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  • Newbie off grid setup advice

    Hello!

    I have six 265w Hyundai mono solar panels and I'd like to build an off grid setup for some land I own. Would 24v (3p2s) or 48v (2p3s) be better? What amp rating mppt controller should I purchase? I am on a modest budget so any equipment recommendations are appreciated too.

    Thanks!

  • #2
    48 V battery? If so, 2P3S with a 30 Amp charge controller should be fine. Higher voltage keeps the amps down, and 3P would also need a fuse on each string (2P does not). Tracer/Epever 3210A is good on a budget.
    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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    • #3
      Originally posted by Gingerjames View Post
      Hello!

      I have six 265w Hyundai mono solar panels and I'd like to build an off grid setup for some land I own. Would 24v (3p2s) or 48v (2p3s) be better? What amp rating mppt controller should I purchase? I am on a modest budget so any equipment recommendations are appreciated too.

      Thanks!
      With 1590watts a 24volt system will require an 80amp MPPT CC. A 48volt system will require a 45amp CC or 60amp with room for expansion.

      Big question is what is your estimated daily watt hour usage? Without that information it will be hard to properly size your battery system.

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      • #4
        265 * 6 = 1590watts

        1590 / 24V = 66.25 amps
        1590 / 48V = 33.125 amps

        Your charge controller needs to be larger than those numbers.

        WWW

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        • #5
          Tracer 3210 is a 100 max Voc. 12/24 volt controller. Two strikes against 3s2p and 48 volt. Morningstar Tristar 45 amp MPPT controller is more appropriate.
          2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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          • #6
            Sorry, it was late. Yeah, the Tracer I suggested is only 24 V, no good for 48 V. However, it is a waste of money to buy more than a 30 A output.

            (Deleted mistake)

            An important question, what is the battery capacity? That will help inform charge current requirements as well.
            Last edited by sensij; 05-17-2017, 09:43 AM.
            CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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            • #7
              Originally posted by sensij View Post
              Sorry, it was late. Yeah, the Tracer I suggested is only 24 V, no good for 48 V. However, it is a waste of money to buy more than a 30 A output.

              Also 3S of 60 cell panels is fine on 100 V controller.

              An important question, what is the battery capacity? That will help inform charge current requirements as well.
              I agree that going with a higher amp rated CC may be a waste of money but if the OP has not calculated his daily watt hour load they may need more than 30amps because that 1590watts is not enough to charge a battery system to meet their needs. Then having a CC that is maxed out can be costly since you now need to get a bigger one.

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              • #8
                Originally posted by SunEagle View Post

                I agree that going with a higher amp rated CC may be a waste of money but if the OP has not calculated his daily watt hour load they may need more than 30amps because that 1590watts is not enough to charge a battery system to meet their needs. Then having a CC that is maxed out can be costly since you now need to get a bigger one.
                If we assume the system is reasonably balanced and sized for the OP's needs (rarely a safe assumption around here), the Windy Nation Trakmax 30L looks like a less expensive option for 48V than the TriStar suggested above.
                Last edited by sensij; 05-17-2017, 11:09 AM.
                CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                • #9
                  The OP is just guessing at what he or she needs. At any rate the expense of the controller is meaningless, it is what it is. No short cuts. The expense as with all off-grid systems is the batteries. At 1590 watts requires a 16 Kwh battery that weighs around 800 to 900 pounds and cost $1000 to $2000 every few years. It would be silly to cut corners using a cheap controller on an expensive set of batteries.

                  Best advice is to buy a Morningstar TS-MPPT-60. It an be configured for 24 or 48 volts. Configured at 48 volts will allow you to grow the system up to 3200 watts. At 24 volts is maximum capacity (1600 watts).

                  Makes no difference if you run 24 or 48 volts. Smart money is configure the panels 3S2P which require no expensive fuses or combiners, and use smaller less expensive wire. As stated the price of the controller is insignificant compared to the batteries. If budget is a huge concern then you could use the Morningstar TS-MPPT-45 and at 48 volts will allow you to grow to 2400 watts @ 48 volt battery. 24 volt is not an option on the 45 amp controller.
                  Last edited by Sunking; 05-17-2017, 11:42 AM.
                  MSEE, PE

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                  • #10
                    8 x T-105RE could be a decent less expensive option, if the OP can limit consumption to 2-3 kWh, and has the array in a location that can deliver enough to replace that.
                    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                    • #11
                      Thank you all for such useful info!

