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  • Aquions How low can I go?

    Aloha,

    This is our third day in a row of cloudy skies. Have only been able to get to 55% SOC these past days. In the morning were down to around 37% SOC. Currently is heavy clouds and rain at 10:24am. Only generating 34W. Battery monitor says 46.6V and -12.7A 30%. Load is currently 785W and increases every now and then because of our 4 refrigerators. Still using the microwave and a hair drier just went on.

    The dark clouds passed and its still raining steady, pulling in 336W from our panels.

    Will be interesting at 80% DOD
    AlmostOffGridHawaiian

  • #2
    You can go down to 0%. Do you want to, is the question. Do you have any generator ?

    Soon, you are going to start getting some steep voltage sags that will start shutting the inverter down, then you are dark.
    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 OffGridHawaiian View Post
      Battery monitor says 46.6V and -12.7A 30%.
      Something is not right here. 46 volts is actually a very high voltage on these batteries indicating you are somewhere around 50 to 70% SOC according to the discharge curves. Depends on what C-rate you are discharging at. Example if you are only discharging at say a very tiny low C/25 or 2 amps per battery string you are down to 10% SOC. If you are discharging at maximum C-Rate of C/5 or a whopping 10 amps per string you are near 100% SOC. At C/10 or 6 amps around 50 to 70% SOC.

      FWIW for those wondering how 46 volts can be anywhere from 10% to 100% is a result of very high internal resistance batteries. They really cannot provide very much current, and what current they do provide is very inefficient. The batteries on discharge use about as much as the load is burning up. Same on the charge side half the power from the panels is turned into heat while charging the batteries.
      MSEE, PE

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      • #4
        Originally posted by Sunking View Post
        Something is not right here. 46 volts is actually a very high voltage on these batteries indicating you are somewhere around 50 to 70% SOC according to the discharge curves.
        OffGridHawaiian, not sure if you received discharge curves from Aquion, but I do believe you have the older S10 stacks?, and the link provided is for the newer S20 stacks. Not sure how much difference there is between them, but I have heard that there is less voltage sag with S20 stacks vs the S10, and of course there is a difference in capacity.

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        • #5
          OFH, I sent you a PM a few days ago. Would be really interested to hear where you bought the Honda generator from and what your thoughts are on the level of service you've received. Or did your solar contractor handle the generator?

          Comment


          • #6
            This morning battery monitor read 8% SOC @ 43.2V. Inverters had LOW DC VOLTAGE warning, but we were still OK. Refrigerators kicked on, inverter started humming like usual. Couldn't get down to the 40.0V cutoff.

            Had full cloudy day today, Battery is @ 30% now. Had to flip the switch back to utility power since generator is not hooked up yet. Tomorrow is expected to be the same, mostly cloudy with 50% chance of rain.
            AlmostOffGridHawaiian

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            • #7
              What are you using for a battery monitor? If it's the Schneider, it may not understand the SoC numbers for the Aquion, so 30% for lead acid batteries may be higher for the Aquion.

              I know the XW has the ability to configure a delay on the low voltage shutoff, I'm assuming the tech set that delay so that momentary voltage sags don't turn off your inverter prematurely.
              Solar Queen
              altE Store

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              • #8
                Originally posted by Amy@altE View Post
                What are you using for a battery monitor? If it's the Schneider, it may not understand the SoC numbers for the Aquion, so 30% for lead acid batteries may be higher for the Aquion.

                I know the XW has the ability to configure a delay on the low voltage shutoff, I'm assuming the tech set that delay so that momentary voltage sags don't turn off your inverter prematurely.
                Aloha Solar Queen

                Yes we are using the Schneider battery monitor. There is a custom battery menu that we can input our own set points instead of the defaults. Aquion's are just a different animal.

                More Schneider techs are here in Hawaii working with my installer. There are 3 of us who are using the Aquions on the Big Island now, The company that installed my system's owner, his son, and myself. The 3 Little Guinea Pigs
                AlmostOffGridHawaiian

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                • #9
                  Schneider gets to be in Hawaii, while the Aquion guys are up here in snowy Boston at PV America. At least the sun is shining here.

                  Definitely keep us up to date with what the techs are doing, and if there's anything we should be keeping our eye out for.
                  Solar Queen
                  altE Store

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                  • #10
                    Originally posted by OffGridHawaiian View Post
                    This morning battery monitor read 8% SOC @ 43.2V. Inverters had LOW DC VOLTAGE warning, but we were still OK. Refrigerators kicked on, inverter started humming like usual. Couldn't get down to the 40.0V cutoff.

