Newbie question on finding DC wind motors

[Billystack]

Hi all, been reading alot the last few days, and am excited to be learning so much. Thanks for all the great info!  

I'm wanting to build a light duty wind gen that will power a small 12v battery to power some lights for the camp.  I've made some LED lights for the tent that run off a 12v bat pack, and was thinking it would be fun to have some light strings up running off a 12v bat that gets charged by a wind gen.  I understand the basic concepts of how to do this, but have a few questions about the details:  

When looking for a DC motor how do I determine its a good candidate for a gen?  I've seen some #'s thrown around but can't quite seem to figure out how to determine to the cut in speed,  etc.  For instance, I found an old singer kenmore machine that runs off ac and dc and the info on the motor says: 25-75 cycles, 110v 80w .8amp  something tells me this won't work.  I also found a cordless dustbuster, but the only info says 14.4v.  I was excited at first because I know you need >12v to charge the battery, but then I thought that the cut in speed would be really high, and didn't buy it.   I did find a small dc powered cordless fan that runs off 2-12v bat packs that I got for $3.  I'll be playing with that later today.

Couple more questions:

1. treadmills:  how do I determine if the treadmill will have a DC motor, and will it be a good one?
   
2. Surplus center website: looking at all the motors makes my head spin....how do I find a good candidate?
   
   

I've been enjoying reading about the DIY alternators, and think that I would be interested in possibly building one later on down the line, but should probably get a better handle on phases and wiring schematics first.  

thanks so much,

-Jeff

[ghurd]

What size 12V battery?  Like a 35 pound deep cycle, 7AH SLA, or a stack of rechargable AAs?  It does not take much for LEDs.

The AC/DC motor is the worst type.  It is not even good to convert.

Next worst is the tiny cordless or DC motors.  Most run at too many thousand RPMs.

Cut-In speed is related to the diameter.  Sounds like you want something small at this point, so 400RPM is not that fast if you intend to carve wood blades.

Easiest will be a higher voltage, lower RPM, brushed DC motor.

Avoid spending much until you have a better idea.

Might check ebay for a 90 or 180V DC 1750 RPM motor, say something in the 1/10 to 1/4HP size to get your feet wet, and should get a bit of power with small PVC blades.

The tower needs to be taller than the trees.  Costs more than a small solar panel.

Not much suitable for a small windmill at the Surplus Center for a decent price any more.  The days of the $10 and $20 treadmill motors are gone.

G-

[ghurd]

Also, No gear motors, and make sure it says "PM" or Permanent Magnet.

Not much on ebay right now.

G-

[Billystack]

Thanks for the help.  I've been messing around with my "fan" motor I picked up from the thrift store, and you're right...it's not so hot.  most I could get out of it was 4.5v.  I'll be continuing to look around for motors.  As far as a battery, I don't have anything built up, and would probably try and match it as best as I could to the motor.  I'm still learning a ton, and so really at this point its probably best to continue to read FAQ's and instructions...thank again.

-Jeff

[wooferhound]

Here are some ideas on Camping Power . . .

http://www.fieldlines.com/story/2007/6/15/181759/658

http://www.fieldlines.com/story/2008/7/3/8521/14163

http://www.fieldlines.com/story/2007/8/12/133145/653

[Electron Pump]

  I ran an add on the lockal community web site under classifieds asking people if they had treadmills that for what ever reason they needed to get rid of. I have accumulated quite a few. Only one of them produced any power for me with my homemade pvc blades. It took high winds and when it spun up to charging voltage it was very scary. You have to treat it like high speed swords. Swords that could let go and fly off with crazy potential energy.

  Not good for a camping where people will be walking around. It will be difficult to cary the stuff to stick it very high up in the air, and let me tell you of the scaryest part of all of it. Shutting it down when its time to pack up and leave, if it is producing any good power.

  If you want to persue experimenting with wind in a safer environment super. There are some good motors out there that can be had very affordably. I ended up buying one off the innernet that I'm using exclusively now. And I still have all of those treadmills to haul off but its all fun.

  When searching for a motor the most important thing to remember is High Voltage, Low RPM. But that isn't all. Now that I have one up and producing I have come to realise the importance of the Amp rating also. The amps measure how much electricity is actually moving from one place to another.

