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What Do I Need for Batteries?

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  • What Do I Need for Batteries?

    Hi there. I posted a couple of weeks ago on an off grid cabin that I purchased. We finally closed, so I was able to get more details on what the current set up is, etc.

    Current system is a 250 watt panel that runs to 2 6v Duracell GC2 batteries, set up as 12 volt and just running into the cabin as DC.

    I just ordered 3x270 watt panels to add to the system, and am looking at inverters now as well and will probably get a 5,000 watt one so I have room to expand.

    I would like to have everything setup as 24v.

    Could someone please help guide me on what I should be looking at for a battery setup? I'm trying to balance quality and price, so probably looking at mid-range and I want to make sure that I am not wasting anything that my panels are collecting.

    Thanks in advance, and I apologize for any ignorance. I am trying to read as much on this forum as quickly as possible to get up to speed.

  • #2
    Well my first question is what type of CC do you have? For a quick math you need about 1/10th the battery system Ah rating for proper charging.

    With over 1000 watts of panels you will need at least a 40amp CC for a 24V 400Ah battery system.

    As for the inverter. Going bigger can be a problem because they are not efficient and just being turned on without any load that can use 10% of their watt rating. Also a 5000watt inverter connected to a 24V battery system will need wire and fuse that are good for over 200Amps. Those are pretty big and are hard to terminate.

    With a 24V 400Ah battery I would use an inverter closer to 1500watts depending on what your load is.

    As for not using all of what your panels can produce. That is a moving target because there will be some days that you won't use it all and other days you do not get enough. It is best to just concern what your batteries need to be properly charged and do not worry about what is "wasted".
    Last edited by SunEagle; 03-31-2020, 01:06 PM.


    • #3
      Thanks SunEagle! My charge controller is a ProStar PS-30M...which I'm seeing is 30 amps, so that is now on my shopping list as well

      So, at this point, I guess I am looking for recommendations on:

      - Charge Controller >40 amps
      - Inverter (~1500 watts)
      - Proper batteries


      • #4
        Before you build up anything, you must establish what your loads will be. Otherwise, you build too small of a system (it will fail quickly) or too large (wasted $$)
        Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
        || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
        || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A