Configuration Question

deltarat
deltarat Registered Users Posts: 9 ✭
in Solar Beginners Corner #1
I am having a hard time deciding whether to go with a 12v or 24v system, and what kind of charge controller to use.

I have 2ea 205w solar panels 27.9 Vmp 7.36 Imp. We will hook them up in parallel. Is this enough voltage to charge a 24v system? Also should I be using a MPPT controller. I know they are supposed to be better, but in my case is the cost worth it.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #2
    Re: Configuration Question

    I think your voltage (with panels in parallel) will not be enough to charge 24 volt batteries. If you put the solar panels in series and use a MPPT controller you can have a 24 volt battery bank. If you think you might like to expand the system in the future, start out with a 24 volt system.
    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • deltarat
    deltarat Registered Users Posts: 9 ✭
    #3
    Re: Configuration Question

    Assuming I don't ever want to expand. Is it better to run 12v or 24? And If I ran a 12v system would I need the mppt controller?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #4
    Re: Configuration Question

    Watt Vtmp says...

    Note that higher input voltage MPPT controllers (and higher current controllers) are not cheap--You are looking at $300-$500+ for higher end controllers.

    And it is very difficult to "grow" a system. New inverter, possible new charge controller, rewired/more solar panels, new/larger batteries, etc.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #5
    Re: Configuration Question
    deltarat wrote: »
    Assuming I don't ever want to expand. Is it better to run 12v or 24? And If I ran a 12v system would I need the mppt controller?
    If you run a 12 volt system you will not need a MPPT controller, although it would be more efficient with a 27 volt array.
    As far as which system voltage is better... a 24 volt system is better, with certain exceptions:
    1) if you have 12 volt loads (lighting, pump, etc) a 12 volt system may make sense. There are more appliances, lights, etc for 12 volts than 24 volts.
    2) 12 volt systems may be less expensive.

    What sort of battery capacity do you intend to have? You would certainly be better off with (for example) two 12 volt batteries in series (24 volt system) than two 12 volt batteries in parallel (12 volt system).
    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • jtdiesel65
    jtdiesel65 Solar Expert Posts: 242 ✭✭✭
    #6
    Re: Configuration Question

    For sizeable systems, I think probably 24v is getting toward the edge of extinction too.

    I wouldn't bother with a charge controller like a c40. I had a c40 once with 34vmp strings on 1000 AH 24v. It was night and day between that and the SolarBoost 50 that replaced it. The Solar boost was like getting another panel or two. As a side note, for a larger array I wouldn't go with a Solar Boost 50 now either, but would opt for an outback or midnite solar unit. That's my preference/experience. I don't know what exactly is available for mppt controllers. My experience is limited to the ones I listed. But from my experience, unless it's a smaller system, I would opt for mppt.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #7
    Re: Configuration Question

    are you only asking of the pv system configuration or are you asking of the battery configuration? if the batteries are in a 24v config then those pvs need to be in series. a 12v battery system can have either the series or parallel arrangement. in both cases with the odd vmp presented by the pvs i'd recommend an mppt controller in either case. many opt for the series pv arrangements to help offset resistive losses presented by the wires.
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