Thickness and number of windings for 12 or 24 volt 17 foot wind turbines?

[cdog]

Thanks Bob, good to know, I see the rack units on fleabay from time to time, may be worth looking into,
Cdog

[fabricator]

Wow! That reliability is incredible! I'm gonna have to google those just for the reading.

[rossw]

although exeltech will build them from 12, 24, 36, 48, 60, 72 and 108dc and they also state they will build to custom voltages as well.
my bet all the exeltech inverters are built to the same high standards
last i checked they are 100% built in the good old USA too

Someone should pop them an email. Anything above 12V is wasted and unnecessary. They should reduce their inventory.
While they're at it, there's no gain in wasting all that extra circuitry to make such low THD when MSW is perfectly good enough for everything known to (most) men.


Couldn't resist...

[cdog]

Rossw, life would suck if there was only vanilla ice cream to choose from?

[fabricator]

With all his thinly velied snide remark it's clear that he believes anyone who uses a modified sine wave inverter is a rube, a hick, personally I cannot fathom anyone spending ten thousand dollars on a residential inverter but hey i' his money, it better be the longest lived most trouble free 100 year warranty bullet proof unbreakable piece of electronics on the planet, because I can buy one of the aims units per year for 22 years for the price of that ten thousand dollar unit and power everything I own with it without a single problem.
So ross you have a pretty system there but it dont mean $hit to me, I personally think it's stupid to pay so much for such an inverter, and yoiu think I'm an idiot for buying an inferiour unit so there it is, you need to live wirth the fact that 98 percent of the members here are not going to worship at the miracle inverter altar, come to terms with it, deal with it and move on, your happy with what you got (or possibly not, thus the intense need bordering on religious zeal to justify it) and I'm happy with what I got, that is the way the world rolls.

[windvision]

Maybe TomW will come to the same conclusion I have. It's time to close this post. It's certainly not moving forward.

[fabricator]

It tends to take a step back evertime the "Global moderator" chimes in.

[ChrisOlson]

It tends to take a step back evertime the "Global moderator" chimes in.

Indeed.  No more, ahhh..... "chiming in" really needed, or even wanted.

For swaro - Call Elektrolindningar AB.  They're the Cummins Onan dealer in Sweden and deal exclusively in standby and prime power systems for many different applications, including diesel and gas gensets, inverters, switchgear, UPS systems, etc.  They might not have inverters directly for your application but they might know where you can get them there.  Their phone number is (46) 3461-7490
--
Chris

[rossw]

With all his thinly velied snide remark it's clear that he believes anyone who uses a modified sine wave inverter is a rube, a hick

Horses for courses. I certainly DON'T think that across the board.
As you (and others) don't seem to understand, what DOES irk me is unqualified MISinformation.

I cannot fathom anyone spending ten thousand dollars on a residential inverter

1. Who said I WANTED to?
2. Who said it's purely RESIDENTIAL?

it better be the longest lived most trouble free 100 year warranty bullet proof unbreakable piece of electronics on the planet

I have no false illusions of that. It has however, given 6 years trouble-free operation, 24/7, and showing no signs of anything changing. It's endured quite a lot of abuse (like I said, I weld with it frequently and use some quite hefty industrial stuff on it from time to time)

[qoute]
power everything I own with it without a single problem.
[/quote]

What *YOU* own, and what *I* use (not necessarily own) are unlikely to be even remotely similar.
I don't intend to justify it beyond this but it may go a way towards you understanding WHY I have this and WHY I'd never consider using a MSW.
Part of my work involves calibration, repair, testing, configuring and setting up a variety of highly expensive devices. Some of these things can't TOLLERATE even slightly crook power. High power satellite uplink station - with a 400 watt TWT amplifier. The whole thing - encoder, exciter and amp cost in excess of $150,000. My RF spectrum analyser, used to set the thing up would cost in excess of $40,000 to replace.
Expensive SAN arrays - not much change out of $100,000. High performance servers and routers - over $50,000 a piece. Sure, they're not MINE, but once they're here for me to work on, I'm pretty sure if I blew them up the customer would expect me to replace them. And I'm not sure my insurance would cover it if I did "knowingly power them from something I knew was unsuitable".

Do you see what I'm getting at?  I suspect not.

I personally think it's stupid to pay so much for such an inverter, and yoiu think I'm an idiot for buying an inferiour unit so there it is

So, you can demand an apology from *me*, but feel perfectly happy calling me stupid. Nice double-standard there.
I also didn't say you were an idiot, nor [intentionally] imply it. Everyone seems to have missed the point. But then, perhaps I should have learned that you guys have skin thinner than vacuum-deposited gold.

It's easy, I'll fsck off and leave you all to it.

[ChrisOlson]

As you (and others) don't seem to understand, what DOES irk me is unqualified MISinformation.

ROTFLMFAO!  This is so hilarious I can't even believe it!

When us off-grid types get:
$150,000 High Power Satellite Uplink Station
$40,000 Spectrum Analyzer
$100,000 SAN Arrays
$50,000 High Performance Servers and Routers

LMAO!

THEN maybe we'll........ahhhh.........drop $10 Grand on an inverter.  Maybe.

But until that happens, which is not likely, most of us are stuck with:
$300 'fridge
$250 well pump
maybe a $300 freezer
some other small stuff

Being that probably 95% of us are pretty much not a member of the elite, I think we're going to stick with our modified sine inverters because the stuff we got seems to work perfectly fine with them.  Now, if there's some mysterious forces at work in our stuff from that modified sine wave, and one day all our stuff just Blows Up - we'll be like ol' Burt Gummer in Tremors III when he jumped out of that truck and said, "I feel......I was denied .......CRITICAL.......NEED TO KNOW.......INFORMATION!"

