Simple Solar Fan System

Discussion in 'The Projects Forum' started by AK1, Feb 7, 2016.

  1. AK1

    Thread Starter New Member

    Oct 22, 2015
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    I want to wire two fans in parallel with this simple solar scheme. I've filled in some of the blanks, but I'm confused on what to calculate to make sure it will work... I'm making a bicycle camper. I've already got that drawn up and it should weigh around 50lbs. If anyone could suggest a cheap small/light battery that would work good with this setup, that would be appreciated too.
     
  2. Lestraveled

    Well-Known Member

    May 19, 2014
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    How long do you want your fans to run? Will they power anything else??
     
  3. AK1

    Thread Starter New Member

    Oct 22, 2015
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    I live in FL and plan to take the camper on overnight trips, possible 2-3 nights. During the hotter months (so practically all year) the fans are an integral part of my plan. The power controller I'm looking at is on Banggood and I'd probably use it to plug my phone in, too. http://www.banggood.com/10A-12V-24V...Charge-Solar-Panel-Auto-Switch-p-1014032.html

    The battery will prob have to be a decent one.

    I'm also going to wire in 4-6 small LED's for lighting, but I think I'm going to just use a 9v battery for that.

    What kind of run times am I looking at/how to calculate?
     
  4. Lestraveled

    Well-Known Member

    May 19, 2014
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    OK, pretty easy.
    If I read your data right, each fan draws .25 Amps times two for .5 amps total. If you got a 1 amp hour (AH) battery then they would run for two hours. So this is a pretty easy way to determine how big your battery needs to be. (How long do you need them to run between charging the battery. This will set the minimum size of the battery.)

    What do you think?
     
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  5. AK1

    Thread Starter New Member

    Oct 22, 2015
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    Excellent, looks like a 4AH battery is <4lbs. Id happily pedal that to run a fan all night! Thanks, now with such a small solar panel how long will it take to charge that battery?
     
  6. Lestraveled

    Well-Known Member

    May 19, 2014
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    OK, again simple (Not really)
    Under Ideal conditions, a cloudless sky, no obstructions, panel pointed at the sun always.

    4AH divided by .42 amps equals 9.5 hours. Practically speaking it ain't going to happen. You solar panel is way too small.

    First, you only get about 7 hours of 100% sunlight a day. A single shadow falls across your panel and the output drops to 10-20%. Triple your panel power and it might work.

    Suggestion - do you really need 6 watts of fans. Look for high efficiency fans. If you can drop the power requirement in half, you can cut the battery and the panel size in half.
     
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  7. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    When calculating battery capacity you should allow a generous margin, since running a battery completely flat will kill it quickly.
     
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  8. AK1

    Thread Starter New Member

    Oct 22, 2015
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    That makes sense, I had chosen these fans because they were only $3 each. The camper will be 35 sq ft, so I wanted to make sure air gets circulated. I think your suggestion is good. Ill look for a lower power fan, maybe something that spins slower, but with bigger blades.
     
  9. AK1

    Thread Starter New Member

    Oct 22, 2015
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    Agreed, price differences for extra capacity arent too bad either.
     
  10. AK1

    Thread Starter New Member

    Oct 22, 2015
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    I could always double the panel, too. The panel is only $12. I'll see how the fan prices change and go from there. I have a budget I'd like to stick to.
     
  11. Lestraveled

    Well-Known Member

    May 19, 2014
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    @AK1
    When you are looking for fans you should keep in mind a few things.

    I went on DigiKey and looked up 3Watt, 12 volt fans. They had one. It ran at 13000 rpm and had a noise rating of 57.3 dBa. This is a screamer and will keep you up all night. Plus it only moved 18 CFM of air.

    A different search found a 1.7 watt, 12 V fan that ran at 3200 RPM and only produced 33dBa of noise. Plus it moved 41 CFM of air. Over twice as much as the screamer at about half the power. Plus it is a lot quieter.

    Look at CFM, noise and power consumption.
     
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  12. AK1

    Thread Starter New Member

    Oct 22, 2015
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    Wow great site and nice search features. I was familiar with the CFM ratings; good added point on the noise level.
     
  13. Lestraveled

    Well-Known Member

    May 19, 2014
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    DigiKey is a great company but you pay full retail. Shopping on EBay and Amazon will save you bunches.
     
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