Author Topic: Newbie: Lots of questions... Charge Controller (Read 3031 times)

dragontowerpc · « **on:** April 08, 2009, 05:28:28 AM »

Hi all!

I have spent a great deal of time reading a lot of posts on this site and have been learning as much as I can. However, due to my lack of knowledge in electronics there are many things I don't understand. I'm not going to go into much detail about what I don't understand right now, that would be a waste of time. I am however, going to go into great detail about what I would like to accomplish.

I have built a wind generator. It is small and made out of very cheap and very readily available household items. My next task, I believe, is to build or buy a very cheap charge controller. I would prefer to build it so I can learn while I'm doing. But if buying would be a better option, please don't hesitate to tell me.

My wind generator only produces a few volts at best. Spinning it by hand it generates about +-1 volt. Don't laugh, it's a start! You can check out my progress at http://dragontower.homeip.net/DragonTower/WindTurbine.html I have also posted pictures on my site.

I am unable to get an amperage reading either because it's to miniscule or because I'm not using my multimeter right. But I have tried all the options I can think of with the multimeter and still no luck.

Now, to the point... I want a charge controller to be hooked up to one or two AA batteries that in turn power an LED or three just to prove concept and to have fun experimenting. However, google searches have yielded only results for systems that produce large amounts of power. I am interested only in a controller that is intended for a volt or three, if it's even possible.

I have considered taking apart an existing charger for batteries that runs off 120V mains power but I don't know enough about electronics to perform such a task.

I have scoured many forums and alt energy web sites trying to figure something out and I decided that this place would be the friendliest and seemingly the most intelligent.

Any info would be great!

Thanks in advance!

Flux · « **Reply #1 on:** April 08, 2009, 01:13:41 AM »

Effective chargers for AA batteries are quite complex, the method of determining end of charge is tricky. Those batteries don't respond effectively to constant voltage chargers like lead acids.

If your power levels are as low as you say then charging at a low constant current may be good enough. If you limit current to about 20mA you can leave them on charge for long periods and with some load from the led it may be good enough.

As you say you could use the control bit of a commercial charger if you manage to find an older design with a mains transformer. Modern things may be switchmode and far too complex to adapt.

The modern chargers are fairly complex microprocessor controlled things. There may still be a few dedicated IC charger chips using reverse slope detection but not suitable for someone with limited electronic skills.

The old method of shutting down when case temperature rises works tolerably well for cyclic loads such as drills but may not be so useful for your type of charging and load.

Flux

Ekij · « **Reply #2 on:** April 08, 2009, 06:23:29 AM »

The comments Flux made above are appropriate for NiMH batteries, he's assuming you are considering using these although he doesn't spifically call it out.

Unfortunately the charge requirements of NiMH are non-trivial, NiCad on the other hand are much easier to charge although the technology is hard to get these days as Cadmium is nasty stuff and the charge density of NiMH is about twice as good.

Is the 0.4V coming off the wind generator for one coil or for all the coils in series? 0.4V is too low to do anything.

If it's one coil and you can get them all in series you might have enough power to do something but with no measurable current it's probably not enough to run the LED when you have wind, let alone also charge the batteries for when you don't.

A big capacitor might be a better choice than batteries as charging these is trivial (fit a zener diode in parallel to ensure you don't over voltage them and just connect across the cap, done).

To answer some of the questions you had in the footnotes:

Plugging into the utility is very complicated, it's not as simple as matching voltage, you need to match frequency and phase too and even then it's complicated.

Gauge of wire is important because current is limited by the thickness of the wire and resistance is decreased by thich wire. For these reasons you want thicker wire.

The number of windings governs the voltage, for this reason you want many turns of wire.

However the voltage and current is proportional to the gauss which is dependent on the proximity of the coil to the magnet. You therefore want the coil close to the magnet which drives fewer coils and thinner wire (to get the coils closer). This drives compromise in the design.

Working it out theoretically is far too complicated and involves too many unknows. Generally it's simpler to wind a test coil and see what happens.

Ideally the 'hole' in the coil is the same size as a magnet. YOu want one side of the coil to be passing over a N pole of a magnet as the other side of the coil passes of a S pole of the adjacent magnet.

Read:

http://www.sparweb.ca/2_Gen_Ax/AXIAL_FLUX_HowItWorks_V1a.pdf

ghurd · « **Reply #3 on:** April 08, 2009, 08:46:02 AM »

There are some strange things going on with the alternator itself.

6 magnet and 9 coil single phase? Not good.

Looks like the output voltage numbers are AC? Hardly enough voltage in 15 MPH wind to get past forward voltage drop of a bridge. That's why there is no current reading.

Get the alternator sorted out and you can see some output.

G-

dragontowerpc · « **Reply #4 on:** April 08, 2009, 10:40:40 AM »

Wow! Thanks everyone for the awesome info.

