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laknox's avatar
laknox
Nomad
Jul 14, 2015

Need some electrical edjumakashun...

I'm trying to cobble together a small exhaust fan, solar powered. I have a bunch of old computer fans, both 5v and 12v, and am having trouble figuring out what I can run and how much panel I need. Main questions are:

1. With 12v fans, how far down in voltage can I run them before I start damaging the motor? (Assume the usual cheap computer case fans you're likely to get in a desktop.)

2. When voltage goes down, amperage goes down; will low amperage damage the fan?

3. If I use a "quick and dirty" 12v to 5v USB car charger to run a 5v fan, will the loss of voltage (and amperage) between 12 and 5 as the panel becomes less effective cause any issues?

4. What's more important to fan speed; volts or amps?

I know there are a lot of DIY "instructions" out there, but they're usually not real detailed, nor do they explain a lot. Any info is appreciate.

Lyle
  • magicbus's avatar
    magicbus
    Explorer II
    Jul 14, 2015
    I hooked 4 computer fans in parallel to a 12x18 inch solar panel to ventilate a crawlspace. Two intake and two exhaust. That was 4 years ago. I leave them on all summer so they run with the sun. I flipped the switch this spring and they started right up.

    Dave
  • MrWizard's avatar
    MrWizard
    Moderator
    Jul 14, 2015
    Gordon pretty much nailed it
    I have 12v PC fan wired directly to a 40w 16v panel output
    spins all day stops at night
    that panels power does go someplace else
    it was just the easiest way to get that fan powered, it sees full panel voltage
  • GordonThree's avatar
    GordonThree
    Explorer
    Jul 14, 2015
    Computer fans are amazingly durable. A 12v fan will run as low as 7v no problem or as high as 17v (from my own experience). They are electronically commutated so the winding switch on and off as needed to make it spin.

    Low amps or volts will not harm the fan. They have protection against that as well as a locked rotor.

    High volts will eventually kill the microchip inside the fan.

    For these tiny DC brushless fans voltage is the only thing that matters. They'll not draw more amps than needed.

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