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How many batteries with a 160 watt solar system?

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  • How many batteries with a 160 watt solar system?

    I have enough solar panels to equal 160 actual watts of output in fairly bright sunlight. I also have a Xantrex controlled that can handle up to 60 amps of input current.

    How many deep cell batteries can I charge with this setup based on a very light load?

  • #2
    Depends on your location. If you live up north only around a 75 AH battery at 12 volts, up to 150 AH if you live in Arizona.

    What do you mean by a tight load? Systems are designed around the amount of power you use in a day and your location.
    MSEE, PE

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    • #3
      I was hoping you would say 5-6 deep cycle batteries lol. I live in the high desert of California. Lots of sun. What I mean by light load is that I will not put any draw on the batteries at all for weeks at a time.

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      • #4
        Originally posted by tundrawolf View Post
        I was hoping you would say 5-6 deep cycle batteries lol. I live in the high desert of California. Lots of sun. What I mean by light load is that I will not put any draw on the batteries at all for weeks at a time.
        Sorry to disappoint you but it is a simple physics problem.

        You say high desert but that does not answer the question of your solar insolation. But for argument sake let's say you get a 4 Sun Hour Day. The most power your 160 watt solar panel array generate in a day with a battery system is 160 watts x 4 hours x 66% efficiency factor = 422 watt hours at best.

        Ok to size the battery properly you select a size based on 20% discharge per day. So with 422 wh we can multiply by 5, so 422 wh x 5 = 2110 wh capacity. Now to find the battery amp hours all you have to do is divide by the battery voltage so 2110 wh / 12 volts = 175 Amp Hours.

        So as you can see from the example you design based on your daily power requirement and location, not buy something and pray it works.
        MSEE, PE

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        • #5
          Looking at it another way, 160W of panels, gives you 130W of power (after de-rateing) at 14V, (standard charging voltage) thats only 9.2 amps. That would maintain 9, 100ah batteries, but if a battery is discharged, you would not have enough power to recharge it before it begins to sulphate, and degrade, from not being charged. Might take 4 or more days to "top off" the battery bank, and damage is done after 24 hours.

          2 batteries would be rechaged in 2 days, preventing damage. After a year of weekends, you could have 5 dead batteries, or 2 working ones.
          spreadsheet based voltage drop calculator:
          http://www.solar-guppy.com/download/...calculator.zip
          http://www.solarpaneltalk.com/showth...oss-calculator

          http://www.mike-burgess.org/PVinfo_2.html

          solar: http://tinyurl.com/LMR-Solar
          gen: http://tinyurl.com/LMR-Lister ,
          battery lugs http://tinyurl.com/LMR-BigLug
          Setting up batteries http://tinyurl.com/LMR-NiFe

          gear :
          Powerfab top of pole PV mount | 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

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