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  • 48v system what volt panels to match up

    I am interested in putting in a 48 v system to operate my home off.

    We have been using 640 kw per month average and have been making changes to limit usage i.e. all led lights and new energy star refrigerator.

    My question is does it matter what voltage the panels are to match up to the 48v battery bank?

  • #2
    Originally posted by Douglas View Post
    My question is does it matter what voltage the panels are to match up to the 48v battery bank?
    It is extremely important. Last thing you want to use is 12 volt battery panels because they cost anywhere from $2/watt up to $6/watt. Higher voltage grid tied panels cost from less than $1/watt up to $1.25/watt. Today above 200 watts in panel would be extremely foolish to even consider using 12 volt battery panels like the Tasman.

    Secondly you want the voltage to be as high as your MPPT can use efficiently to save on wiring and hardware cost between the panels and controller. The difference can be using wire that cost 50 cents per foot or $1.50 per foot. The higher the voltage, the less expense and higher efficiency. If you use 600 Kwh per month you are looking at 8000 to 12,000 panel watts and two or three very expensive charge controllers. Minimum panel voltage required for 48 volt battery is 72 volts, but most controllers work most efficiently at 100 to 120 volt input. Some can go as high as 550 volts.
    MSEE, PE

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    • #3
      semantics labeling?

      Why do people call them grid tied panels?

      Can you not use the higher watt panels on any system as long as you use mppt charge controller.

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      • #4
        Originally posted by Douglas View Post
        Why do people call them grid tied panels?

        Can you not use the higher watt panels on any system as long as you use mppt charge controller.
        Yes, although the wattage doesn't matter, the voltage is how they are grouped. That is why some have starting calling the common 60 cell panels being made now "20V", instead of grid-tied. Since grid-tied can also mean 72 cell, 96 cell, or some other non-standard design, it is really a category type more than an individual panel type. Mostly, grid-tied is meant to distinguish that category from 12 V and 24 V panels, which are designed specifically to be compatible with PWM battery applications, and tend to be more expensive per W
        CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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        • #5
          Originally posted by Douglas View Post
          Why do people call them grid tied panels?
          To distinguish them from low voltage high cost battery panels. Battery panels are 36 cell panels. That means the vmp voltage is fixed at 18 volts, and with only 36 cells the highest power you are going to find is around 160 watts. In the early days of solar panels from the 50's up until early 90's solar systems were based on 12 batteries using 36 cell panels. The advent of Switch Mode voltage regulation, and the use of Grid Tied applications allowed and demanded much higher voltage applications. A grid tied system system voltages run as high as 1000 volts in Europe, and 600 volts here in the USA consumer market. It takes a lot of 100 watt 12 volt battery panels to do that. Much easier and economic with larger wattage and higher voltage.

          Grid Tie or high voltage panels are made from 50 to 80 cells and the voltage and wattage are are higher from 25 to 40 volts and wattage from 200 to 350 watts. In addition to cost per watt differences, the grid tie panels allow you to use far less wiring and hardware. Higher voltages means lower current and smaller wires. Higher voltages also means less power losses on wiring.
          MSEE, PE

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          • #6
            I am still trying to get my head around the plan of the OP to have batteries to lower his power bill.

            He should certainly look into a "grid tie" system with a legal "grid tie" inverter before he even should think about batteries.

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            • #7
              Originally posted by SunEagle View Post
              I am still trying to get my head around the plan of the OP to have batteries to lower his power bill.
              Let him learn the hard way with his money. He will never forget the lesson.
              MSEE, PE

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              • #8
                Originally posted by SunEagle View Post
                I am still trying to get my head around the plan of the OP to have batteries to lower his power bill.

                He should certainly look into a "grid tie" system with a legal "grid tie" inverter before he even should think about batteries.
                I did not write that I was looking at batteries to lower my power bill. You in your own mind are making assumptions because you believe you are incredibly intelligent and every one else including me. Is dumb. I am looking into a high bred grid tied with battery system. I do understand the cost and time for replacement.

                I was a member on this forum six months ago and stopped coming for a while because I was disgusted at the pompous ass persons acting smuggly not wanting to explain hard learned lessons to newbies. It is really to bad that you will not be helpful and share your infinite wisdom. Please start at the top re read and restate your platitudes or Piss off. I am not gaining any knowledge which is what I came here for.

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                • #9
                  Originally posted by Douglas View Post
                  I am interested in putting in a 48 v system to operate my home off.

                  We have been using 640 kw per month average and have been making changes to limit usage i.e. all led lights and new energy star refrigerator.

                  My question is does it matter what voltage the panels are to match up to the 48v battery bank?
                  You can use any panels, AS LONG as the voltage is at least 65-70V at load (Max Power). This will allow for voltage droop as panels heat up and loose voltage. You have to have at least 65V at the controller input terminals to have enough voltage for EQ . A 75V array would be a safe bet. And you can use a MPPT controller, and feed 200V to the controller as I do. Above 200v, the downconversion losses in the controller start to swamp out the gains of running high voltage/low amps. (That's all covered in the MPPT FAQ
                  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
                    Originally posted by Douglas View Post
                    I did not write that I was looking at batteries to lower my power bill. You in your own mind are making assumptions because you believe you are incredibly intelligent and every one else including me. Is dumb. I am looking into a high bred grid tied with battery system. I do understand the cost and time for replacement.

                    I was a member on this forum six months ago and stopped coming for a while because I was disgusted at the pompous ass persons acting smuggly not wanting to explain hard learned lessons to newbies. It is really to bad that you will not be helpful and share your infinite wisdom. Please start at the top re read and restate your platitudes or Piss off. I am not gaining any knowledge which is what I came here for.
                    Well Douglas. I am not calling you dumb.

                    Although I was confused by how you asked your question because all you mentioned was what you use in kWh and how you were reducing your load with LED lights and then asked what type of panels are needed to run your home from a 48volt battery system. So I put 2 & 2 together believing you wanted to use solar to save on your electric bill and felt a battery system was necessary to do that. So maybe my math was wrong and instead of 4 I got 5. So I apologize for jumping to a conclusion with my answer and misunderstanding.

                    Now that this misunderstanding out of the way. I wonder why you used the same type of response that you were so disgusted with concerning the "smug and pompous" answers you read a few months ago. While I didn't understand your question I do not believe I was rude or degrading with my answer so I am a little set back to have your anger thrown in my face. For that matter I thought I provided an option concerning the more economical use of grid tie solar.

                    So with that behind us I would suggest you hang around and ask more questions on how to build the best solar hybrid system to meet your needs. You will get some good data and maybe also some not so friendly answers. I will suggest that you try to be less thin skinned and just ignore what you do not like and get through the noise to what is underneath.

                    Take a breath and cool down. Getting angry will only raise your blood pressure.

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