New to solar and looking for some battery advice

Marc Registered Users Posts: 1
I have a yurt located in Hoodsport , WA which is completely off the grid and currently has no power what so ever. Recently I purchased a few solar system items and am hoping to get things up and running with the next month. The stuff I purchased is:

4 - 305 watt panels ( plan to purchase 3 more of these)
Midnite Solar mnpv6 combiner box
Xantrex 60 amp charger

I am currently shopping for a 4000 watt inverter and batteries.

On the worst of winter days I anticipate my usage would be a max of 3910 watts but that is heavily padded. With all that said my primary question is I initially planned on purchasing 12 6V batteries and running 3 strings connected in parallel in order to get 24 volts and roughly 675 amp hours. Are there any issues with running 3 strings like that? Would I be better off buying larger batteries and running less strings?

Any advice is greatly appreciated.



  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New to solar and looking for some battery advice

    Welcome to the forum Marc. Gee, that's a really good name. :D

    Another yurt install! :D Yes, they've come up before!

    Your sort of putting the yurt before the horse by buying equipment and then seeing if it will work out for you. It's far better to try and determine how much power you'll need, and then work out how to supply it. But that's as may be at this point.

    So you've got four 305 Watt panels and want to purchase three more. Nope. Buy two more or buy four more but don't by odd numbers of panels. Even numbers are much easier to configure in various ways.

    For example right now you've got 1220 Watts of panels that probably spec a Vmp around 30. That's too low a Voltage for a 24 or 48 Volt system, and you do not want to use a 12 Volt system. But if you put two panels in series you get 60 Vmp which will work for a 24 Volt system. Three in series and you get 90 Vmp which would work on 48. You will need an MPPT type controller no matter what, so I hope that Xantrex isn't the C60 unit.

    A couple of pertinent threads for you to peruse:

    Next question: why a 4kW inverter? Are you likely to need 4kW at any given time? Do not confuse the maximum capacity of an inverter with the daily Watt hour consumption. That "hour" makes absolutely vital difference.

    You probably want to avoid having three parallel battery strings too, btw.

    Now, we can work out what sort of power you can expect from your array using the Icarus formula:

    1220 Watts * 4 hours minimum sun * 0.52 over-all efficiency = 2.5 kW hours per day.

    How are we doing so far?

    (Another Marc - the forum has lots of them!)
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: New to solar and looking for some battery advice

    Please add a description of your yurt's dimensions and how you plan to use your electricity daily.
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada