Announcement

Collapse
No announcement yet.

Opinions on this system design please

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Opinions on this system design please

    My next home will need to be off grid and this is the system I have in mind. I've only ever built one off-grid system before and it was much smaller.

    Location: On the equator, min temp 5C max about 30C
    1400W array, 7x200w panels
    Tristar 45A PWM controller
    18x 70Ah 12V FLA batteries (chosen for price) total Ah at 24V = 630Ah

    Power use per day if we go crazy would be about 2.6kwh. We have lived in off grid before with only 1x 70Ah to sustain us so we do know how to conserve power if necessary.

    Will the array be sufficient for the battery bank?

    Is it crazy to have 18 FLA batteries to save some money rather than a few higher capacity sealed or FLA batteries? I already have 6 70AH batteries I can use, which is why I'm leaning towards 70Ah, in addition to the fact that they are the cheapest battery in terms of $/Ah.


    Panel spec sheet: http://www.ubbink.co.ke/ubbinkcoke/m...e.pdf?ext=.pdf
    Inverter ep1524: http://www.mustups.com/pure-sinve-wa...ep3000-series/
    Last edited by choob; 02-08-2016, 08:08 AM.

  • #2
    Forget the PWM controller and get an MPPT. That will allow you to reduce the array size some to help offset the cost.

    If you want a 630AH battery bank then but 630AH batteries. That 9 strings of batteries would be an accident waiting to happen. No way to get a balanced charge into all strings so you'd easily be cutting there live in half. Also look at the number of cells. Do you really want to do maintenance checks on that many cells? One string means you have 12 cells to check. 9 strings would be 108 cells.

    WWW

    Comment


    • #3
      Listen to White Wolf. You do not want to wire that many batteries in parallel. They will not last as long as the manufactured indicated. Use higher Ah rated / lower voltage batteries to build your 24v 630Ah system.

      If you do decide to go with a MPPT type CC (which I also recommend) you will need one that can handle 60Amp for that 24v battery system.( 1400 watt / 24 volt = 58.3 amps).

      Comment


      • #4
        PWM CC is unfortunately the only option as I already have it.

        I hear you on the battery bank...just wiring it would be a headache.

        The morningstar website states that a 1400W array is 'optimal' for the 45A tristar, but won't the current be too high? Or is it different for PWM?

        Comment


        • #5
          Wrong batteries, wrong battery bank voltage, wrong CC. I notice you are outside US, If those are the only batteries you can get, wire them as four banks of 48 volts and get an appropriate inverter. and use the extra batteries for something else. In a perfect world, you would do better with 8 L16's 6 volt and even better would be 24 L16's 2 volt. I have learned it is much harder to get products in some remote parts of the world. and that some countries charge huge import tariff's. Good luck.
          4X Suniva 250 watt, 8X t-105, OB Fx80, dc4812vrf

          Comment


          • #6
            Originally posted by choob View Post
            PWM CC is unfortunately the only option as I already have it.
            There is nothing we can do to help you. You made way too many fatal mistakes.

            1. You have 7 Grid Tied Panels of 200 watts each. That gives to 2 unsolvable problems.
            a). 7 is a prime number which means you only have 1 option of wiring all of them in parallel.
            b) Grid Tied panels require a MPPTcontroller. That means you are changing your 1400 watt panels into less than 900 watts.

            2. You will destroy your batteries in a short time. Using 12 volt batteries was fatal mistake for which you cannot fix. A 630 AH battery must have a minimum 55 amps of charge current. At very best you will only have 38 amps.


            MSEE, PE

            Comment


            • #7
              The panels are off-grid, don't have them yet.

              12V batteries is ALL that is available here. Don't have batteries yet either.

              All I have at the moment is an older system of 3x200W panels, 1500W 24V inverter, 45A tristar PWM and 6x cheap 70Ah FLA batteries which can be sacrificed. This was running lights and a small pump but the pump will be replaced with a solar unit and the lights only need a small system.

