how do I get my 12vdc fan to work with my 5w panel

System
System Posts: 2,511 admin
in Solar Beginners Corner #1
Hello forum,

I have a 5 watt solar panel that i am trying to power a 12v dc computer fan and its not working. I thought it would be straight forward. spec on panel (pmax= 5w
vmp =18.v imp= .27 voc= 21.5v isc= .29a mas system 600v ) I Tried two fans
1 first a 3 wire fan 12vdc 1.6w and the 2nd 12vdc 2.0 w.



Thanks

Barry
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #2
    Re: how do I get my 12vdc fan to work with my 5w panel

    Do you have the specifications for the fans... Three wire fans typically use the third wire for RPM sensing or fault indication. So you have to make sure you have the right wires connected.

    Next--I assume that these are 12 VDC fans (DC?)?

    Also, solar panels need full noon-time direct sun to produce full current... If you are in the morning or evenings, or under a lamp--probably not enough current to start the fans turning.

    Lastly, motors typically need a fair amount of current to start turning (hopefully, a free turning fan requires less torque). For motors, lots of torque means lots of current--Solar Panels have zero surge current capabilities.

    Have you tried running the fans off of a small battery or DC power supply to verify they work and their polarity (some fans are polarity sensitive).

    You can also check your voltage (open circuit voltage) and current (short circuit current into the dead short of your meter set to amps). If panels have been incorrectly connected to a battery (backwards polarity)--it is veru possible to permanently damage the solar panel.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • System2
    System2 Posts: 6,290 admin
    #3
    Re: how do I get my 12vdc fan to work with my 5w panel

    Hi Bill,

    Yes both fans are 12v dc..... I have not tried using a battery yet but 1 fan was connected to a power supply and worked. My multi meter leads from the panel say if in sun light 20 v if in a room 12v .



    Thanks


    Barry
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  • System2
    System2 Posts: 6,290 admin
    #4
    Re: how do I get my 12vdc fan to work with my 5w panel

    Bill,

    do i need a battery with system?.


    Barry
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #5
    Re: how do I get my 12vdc fan to work with my 5w panel

    Hi Barry,

    The voltage from a room lite solar panel provides almost no useful current... So you will need to do this in full sun (and/or need more panels in parallel).
    Batteries are a painful addition to the system... You need 2x the amount of solar panels to make up for losses, and you (usually) need to setup a charger to properly manage the battery. Plus something to limit discharging the battery too deeply.

    Measure voltage and current flowing into the fan from the solar panel/array...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #6
    Re: how do I get my 12vdc fan to work with my 5w panel

    I am going to guess the no-load voltage is too high and shutting down the electronics in the fan.

    Find a small lamp to load the panel so the voltage is no more than 15 volts.
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  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    #7
    Re: how do I get my 12vdc fan to work with my 5w panel

    Does the fan list it's Current on the back? A 12V fan might list its number either A or mA .

    Your 5Watt solar panel's output is in milli-amps, and your fan's Current requirement is probably Amps, so there's not enough power to turn it.
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  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    #8
    Re: how do I get my 12vdc fan to work with my 5w panel
    1 first a 3 wire fan 12vdc 1.6w and the 2nd 12vdc 2.0 w.
    Are you sure the rating is in watts instead of amps?
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  • 2manytoyz
    2manytoyz Solar Expert Posts: 373 ✭✭✭
    #9
    Re: how do I get my 12vdc fan to work with my 5w panel

    I've used a number of 12V computer type muffin fans with small solar panels. Never had to worry about voltage regulation. Since the fan itself is a load, and the panel is relatively small, over voltage really won't be an issue. It can't supply enough current to get anywhere near the no load voltage measurement.

    Here's a few I've tried:

    Single fan, connected to a HF 5W panel.

    fan1163s.jpg

    Dual fans, connected to a HF 15W panel.

    dscn6212-1.jpg

    dscn6214-1.jpg

    I have a larger 5" 12V fan that also works well. Don't have a picture of it at the moment.

    But all of these work well, simply connected directly to a panel, just large enough to supply the required start up/running current.

    I will tell you these blades are SHARP, and accidently sticking a finger into a blade with the fan running will slice you to the bone! Don't ask! This is why I use blade guards, as shown above, from this point forward. :blush:
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