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Got my Little Starter Off-Grid 2.5+Kw System about where I want it

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  • #31
    Originally posted by Sunking View Post
    I must be missing something. Why would you pay 60-cent to $1 per Kwh using power from batteries, when you could buy it from the POCO for 15 cents. Do you like throwing and giving money away?
    I guess there is no other real answer to this than to say "Hobby". I really just enjoy learning all about this tech and what can be done (or not done) with it. I got into the "Hobby" after the last 2 storms and wanted to see what could be done. I realize I will never save any money doing a solar thing - and it is a laugh to think a person is "saving" the planet. About as funny as electric cars.

    So now that it is up and running, I guess I could just flip on the AC line, use the batteries occasionally and keep them on float until the next natural disaster, EMP or whatever.

    But something else I have been wondering about charging. I follow many of your comments on the forum, And you and I have discussed charging before. But I noticed the other day you mentioned to someone about charging their 24v system at the recommended Trojan volts of 29.4v (or something close to spec). I am still not getting 100% of my Trojans unless I up the voltage to 31v in Bulk/Absorb. They do get charged fully (SG tested) but only if I use the higher voltage. Is that a problem?
    Last edited by Matrix; 12-09-2017, 04:20 PM.
    285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

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    • #32
      Originally posted by Matrix View Post
      But something else I have been wondering about charging. I follow many of your comments on the forum, And you and I have discussed charging before. But I noticed the other day you mentioned to someone about charging their 24v system at the recommended Trojan volts of 29.4v (or something close to spec). I am still not getting 100% of my Trojans unless I up the voltage to 31v in Bulk/Absorb. They do get charged fully (SG tested) but only if I use the higher voltage. Is that a problem?
      No it is not a problem, just a misconception. You can fully charge your batteries at 27 volts aka FLOAT

      Tere i snot a data company, telephone company, communication facility, electric utility, or any other professional operation that would use Bul/Absorb to charge batteries. Their batteries are mission critical and way too expensive to put them through that kind of abuse. If they did that they would be like you and have to replace them every few years. There are FLA batteries that last 50 years and every one of them Float Charge batteries. A 24 volt plant depending on actual battery chemistry floats from 27.0 for FLA and up to 27.2 volts for AGM.

      The reason solar or really any daily cycle battery uses higher voltages of Bulk/Absorb is time, and you do not have the luxury of time, you only have in reality 4 hours. To Float Charge a fully discharged battery, you can use as low as a C/20 charge rate or in excess of 1C. Makes no difference, it takes 24 hours to saturate a battery on what is called a Float Voltage.

      Do not be confused by fancy technical terms like Float, Bulk, Absorb, Equalization, Refresh or whater the marketing department calls it. They all use the exact same circuitry. The only difference is the voltage, A Float charger has a Bulk stage it is just not called Bulk, it is called what it really is, Constant Current, all the other fancy names are Constant Voltage. Every battery charger made has a Constant Current and Constant Voltage phase. It is just the way the current and voltage regulators work. No magic a 14 year old kid can make a battery charger. I made lots of them at age 14 and up. Sold them to ham radio operators.

      Here is the deal, it is called Gassing Voltage where the water electrolysis occurs and the water is split into hydrogen and oxygen. Nasty things happen when you gas batteries. It corrodes and warps the plates, and waste water. So much water it can expose the plates which spells death. So in a solar system, you do not have time to wait for the battery to saturate, you have to force it in by turning up the voltage, which forces the charger to stay in CONSTANT CURRENT longer before switching to Absorb aka Constant Voltage until current stops flowing when the battery saturates. That is why you cannot use voltage to set the charger voltage. You have to keep cranking the voltage up until your hydrometer says it is fully charged. Gassing voltage is roughly 2.34 to 2.4 volts per cell so on a 24 volt battery is 28 to 28.8 volts. Float chargers stay at 27 volts and never touch gassing voltage. You on solar go way beyond that, and doing so destroy your battery in the process.

      If all you want is Emergency Power, then do what every pro does, Float Charge your batteries at 27 volts 24 hours a day and never use them until needed. Do that and they wil last at least as long as the warranty period or longer. Otherwise you are making your battery supplier very happy selling you new batteries every few years. They laugh all the way to the bank on what you do not know.

      Those $1000 dollar batteries if you utilize them every day will return you $200 to $400 dollars worth of electricity. If you use them as emergency power will return as low a $0 because you never use them, or a few dollars worth if used once in a while. Utilities and pros only design their battery banks to run for 15 minutes to 4 hours. If the outage last longer than that is what they have generators for, much less expensive and more reliable than batteries or solar. Most sealed AGM utilities use last 10 years, and FLA up to 50 years using a pure lead design. If they used them every day less than a year.
      Last edited by Sunking; 12-09-2017, 05:12 PM.
      MSEE, PE

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      • #33
        Originally posted by NEOW View Post
        Do you have any solar coming in? I'm not familiar with how the com box will monitor a non Schneider charge controller, which leads me to the question as to the possibility that using their Xanbus MPPT controller would alter the situation. The XW is about a grand more last I looked for the 5KW model. It also about twice the weight.
        Yes I do have solar coming in, about a 2000w array this time of year (array is rated for 2.5kw). Yes the Xanbus MPPT would be better and would show on the Schneider combox display, but I do not think it would help with the AC support mode issue.