                      I was planning on a battery bank of 48v 200ah or 24v 400ah. I have a 12v fridge, some lights, and fans. A small tv or video games for the kids too. We mostly use it as a weekend getaway so I was guessing ~2kw/day, maybe less.

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                      • #12
                        Originally posted by Gingerjames View Post
                        Thank you all for such useful info!

                        I was planning on a battery bank of 48v 200ah or 24v 400ah. I have a 12v fridge, some lights, and fans. A small tv or video games for the kids too. We mostly use it as a weekend getaway so I was guessing ~2kw/day, maybe less.
                        Either the 48v 200Ah or 24v 400Ah system has a 100% rating of 9600wh. And if you only use between 20% - 25% you will have enough for that 2kWh a day load.

                        With that 1590 watt of panels and a 48V CC you should be able to generate about 33 amps which is a little fast for a 200Ah battery. You might look into getting a 48v 330Ah battery system. It would be more matched to your panel wattage and increase your available daily watt hour output to about 3kWh as well as allow you to stay at only a 20% DOD.

                        By the way you would have the same issue with a 24v 400Ah system where you could generate 66amp of charging which is again a little fast so again you would enlarge it to stay at a C/10 charge rate.

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                        • #13
                          Originally posted by SunEagle View Post

                          Either the 48v 200Ah or 24v 400Ah system has a 100% rating of 9600wh. And if you only use between 20% - 25% you will have enough for that 2kWh a day load.

                          With that 1590 watt of panels and a 48V CC you should be able to generate about 33 amps which is a little fast for a 200Ah battery. You might look into getting a 48v 330Ah battery system. It would be more matched to your panel wattage and increase your available daily watt hour output to about 3kWh as well as allow you to stay at only a 20% DOD.
                          You don't match components to panel wattage, that is backwards. Excess panel wattage is usually a good thing with quality mppt controllers, all of which are smart enough to regulate the array to stay within the controller's rated output.

                          The 8 x T-105RE design gives a 48 V x 225 Ah battery. That is a perfect match to a 30 A CC, powered by the 1590 W of panels the OP already has (in a 3S2P configuration).

                          From Trojan's site:

                          There are many types of chargers available today. They are usually rated by their start rate, the rate in amperes that the charger will supply at the beginning of the charge cycle. When selecting a charger, the charge rate should be between 10% and 13% of the battery's 20-hour AH capacity. For example, a battery with a 20-hour capacity rating of 225 AH will use a charger rated between approximately 23 and 30 amps (for multiple battery charging use the AH rating of the entire bank). Chargers with lower ratings can be used but the charging time will be increased.
                          Last edited by sensij; 05-17-2017, 02:45 PM.
                          CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                          • #14
                            Originally posted by sensij View Post

                            You don't match components to panel wattage, that is backwards. Excess panel wattage is usually a good thing with quality mppt controllers, all of which are smart enough to regulate the array to stay within the controller's rated output.

                            The 8 x T-105RE design gives a 48 V x 225 Ah battery. That is a perfect match to a 30 A CC, powered by the 1590 W of panels the OP already has (in a 3S2P configuration).

                            From Trojan's site:
                            I agree what I had suggested was backwards but if the person does not purchase a quality battery they could over charge it on some days.

                            Since the OP stated he was going for a 48volt 200Ah battery it is possible that they were looking at some cheap FLA and not the Trojan model that you suggested. Based on the quote " I am on a modest budget" leads me to believe money is an issue..

                            IMO 30 amps of charging can hurt a cheap FLA type battery system that is only rated for 200Ah. Given the Trojan is 225Ah and is a much better quality battery the 1590 watts would fall into their recommended charging range.

                            The last thing I want is for someone to destroy their battery because they can't afford a quality set or because they purchased a cheap off shore CC that does not have the controls to keep the batteries safe.

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                            • #15
                              Originally posted by SunEagle View Post
                              IMO 30 amps of charging can hurt a cheap FLA type battery system that is only rated for 200Ah. Given the Trojan is 225Ah and is a much better quality battery the 1590 watts would fall into their recommended charging range.
                              You are thinking that a 1590 W array will actually generate 30 A of charging for a meaningful amount of time. Once you account for actual irradiance and environmental conditions, controller and transmission losses, and the state of charge of the battery at those rare peak times, you'll find that 30 A isn't hit often enough or long enough to be much of a risk. Yeah, the 200 Ah the OP speculated is on the small side, but I don't know why you'd recommend jumping all the way to 330 Ah when a very attractively priced, high quality 225 Ah option is available.
                              Last edited by sensij; 05-17-2017, 03:12 PM.
                              CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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