12v 80watt fan on 18v 60watt panel

Discussion in 'The Projects Forum' started by Mohammad abdullah, Apr 28, 2015.

  1. Mohammad abdullah

    Thread Starter New Member

    Mar 30, 2015
    25
    0
    Hay,
    I want to connect 12v 80watt fan direct to 18v 60watt panel is it ok or it will burn the fan.
     
  2. #12

    Expert

    Nov 30, 2010
    16,298
    6,810
    All bad. Too much voltage for the fan and too little power from the supply.
     
    Reloadron likes this.
  3. Reloadron

    Active Member

    Jan 15, 2015
    963
    232
    Well lets see.
    The Supply 60 Watts
    The Fan 80 Watts
    Nope, not looking good from where I am sitting. I see bad things happening and I see the power supply crying. We could do the math but even sans math I figure 80 is bigger than 60.

    Ron
     
  4. Mohammad abdullah

    Thread Starter New Member

    Mar 30, 2015
    25
    0
    It will not work with it max power for 60W that I'm sure but if I had 12v regulator in between is it good.
     
  5. Mohammad abdullah

    Thread Starter New Member

    Mar 30, 2015
    25
    0
    my panel Vmp=17.6 and Imp=3.4A
     
  6. wayneh

    Expert

    Sep 9, 2010
    12,126
    3,048
    It won't burn out the fan. In fact it may not run the fan very well and it may have a hard time getting the fan to start spinning after it has been stopped. But there is no risk in trying it out.

    Watch the voltage on the fan when the panel is in full sun. I think you'll see less than 12V.
     
    Johann likes this.
  7. Reloadron

    Active Member

    Jan 15, 2015
    963
    232
    No it isn't good. You have 18 volts 60 Watts which is 18 Volts at 3.333 Amps. You have 60 watts total power and that is as good as it gets.

    You need 12 Volts at 80 Watts which is 12 Volts 6.666 Amps. Your load requires 80 Watts. You have 60 Watts and need 80 Watts so tell me where the extra 20 Watts which you do not have will come from? You can't use power that you simply do not have.

    The fan may turn slow but the fan can never run correctly at its rated current.

    Ron
     
  8. Mohammad abdullah

    Thread Starter New Member

    Mar 30, 2015
    25
    0
    Thank you all for you Reply that what I got I don`t know if there is any way to rewind the motor coil so it match the panel rated power.
     
  9. wayneh

    Expert

    Sep 9, 2010
    12,126
    3,048
    The problem is bigger than that. The blades were designed to spin at a given rpm and to move a certain amount of air. No jiggering with the wires can change that.
     
  10. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,540
    1,251
    IF the fan has a brushless DC motor, they you should be ok. A switching buck regulator will decrease the 18 V from the panel down to 12 V, and will increase the 3.3 A from the panel up to something near what the fan expects, all at pretty high efficiency. It might take some experimenting to get the right combination of output voltage and current, but at 75% of its rated power the fan should start reliably. It will not run at full speed 60 W is in fact less than 80 W, and there is no modification you can do to the motor to change that.

    Note above the big IF. Brushless DC motors are fairly forgiving within limits, but everything above does not apply if the fan has a different motor type.

    ak
     
  11. Roderick Young

    Member

    Feb 22, 2015
    408
    168
    As others have said, the panel can't provide what the fan needs to run at full speed. But if it's the kind of motor that we used in DC fans in our servers, then the speed is highly variable, and the fan will turn at some speed even at 6 or 8 volts. My suggestion would be to connect the fan to your solar panel, and see what happens. If it's the kind of motor I think, you can't hurt the motor by undervoltage, and probably can't hurt the panel, either. If you have an oscilloscope available, you might want to monitor the panel terminals to see if the motor is producing unacceptable noise spikes. I found that wasn't the case, though, in my ongoing solar bike project.
     
    Johann likes this.
  12. Johann

    Senior Member

    Nov 27, 2006
    190
    30
    Give the fan a try on the panel. It should "pull down" the panel voltage so no harm to the fan. The panel can not be damaged because you could even short circuit it indefinitely without any harm; it generates current.
     
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