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  • #16
    Originally posted by Sunking View Post
    That is one of the Niche applications I did not mention. I just want to make sure you make an Informed decision and know what the pros and cons are.

    Good luck to you.

    BTW the coffee in Panama is every bit as good as Kona. It is really cheap here as I live right in the middle of the farms that grow it. Originally I was not much of a coffee drinker until moving here. Personally I put Kona Hawaii, Jamaica Blue Mountain, and Boquete Panama coffees best in the world. Those are the only three I really like enough to drink every day.
    Thank you for watching my back... ( as I sit here drinking my 2nd cup of Kona for the day)

    Actually, most coffee labeled Kona is a blend with coffee from other parts of the world...
    Blends usually contain only the minimum required 10% Kona coffee and 90% cheaper imported beans.

    I feed my java-junkie the blend, since pure Kona coffee cost about 4x as much.
    [CENTER]SunLight @ Night[/CENTER]

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    • #17
      One thing I use for IR is a relatively inexpensive meter, a Centech 66892 digital battery analyzer:

      http://www.bobistheoilguy.com/forums...Number=2490373

      I use it solely for the IR measurement, and do not care a thing about the CCA. Nor do I have to set a specific CCA to get the IR to read properly. Yes, it is built like a toy. And kind of smells like one too.

      It is not a high-end midtronics, nor a lab-grade instrument, BUT is is valuable for watching baselines and trends. Fortunately, for the Odysseys and Optima AGM's I've used them on, the IR was pretty close to spec. I have not used these on very small ups-style agm's.

      What it can provide are clues to possible problems down the line that your charger / controller may not catch, like high-resistance / poor welds etc on the inside.

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      • #18
        Originally posted by Sunking View Post

        A 24 volt 400 AH battery IR in good condition in a discharged state should be able to take 200 amps or more charge current to even rise the voltage of 1 volt which would be on the order of 1 volt / 200 amps = .005 Ohms. A battery that rises 2 volts with only 20 amps means the IR = 2 volts / 20 amps = .1 Ohms which means way beyond dead battery.

        Guess what time it is?

        Quit using batteries and go back on the grid. Grid power is much less expensive than batteries.

        Question back at you. Why have not you been using an AC commercial charger to charge your batteries or a generator? Every battery system is required to have a generator or AC power with a charger. It would have prevented pre-mature death?
        The reason I have batteries and do not use the grid is because I want to have back-up capability for power failures too.

        I'm still not totally convinced these batteries are duff yet - after 2 hours under a load of 20 amps a sudden increase to 50 amps does not cause more than a 0.2 volt drop. This would suggest a maximum IR for the battery pack of 0.007 ohms which doesn't sound too bad.

        I'm just concerned that they are not reaching full charge due to the short winter days. Also they are not true deep cycle batteries, they are a hybrid type (Silver Calcium). The manufacture specifies a maximum occasional DOD to 80% and a cycle use DOD to 50%. They are warranted to provide at least 250 cycles to 50% DOD by the manufacturer. I have at most cycled them 30 times since purchase. I dont expect miracles from these cheap batteries, I just want to learn the ropes with them, hopefully for at least a year so that I have some experience before buying the expensive ones later on.

        Does this type of battery have the same set of rules as a true deep cycle?

        D

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        • #19
          Originally posted by Dave3011 View Post
          I'm just concerned that they are not reaching full charge due to the short winter days.
          Dave this is one reason why an off-grid battery system or a Hybrid System requires a generator. It sounds like you have a hybrid system. In a Hybrid System the batteries are charged with commercial line power from the Inverters built-in charger. The power may come from the grid if the panels are not producing enough power, or if the panels are producing excess power it may go to the batteries. Really does not matter as it is autonomous. Point it is comes from AC power via the Inverter's built-in AC battery charger and the batteries are never used except in an outage. Once charged up the batteries set there in Float and collect dust. When a commercial power outage happens, then power comes the batteries, and the batteries are charged up from solar and a generator if the panels cannot keep up.

          What I am trying to tell you is your system appears to be setup completely wrong and used improperly.
          MSEE, PE

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          • #20
            Originally posted by Shockah View Post
            The one and only reason I use AGM is because I am not able to maintain FLA batteries in all of the installations.
            Most are atop posts... where it is not advisable to be removing caps and checking acid levels
            I'll have to respectfully disagree with Sunking about it being solely for niche situations, but if you are dealing with limited time, and limited solar insolation, then consider that AGM has less internal resistance than FLA. That means you can get out of bulk faster. An FLA is limited to about C/8 max current charge. A conventional agm like a Deka is limited to about C/3 max. If you have the panel power, and your project budget can afford it, it MAY bet the better choice.

            Quick napkin-calc for conventional agm: AH withdrawn / amperage of charger * 1.78 (includes inefficiency) = hours needed to complete charge. Well, get to float anyway.

            In extreme cases, going to pure-lead like Enersys Odyssey, Concorde, SBS or similar removes that C/3 limitation altogether, but that means your panel array would be ridiculously huge. Still, for small projects, this may be the only way to go.

            I'm not saying Sunking is wrong, but I am saying keep your options open since you are encountering a wide variety of situations.

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            • #21
              Originally posted by PNjunction View Post
              I'll have to respectfully disagree with Sunking about it being solely for niche situations, but if you are dealing with limited time, and limited solar insolation, then consider that AGM has less internal resistance than FLA. That means you can get out of bulk faster. An FLA is limited to about C/8 max current charge. A conventional agm like a Deka is limited to about C/3 max. If you have the panel power, and your project budget can afford it, it MAY bet the better choice.

              Quick napkin-calc for conventional agm: AH withdrawn / amperage of charger * 1.78 (includes inefficiency) = hours needed to complete charge. Well, get to float anyway.

              In extreme cases, going to pure-lead like Enersys Odyssey, Concorde, SBS or similar removes that C/3 limitation altogether, but that means your panel array would be ridiculously huge. Still, for small projects, this may be the only way to go.

              I'm not saying Sunking is wrong, but I am saying keep your options open since you are encountering a wide variety of situations.
              Yes, PNJ... good point.

              In fact I did use AGM on an installation simply because of that...
              but I don't go more aggressive than C/4 with AGM.

              It is a 105ah battery in a location that might get morning shading in the winter from south-east tall trees... no trees to the west though.
              So I had to design it to charge quickly with a worse case scenario of 2 sun hours.
              I used a 260watt panel with MPPT CC. I would not have been able to use such a big panel with an FLA.
              [CENTER]SunLight @ Night[/CENTER]

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              • #22
                Sounds like a good plan. Conventional agm's like a good quality East-Penn / Deka can withstand 0.25C no problem. It also means that since you aren't really deep-cycling it every day, you'll get to float faster, which agm's require, unless you compensate by setting the float voltage the same as absorb. Provided you don't exceed the manufacturer's time limit on staying in what is effectively and endless absorb before the sun goes down. Temp comp of course.

                You are definitely on the right track!

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                • #23
                  All I know from living with batteries and SOC for a year now, is that SG is everything. Voltage is a working system is useless as a measure. Often, I only get to 80% charge due to clouds etc, i,e 1240 odd SG and battery voltages on the mppt and inverter and mulitmeter all indicate a 100% full batt.

                  They are wrong, as we know, voltage reading are only useful on standing batteries and then still you dont know if they can take a load, while SG tells you everything you need to know, SG at spec is a healthy batt, or so I am to understand. So only SG seems to be reliable way of determining SOC.

                  So if you buy sealed (as a friend has, who is battling to figure if he's batts are still ok) you cannot know with any certainty whats up or down.

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