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Powering several small fans

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  • #16
    Originally posted by Rainwulf View Post
    Just power the fans with these:
    http://www.ebay.com.au/itm/LM2596-St...-/251066005460

    They will limit the voltage to whatever you set. As a bonus, as the solar panel starts putting out more voltage, the step down converter will use even less power as its a power in= power out. You could ran more fans that way.
    I just wish that the the sale page gave some information about the available current output. Do you have one and can you post the actual specs?

    PS: solar panels do not put out more voltage as the incoming light increases, they put out more current.
    That limited current at roughly the same voltage is why MPPT controllers make sense and why simple buck converters may not.
    With a constant voltage out the fans are going to try to pull a constant amount of power regardless of how much sunlight is hitting the panels. If they want more than the panels can produce, it is likely that the panel voltage will drop, causing the converter to drop out of regulation or shut down.
    Last edited by inetdog; 09-30-2015, 03:24 PM.
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

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    • #17
      Originally posted by SunEagle View Post
      In the long run it might be cheaper to run that extension cord.

      Most people think that solar is low cost and provides free energy. It is neither.

      Purchasing cheap equipment to keep your costs down ends up just wasting money and costing you more to get it right. (Trust me I know because I did it). You could end up purchasing all types of panels, charges, batteries, voltage regulators until you come up with the right combination to make your fans works the way you want but at what cost.

      A solar grid tie system can lower your electric bills but will take years to break even. A solar / battery system will never break even.

      A solar driven DC motor may work but on days you do not get the sun then you have no power to run that DC motor. That is when you start thinking about batteries and then the costs start to spiral out of control.
      Yes, but this isn't about saving money. This is about not running a big orange extension cord across the middle of my wife's (our) backyard. And it's ok if it doesn't work when the sun's not around. I only need it when the sun is around.

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      • #18
        Originally posted by SolidFooting View Post
        Yes, but this isn't about saving money. This is about not running a big orange extension cord across the middle of my wife's (our) backyard. And it's ok if it doesn't work when the sun's not around. I only need it when the sun is around.
        If the issue isn't about saving money then why did you bring up the fact that you only had $80 to complete your project?

        I didn't say anything about saving money. I just tried to tell you that what you want to do that works and is not just a bunch of parts will end up costing you some money.

        $80 is not going to get you something that will work over a long period of time. The choice is yours.

        There is also a piece of equipment that you can rent that will bury an U/G rated power cable without destroying your lovely backyard grass.

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        • #19
          Another option is just use direct burial 120 VAC wire out there. Acres of buried wire here. Bruce Roe

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          • #20
            Originally posted by bcroe View Post
            Another option is just use direct burial 120 VAC wire out there. Acres of buried wire here. Bruce Roe
            Or direct burial DC landscape lighting wire. Cheaper, safer and very common.

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            • #21
              Originally posted by jflorey2 View Post
              Or direct burial DC landscape lighting wire. Cheaper, safer and very common.
              This.

              And you can get something that has a built in timer to drive it.

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              • #22
                Originally posted by jflorey2 View Post
                Or direct burial DC landscape lighting wire. Cheaper, safer and very common.
                Safe as long as you only use it what the NEC recognizes as a Class 2 Limited Power circuit.
                That means that you supply power to the wire through a Class 2 listed power supply or transformer and do not try to use it for 120V AC wiring(!) it is OK.
                SunnyBoy 3000 US, 18 BP Solar 175B panels.

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                • #23
                  Originally posted by SolidFooting View Post
                  I've got maybe $80 or so to work with, but if I can spend less, I will. I saw a battery on Amazon for about $15 too. So far I can't find a better deal than this:
                  If anyone knows of a better deal, I'm all ears.
                  Here is one with a little higher output and also just a couple of bucks cheaper:http://www.ebay.com/itm/12-Volt-35-W...item567a3f62e9

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                  • #24
                    Originally posted by LETitROLL View Post
                    Here is one with a little higher output and also just a couple of bucks cheaper:http://www.ebay.com/itm/12-Volt-35-W...item567a3f62e9
                    And a solar charger you can look at also

                    http://www.ebay.com/itm/10A-PWM-Sola...item43e10cdc74

                    It is cheap stuff, but I think it would work fine for your project, your draw is so low (15w) and you only need it to work when the sun is out, Solar is really fine for your situation, most people want to run appliances at night or in the rain and that is where the bad rep comes from.
                    good luck

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                    • #25
                      Originally posted by LETitROLL View Post
                      And a solar charger you can look at also

                      http://www.ebay.com/itm/10A-PWM-Sola...item43e10cdc74

                      It is cheap stuff, but I think it would work fine for your project, your draw is so low (15w) and you only need it to work when the sun is out, Solar is really fine for your situation, most people want to run appliances at night or in the rain and that is where the bad rep comes from.
                      good luck
                      That puts me pretty darn close to budget too. Thank you for the recommendations.

                      I'll look into the underground wiring option too. It's gonna travel a long way, but I'm no stranger to digging.

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                      • #26
                        Originally posted by SolidFooting View Post
                        That puts me pretty darn close to budget too. Thank you for the recommendations.

                        I'll look into the underground wiring option too. It's gonna travel a long way, but I'm no stranger to digging.
                        The landscape wiring usually runs at 12VAC - so you'll have to deal with it being AC (solvable) and figure out what your actual DC voltage will be and how to solve that if it's too low.

                        IIRC the landscape wiring is allowed to be pretty shallow. (maybe even allowed to be just under the sod - which would mean minimal digging)

                        An underground 120VAC circuit is another option - but there's a lot more restrictions on that - like making sure it's buried sufficiently.

                        AND ALWAYS CALL YOUR CALL BEFORE YOU DIG HOTLINE.

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                        • #27
                          Originally posted by inetdog View Post
                          I just wish that the the sale page gave some information about the available current output. Do you have one and can you post the actual specs?

                          PS: solar panels do not put out more voltage as the incoming light increases, they put out more current.
                          That limited current at roughly the same voltage is why MPPT controllers make sense and why simple buck converters may not.
                          With a constant voltage out the fans are going to try to pull a constant amount of power regardless of how much sunlight is hitting the panels. If they want more than the panels can produce, it is likely that the panel voltage will drop, causing the converter to drop out of regulation or shut down.
                          They have about 2 amps continous output, enough to drive a few fans. And yea, if you drive too many fans, they will drop out. Would just need some experimentation to see how many fans you could run vs the drop on the panel.

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                          • #28
                            Originally posted by SolidFooting View Post
                            That puts me pretty darn close to budget too. Thank you for the recommendations.

                            I'll look into the underground wiring option too. It's gonna travel a long way, but I'm no stranger to digging.
                            You would be able to pick up cheap panels from craigslist or equivalent. Here in australia we use "gumtree.com.au" and i have been able to pick up new 240 watt panels for 120 each, and second hand grid tie panels for under 100.

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