Newbie with 12v fan garage cooling

[tabletuser33]

I purchased a 100w WindyNation Mono panel and started playing around with a 12v radiator fan and a few PC fans. When I have good sun, about 85 watt output, my radiator fan gets LOUD. If I add a second smaller fan, it reduces the voltage and makes the fans quieter. What I was wondering how I can use Zener diodes, 12v car relays and 2 DC fans to create quieter garage cooling.

example
At 13v (or higher) zener diode passes voltage to relay, turns on second fan.
Both fans running, voltage drops to 9v and second zener passes voltage to shut off relay for second fan.

Seems like a low cost way to add cooling when the sun is hitting hardest and not create extra noise.

[bcroe]

I purchased a 100w WindyNation Mono panel and started playing around with a 12v radiator fan and a few PC fans. When I have good sun, about 85 watt output, my radiator fan gets LOUD. If I add a second smaller fan, it reduces the voltage and makes the fans quieter. What I was wondering how I can use Zener diodes, 12v car relays and 2 DC fans to create quieter garage cooling.

example
At 13v (or higher) zener diode passes voltage to relay, turns on second fan.
Both fans running, voltage drops to 9v and second zener passes voltage to shut off relay for second fan.

Seems like a low cost way to add cooling when the sun is hitting hardest and not create extra noise.

That drawing is as clear as mud. What I have done, is use 2 similar fans in parallel for
max speed, and in series to slow them down. But that would depend on a decent match
to the panels capabilities here. good luck, Bruce Roe

[SunEagle]

Fan noise is generated by the tips speed. Smaller diameter fan at a high rpm is noisy. Large diameter fan at low rpm is less noisy but can still more the same CFM of air.

I have a couple of solar attic gable mounted fans that each run directly off a 10 watt panel. They are not noisy yet move about 1000 CFM. You might want to look into something like those fans.

[Sunking]

All zeners are doing is shunting current and robbing power. You want to find a Fan made to run at 12 volts and 60 to 80 watt consumption.

[Johann]

You are lucky that you did not burn up your fan motor yet. Those panels could put out more than 12 volt under a good sun.
That noise could be from over voltage and over driving the rpm on that fan. Most radiator fan are noisy to start with
You could use a buck converter, this way you could regulate the max voltage and with some units you could even regulate the amps.

[paulcheung]

I would get a cheap 12 volt 45 AH automobile battery and a cheap 10 amp charge controller.

[Rainwulf]

I purchased a 100w WindyNation Mono panel and started playing around with a 12v radiator fan and a few PC fans. When I have good sun, about 85 watt output, my radiator fan gets LOUD. If I add a second smaller fan, it reduces the voltage and makes the fans quieter. What I was wondering how I can use Zener diodes, 12v car relays and 2 DC fans to create quieter garage cooling.

example
At 13v (or higher) zener diode passes voltage to relay, turns on second fan.
Both fans running, voltage drops to 9v and second zener passes voltage to shut off relay for second fan.

Seems like a low cost way to add cooling when the sun is hitting hardest and not create extra noise.

I would just use a regulator to turn the voltage down to where the fans dont make as much noise.

http://www.ebay.com/itm/5Pcs-Output-1-23V-30V-DC-DC-Buck-Converter-Step-Down-Module-LM2596-Power-Supply-/321476590827?hash=item4ad97f7ceb

That will get you step down.

[vudu]

Fan noise is generated by the tips speed. Smaller diameter fan at a high rpm is noisy. Large diameter fan at low rpm is less noisy but can still more the same CFM of air.

I have a couple of solar attic gable mounted fans that each run directly off a 10 watt panel. They are not noisy yet move about 1000 CFM. You might want to look into something like those fans.

I'm voting for this answer. This way you also get a panel sized for the fan.

http://www.solarpaneltalk.com/showthread.php?5359-DC-attic-fan-motor

https://www.google.com/search?q=12v+attic+fan&oq=12v+attic+fan

I've seen them on ebay for as little as 99 bucks.

Or, if possible, consider using a ridge vent.

https://www.google.com/search?q=ridge+vent

PS: Use the panel (+cc/batt) for LED lighting perhaps.

[PNjunction]

All zeners are doing is shunting current and robbing power. You want to find a Fan made to run at 12 volts and 60 to 80 watt consumption.

