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Thread: Help with a simple question

  1. #1
    pspjim Guest

    Default Help with a simple question

    I spend each September in Puerta Vallarta and each year I swear that I will figure out how to hook up a 12 volt automotive clip on fan to my Palapa (shade on the beach) using a small? solar panel, I cannot find anyone who can tell me what size solar panel will operate a 12 volt fan (that is suppose to plug into a cigarette lighter)
    I don't know if the solar panel will be small (fit in suit case) or large? any idea where to get one? I leave in 10 days?

  2. #2
    Join Date
    Mar 2006
    Location
    SF Bay Area (California)
    Posts
    21,228

    Default Re: Help with a simple question

    You need to know how much power the fan will draw... Say it draws 2 amps at 12 volts DC...

    12V*2amp=24 watts

    So, at a minimum, you would want a 24 watt panel for this mythical fan. And picking the panel, you would want a crystalline silicon panel (not an amorphous panel). A crystalline panel will be about 1/2 the square inches as a amorphous panel.

    A typical 30 watt 12 volt panel will cost around $230 (plus shipping and handling--and I am sure you can find specials for less). Such a panel will be 16"x26" and weigh 8.5 lbs (includes an aluminum frame).

    You can use a smaller fan and get a smaller panel.

    Also, there are "flexible" amorphous panels that will be larger in square inches--but are not as easy to break (a glass panel is like trying to carry a sheet of glass in an aluminum frame--very easy to break).

    Lastly, as a warning... 12 volt panels are typically around 17 volts Vmp (voltage maximum power)--So, the average solar panel will be outputting higher than 12 volts to the motor... The motor may run fast and wear out sooner. Probably not an issue for a "beach fan"--but if you want it to be reliable, you may need to monitor the current and voltage between the panel and the fan to make sure everything is OK.

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  3. #3
    Join Date
    Jun 2003
    Location
    pittsburgh, pa
    Posts
    10,278

    Default Re: Help with a simple question

    there are also smaller pvs that were placed on vw cars to keep the battery charged. these are on ebay and they have a smaller vmp. should power a small fan as some are 5w and i believe some were 10w. you didn't leave much time for yourself to get this stuff and you should do a search to see if anybody has a walk-in store near you or along the way that may have what you need.
    NIEL

  4. #4
    Join Date
    Mar 2009
    Location
    Los Angeles, Ca.
    Posts
    1,332

    Default Re: Help with a simple question

    I have one of these:

    http://www.boatandrvaccessories.com/RP-1137.htm

    12v, single speed, oscillating, clip and/or screw mount.

    According to the specs on that site:

    "12 WATTS, 1.1 AMP DRAW"

    I haven't put a meter on mine to check it, so those specs may actually be correct.

    I have to say, that it works works very well. It moves a LOT of air - but it's also incredibly noisy. Like...loose bearings rattling sort of noise. It's made that noise since I got it, and it works fine so I haven't tried to take it apart to made it better.

    Dunno how long it would last running at an over-voltage of say 17v, but it works great at 14v.

    They sell the same unit at Camping World:

    http://www.campingworld.com/shopping...p-on-fan/26213

    And that page says:

    "Tech Notes: Working current range 0.4~0.8Amp".

    YMMV.

    I would think it would work fine with a 15w or 20w PV.

  5. #5

    Default Re: Help with a simple question

    As an experiment, I made an attic fan.

    Harbor Freight had their 5 Watt solar panel on sale for $39.99. I had several 12 Volt muffin fans. The largest one is 6" in diameter, but is rated at 500 mA. The solar panel will spin it, but not up to full speed. The voltage drops to about 8 Volts. The next largest fan I had was a 3.5" 12 Volt computer fan. It was rated at 180 mA, below the rating of the solar panel. Consequently, the fan instantly jumped to full speed, moving quite a bit of air.




    Had it in place for about a year before moving to a much larger (grid powered) attic fan. Ultimately, my attic doesn't breathe well enough, and this fan was too small to move a huge volume of hot air. But close to someone, it would keep their hair out of their face!

    As clouds would pass over, the fan would slow down a bit. Since the panel was larger than needed, and no sort of voltage regulation was used, the fan did see a higher voltage than designed for. But it still worked even after a year. The fan was eventually given to a coworker who now uses it to cool his shed (better size for the small fan).

    So for $39, you could get a cheap solar panel, and a $2 muffin fan might do all you ask if you intend to cool off one person, with the fan reasonably close. Bigger fan (obviously) going to need a bigger panel. If you plan on traveling with it, might consider one of those flexible solar panels (rolls or folds up).
    Robert
    Central FL
    http://www.2manytoyz.com
    900W of solar panels, 860 AH 12V battery bank (8 6V Golf Cart Batts), Xantrex Prosine 1800W inverter, Xantrex Prowatt SW2000 inverter, 2 Prostar 30M controllers, 1 Morningstar Sunlight 10L controller, Iota 75A charger (for rainy days), Furrion 30A automatic transfer switch, Yamaha EF2400iS generator.

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