        Originally posted by NEOW View Post
        The way you are setup it's totally up to SOC correct as to what the SW will do in regards to load shedding, correct?
        It's not so much how I am set up, but rather that is how the SW is supposed to work. But you are correct, it is up to the SOC or if you do not have the battery monitor it is up to the battery voltage

        Originally posted by NEOW View Post
        I think your display says generator because the SW is considered an off grid unit isn't it?
        Not sure as the SW is billed as a off-grid and grid-support system.

        Originally posted by NEOW View Post
        In my case I want to totally disconnect from the grid at peak times and run directly off solar and my small battery bank. So I may just use a whole house generator xfer switch, I have central AC that is normally turned off during peak hours so when they're not running I don't have any large loads.
        You actually can just use the breaker for the AC Line in as the transfer switch between Line AC (be it Grid or Generator) and the Solar / Battery system for Off grid as the SW has an auto transfer switch for that purpose built in ... you may need a gen breaker lock switch if (back feeding gen power into a main load panel) or a gen transfer switch between the grid and the gen if you want to control where your external power source is coming from. I used the Reliant 6 circuit switch to be the transfer between Solar and Grid (see pics on page 1) but it is actually made to be a Gen transfer switch.

        285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

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        • #34
          Originally posted by Sunking View Post
          No it is not a problem, just a misconception. You can fully charge your batteries at 27 volts aka FLOAT

          The reason solar or really any daily cycle battery uses higher voltages of Bulk/Absorb is time, and you do not have the luxury of time, you only have in reality 4 hours.
          Thanks again, Always a wealth of knowledge, whether I have asked the question or if it was others, I always come away more informed when reading your responses.

          Just to be clear, I have to use 31v NOT because I run out of time, but rather because the charge (be it solar or my inverter/charger) kicks off and "thinks" I am at 100% when I am actually only at about 1.250 SG (or about 90%). I have the absorb time set to way more hours than the charger ever uses and the amps are set at C13 ... but unless I use about 31v the batteries never reach 1.277 SG or 100%.



          285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

          Comment


          • #35
            Originally posted by Matrix View Post

            Thanks again, Always a wealth of knowledge, whether I have asked the question or if it was others, I always come away more informed when reading your responses.

            Just to be clear, I have to use 31v NOT because I run out of time, but rather because the charge (be it solar or my inverter/charger) kicks off and "thinks" I am at 100% when I am actually only at about 1.250 SG (or about 90%). I have the absorb time set to way more hours than the charger ever uses and the amps are set at C13 ... but unless I use about 31v the batteries never reach 1.277 SG or 100%.
            That is because you are cycling? Not sure what Inverter you are using, but if you set it up to only use battery power when there is a power outage only, you can float the batteries at 27 volts.


            MSEE, PE

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            • #36
              Originally posted by Sunking View Post

              That is because you are cycling? Not sure what Inverter you are using, but if you set it up to only use battery power when there is a power outage only, you can float the batteries at 27 volts.

              The charger is the SW 4024 Inverter/charger. Highly customization, can be set up to 90 amps. I use 54 amps which is C13 of the 435 ah batteries (I think). When on solar it is the MidNite Classic 150 and the array in full sun will supply about 64 amps to the batteries.
              285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

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              • #37
                While thinking about charging, got to wondering about my battery bank and using a busbar. I have 4/0 battery cable for the 24v system to the 3400 watt inverter. But inside the battery box I was thinking about adding a busbar so I could add to my 4 batteries that are now in series, by adding 4 more in series for a total of 8 batteries 4s/2p. Never mind the whole "you cant add old and new batteries", dont plan to. BUT is this bus bar large enough to be equivalent to the 4/0 cable for making the main connection and the 2 "break-off"parallel connections to the sets of series batteries?

                These are rated
                • Max Amperage: 250 Amps at 12VDC per connection
                • Max Voltage: 48VDC



                The bus bar in this unit is about 2.5mm thick x 19 mm wide (not the plastic part) . The total dimensions are : (with cover): 6.6 x 1.4 x 2.0 inch (168 x 35 x 50 mm)


                busbar.jpg
                Last edited by Matrix; 12-09-2017, 06:00 PM.
                285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

                Comment


                • #38
                  Originally posted by Matrix View Post
                  . I use 54 amps which is C13 of the 435 ah batteries (I think).
                  FWIW C13 would be 5655 amps. C/13 = 435 AH / 13 hours = 33.46 amps.

                  54 amps on a 435 AH battery would be 435 AH / 54 Amps = 8 hours or C/8

                  MSEE, PE

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                  • #39
                    If you use a buss bar is fine but requires 3 fuses. One on each battery term post feeding the buss bar, and one on the buss bar feeding distribution. Or you can do something like this without shunts and different sized fuses to match your application.




                    Last edited by Sunking; 12-09-2017, 06:20 PM.
                    MSEE, PE

                    Comment


                    • #40
                      Ok ... thanks
                      285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

                      Comment


                      • #41
                        OK ... looking at the SW, it does not have what appears to be a Constant Float charge. It has
                        1. Three stage charge that ends in float,
                        2. A recharge voltage setting that is user definable by voltage and sets the voltage at which the charging starts.

                        So could I "trick" the charger by setting all 3 stages, Bulk, Absorb and Float to 27.2v and set the start voltage to ???? I dunno ... 27.1v?

                        Would that keep it in a constant or near constant float state?
                        285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

                        Comment


                        • #42
                          Originally posted by Matrix View Post
                          Ok ... thanks
                          You are welcome.
                          MSEE, PE

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