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  • inverter / mppt low range question

    Hi,

    I want to install a 5kw hybrid inverter and start off with only a few panels and extend as I go. My question is the MPPT spec on the inverter is 225v - 800v. If I start off with say 6x 250w (+-30v each) connected in series, I would only be getting about 180v and my input voltage would be below the listed spec. How would this effect the operation of the inverter, would the system function in this setup? Also if there are two MPPTs, is the listed spec for both MPPTs combined?

    Thanks,

  • #2
    Inverters will have a minimum startup voltage and a mppt minimum voltage. In general the efficiency will be reduced at lower voltages and/or outside mppt range. No you can't divide the mppt voltage in half.

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    • #3
      Originally posted by justin334 View Post
      I would only be getting about 180v and my input voltage would be below the listed spec.
      At best you simply wouldn't get full power. At worst the system would not start up at all.

      What is the MPPT you are planning to use?

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      • #4
        Originally posted by sensij View Post
        I would suggest ignoring what eleceng1979 wrote in the post above this one... lots of misinformation in there.
        Last edited by Eleceng1979; 06-24-2016, 12:51 PM. Reason: Because Sensij said so!

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        • #5
          Thanks guys, Its a 10kw grid tie/off grid hybrid - meaning it has mains input with the ability to feed back to the grid (As an option - which i wont be using) and it has PV inputs as well as the ability to install batteries. So basically it starts up and runs on the mains with no PV inputs, then if the mains dies it switches over and supplies power from the batteries. So it can be used as a sole battery backup. So im thinking if it runs with no PV panels at all, if I connect say 6 panels - it should just take whatever power is available from the PV panels but the MPPT wont track if the voltage is outside of the MPPT range. I think?

          The more I learn about solar the more complicated it actually becomes :P

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          • #6
            Originally posted by sensij View Post
            I would suggest ignoring what eleceng1979 wrote in the post above this one... lots of misinformation in there.
            Last edited by Eleceng1979; 06-24-2016, 12:50 PM. Reason: Because Sensij said so!

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            • #7
              Oh - my apologies, I did forget to mention its a 220v 3phase inverter, if that makes a difference - I'm not sure.

              http://www.voltronicpower.com/oCart2...l-20150130.pdf

              Have at it!

              Comment


              • #8
                Originally posted by justin334 View Post
                Thanks guys, Its a 10kw grid tie/off grid hybrid - meaning it has mains input with the ability to feed back to the grid (As an option - which i wont be using) and it has PV inputs as well as the ability to install batteries. So basically it starts up and runs on the mains with no PV inputs, then if the mains dies it switches over and supplies power from the batteries. So it can be used as a sole battery backup. So im thinking if it runs with no PV panels at all, if I connect say 6 panels - it should just take whatever power is available from the PV panels but the MPPT wont track if the voltage is outside of the MPPT range. I think?
                Look closely at the specs. If it has a DC input range that is distinct from the MPPT input range, you can expect the mppt to be functional across the entire DC range, but less efficient outside the mppt range.

                I would suggest ignoring what eleceng1979 wrote in the post above this one... lots of misinformation in there.
                CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

                Comment


                • #9
                  Originally posted by Justin334 View Post
                  So im thinking if it runs with no PV panels at all, if I connect say 6 panels - it should just take whatever power is available from the PV panels but the MPPT wont track if the voltage is outside of the MPPT range. I think?
                  Sort of. As Sen mentioned, there's often a separate DC input range (where it will work) and an MPPT range (where it will work efficiently.) There are also a few other considerations, like making sure the maximum DC voltage is never exceeded, even on cold days (panel voltage goes up when it's cold out.)

                  Also, every MPPT controller I have ever seen is a buck converter, which means that it can only drop voltage, not boost it. That means that if your panel voltage is lower than your battery voltage, the MPPT will not be able to charge the batteries. In general the _minimum_ loaded voltage of the panels in hot weather (=lowest voltage) must be several volts higher than the _maximum_ voltage of the batteries, to take into account wiring and conversion losses.
                  The more I learn about solar the more complicated it actually becomes :P
                  Yep. That's good and bad; bad because there's a lot to learn, but good in that modern inverters/charge controllers can do so much.

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                  • #10
                    Originally posted by sensij View Post
                    I would suggest ignoring what eleceng1979 wrote in the post above this one... lots of misinformation in there.
                    Care to point out what you are suggesting as misinformation? Is there not a feed in voltage? or a min voltage?

                    The OP has an inverter not a charge controller, in which they will not share the make and model to further help themselves, that has grid tie + off grid battery inverter + battery charger capabilities + direct PV inputs all built in one, which Is strange and honestly I do not know if it even exist - maybe the storedge?... but I am full of it according to you... with a MPPT voltage range higher than anything for residential usage on the market in the USA. I think the OP told us the min mppt full power voltage as I can believe 225 for that value. 225VDC is not required to make 240VAC at lower power as you can do it with way less DC, hence my technology comment. Nor does a charger need 225VDC to charge less than 48V of batteries.

                    My whole point is not enough PV will do nothing if the spec sheet says XXXVDC and he has YYYPV DC...but no one knows what the inverter is?

                    Sensij, when your crystal ball tells us what inverter the OP has, please inform myself as I am really trying to help. The OP looked at the specs already, came here to this site, registered, clicked a verification email, asked a question in his first post, you told him to look at the specs? and at the same time the only person that asked what the brand was to better help the OP was to be ignored according to you... I see why your post count is so high and mine is so low... you seem to run dumb people like me off...

                    Comment


                    • #11
                      An example of what the OP might be using is this:

                      http://www.voltronicpower.com/oCart2...&product_id=73

                      Note that although the mppt range for the 10 kW is 400-800 V, it will actually operate down to 320 V (just less efficiently). The mppt spec alone is not enough to answer the question.

                      I agree with asking for model information, but some of the assertions that were made in that post were not accurate.
                      CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

                      Comment


                      • #12
                        Originally posted by Eleceng1979 View Post
                        with a MPPT voltage range higher than anything for residential usage on the market in the USA.
                        Fronius primo has min voltage of 80 but MPP range starts at 250. Nominal input voltage is 420.

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                        • #13
                          Original post = My question is the MPPT spec on the inverter is 225v - 800v
                          My comment = with a MPPT voltage range higher than anything for residential usage on the market in the USA.
                          Your comment = Fronius primo has min voltage of 80 but MPP range starts at 250. Nominal input voltage is 420.

                          225 to 800 is a bit off from 80-250-420... most are less than 600...hence my issue.

                          My previous comment = I think the OP told us the min mppt full power voltage as I can believe 225 for that value

                          My issue = without a name/model no one can guess what he has to help him. Everyone else can debate the startup power volts to an unknown inverter, but I will not and have taken offense to comments by others while trying to help someone.

                          The OP wants to know the min volts to start up the inverter, not make full power! MPPT range is pointless as he will never make full power with limited panels...this is the whole point to his post. We need the real min voltage as we all agree that it probably isn't 225. This will only come from the unknown make/model datasheet, not everyone's opinion of my responses.

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