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  • #16
    Thanks again for the useful feedback.

    I already have my batteries, I should have mentioned that. I have four 24v 100ah lithium ion batteries. I was thinking 2s2p for 48v and 200ah. The modest budget comment was only for the solar system itself.

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    • #17
      Originally posted by sensij View Post

      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.
      Again I agree with you that the Trojan 225Ah system is both more realistic and hopefully within the OP's price range.

      The 330Ah was just a calculation based on the projected 33Amp of charging from a 1590w system using the C/10 value.

      Again not knowing exactly how the panels are pointed or what type of CC the OP was getting I would rather lean to the conservative side and not end up spending money on a system that does not provide what I want. Best way to kill off a battery system.

      What if the 2kWh daily usage requirement is an underestimation? Then that 225 AH system may be too small.

      Unfortunately (as you know) you can't start small and easily enlarge a solar / battery system. Best to over design up front then to have the lights go out when you need them.

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      • #18
        Originally posted by Gingerjames View Post
        I already have my batteries, I should have mentioned that. I have four 24v 100ah lithium ion batteries. I was thinking 2s2p for 48v and 200ah. The modest budget comment was only for the solar system itself.
        Does not compute. Lithium batteries are 3.2 volts. Are you saying you have 4 sets of 8S 100 AH cells? Total of 32 cells?

        Do not wire them as 2 or 4 strings. You connect Lithium batteries differently in a Ladder Configuration. Shown below as Alternative. DO NOT USE CONVENTIONAL on Lithium batteries. You will destroy them.



        Using Lithium batteries requires a different charge strategy and not many Charge Controllers will allow you to use them on Lithium batteries. You have a lot of challenges ahead of you like how you will initially charge them before putting into service. You will need a CC that you can set Bulk = Absorb = Float = 54.4 volts. Very few CC's allow you to do that, and limits your options.

        Additionally forget charge rates. On a 48 volt 200 AH LFP battery you can charge them anywhere between 20 and 200 amps. You are leaving out vital information. Everything up to this point does not apply.
        Last edited by Sunking; 05-17-2017, 04:35 PM.
        MSEE, PE

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        • #19
          Lithium batteries? Sheesh. Ignore everything I've posted in this thread. See Sunking's post immediately above to get started.
          CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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          • #20
            Originally posted by sensij View Post
            Lithium batteries? Sheesh. Ignore everything I've posted in this thread. See Sunking's post immediately above to get started.
            As I said. It is hard to know what an OP has and wants to do when they just provide a piece of the puzzle.

            Also with lithium batteries just about everything I posted about charging and battery size is not usable.

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