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  • Solar setup problem

    Hi guys, I hope you can help me
    I've currently got a off the grid set up as follows
    5000 watts of panels
    Sma inverter
    Sma sunny island
    8 x 48 deep cell batteries
    It been working great over the past 18 months apart from a few teething problems, but being the first off the first off the grid set up these guys have done I don't think that it's been set up correctly. For example
    It seems to be using only battery power during the day. I run a small aircon during the day only in full sun however come five o'clock the system shuts down due to low batteries. I thought the system would use generated power from the panels when available and then use any additional solar generated to charge the batteries, any thoughts?

  • #2
    If I had to guess you are using more power than you generate. But yeah it sounds like it was designed completely wrong if you are saying you have 8 parallel battery strings, That was a huge costly mistake.
    MSEE, PE

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    • #3
      There is only 8 batteries, but was told they would have 19kwh of storage when fully charged. It doesn't make sense, it only gets used in the middle of the day when it would be generating 4000 watts on average

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      • #4
        Originally posted by Beno View Post
        There is only 8 batteries, but was told they would have 19kwh of storage when fully charged. It doesn't make sense, it only gets used in the middle of the day when it would be generating 4000 watts on average
        You might get a little over 4000 watts for an hour or so in the middle of the day, but mostly they will be generating less. Another forum user in southern CA has shared the output of his 4.8 kW system. Total generation for him daily right now is about 22 kWh... so if your system were similar, you would need to be running almost nothing during the day just to back to fully charged. What does that AC draw? Is there anything else on the batteries?

        You might want to check your battery datasheet, but I doubt it is good for their longevity to be getting discharged so deeply every day.
        CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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        • #5
          Originally posted by Beno View Post
          There is only 8 batteries, but was told they would have 19kwh of storage when fully charged.
          That means you have a 48 volt 400 AH battery which is only capable of providing you 4 Kwh per day.
          MSEE, PE

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          • #6
            So 8 x 4kwh?. It works fine without the ac, it only running a couple of Fluro lights a tv and pressure pump. In the morning the batteries are only down to about 70 percent which charges up to 95 no problem. I was under the impression of there was power generated off the solar it would use that first then any remainder would trickle feed the batteries. The system has been up and running for 18 months fine even on cloudy days it charges back up.
            One other point do you guys know anything about gas powered auto start generators. Was thinking of installing one into the sunny island in case of weeks of wet weather

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            • #7
              Did you have the AC on all the time in the day the past 18 months, the batteries might be sulfated by insufficient charges over the past 18 months. Get a hydro meter to check the condition of these batteries.

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              • #8
                No the ac rarely gets used, they are a sealed unit 48 volt century marine battery

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                • #9
                  Originally posted by Beno View Post
                  No the ac rarely gets used, they are a sealed unit 48 volt century marine battery
                  Never heard of a sealed 48v battery. I think you are using some terms without knowing the common definitions.

                  Battery: A chemical storage device.
                  Battery Bank: A group of batteries wired together to form the equivalent of a larger battery.
                  Marine Battery: Not deep cycle, not starter battery, but a compromise of the 2 types.
                  Sealed: could be 3 things:
                  a) a plain flooded battery with chemical package to reduce water consumption
                  b) a sealed (VRLA) GEL battery (poor choice for RE applications because the electrolyte gel can be burned)
                  c) a sealed (VRLA) AGM battery (good performer, high charge & discharge rates, but shorter lifetime than flooded)
                  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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                  • #10
                    Century is an Australian battery company, their marine product line is listed here. 12 V batteries, so the configuration must be two parallel strings of 4?
                    Last edited by sensij; 11-09-2014, 03:23 AM. Reason: edit - bad guess
                    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                    • #11
                      solar.JPG
                      sorry guys my mistake, they are 12volt 200ah century sealed lead acid batteries, each capable of 2.4 kwh.

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                      • #12
                        Beno you are not really giving us much to go on. You have a battery bank of 48 volts @ 400 AH for a total capacity of 19.2 Kwh that can yield 4 Kwh per day on average or up to 10 Kwh for an occasional cloudy day or two. You have a 4000 watt solar panel array with an unknown charge controller, unknown location, and unknown daily Kwh usage.

                        All I can make of that is hope you have at least a 80 amp MPPT charge controller as that is the minimum a 4000 watt solar array should have. Only other thing I can say is you battery banks of 400 AH is too small for your panel wattage. With up to 80 amps of charge current the minimum size should be up around 650 to 700 AH. You are way short of that. If you have been discharging your batteries regularly to the point your system is shutting down from under voltage you have serious problems. One sounds like your batteries are ready for replacement from abuse. You have abused your batteries with too high of a charge current, over discharge them, and likely never have fully recharged them.

