We built a 1000 watt wind turbine to help charge the battery bank that powers our offgrid home. It's a permanent magnet alternator, generating 3 phase ac, rectified to dc, and fed to a charge controller. The magnets spin with the wind, the coils are fixed, so no brushes or slip rings necessary.

Update: DIY Amp Hour meter for monitoring charge!

All about homebrew wind and offgrid power systems, the complete reference!
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Step 1: Build the magnet disks

We had 12" steel disks hydro cut. We cut a template for mounting the magnets. Then we mounted 12 grade n50 magnets around the outside edge. We then built a form, and poured the resin with hardner.

Step 2: Build the coil disk

We wound the nine individual coils, soldered them in a 3 phase wye configuration, and encased them in resin. We used 35 turns of 2 parallel strands of 14 gauge enameled (magnet) wire for 12 volts. Use 70 turns of single strand for 24 volts. # 3 phase diagram shown here shows 3 stator coils. each of those coils is actually 3 coils in series. coils 1,4, and 7 are series together, 2,5, and 8 are series together, and 3,6, and 9 are series together.

more details, see the following page 15 for the series star, 1-y diagram.


Step 3: Build the bearing assembly

Picture of Build the bearing assembly
Two Harley Davidson wheel bearings are inserted into the pipe, with a smaller pipe locked between them to keep them in place.

Step 4: Construct the blades

The blades are 2" x 6" pine, cut at 10 degrees on a table saw, and sanded into a rough airfoil. Not perfect, but close enough.

More can be found at

Step 5: Further Reading

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sspence (author)  menahunie4 years ago
We documented what we did, and tried to show how to do it with enough detail that anyone can duplicate.

4 ft. blades in 10 mph winds can only output about 60 watts.

4 ft. blades in 20 mph winds can only output about 500 watts. No way can it do 1200 watts.
bertzie4 years ago
Could this alternator also be used on VATW?
sspence (author)  bertzie4 years ago
It can yes. this design is for 650 rpm, though.
Gmba4 years ago
a question about the coils. Would the coils be wired by joining each individual coil wire together and then connecting it to the wire which will be connected to the regulator or battery.
sspence (author)  Gmba4 years ago
There are 3 sets of 3 coils. Each set is 3 in series. One end of each series connects at a center point. The other end of each series drops down the tower to the rectifier array.
2061368544 years ago
 Hi Im wondering if anyone can help me, Im an engineering student from Cape Town, South Africa and im trying to design a 1kw wind turbine, Axial flux permanent magnet turbine like the DIY turbine shown on this website, however im have trouble, determining why we use 9 coils, 35 windings for 12 v etc. by calculation. 

Is there anyone with a calcualated design for this 1 kw 12v wind turbine, it would be greatly appreciated.

