windcharger made with dc brushless fans

Hello,

I am creating a wind charger with computer brushless fans: Foxconn DC 12v .2A Model:PV802512L

I am certain you all have better ideas for an off the shelf fan to be turned into a wind charger.

In any case it was windy today so I took my multimeter and hooked the leads to the fan and wala I measured about .3 volts max.

I am assuming I cannot hook these fans up in series and I must connect them in paralllel?

However, if I connect them in parallel then I'll never get over .3 volts. So I must have a way to multiply the voltage to 14 volts to charge a 12v battery.

Then again is it ok to charge a 12v battery below 12 volts? Say 11 volts or less. If not then how do I protect the battery from low voltage?

Then to regulate exceeding voltage at 14 volts, I purchased a 7812  +12vdc 1 amp voltage regulator from Radio Shack( 276 1771).

What is necessary to make this happen?

John

-------------
John

Without looking into the fan specs, you want to connect them independently - neither series nor parallel.
In parallel - if they did generate, what stops one from driving another?
In series, how does the generated current from one flow thru the other(s)?

And I suspect they are not suitable for what you want.
As you may know, there is no such thing as a "DC Brushless" motor - they are DC input things with an inverter that drives an AC motor (or so i understand).
If there is no magnet in the rotor, how is electricity generated? (IE - how do you get electricity into the rotor to magnetise it?)


Wind generators are usually done with washing machine motors - ie, the Fisher&Paykel "direct drive". They can output 200W-300W making the required circuitry worthwhile.

To charge a battery, you need a DC-DC converter that provides 14.4V-13.8V regardless of the input voltage (that can convert up and down).

Hello oldspark,

Well I put a rectifier diode on the positive of the fan and was able to block current to the fan. I just thought it might have been possible to connect multiple brushless fans with diodes so that current could only go out of each fan and into a battery.

Thanks,

John

-------------
John

Yeah - the diode will block current flow one way - ie, from battery to the fan (when fan output voltage is less than the battery) but allow fan to "power" the battery (when fan voltage exceeds the battery voltage plus the diode voltage drop - typically 0.6V).

A similar thing is done with PV cells (Photo-Voltaics - aka solar panels) when the panels are of small output (up to say 15W), though I don't like that in case the battery is overcharged - ie, goes above 14.4V.
[ Some assume a small solar cell or charger will never fully charge a battery. But if it does, gassing occurs, else damage and heat if not a "wet" battery. Some assume that because a "typical" vehicle 12V battery may have a leakage/float current of 1A-2A - ie, 14.4W if 1A @ 14.4V - you need at least ~14.4W to "overcharge". (Float current is the current a battery still absorbs when fully charged. A 12V lead-acid battery's long-term charge voltage should not exceed 14.4V, and should be reduced to a [float voltage of 13.8V once charged (ie, 13.8W if 1A @ 13.8V). ]


The only way your fans can charge the battery is to exceed the battery voltage, else you need a dc-dc converter to boost their voltage (0.3V or 3V or 30V whatever) to 14.4V...


In simple terms, the most you will get from your fans is whatever power they consume. (They do not consume much do they?)

Try using a car alternator instead - spin it to (typically) above 500RPM. It has its own regulator specifically for 12V batteries, and will output several amps. It's much cheaper than the circuits and conversion needed for PC and brushless fans.

Though I am keen to be enlightened and corrected.... (But not by hydrogen power fanatics that reckon "higher voltage" and "the cloudier the better"...)

To Oldspark:

I see. So, if the brushless fan ever actually made .6v then the voltage drop across the diode would be -.6v. So, zero is the net effect?

Also, I had thought of origiinally using the car altenator/regulator, but an Autozone person talked me out of it because of the High RPM necessary for a car altenators. However, I recently spoke to Grainger tech support and they suggested I get a "speed reducer" to increase RPM.

Thanks!

John

-------------
John

Yes - the .6-.6=0 is correct. Though diode drops can be lower - eg 0.2V.

But the issue is mainly that it's a 12V 0.2A fan. If it were to be spun at full speed (and we could somehow excite it to get power), it could produce 2.4W (12V x .2A = 2.4W).
Compare that to a car alternator of 1,000W-plus.

The car alternator would probably have to spin at >500RPM to produce some output, and probably 3,000-6,000 RPM for full output.
And of course lots of wind power - almost 2 horsepower worth for 1000W output.

But an alternator is worth interconnecting with other alternators etc.
But such circuits themselves consume power (and money) so using them for 2.5W outputs isn't worth while.
A single 2.5W wind generator connected to some load might be worthwhile (eg, a LED, or battery etc), but no as a windfarm.


Question/experiment:
If you short the fan's 2 power wires together (or all 3 wires), is it (still) easy to blow & rotate?
If so, it is NOT producing power. Shorting it's output acts like a brake if it is a generator. (Like an alternator - the greater the output power, the greater the input power required. Or to paraphrase, 745 Watts out requires AT LEAST 1 HorsePower in (1HP ~745W; the add inefficiencies).

I suspect those fans will not be generating power....


PS - yes - any gearing can be used to achieve appropriate speed. (How were you going to get the PC fans up to speed?)

And it's easier if you provide what you hope to achieve - ie, power output etc.   
If merely experimenting, search the web. Plenty of people do this sort of thing, and I'm some someone will say how to (or not) us PC fans - thereby making a fool of me. (I've given up on being a bigger & better idiot.)
Just be wary - a lot if this stuff is as bad as Hydrogen Power (ie, you can't create energy from nothing - merely convert. But if you can extract hydrogen from some "wasted" energy (heat, sun, etc) or the hydrogen when mixed with fuel gains more energy than was used to create it, then you are on to something worthwhile.).

To oldspark:


Tying all 3 wires together on a similar model brushless fan(12v .2a ONG HUA HA9225L12SA-Z), and holding it up to a battery connected fan(for wind),it still spun but not as high and it stopped spinning in 4 seconds with all 3 wires connected.(Without 3 wires connected, the wind down time was greater than 4 seconds). Intresting experiment.


Again I held it up to the battery connected fan and it sped up to 1.15 volts(yesterday the wind was slower for both fans around .3v).

I haven't thought yet, how to speed up the fans. Possibly some type of gearing box.

Your quite correct the brushless fans were really just an experiment to see if I could "McGyver" up some electricity and experiment and learn some electronics about diodes, voltage regulators,coils, and charging a 12v battery.


I will work on both ideas.

Thanks!

John

-------------
John

Hey John - have you ever read how I hate people that get me to read up on things?
(That's a LOL. It's kinda like the old "YOU make me so angry!" - no - it is "I" that gets angry - nobody made or forced me to.... I can't remember the psych wording - ask Dr Phil.)

Anyhow's, I think things are as I thought they were.
EG - fieldlines.com Using Computer Fans As Generators.

That was one of many sites I looked at after my google search pointed to Makezine's Source for Wind Generator.

Brushless motors are used, but they have permanent magnets. Else are (I presume) large enough to warrant the electronics needed (ie, several hundred Watts or larger).


A few point out that stepper motors make good generators....

oldspark,

Thanks

John

-------------
John