                        Now you have to figure out what else is wrong. We can help, but you have to provide that information so we can spot the problem. There are 3 things we have to know.

                        1. Your daily watt hour usage. That is the very first step one must know before even beginning to design a off-grid battery system. If you fail to do that, the system will fail every time.
                        2. Location and time of year use.
                        3. Generator size. You do have a LPG or diesel generator right?

                        I know this sounds tough, and it is, but we did not do this. You allowed it to happen. Just a wild a$$ guess assuming you have a minimum 3 Sun Hour day in your winter short months, your panels can generate roughly 10 Kwh of usable energy per day, but your batteries are only capable of giving you 4 to 5 Kwh per day so I already know you have a bad setup. What none of us know is what you need other than new batteries.
                        MSEE, PE

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                        • #13
                          Originally posted by Sunking View Post
                          Beno you are not really giving us much to go on. You have a battery bank of 48 volts @ 400 AH for a total capacity of 19.2 Kwh that can yield 4 Kwh per day on average or up to 10 Kwh for an occasional cloudy day or two. You have a 4000 watt solar panel array with an unknown charge controller, unknown location, and unknown daily Kwh usage.

                          All I can make of that is hope you have at least a 80 amp MPPT charge controller as that is the minimum a 4000 watt solar array should have. Only other thing I can say is you battery banks of 400 AH is too small for your panel wattage. With up to 80 amps of charge current the minimum size should be up around 650 to 700 AH. You are way short of that. If you have been discharging your batteries regularly to the point your system is shutting down from under voltage you have serious problems. One sounds like your batteries are ready for replacement from abuse. You have abused your batteries with too high of a charge current, over discharge them, and likely never have fully recharged them.

                          Now you have to figure out what else is wrong. We can help, but you have to provide that information so we can spot the problem. There are 3 things we have to know.

                          1. Your daily watt hour usage. That is the very first step one must know before even beginning to design a off-grid battery system. If you fail to do that, the system will fail every time.
                          2. Location and time of year use.
                          3. Generator size. You do have a LPG or diesel generator right?

                          I know this sounds tough, and it is, but we did not do this. You allowed it to happen. Just a wild a$$ guess assuming you have a minimum 3 Sun Hour day in your winter short months, your panels can generate roughly 10 Kwh of usable energy per day, but your batteries are only capable of giving you 4 to 5 Kwh per day so I already know you have a bad setup. What none of us know is what you need other than new batteries.
                          Those CC in his picture look like a Sunny Boy Island (yellow) and the (red) may be a SMA TL-US. But I am just guessing.

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                          • #14
                            Originally posted by SunEagle View Post
                            Those CC in his picture look like a Sunny Boy Island (yellow) and the (red) may be a SMA TL-US. But I am just guessing.
                            That was my point, we don't really have any useful information to help him out. The Devil is in the details. If it is grid interactive hybrid, he should never be using battery power, and way too much battery for hybrid.
                            MSEE, PE

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                            • #15
                              Again I'm sorry for the miss information, 8 x 12volt 200 ah clustered into 2 banks of 4 to create 2 x 48volt battery banks. Each battery capable of 2.4 kWh so in total 8 x 2.4 kwh = 19.6 kwh of storage. This is on a small getaway cabin. Which I might add has had no problems up until now with the load being drawn. I rent this out so im not there all the time but after further inquiries it was in fact a system shut down, which occurs to protect the batteries from overheating which is inbuilt into the sunny island. We have had some hot days lately
                              My home solar which is connected to the grid with the same panels and inverter creates 30+ kWh a day in the summer and 20+ in the winter. I am located on the Queensland, New south wales border in Australia close to the coast, sunshine isn't a problem
                              My original question was does the appliances use generated power first if available, I also found out today through sma and other solar people locally that yes it does and yes the batteries are ample for the required draw.
                              No I don't have a gas generator as I have not needed one, even when we have had wet weather the solar generates enough to fully charge the batteries. I am getting a gas autostart generator hardwired into the sunnyisland so if we do have extreme weather it will recharge the batteries when required as a back up.
                              I agree that I am no solar expert, however I trust the people who are qualified in this field and accept their recommendations.
                              In the morning the batteries are always in the 70% range and by lunch area at 95%,
                              I made a mistake when trying to explain the batteries and I apologise, but I was a bit taken aback by the condescending replies. when one must philosophise please don't quote the simpsons, it doesn't display high intelligence at all.
                              Anyway apart from ripping my "inferior" system to pieces, you might have said, Hey Beno, don't know much about SMA invertors or their equipment, (which you guys obviously don't) try to get help locally or ring SMA, which I did today. I didn't think that this was a p*ssing contest so thanks anyway guys problem solved

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