Magnet_Dude4 years ago
Awesome design. Ive taken the liberty of modifying your general design to make it compatible with a Vertical Axis Wind Turbine. Currently working on building it and will hopefully be able to post the results online in the near future.
Since my budget was some what smallish i was only able to get a hold of 20 2"x1"x1/8" Grade N52 Rare Earth Magnets and was lucky enough to get some aluminum sheeting 'donated' and cut down to the dimensions i needed for my turbine blades. Still trying to get the amount of wire i need to make my coils.... Do you recommend any supplier in particular that could ship it our relatively quick?
sspence (author)  Magnet_Dude4 years ago
Which is the thickness of wire that you used?
sspence (author)  alain_kovacs20074 years ago
 2 in hand 14g for the 12v unit, single strand 14g for the 24v unit.
uguna4 years ago
approximately  how much torque does it take to turn the alt i plan on making a portable gen and need to know what the smallest engine i can use would be and still get max power
sspence (author)  uguna4 years ago
 Plan on 2hp per kw of output.
hi there, i plan on running your stator design off a bedini motor running at a few thousand rpm instead of wind power, any tips much appriciated any idea of possible power output?
I want to know if I want to produce ac how changes will be done? If you send information to my e-mail I would be happy.(
sspence (author)  captain jack sparrow5 years ago
I doubt the bedini motor will be able to turn the AF with a load attached.
bertzie5 years ago
Could you possibly post a more in depth instructable on just how to assemble the generator part?
sataipan5 years ago
Hello sspence, if the magnets are 2"x1"x.5" and the coil centers are 2"x1" how thick are the coils and is there a max thickness for the size of magnet you are using? Thx
sspence (author)  sataipan5 years ago
The coils are about 1/2" thick or so, give or take. depends on how good you are at winding. We recommend a jig to make uniform coils sizes. the thicker the magnet, the stronger it is. the .5" we use are N50's.
weirdtop3605 years ago
You say "We used 35 turns of 2 parallel strands of 14 gauge enameled wire for 12 volts. Use 70 turns of single strand for 24 volts." What exactly are the pros/cons of each method? Obviously the 70 turn single strand method is creating 24V compared to the 12V 35 turn 2 strand. Is either way more reliable than the other? I'm very interested in attempting to build a generator like this; however, I don't know what options are best.
sspence (author)  weirdtop3605 years ago
It depends on your battery bank voltage. If you have a 12v battery bank, use the 35 turns. If you have a 24v battery bank, use the 70 turns. If your inverter is over 2kw, I suggest a 24v battery bank.
gekarav5 years ago
Hello, looking in turn placing the coils and the exact way to connect them.
mauser5 years ago
Would like to know what type and what size diodes for 12 volts unit, and can I use a 12 volt 30 amp solar charge controller with it
sspence (author)  mauser5 years ago
A solar charge controller will not work. You need a diversion controller (some can do both, but get wired differently). We use a 100 amp 3 phase diode bridge. We have them available for $35 at
Your diodes, how many in each bank? I have to build 3 phase rectifiers for RF welding machines, some take up to 16 diodes per column, 2 columns per phase. I think the last one I built took 96 diodes( 1600A 2KV ) , cost me about 200 bucks, also do you put VOM's to help protect the diodes? Do you use capacitors to filter, or do you even need to filter it? just wondering....
sspence (author)  vernonstien5 years ago
6 diodes total, two per phase, just like a car alternator. we sell a complete 3 phase rectifier for $35 No caps are necessary, as this is a battery charger.
CARANOD sspence5 years ago
Couldn't we just use a "car alternator" with the same effect?
sspence (author)  CARANOD5 years ago
Absolutely not. A car alternator needs too high of an rpm, and has a power robbing field coil. Totally inappropriate for a wind turbine.
Hi SSpence, in the text of step 2 you say: We used 35 turns of 2 parallel strands of 14 gauge enameled wire for 12 volts. Use 35 turns of single strand for 24 volts. To make 24 volts i presume you need at least 70 turn in stead of 35. P.S. What dimensions do the magnets have?
sspence (author)  hans blommers5 years ago
It's 70 turns for 24v. Our magnets are 2"x1"x.5"
ChuckP5 years ago
I am on the grid, and would prefer to develop a generator that connects directly to my panel so as to avoid the cost and maintenance of batteries and an inverter. It this possible with this system? Thanks for all the work you have put into this.
sspence (author)  ChuckP5 years ago
This unit is not appropriate for direct grid tie.
How would you modify the alternator design for 48volt with roughly the same wattage? Would you use the same gauge wire? Will the performance of the machine be negatively impacted by running 48v vs 12v? Will there be enough room to physically fit the coils in your alternator as designed? My machine would be about 300ft away from the house and think I would like the benefits that higher voltage offers due to size and length of cable.
sspence (author)  notanarborist5 years ago
144 turns of 18 gauge wire should do you.
liqudice5 years ago
hey sspence just wondering did you make your rectifier or is this just the schematic for what you used? if you did what diodes did you use. just trying to work on an all in one controller I can adjust. i know they make them but i like to leave myself the option to build my own. also could you show a picture of the coils tied up in wye before the resin poured if you can, i have some creative ideas for it (i.e. quick plugs)? thanks for your time and of course patience. and also for educating the masses with your knowledge.
sspence (author)  liqudice5 years ago
I ordered a heavy duty rectifier from china. handles at least 100 amps. I sell them at

Davorin5 years ago
How did you connect the coils? There is double winding wires. is there one end connect so in one coil current flows parallel up and down or there is some other way?
sspence (author)  Davorin5 years ago
In the coil, the strands are in parallel, both end of each strand are connected to each other. This is to share the current between the strands, it acts as a larger wire, but is easier to wind. 3 coils are connected in series, and the 3 series are connected in the center, leaving one end of each series to come down the tower to the rectifier.
Someone told me that the way that the coils are hooked up to each other is crucial because there is, in a sence, a polarity, in that one side is positive and the other side is negative. He said that if you have 2 coils hooked up the wrong way that they could actually just cancel each other out. Is this true?
nickk5 years ago
Hello , You say "We used 35 turns of 2 parallel strands of 14 gauge enameled wire for 12 volts" does this mean that the final output will be 12 V DC ? if yes then it is not enough to charge a battery, we need 13.5 VDC to do so, what do you say ?
sspence (author)  nickk5 years ago
it doesn't output 12v, it's a turbine designed for a 12v battery system. just like when you buy a "12v" solar panel, it actually outputs 17v.
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