                    Had full cloudy day today, Battery is @ 30% now. Had to flip the switch back to utility power since generator is not hooked up yet. Tomorrow is expected to be the same, mostly cloudy with 50% chance of rain.
                    First off, thanks for keeping us in the loop on how your system is working.

                    I am a little confused (but it also might have to do with me not understanding the Aquion performance curves).

                    In your first post you stated the battery was at 37% SOC @ 46.6V. Now you have seen the monitor state the battery is at 8% SOC @ 43.2v. Is that correct?

                    Comment


                    • #11
                      Originally posted by SunEagle View Post
                      I am a little confused (but it also might have to do with me not understanding the Aquion performance curves).

                      In your first post you stated the battery was at 37% SOC @ 46.6V. Now you have seen the monitor state the battery is at 8% SOC @ 43.2v. Is that correct?
                      Sun Eagle voltage on these batteries are useless to determine SOC. The internal resistance and Peukert are so high on this battery, you would have to have some sort of Coulomb Counting device that also takes into account Peukert. If you look at theses Specs on the S20 there is a lot of information in them in graphical form. Since the data is in Graphical form makes it meaningless to just about every consumer. If in the form of a table would look really bad.

                      Here is an example of what you can pull off the graphs starting with internal resistance. Using the Voltage vs Capacity curve we can determine Ri by using the current and voltage lines of 2 and 10 amps with a fair degree of accuracy. If we reference the voltage at 10 AH capacity we can see the voltage of the 2 amp line = 50 volts, and on the 10 amp = 41.5 volts.

                      50 - 41.5 volts = 8.5 volts
                      10 - 2 amps = 8 amps
                      R = V/A, 8.5 volts / 8 amps = 1.06 Ohms.

                      Now to most people especially yankees for the NORTHERN part of the country has no idea what that means. As a comparison your average of 4-12 volt 50 AH FLA batteries in series has an Ri of around .2 Ohms. That is roughly 5 times higher than FLA. Just from that we know I x I x R losses are 500% higher. If you draw a C/20 current of 2.5 amps the battery is burning 2.5 x 2.5 x 1.06 = 6.625 watts as waste heat or 6% loss of energy.

                      It also means for every amps of current you loose 1 volt as voltage sag or 6%

                      They also list the Peukert effect, but it is disguised in every graph. But when you pull the info out of Voltage vs Discharge you get this.

                      20 Hour Rate 2.5 amps = 50.2 AH
                      8 Hour Rate 6 amps = 40 AH
                      6 Hour Rate 8 amps = 29 AH
                      5 Hour Rate 10 Amps = 20 AH
                      3 Hour Rate 15 amps = 10 AH (Maximum charge/discharge rate.
                      MSEE, PE

                      Comment


                      • #12
                        Originally posted by SunEagle View Post
                        First off, thanks for keeping us in the loop on how your system is working.

                        I am a little confused (but it also might have to do with me not understanding the Aquion performance curves).

                        In your first post you stated the battery was at 37% SOC @ 46.6V. Now you have seen the monitor state the battery is at 8% SOC @ 43.2v. Is that correct?
                        Aloha SunEagle,

                        Yes it is correct
                        8%.jpg
                        AlmostOffGridHawaiian

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                        • #13
                          Originally posted by OffGridHawaiian View Post
                          Aloha SunEagle,

                          Yes it is correct
                          [ATTACH=CONFIG]6035[/ATTACH]
                          Ok. I see the scaling on that chart where 0% SOC equates to 40V.

                          Too bad you are getting some bad weather and have to use other means to recharge your batteries.

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                          • #14
                            Originally posted by OffGridHawaiian View Post
                            This morning battery monitor read 8% SOC @ 43.2V. Inverters had LOW DC VOLTAGE warning, but we were still OK. Refrigerators kicked on, inverter started humming like usual. Couldn't get down to the 40.0V cutoff.

                            Had full cloudy day today, Battery is @ 30% now. Had to flip the switch back to utility power since generator is not hooked up yet. Tomorrow is expected to be the same, mostly cloudy with 50% chance of rain.
                            You have utility power? I somehow missed this important point. I am curious why you spent $90,000+ on a solar system if you are on-grid? Now I can see why your generator isn't set up, which I was wondering about weeks ago.

                            Your user name now confuses me.

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                            • #15
                              Originally posted by OffGridHawaiian View Post
                              Had to flip the switch back to utility power
                              Interesting, you have utility power.
                              MSEE, PE

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