12v PC Fan - Powered from 18V 36w solar panel, can i?

[loggio]

Hi guys,

Ok, i need some intelligent input on this as i have little knowlege on this stuff.

Ok, so i have a 3-way portable absorption fridge i use on GAS for camping. It works great, however i have heard that adding a DC 12v PC fan to exhaust out heat from the condensor fins can increase its performance dramitically. I have a heap of PC 12v fans laying around and thought why not put them to good use.

I also have a portable 18v 36W solar panel i bought off ebay a while back and actually don't use it for anything. So i thought, why not marry the two together and let it run the fan in the fridge... then i don't have to worry about batteries.

So my question to you guys is, will this work? ... do i need to do anything special, or can i simply hook up the fan to the solar panel and it will work.

the specs of the panel are:

outgoing current: 2 A
Power : 36W
Voltage : 18V,

Output interface
DC 3.5mm

My worry is that the fan is a DC 12v fan and the solar panel is 18v 36W... I have no idea if the fan will simply only draw what voltage it needs, or if it needs to be regulated and if so, how?
will running the fan this way destroy it?

I'm sorry for my ignorance with all this, but i'm reading around and getting mixed messages from a lot of forums. A lot of the info out there is for 12v fans running on 5w or 10w 12v solar panels.

I hope someone can explain this all to me.

Thanks in advance,

Loggio.

 

[Haf-E]

Well - here goes...

The solar panel will put out a range of voltages depending on the load and the amount of sunlight. If you look on the specifications it should list a value called "Voltage Open Circuit" which is what it produces without a load in bright sunlight. This also can be easily measured as well.

As a load is connected to the solar panel the voltage will drop as the current increases. The 18vdc rating is what is called its "peak power point" where it produces the most power - watts. Its the ideal point for the solar panel to operate around.

All of the small DC fans can tolerate a range of voltages - some more than others - but - I would be concerned about trying to run one at a voltage about 16vdc. Its likely your solar panel will produce something like 24vdc open circuit / unloaded - and the fan is a very small load - typically about 2 to 4 watts - so the voltage will remain high even if the fan could tolerate running at that high of a voltage.

So - the solar panel is too large and to high of voltage for a small fan like your proposing. you could try a 24 vdc fan or connect the solar panel to a controller and run the fan off of a battery that is charged by the solar panel. That would allow it to run 24 hours a day as well.

 

[seanz0rz]

get a 12V voltage regulator.

http://www.radioshack.com/product/index.jsp?productId=2062600

 

[loggio]

Well - here goes...

The solar panel will put out a range of voltages depending on the load and the amount of sunlight. If you look on the specifications it should list a value called "Voltage Open Circuit" which is what it produces without a load in bright sunlight. This also can be easily measured as well.

As a load is connected to the solar panel the voltage will drop as the current increases. The 18vdc rating is what is called its "peak power point" where it produces the most power - watts. Its the ideal point for the solar panel to operate around.

All of the small DC fans can tolerate a range of voltages - some more than others - but - I would be concerned about trying to run one at a voltage about 16vdc. Its likely your solar panel will produce something like 24vdc open circuit / unloaded - and the fan is a very small load - typically about 2 to 4 watts - so the voltage will remain high even if the fan could tolerate running at that high of a voltage.

So - the solar panel is too large and to high of voltage for a small fan like your proposing. you could try a 24 vdc fan or connect the solar panel to a controller and run the fan off of a battery that is charged by the solar panel. That would allow it to run 24 hours a day as well.

Hmmm, i see...

What small battery/controller combo could i use to run this safely?

This is the solar panel i have:
http://www.ebay.com.au/itm/36W-18V-.../261184996135?pt=AU_Solar&hash=item3ccfd6c327

would i be able to use a battery like this:
http://www.supercheapauto.com.au/on...-12V-2Ah.aspx?pid=128926&menuFrom=70705#Cross

and a controller like this:
http://www.ebay.com.au/itm/15A-Sola.../140926289474?pt=AU_Solar&hash=item20cfdc8642

perhaps?


Cheers,
loggio.

 

[Crom]

I think your panel should work just fine, sounds like a 12v panel to me. Think of your panel as a current source, not a voltage source. if the sun shines, it's going to spin the fan. If it's shady or no Sun, then fan speed will reduce or stop. The fan will draw what current it needs from the panel as long as the panel can produce it, it should work fine.

 

[Rando]

It may work directly, but the 7812 12V regulator mentioned earlier ($1.99) is the way to be sure. Make sure you heat sink it though - bolt the tab to a metal part of the fridge/vehicle and you will be golden.

 

[Haf-E]

While it may work I think its a lot more likely to fry the fan as the voltage will go too high in full sun. Adding a small "three terminal" voltage regulator is a good solution and will work and should still allow operation at the beginning and end of the day when the panel is struggling to produce enough power.

I still would consider just power the fan from the vehicle's battery and adding a small charge controller to prevent over-charging and over-discharging of the battery. It would allow operation at night if needed.

 

[teotwaki]

It sounds as if a simple combination of the suggestionss might be a good way to go. The panel has decent output so use a inexpensive charge controller and apply that output to the car battery. Then run the small fan from the car battery.

high quality $46 http://www.wholesalesolar.com/produ...gle_shopping&gclid=CMCX6NGO4bYCFcud4Aodm3AAgg

Chinese cheapo http://www.ebay.com/itm/15A-12V-24V...551?pt=LH_DefaultDomain_0&hash=item3a78bc5c8f

 

[wrcsixeight]

Voltage open circuit and voltage max power are different, so is the panel voc 18 or vmp18?

I use a 24 volt fan powered by 12 volts. Sure would spin faster at 24+, but it is silent at 12 to 14.8v and it does not have to move a lot of air for what I am using it for.

proper baffling of the condenser fins, so natural convection currents draw air up and through the fins should be good enough until 85+f or so. Too much space behind condenser fins allows a portion of the convection currents to not flow over the fins. 1 inch space is recommended and no more.