              Comment


              • #8
                Actually they also have 2V batteries.

                Comment


                • #9
                  Just to clarify - I haven't bought anything yet! I would preferably like to reuse my Tristar CC, inverter and 3x200W panels to save cost but if you have a better idea how I can cover these needs please tell me before I pull out my wallet and make a real mistake.

                  Comment


                  • #10
                    Then don't buy anything, read the wiki's and ask lot's of questions and expect some smart remarks. Hold onto your cash until you better understand what you need and are getting into. 12volts is for cars and toys. your system will need to be 48 volts. don't buy any 12 volt junk and stay away from car batteries, you need real quality deep cycle batteries.
                    4X Suniva 250 watt, 8X t-105, OB Fx80, dc4812vrf

                    Comment


                    • #11
                      Yes, done all that.

                      These are 12V solar batteries. 48V not an option - no inverters available locally for under $1000. 24V is possible.

                      No offence but you're not really reading what I'm writing, I don't know why you think I'm using a 12V system?

                      I have limits on what I can get locally, it's all very easy to write out on paper what you want, but what I'm trying to do is figure out what is actually *possible* with what's realistically available.

                      According to what I've read MPPT advantages over PWM in hot areas is minimal, is this wrong?

                      Not to be churlish, but please, I'm not using a 12V system or car batteries or grid-tie panels.
                      Last edited by choob; 02-08-2016, 12:57 PM.

                      Comment


                      • #12
                        Originally posted by SunEagle View Post
                        Listen to White Wolf. You do not want to wire that many batteries in parallel. They will not last as long as the manufactured indicated. Use higher Ah rated / lower voltage batteries to build your 24v 630Ah system.

                        If you do decide to go with a MPPT type CC (which I also recommend) you will need one that can handle 60Amp for that 24v battery system.( 1400 watt / 24 volt = 58.3 amps).

                        Thanks, I can also get 2V batteries locally, so you would recommend 12x 2V batteries in series over strings of 12V batteries?

                        Comment


                        • #13
                          if you can only get a 24 volt inverter where you are then the 2 volt batteries may/could work for you. but you will need a lot of solar panels to charge them. 6 volt L16 style would be better. you need to make sure you know all of the product's avail to you before you decide. yes 48 volt inverters are expensive here too. if you can get a good one for 1k I would jump on it. for the size of system you desire, 600amp hrs or so, you are looking at the wrong equipment. unless that is truly all that is avail. If you have access to the grid stick with that.
                          4X Suniva 250 watt, 8X t-105, OB Fx80, dc4812vrf

                          Comment


                          • #14
                            Originally posted by choob View Post


                            Thanks, I can also get 2V batteries locally, so you would recommend 12x 2V batteries in series over strings of 12V batteries?
                            Yes. A series wired battery system will always be a better option then any parallel wired system.

                            The biggest advantage of an MPPT over a PWM is the increased efficiency.

                            A MPPT is Watts in = Watts out. So your total panel wattage can be converted into a higher amount of charging amps for your battery system. (1400 watts / 24volt = 58.3 amps)

                            A PWM is Amps in = Amps out. So your total panel wattage will be reduce by ~ 1/3. Panel Imp = 5.7A. Total input amps = 5.7a x 7 = 40amps. 40 amps x 24volt = 960 watts which is ~ 68% of that 1400 watt system.

                            Oh last clarification. A panel that generates more that 24volt (like the ones you have) are considered Grid Tie panels as opposed to be a Battery Panel.
                            Last edited by SunEagle; 02-08-2016, 01:20 PM. Reason: added last sentence

                            Comment


                            • #15
                              Ok, thanks, that clears things up a bit.

                              Strange about the grid-tie thing - the manufacturer specifically markets them as off-grid panels. Could be a regional thing? They're locally made for local conditions.

                              Comment

                              Working...
                              X