  My motor is 260 volts D/C rated at an RPM of 5100 but, it only has an amp rating of 5amps which is tiny. To get watts you multiply the volts times the amps. So lets say she is at charging voltage, about 13.8, and she is really gettin with it lets say the full 5 amps. Thats 69 watts. My point is you want more amps. Now I do see more than 5 amps with it periodically, I've seen 14 before, but it is rare and dont last long. I also have purchased commercially made blades so mine does better than homemade but not as good as the guys on this board do with carved wood. Thats the best and they say that they are alwayse blown away by how easy it is after they have made a set. That I dont know about. I'm still to scared to undertake that challenge. Some day I'll build an axial flux turbine with carved blades but I had to go threw all this other stuff to understand the difference it makes. And dont get me wrong I have a working system that is fairly consistantly producing, not much, but it is producing and it was cheap and a wonderful learning experience.

  Its a lot to grasp and a lot of work, but very fullfilling. Just keep tinkering and the rest will follow.

  I'm sorry I rambled on for so long. I used up my whole caffine buzz on this this morning. Man good luck dude, I'll close out saying though that I personally believe windmills are way more fun to watch than solar pannels and there are many here on this board that believe the same thing. Some super good people willing to help.

  I gotta go there is a cute blond jogger out front looking at the windmill. See ya.

 

[Billystack]

how bout this one:

http://cgi.ebay.com/Schwinn-350-Watt-24volt-Bike-DC-Electric-Scooter-Motor_W0QQitemZ120380966512QQih
Z002QQcategoryZ11332QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[wooferhound]

OK ,  here is the math, it's not tough and will save you from asking us about every motor you find.

The motor in your link is 2600 RPM at 24 volts

Now divide the RPM by the voltage, 2600 / 24 = 108.33

you will need 108.33 RPM to make 1 volt

Now multiply the RPM per volt times your planned Cut-In voltage

108.33 RPM times 12 volt Cut-In voltage equals 1300 RPM

There you go, your motor will make 12 volts when it reaches 1300 RPM

A proper Flooded Lead Acid battery is not really fully charged until it reaches 14.6 volts.

108.33 RPM times 14.6 volt Full-Charge voltage equals 1582 RPM

Too doggone fast.

[Billystack]

Thanks for the all the help...I've made a little excel spreadsheet to calculate voltage and watts based on the motor specs. Thanks for the math!  It has really helped me develop a sense of what would be a good motor as I scourge ebay and the internet searching for a motor.  Seems like its gonna take a while to find a winner.  

I'm looking to build a 12v system, but this is really just a fun project (for now), and I don't want to spend a ton of cash on an Ametek or equivalent motor.   So I'm thinking that I might just go with a 6 volt system, since it would be easier to find a motor that would charge a 6v battery.

 I'm wondering though, if a motor exceeds its rated rpm, would it also exceed its rated voltage, or just stop at its rated output?   For instance a 24v/200 rpm motor spinning at 300 rpm: would it produce 30v or still 24v?  I'm sure it would have negative impacts on the motor and is probably not a good idea to do.

Also, I'm thinking gear drive motors present too much internal resistance?

thanks, wish me luck...

[Billystack]

disregard gear drive comment...had been a couple days since I read this thread.  question already answered.

[wooferhound]

The battery will always try to keep the voltage going into it, at the voltage level of the battery itself. The battery will be sitting at 13 volts, and your Wind/Solar power will be 22 volts open circuit. As soon as you connect your open circuit Wind/Solar power to the battery, POOF ,everything is now running at 13 volts. It pretty much doesn't matter what voltage you want to charge the battery with, Your genny may be making 65 volts open, but connect it to the battery and then everything is at the battery voltage.

What happens to all that extra voltage? It's converted to amps and that is where you start to worry about your stator burning up. Once your wind genny reaches Cut-In (battery voltage) the measured volts will be the battery voltage which should be increasing slowly as it is charging. As your genny speeds up past cut-in the voltage doesn't increase, but the amps do. Under most circumstances you don't have to worry about the voltage of the device you are connecting to the battery, your worry will be with the ability of the charging device to deliver the Amps without burning up.

When Charging a battery try to keep the current going in to less then 10% of the capacity of the battery. For Example: a 100 amphour battery should be charging at 10 amps or less.