I guess I should have included more detail about the alternator itself. After all, that's what I have spent most of my time trying to figure out so far.

I wasn't sure of the magnet to coil ratio so I went with 3 coils per pair of magnets. 3 pairs of magnets would mean 9 coils.

To avoid any complicated wiring right now, I went with single phase wired in series. I also wasn't sure of the gauge of wire so I just went to radio shack and got the 3 spools of 3 different gauges for $5.

I didn't know how many coils I could get out of such a small amount of wire so I did some experimentation with winding one coil per each gauge and then measure the length and divided that by the total length of the wire, to make sure I could get the most coils out of the whole length of wire with equal number of turns.

Which gave me nine coils with about 75 turns for the smallest gauge, 6 coils with about 50 turns for the second largest and 8 coils with about 25 turns for the largest. Don't ask me how I ended up with those numbers though!

I only used six magnets because that's how many I could comfortably fit onto a CD with out them touching each other or flipping over onto each other. Plus it seemed like a nice even number to work with.

I think I could get eight magnets on the disc. I think I'll try that and then reduce the number of coils to six like the chart shows.

I assumed that a store bought charger would be too complicated. I'm glad I have a second opinion to steer me away from that idea.

I have been reading a lot about capacitors and diodes... I never would have imagined just connecting those directly. When I get an alternator that puts out some amps I'll be back!

Again, THANKS for the awesome info!!!

ghurd · « **Reply #5 on:** April 08, 2009, 10:58:02 AM »

Get those magnets mounted on iron. And N-S-N-S...

G-

dragontowerpc · « **Reply #6 on:** April 08, 2009, 11:27:05 AM »

What if I just put magnets on both sides of the disc? Would that produce the same effect as iron? The magnets are alternating N.S.N.S...

Bruce S · « **Reply #7 on:** April 08, 2009, 11:30:39 AM »

I picked up on one thing you mention now. The magnets are on a CD. That's very good use of what's on hand :-), however the Al used in CDs isn't the best and surely isn't enough to get a good flux path. Since it's small enough and or CDs can be found for free ;-) also go looking for a #10 coffee can or food can. These are mostly tin and will help a whole bunch more for getting the flux path where it needs to go.

NiCd batts: These can be found in the solar lawn lights that a lot of people bought. The very early ones I'm still able to find in dumpsters has the tops are now glazed and not keeping the NiCds up to a decent amount of time at night.

You could also use the little charger that's in them as a cheap to free controller, plus you get a spare LED which each one

)

These little batts will take abuse fairly well, cold weather, low charging times, and usually bounce back, keep the charging current down to 1/10 of the max storage and you'll be just fine.

Keep one going!! You certainly have the right idea of getting hands-on learning!!

Cheers;

Bruce S

ghurd · « **Reply #8 on:** April 08, 2009, 11:37:11 AM »

No. The iron closes the magnet circuit behind the magnets. Your PMA is not closed on the coil side of the magnets, so you need all the help you can get.

Problem is finding a ready made piece of iron / steel that size. (I resorted to having mine made by Windstuff Ed)

Need to make something is my bet. Even if it is a few layers of sheet metal cut with tin snips.

G-

dragontowerpc · « **Reply #9 on:** April 08, 2009, 11:50:55 AM »

I think I see better now, I have to consider the magnetic field as it's own circuit as well. Interesting. And since each magnet is simply floating by itself, there is nothing to complete the circuit.

Understanding that, coffee cans would be perfect for the job. Those are easy enough to find and manipulate.

I thought of using a solar light charge controller but I didn't think that it would be able to handle the varying current as is often associated with wind.

Thanks again for the awesome info.

I'm off to work for money now, will probably try all this out tonight!

Ekij · « **Reply #10 on:** April 08, 2009, 11:51:35 AM »

IF you're single phase you need the coils to be hitting the magnets at the same time in order for the voltage to add.

If you're a different number of magnets and coils (and it's not an integer ratio) some of the coils are probably subtracting voltage from other ones!

Take a single coil measurement or ideally post a representation of the interaction of the magnets and coils.

Ekij · « **Reply #11 on:** April 08, 2009, 11:55:53 AM »

Solar light controller will not be able to handle AC. You would need to rectify the AC to DC (with a bridge rectifier, just 4 1N4001 diodes (from radio shack) would do for the small amounts of current from this alternator) first.

Bruce S · « **Reply #12 on:** April 08, 2009, 12:05:23 PM »

To consider the magnets as their own circuit is good, but to go a little further in understanding the need for iron/steel/tin backing. These are better as concentrators rather than seperate circuits. The steel based backings concentrate the magnetic flux so there's a more effective flux up around the wire were you want it rather than just dropping off the back (so to speak :-]).

