or 80A into the battery.
                Morningstat, Schneider and Midnight Solar make high voltage controllers. I don't know if they all auto-select voltage at boot time, but I do know if you connect the solar before you connect the battery, they will fry.
                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


                • #9
                  Originally posted by Mike90250 View Post
                  ..., but I do know if you connect the solar before you connect the battery, they will fry.
                  Good to know.
                  So much to learn. I appreciate your help and patience.

                  Comment


                  • #10
                    The SMA Sunny Boy grid tied inverters have what is called a "Secure Power Supply" circuit that will deliver up to 2000 watts at 120 volts so long as the sun is shining.. When the grid goes down, you just flip a light switch and a special 120v 20a outlet gets energized. You can then plug whatever you want into that outlet.

                    2000 watts will deliver over 150 amps at 12v dc. That's enough to charge several batteries at once with a standard automotive battery charger. Or run your microwave or coffee maker, computers, etc.

                    We are also grid-tied with 2x SMA Sunny Boy inverters, but instead of using the two (one each) 2000w SPS circuits in them, we use Sunny Island inverters to trick the grid inverters into making full power as if the power grid was still connected. We feed that energy into the house and any excess goes to charging a 25kWh lithium battery bank.

                    When the grid goes down out here in the rural countryside, as it does 3 to 5 times a year for several days at a time, we just continue life as normal.

                    Generally speaking, if your power outages are infrequent, a normal portable generator is probably the best option. Run it on propane or natural gas so you don't have to worry about the carb plugging up when its in storage.

                    Comment


                    • #11
                      Originally posted by Wolfeie View Post
                      We've got a ground mount 13.7kWp grid tied system, with SolarEdge SE11400H - US inverter, no batteries. If the grid goes down, as a community service, we would like to be able to charge as many "large" batteries during the day as possible. By large I mean RV or heavy equipment types of batteries or the occasional car battery for a family with a small inverter to get through the night. Right now we average about 90kWh/day production. 300+ days of sun. We have a sufficient solar generator to get us through night-to-night so "lighting the house" is not the goal.

                      The array has a quick disconnect along with the inverter and it's about 130' to the house load center & meter and additional disconnect, if that matters.

                      We don't want to make the investment in batteries for the house alone for the unlikely need and would like as flexible system as possible if the need arises. We are looking for recommendations on charge controller and how "easy" it would be to accomplish our goals with our existing setup.

                      Curious about your thoughts.
                      It seems as if most it not all the comments are missing the fact that the SE11.4 uses Optomizers. Unless you use an ac coupled battery system. There is no way to get the Optomizers to come out of Safety Mode. Short of changing to a string inverter & a charge controller I don’t see a way to charge batteries.

                      Andy

                      Comment


                      • #12
                        Originally posted by Wolfeie View Post
                        We've got a ground mount 13.7kWp grid tied system, with SolarEdge SE11400H - US inverter, no batteries. If the grid goes down, as a community service, we would like to be able to charge as many "large" batteries during the day as possible. By large I mean RV or heavy equipment types of batteries or the occasional car battery for a family with a small inverter to get through the night. Right now we average about 90kWh/day production. 300+ days of sun. We have a sufficient solar generator to get us through night-to-night so "lighting the house" is not the goal.

                        The array has a quick disconnect along with the inverter and it's about 130' to the house load center & meter and additional disconnect, if that matters.

                        We don't want to make the investment in batteries for the house alone for the unlikely need and would like as flexible system as possible if the need arises. We are looking for recommendations on charge controller and how "easy" it would be to accomplish our goals with our existing setup.

                        Curious about your thoughts.
                        When you say “community service”, just what do you mean?

                        Comment


                        • #13
                          What I mean by community service is this. I live in a small mountain community. If the grid goes down I, right now, effectively have a gas station full of gas but no way to get the gas out of the ground. What I want to be able to do is to leverage the panels to put energy in cells that I and others may be depleting to get through the nights.

                          The more I've been thinking, and after Andy's post, it might make the most sense in the event of grid failure to simply disconnect "some" panels and wheel out a "mobile charging wagon" (I made that sound fancy, I'm thinking one of those gardening little wagons) that has a solar charge controller that is easily configurable.

                          Since I have "many" Jinko JKM380M-72L-V panels pumping 380W maybe a couple of mobile charging wagons.

                          Thoughts on this approach? Recommendations for equipment?

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                          • #14
                            Cheap is a gasoline or propane generator set, which works regardless of the sun. The one I
                            bought in the 90s probably only has a dozen hours on it. Bruce Roe

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