12 Volt Panel vs 24 Volt

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firefly
firefly Solar Expert Posts: 66 ✭✭
in Solar Beginners Corner #1
I am trying to figure out what the difference is between having say 2 12 volt 80 watt panels or just having 1 160 watt 24 volt panel. Is there any difference, or would the 24 volt 160 watt panel be equall to 4 80 watt panels at 12 volts? :confused:
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
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    Re: 12 Volt Panel vs 24 Volt

    Watts are watts

    As the voltage goes down, to maintain the same watts, the amperage has to increase

    The higher voltage has less loss in the wires.
    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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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #3
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    Re: 12 Volt Panel vs 24 Volt

    It depends...

    If you have a 12 vs 24 volt panel, connected to a PWM controller, connected to a 12 volt battery... Roughly 1/2 the power of the 24 volt panel will be wasted.

    If you have 2x 12 in series vs 1x 24 volt panel, connected through a good PWM controller, connected to either a 12 or 24 volt battery bank... The two are equivalent.

    If you have 2x 12 in series vs 1x 24 volt panel, connected through a good PWM controller, connected to a 24 volt battery bank... The two are equivalent.

    The the second two cases, purchase the best price per watt (including shipping costs), ease of mounting and wiring.

    Personally, I like larger panels because there are fewer mounts and electrical connections required.

    However, panels over 100 watts are typically not "standard" voltages used to charge batteries and, for off grid use, pretty much require MPPT type charge controllers for efficient battery charging.

    But that is OK--usually MPPT controllers are the best choice for larger systems anyway.

    For smaller systems (below ~200/400 watts for 12/24 volt battery banks), the Morning Star MPPT 15 amp controller would be a good fit for the >100 watt panels.

    Also, don't forget to get the remote battery temperature sensor for any solar charge controller--Pretty much required for proper charging of the battery bank.

    -Bill

    PS: And as Mike says, if you have long runs from the panels to the battery shed--Wiring your solar panels for higher voltage can greatly reduce the cost of the wire run (higher voltage, lower current, smaller wire for same drop).
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
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    Re: 12 Volt Panel vs 24 Volt

    if you don't plan on the downconverting mppt type controllers and are using 12v a battery, then use the 12v pvs with a pwm controller. the pvs will list a max power voltage point (listed often as vpm or vmp) about 17.4v typically and it could routinely be +/-.5v of that 17.4v. if it says for a pv vmp=15.9v or 34.5v then these are not good to use, but one that says 17.3v is fine. if it should go slightly higher than 17.9v it could still be used, but you could waste that extra voltage.
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