The little solar chargers may have a problem with the varying voltage but they are current limiters so the NiCd/NiMh AAs don't vent or worse.

To know what your windgen is putting out ( sorry I'm at work and we've locked those type of sites out so I cannot view your setup) will allow you to make a good judgement of what can work, if indeed you bring the unit up to voltages above the 1V mark then you could possible pop the circuit of a solar lawn light, but since they normally are able to accept voltages of 3 - 5Vdc then you should be okay for now. The circuit will hold the current to the load of probably the max those little panels can give (I'm guessing 10ma at best with voltages of ~2Vdc at noon). Will be a good test.

Have Fun

Bruce S

Flux · « **Reply #13 on:** April 08, 2009, 01:43:16 PM »

Yes with single phase you need 6 ( or possibly 3 ) coils. Much will depend on your geometry and layout but with 9 coils there will be virtually no useful output unless you have done something very strange.

Flux

dragontowerpc · « **Reply #14 on:** April 10, 2009, 10:01:58 PM »

Ok, I got a couple of tin food cans, I cut the bottom out of one of them and was able to get 8 neodym magnets on it.

I tried two different coils:

coil of 30 gauge wire with 75 turns produces 0.2V and 0.08A by hand
coil of 22 gauge wire with 25 turns produces 0.05V and 0.2A by hand

When I try six coils of the 22 gauge wire I get the same original results: 1V and 0A

I'm thinking that I am either winding my coils wrong or I'm wiring them together wrong or both. I haven't tried 3 coils yet because I ran out of time. Won't be able to play around more till Sat. night or Easter Sunday.

I haven't tried any more of the 30 gauge coils yet either.

If I didn't live in a basement apartment and had a better place to work, I would try building a coil winding jig, although I'm not sure that would help any either.

Anyway...

Thanks to all for the great info. I'm not going to give up until I get it right!

ghurd · « **Reply #15 on:** April 11, 2009, 08:09:03 AM »

http://www.fieldlines.com/story/2003/9/11/84741/6758

G-

dragontowerpc · « **Reply #16 on:** April 23, 2009, 01:35:00 PM »

Ok, I think I've finally got it figured out...

I used 3 coils of 20 gauge wire with 25 turns which produces 0.2mA and 0.02V when spinning by hand.

I have decided to try 2 phases. Both phases produce the same amps and voltage independently.

I also went to Radio Shack and purchased 4 (1N4001) diodes ($3). Then I went to Walmart and bought one of those small solar lights ($4).

I took the solar light apart and severed the connection to the solar panel. But I left the photovoltaic resistor in tact because I thought it would be neat to have the LED only on at night. Plus I am going to assume that not by having the LED run all the time, since my generator is so small, it would give the single AA battery ample time to charge.

Here are my questions:

Does an alternating generator have a true positive and/or negative?

How do I wire the diodes? Do I wire them in parallel or series? Do I wire the diodes directly at the generator or do they need to be incorporated into the charge controller?

Since I have two phases, can I just take the leads and wire them directly together? i.e. positive to positive and negative to negative, if there is a positive and a negative?

Thanks

Marty

kurt · « **Reply #17 on:** April 23, 2009, 07:01:00 PM »

http://www.windstuffnow.com/main/3_phase_basics.htm

go there scroll down a bit you will see a picture of a 3 phase rectifier made with diodes to make a 2 phase one you would just use 4 diodes instead of 6. the diodes have to be the correct direction to work they should be marked Google a basic electronics tutorial tell you what way to put them.

you are going to have to work on your generator because you are going to loose 1.3v just in the diode drop so you are gonna have to make more voltage than that to light your led

dragontowerpc · « **Reply #18 on:** April 23, 2009, 09:25:50 PM »

Sorry for the double post, I just wanted to make sure that I would get an answer or two, didn't mean to cause harm or disrupt the flow. I will do better next time.

Also, thanks for the info, I really appreciate this forum and all the help that is given.

dragontowerpc · « **Reply #19 on:** April 24, 2009, 09:00:42 AM »

Every attempt I have made at trying to get this damn thing to produce even 1V has failed. It doesn't matter what gauge wire I use, how many or how few windings I make, how many or few coils I use, it just fails, miserably.

I appreciate the knowledge you all have shared.

Thank You.

Bruce S · « **Reply #20 on:** April 24, 2009, 11:39:53 AM »

Don't give up!! keep at it.

I don't know anyone who didn't fail one time or another, I have quite a few under my belt this year alone. Not to mention all the magic smoke I've let loose.

Take a little time off, get your head straight and come back at it.

Best I know WE ALL take time away from one thing or another, sometimes leaving it be is the best way to figure it out.

Keep Smiling :-)

Bruce S

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Author Topic: Newbie: Lots of questions... Charge Controller (Read 3031 times)