need ideas for inverter

alter
alter Registered Users Posts: 31 ✭✭✭
in Solar Beginners Corner #1
I need to add an inverter to an 840 watt panel system with a xantrex xw charge controller that was just set up and working ok but the cheap 300 watt inverter won't do. I plan on getting the big XW inverter eventually but need an interim solution for powering bigger devices. Is there a decent pure sine inverter for less than like 600 bucks that would be recommended by anyone? I'm thinking ~1000 watts will do for now. Thanks
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #2
    Re: need ideas for inverter

    Would be useful to know what your panel arrangement/battery arrangement is. It would also be useful to know what your loads are,,both total wh/day, as well as peak loads and durations.

    Just a guess, but ~840 watt of PF isn't going to power a 600 watt much less a 1kw inverter very long.

    Tony
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  • Dapdan
    Dapdan Solar Expert Posts: 330 ✭✭
    #3
    Re: need ideas for inverter

    check out the xantrex prowatt sw 1000, sells for about $250 works well i have two them, it is 12V tho.


    cheers
    Damani
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  • alter
    alter Registered Users Posts: 31 ✭✭✭
    #4
    Re: need ideas for inverter

    2-6 Volt batteries(12V) ~375 Amp Hours. 4x210wattpanels.

    This is installed in an off grid cabin. I plan on expanding this system little by little and basically want some recommendations for some inexpensive but decent pure sine wave inverters.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #5
    Re: need ideas for inverter

    Loads? Total/peak/duration?

    tony
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  • alter
    alter Registered Users Posts: 31 ✭✭✭
    #6
    Re: need ideas for inverter

    Can't answer that question exactly yet as I'm pretty new to this. But there will be no major devices just tv's lights microwave, etc.
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  • alter
    alter Registered Users Posts: 31 ✭✭✭
    #7
    Re: need ideas for inverter

    That xantrex prowatt looks perfect... Thanks for the suggestion.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
    Re: need ideas for inverter
    alter wrote: »
    Can't answer that question exactly yet as I'm pretty new to this. But there will be no major devices just tv's lights microwave, etc.

    A microwave is a pretty major load: slightly more than 1 kW for even a small one. Don't go by the "cooking power" rating.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #9
    Re: need ideas for inverter
    alter wrote: »
    Can't answer that question exactly yet as I'm pretty new to this. But there will be no major devices just tv's lights microwave, etc.

    I don't mean to be flippant, but I have to quibble with your "no major devices, just TV, lights, microwave etc".

    In order to avoid the Ready, fire, aim syndrome, you really have to understand how loads relate to performance. For example, your ~375 ah of batteries, drawn to 50% would give ~ 2 kwh worth of power. (20% which is what I would prefer would give you ~900 wh.)


    To draw 2 kwh out of a battery based system you are going to need ~1000 watts of PV if you are going to recharge every (good) day. Your 375 ah of batteries are going to want between ~18-35 amps of charge current to charge at a safe rate, necessitating an Pv in the 500-1kw range.

    I suggest you get a kill-a-watt meter, and start logging your loads. I think what you will find is that they add up pretty quickly. Let's use a simple example.

    4 15 watt cfls for 6 hours= 6*4*15=360 wh
    TV 125 watt for 4 hours= 125*4= 500 watt hours
    1000 watt micro for 10 minutes= 1000*.1=100wh
    Add those together and you get a total of 960 wh

    Here is my rule of thumb for off grid PV. Take the name plate rating of your PV, divide it in two to account for all system loses including PV ef, wiring loses, charge controller eff, basic battery charging ef (it takes about 125 whof charge to replace 100 wh of draw, that is just basic battery chemistry and you can't do much about it!) then multiply that number by 4. The 4 represents the average hours of perfect sun you can expect on a daily basis. (Over the course of the year, few places net/net average more than four)

    So, a 1000 watt array might deliver like this:

    1000/2*4=2000wh of power out of the inverter.

    Just for the record, we live off grid, and we draw ~600 wh/day. We do this with 400 watts of panel, into 450 ah of battery. We stay even if we get 4 hours of sun. The battery is big enough so that we routinely draw only ~15%, get that back each day, but we can go three days if we need to without sun without needing to run the genny.

    There are several other 'rules of thumb' that you should also be aware of. People all too often over estimate the amount of good sun they get, they under estimate the loads they will use, and these loa s(my letter d just quit so if my spelling gets strange,, sorry)will grow with time.

    Good luck,

    Tony
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  • alter
    alter Registered Users Posts: 31 ✭✭✭
    #10
    Re: need ideas for inverter

    Tony,

    This is very valuable information and I appreciate it. Lets put it this way, I'm going to adjust my usage to what the system will adequately provide. I'll be sure and monitor usage and the batteries more.

    Thanks again.
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