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  • feeding into inverter

    hi
    SO I am looking to feed say 300dc into my invereter when the sun goes down.
    Does anyone know of any circuits or inveters that could do it?
    thanks

  • #2
    You are wanting to supply DC power to the MPPT input of a Grid Tie inverter ?

    DON'T try it. The MPPT circuit will attempt to load and swing the "array" voltage around to find the MPPT setpoint. A battery does not behave like a PV array would and the results will disappoint you. As in REALLY disappoint. Things might fare better if your inverter does not have a MPPT input.
    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

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    • #3
      Originally posted by techy21 View Post
      hi
      SO I am looking to feed say 300dc into my invereter when the sun goes down.
      Does anyone know of any circuits or inveters that could do it?
      thanks
      I am thinking there is a way, but its very VERY inefficient. Lets say, the panels Vmp is 300V,
      Voc 375V. The supply must have a current limit circuit in line with the solar operational current.
      So the panels drop 75V at the operational current. One could insert a resistance dropping 75V at
      the expected current (ohms law). The inverter might search for MPPT and find 300V, lower will
      bring current limiting like a panel. This will cause 20% of the power supply power to burn up in
      the resistor, it will probably require a water cooled version (hot water heater element).

      Experiment reducing the resistor value and increase efficiency, watch for instability. A supply
      not set up for current limiting may melt down everything. good luck, Bruce Roe

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      • #4
        Find yourself a wind turbine GTI, which will allow you to manually enter an IV curve to suit - obviously the output will track the curve as opposed to your load/use.

        Comment


        • #5
          Not very smart in terms of finances and a good way to destroy the MPPT circuit in the Inverter.

          He is the finance part with T&C humor.

          Two Jew Tailors Abe and Ruben are standing outside their shops one afternoon talking shop. Abe sells his suits for $50, and Rueben sells his for $500. Reuben cannot figure out how Abe sells his suits so cheap.

          Reuben ask: How much does it cost to make a suit:
          Abe replies: $250
          Reuben laughs out loud and ask: How do you expect to make money?
          Abe replies: Simple stupid I make up for it by volume, I sell a lot more suits than you do.

          Don't be an Abe, because that is what you are asking us to tell you how to be Abe
          Last edited by Sunking; 05-20-2017, 06:07 PM.
          MSEE, PE

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          • #6
            Why would it distroy the inverter ? - if the source can cope the inverter will just hit it's current limit, and stay there - being able to manually provide the IV curve simply enables some degree of control over the output (probably to cover the OPs baseload overnight)

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            • #7
              Originally posted by Sean_Ork View Post
              Why would it distroy the inverter ? - if the source can cope the inverter will just hit it's current limit, and stay there - being able to manually provide the IV curve simply enables some degree of control over the output (probably to cover the OPs baseload overnight)
              Go ahead and give it a try. Just stand back and remember to wear safety glasses and fire proof clothing.

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              • #8
                Originally posted by SunEagle View Post

                Go ahead and give it a try. Just stand back and remember to wear safety glasses and fire proof clothing.
                It's well proven in many DIY V2G applications - it works.

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                • #9
                  Originally posted by Sean_Ork View Post

                  It's well proven in many DIY V2G applications - it works.
                  Then you have nothing to worry about until it doesn't work. The choice is yours but I would not recommend doing it because of the potential result of equipment failure.

                  It kind of amazes me that people will try anything or push the limits on a piece of equipment to save a few pennies.
                  Last edited by SunEagle; 05-21-2017, 02:20 PM.

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                  • #10
                    Originally posted by SunEagle View Post

                    Then you have nothing to worry about until it doesn't work. The choice is yours but I would not recommend doing it because of the potential result of equipment failure.
                    You would be more convincing if you'd provided a technical explanation as to why feeding a GTI with a voltage within its rated range would cause the inverter to fail - remembering of course that the inverters output is current limited.

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                    • #11
                      Originally posted by Sean_Ork View Post

                      You would be more convincing if you'd provided a technical explanation as to why feeding a GTI with a voltage within its rated range would cause the inverter to fail - remembering of course that the inverters output is current limited.
                      The simple answer is that a solar grid tie inverter is not designed to accept a dc voltage from anything but solar panels.

                      Sure you can play and experiment all you want on a bench but you would also be taking the precautions not to cause an expensive piece of equipment to fail.

                      I am also letting you know that I will not tolerate someone making posts which encourage others to do something that may be dangerous.

                      Comment


                      • #12
                        Originally posted by SunEagle View Post

                        The simple answer is that a solar grid tie inverter is not designed to accept a dc voltage from anything but solar panels.

                        Sure you can play and experiment all you want on a bench but you would also be taking the precautions not to cause an expensive piece of equipment to fail.

                        I am also letting you know that I will not tolerate someone making posts which encourage others to do something that may be dangerous.
                        Could you please explain why it is dangerous - just saying it's dangerous isn't convincing.




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                        • #13
                          Originally posted by Sean_Ork View Post

                          Could you please explain why it is dangerous - just saying it's dangerous isn't convincing.



                          Hmm. I could also say that touching something hot like fire will burn you but unless you are not convinced you will go ahead and do it anyway.

                          The danger can come in many forms. Most DIY end up doing something that is dangerous and I will not condone it here on this forum.

                          If the inverter has the ability through design to accept a constant DC voltage other than from a solar panel to properly work then it should be ok to do so. But I would imagine that the inverter the OP is talking about is designed for solar panel input only. Pumping a dc voltage into it can be dangerous if the person doing it exceeds the limitations of the inverter.

                          My question is why would someone want to put dc voltage into a solar inverter at night when the sun isn't shining?

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                          • #14
                            You are just exposing how little you know about GTI functionality - consider a WT GTI, which is essentially the same hardware (excluding the over voltage/braking systems) - these have different firmware which allows you to create your own power curve, the solar version of the inverter will track the MPP automatically - the inverter doesn't really care about the source, as long as it's DC.

                            "My question is why would someone want to put dc voltage into a solar inverter at night when the sun isn't shining?"

                            I'll give you some time to think about why someone would want to be doing that .......

                            Comment


                            • #15
                              Originally posted by Sean_Ork View Post
                              You are just exposing how little you know about GTI functionality - consider a WT GTI, which is essentially the same hardware (excluding the over voltage/braking systems) - these have different firmware which allows you to create your own power curve, the solar version of the inverter will track the MPP automatically - the inverter doesn't really care about the source, as long as it's DC.

                              "My question is why would someone want to put dc voltage into a solar inverter at night when the sun isn't shining?"

                              I'll give you some time to think about why someone would want to be doing that .......
                              I do know a lot of people try to go around the internal safeties built into a GTI. I also know that there are very few people that understand the electronics and programing required to change the way a manufactured GTI work differently that they are supposed to.

                              You may be one of those few that can safely make the changes but for the majority of the populace that come to this forum it would be like rocket science.

                              The only reason someone would pump dc into a solar inverter at night is to use cheat their POCO by using the equipment the way it was not designed. Why would you do it?

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