You got that right. In the meantime, the op should get a simple 10a charge controller like a Morningstar, Steca, Xantrex/Schneider and the like. Pair that up with a Fantastic Vent Endless Breeze box fan (basically a highly efficient rv fan in a box format). Runs about 1, 2, or 3A depending on speed. Works very well and is definitely quiet enough for the garage.

Now you won't be killing your batteries, and will actually cool the garage. Less benchtop junk to deal with.

[Johann]

You got that right. In the meantime, the op should get a simple 10a charge controller like a Morningstar, Steca, Xantrex/Schneider and the like. Pair that up with a Fantastic Vent Endless Breeze box fan (basically a highly efficient rv fan in a box format). Runs about 1, 2, or 3A depending on speed. Works very well and is definitely quiet enough for the garage.

Now you won't be killing your batteries, and will actually cool the garage. Less benchtop junk to deal with.

I thought that a charge controller will not work properly without a battery attached to it?

[inetdog]

I thought that a charge controller will not work properly without a battery attached to it?

Most will not, you are correct about that. I am not sure just what PNj was referring to.

A Linear Current Booster is designed to perform a function similar to MPPT with a direct connection to a pump or fan motor. (One where the torque required goes down with speed.)

[Rainwulf]

I thought that a charge controller will not work properly without a battery attached to it?

Most of them dont, as they need the battery to power up the converter itself, it doesn't power itself from the solar panels, as that voltage is all over the place and unreliable.
I would go to the local electronics store and get a small AGM 7ah 12 volt battery, and use the load control on the controller to enable the load only when the sun is up to prevent flattening the battery. Most slightly higher end PWM controllers have various load control options, like "on only when the sun is up" and "on only when its night"

Or, just go with a step down converter like i posted, it will run your fans at the speed you want until the panel cant provide enough current, and then slowly ramp down as the sun goes down. Those controllers do a basic mppt function in that if your panel voltage is higher, the controller can convert that higher voltage to more current, meaning you may be able to run more fans on the same panel.


The best things are the simple things, remember "KISS" keep it simple stupid. Less things to break.

If you do go with a controller and battery though at least you can set up some LED lights in your garage.. but beware, this is how it starts. You get your first panel and a fan or light, and before you know it, you have 2.5 kw on the roof, and 800ah battery banks.

[PNjunction]

Heh, yes I was assuming a battery was going to be used with the charge controller.

Speaking of which, I just picked up a 2nd 12v Fantastic-Vent Endless Breeze fan, and unlike the RV vents they are famous for, which have about 1/2/3a draw, the box-fan conversion runs 1.18 / 1.62 / 2.59a on the 3 different speeds. I'd have to look up the specs on CC's that have lighting control to see if they will handle 1-3A dc if you want that kind of control instead of just running direct from the battery.

Clear plastic vanes instead of white for this new one. Like before, the tips of the blades are attached to a circular surround, which helps keep the noise to relatively quiet levels, unless you are in a hospital, or blasting away at full power. What you are paying for is a very nice motor, and not some pc power supply fan stuff.

This, along with a small inverter for CFL's or LED's makes for some great "gateway hardware" loads to set the imagination (and hopefully calculator) running.

[Rainwulf]

Heh, yes I was assuming a battery was going to be used with the charge controller.

Speaking of which, I just picked up a 2nd 12v Fantastic-Vent Endless Breeze fan, and unlike the RV vents they are famous for, which have about 1/2/3a draw, the box-fan conversion runs 1.18 / 1.62 / 2.59a on the 3 different speeds. I'd have to look up the specs on CC's that have lighting control to see if they will handle 1-2A dc if you want that kind of control instead of just running direct from the battery.

Clear plastic vanes instead of white for this new one. Like before, the tips of the blades are attached to a circular surround, which helps keep the noise to relatively quiet levels, unless you are in a hospital, or blasting away at full power. What you are paying for is a very nice motor, and not some pc power supply fan stuff.

This, along with a small inverter for CFL's or LED's makes for some great "gateway hardware" loads to set the imagination (and hopefully calculator) running.

It's that gateway hardware thats the issue haha, get a panel, controller and battery and you become hooked. solar powered fans are the gateway drug!