What is the attraction to 12 volt panels over 24 volt panels?

softdown
softdown Solar Expert Posts: 3,896 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
A large roof tear off enabled the sale of:
1) 150watt 24 volt panels...mostly BP
2) 120watt 12 volt panels...mostly BP

Was surprised to see the bundles of the smaller panels...the 120watt 12 volt panels...have sold for a little more than the 150watt panels. The 150watt panels produce ~20% more power of course. The 120watt panels are more of a square than a rectangle.
First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #2
    The only attraction I see is that they can be used with PWM controllers on 12 volt systems. 

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    #3

    12 volt stand alone inverters for backup power and micro off grid is the only reason I can see.

    Plus they work best with cheap PWM controllers for 12 volt systems.

    Or maybe I am not the only one that thinks I will buy 12 volt panels, series them for grid tie, then when the power goes out unpair them and hook them up to a PWM charger with battery and power a 12 volt stand alone system.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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  • softdown
    softdown Solar Expert Posts: 3,896 ✭✭✭✭
    #4
    Could of swore I seen that sales point (PWM controller) for the 24 volt 150watt panels. Perhaps I am mistaken.

    vtmaps said:
    The only attraction I see is that they can be used with PWM controllers on 12 volt systems. 

    --vtMaps

    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • softdown
    softdown Solar Expert Posts: 3,896 ✭✭✭✭
    #5
    Does anybody know of the reputation of the BP 12 volt 120 watt  panels? They are ~40" by 48".
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • Johann
    Johann Solar Expert Posts: 245 ✭✭✭
    #6
    12 volt panels can be tied in series to make 24 volts, 36 volt or 48 volt systems or systems with higher voltages..
    Usually 12 volt panels are smaller and lighter and with it can be handled easier when installed.
    In a  shtf situation a 12 volt panel could be more easy taken with you if a relocation is needed. Or you can take 12 volt panels with you for a camping trip to charge cell phones or watch TV etc.
    It may be easier to work around shading with 12 volt panels, since they are smaller and since they may be wired in parallel.
    A 12 volt charge controller is usally cheaper and easier to find and to operate. Higher Voltages may require an expensive charge controller.
    There are thousands of 12 volt electrical and electronic devices on the market that can be had and they are normally cheaper than 24 volt or 48 volt devices.
    12 volt panels carry a higher price tag per watt.
    The current is higher with 12 volt panels with the same wattage and you need bigger wires to run the same wattage.
    More connection could lead to a higher resistance, especially if 12 volt panels are wired in series to gain higher voltages.

    All I can say is. use a panel that fits your purpose and needs.
    For example... It would be a bad idea to get a 250 watt panel if you want to take that panel to your hideout if something happen. On the other hand a 250 watt panel is what may be the best if you think about to install a 48 volt system.
    Every situation is different.
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  • Susido
    Susido Registered Users Posts: 32 ✭✭
    #7
    All my panels are 12 volt because that is what I started out with years ago. I wouldn't do it again because of the cost per watt. Mind you maneuvering panels physically larger by myself onto rooftops would have been a daunting task. 
    Seasonally off-grid ... 468 Ahrs @ 48V (8 Rolls S-605 6v FLA batteries),  24 x 130watt panels, 6 x 260watt panels, 2 x Midnite Classic 150, Whizbang Jr., Magnum MS4448PAE inverter/charger, 2 x Honda eu2000i generators paralleled.


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  • softdown
    softdown Solar Expert Posts: 3,896 ✭✭✭✭
    #8
    Are you using BP 130 watt panels by chance? BP was one of the largest. I have a chance to get some BP 130 watt panels I think. Could buy and resell if the quality is there. I'm thinking 130 watt panels were made around 2004-2006?


    Susido said:
    All my panels are 12 volt because that is what I started out with years ago. I wouldn't do it again because of the cost per watt. Mind you maneuvering panels physically larger by myself onto rooftops would have been a daunting task. 

    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,102 ✭✭✭✭✭
    #9
    softdown said:
    Does anybody know of the reputation of the BP 12 volt 120 watt  panels? They are ~40" by 48".

    Softdown, The panels you are referring to aren't 12 volt "nominal" panels. They are a 42 cell configuration outputting about 21 vmp (my guess). Do you have a model number? I have been trying to find the exact panel you have been referring to and frankly cant seem to find it. Anyway they are a somewhat bastardized configuration and voltage.  I believe they have limited desirability to the 12 volt folks. Of course with an MPPT controller they can be used for charging a 12 volt system, or any other nominal voltage when configured correctly.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • softdown
    softdown Solar Expert Posts: 3,896 ✭✭✭✭
    #10
    I think these panels are pretty much the same:

    Manufacture Spec Sheet (assumes Astro Power Model)
    Model AP 120L
    120-Watt
    Monocrystalline Photovoltaic Module

    Typical Electrical Characteristics(1) AP-120L
    Maximum Power (Pmax) 120W
    Voltage at Pmax (Vmp) 23.8V
    Current at Pmax (lmp) 4.45A
    Short-circuit current (Isc) 7.3A
    Open-circuit voltage (Voc) 23.8V



    littleharbor2 said:
    softdown said:
    Does anybody know of the reputation of the BP 12 volt 120 watt  panels? They are ~40" by 48".

    Softdown, The panels you are referring to aren't 12 volt "nominal" panels. They are a 42 cell configuration outputting about 21 vmp (my guess). Do you have a model number? I have been trying to find the exact panel you have been referring to and frankly cant seem to find it. Anyway they are a somewhat bastardized configuration and voltage.  I believe they have limited desirability to the 12 volt folks. Of course with an MPPT controller they can be used for charging a 12 volt system, or any other nominal voltage when configured correctly.


    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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