LOL!
--
Chris

[bob g]

ahem.... can i make a suggestion

first a preface

there is nothing wrong with spirited and sometime heated debate, however there ought to be some hard numbers
to back up assertions, or so it would seem to me.

as someone that loves to argue a position, and believe me i have gone toe to toe with a fellow on another forum that went on
well over several hundred posts, i can appreciate the passions of others.

if i might be so bold, perhaps each side of this issue, might lay out their rationale for why his position is superior or as good, in a clear, concise and well documented manner.

lay it out with numbers, start with actual efficiencies, losses, step by bloody step, so that anyone with some experience might follow
along and everyone can learn something from the discourse?

personally i feel i could argue either side 12 vs 48 with equal abandon, and as odd as it might seem i might make a better case for 24volt systems (note "systems" not components)

having said all this, i for one would be open to a good discussion where one side presented hard numbers/data/observations, with
analysis of the findings, so that it could be compared to the same from the other side.

also it would seem to me that both sides should also closely examine their own assertions/results and findings and play devils advocate and explain why the system results were as good as reported when they might not be as good, basically prepare to cover
possible arguments before they head out.

i think there is a lot to be learned from both sides of any argument and this one is no exception

at least this is the way i see it

but then again i am blind in one eye and can't see out of the other



basically its time to quit kicking sand at each other and lay out your cases for and against.

bob g

[ChrisOlson]

lay it out with numbers, start with actual efficiencies, losses, step by bloody step, so that anyone with some experience might follow
along and everyone can learn something from the discourse?

Here's the way I see it, Bob - it don't matter what voltage you run if your system works and makes the power you need.  Very few people have the equipment to measure actual efficiency.  So who really cares if it's 95.98% efficient, or whatever.  That doesn't do you one bit of good if you run out of power in the middle of the night when it's 20 below outside and the furnace blower quits because the batteries are dead.

The way I see it - I sit here tonight and my solar panels don't work.  I've had it with solar panels.  They're covered with ice and snow (again) ever since we had the last freezing rain ordeal.  The temperature plunges below zero right after the freezing rain and the ice on those panels is tougher than any steel known to man - can't scrape it off even with one of them hot tip windshield ice scrapers.

Power from solar today: ZERO  I don't care if it's 2 volt or 600 volt.  The number is ZERO.

Got pretty much no wind today - 135.7 amp hours from wind.  1.7 kWh.  I need at least 9 kWh.  I'm short over 7 kWh.  So I ran the gas charger for 5 hours late this afternoon and dumped an extra 250 amp-hours into the bank so my furnace and 'fridge stays going overnight.

As I sit here, it don't make one flippin' bit of difference if my system is 2 volt or 600.  No minute differences in efficiency of this or that is going to make up for the fact that I'm low on power tonight.  The forecast is for 20 mph wind tomorrow.  So I'm pulling the batteries down tonight and I'll catch up tomorrow when the wind blows.

And that's what really matters - you either got enough power or you don't.  You either got a method to compensate when you don't have enough, or you go without.  Whether it runs at 12, 24 or 48 don't make one bit of difference.  I happen to have 12 and I like it because I built it cheap and it works.  If you have 24 and it works, then you're sitting as good as me.  If DanB has 48 and it work, then he's in good shape too.

What starts this "voltage war" is where somebody who has 48 or whatever thinking they are sitting BETTER than me just because their voltage number is bigger.  Well, I got news for ya' - that ain't the way it works.
--
Chris

[bcalmed]

Amen...

[bob g]

Chris:

i fully understand the concept of using what you have, and to hell with efficiency concerns, however
the hope was to try and quantify or qualify some of the assertions made.

surely we can make a system work at any common voltage, with a broad spread of dollars spent, but

the case i would like to make you are illustrating very well

what do you do when the solar is under ice/snow and the wind isn't blowing?

this is a very real problem that is not at all atypical, not so much that everyone experiences the same
level of ice, they might just have a very modest amount ot solar to start with and live in a place like i do
where the sun hardly ever shines.

so again what the heck is one to do?  well you do as you have done, start a genset and bring up the batteries

this is probably the only circumstance that i can make a better case for 24volts than 12, (still working on 48 so i will not comment
on that voltage yet) 
if you are forced to burn gas/diesel/propane/frogfarts to run the generator the cost per kw/hr is likely somewhere between bad and horrible.  typically the efficiency is so bad the last thing a person wants to do is start a generator to charge batteries.
why is this so?  lack of taking the time to fully understand the options and proper design.
12volts is a horrible loser in this regard.

aside from that please remember also that i also stated that i felt i could make a very good case for 12volts, and an equally good case for 48volt systems, so i am not the enemy here.

the hope was to simply get a productive discussion going that everyone might gain something from.

bob g

[bob g]

for those questioning the validity of claims in efficiency for msw inverters vs pure sinewave inverters

http://www.windsun.com/General/Sunfrost.htm

the last paragraph relates to what i stated earlier
that is even if a msw inverter is more efficient and converting dc to ac, the appliance while still operating just fine
on a msw inverter "might" not be as efficient

15-20% less efficient at the load might be very significant to a small system.

bob g

[SparWeb]

I'm sad to see this thread go off track like it has.  Thanks Bob for trying to rescue this.  The "middle child" in me wants to get in between the quarrelling brothers, too.

i fully understand the concept of using what you have, and to hell with efficiency concerns, however the hope was to try and quantify or qualify some of the assertions made.

Nobody knows how efficient their system really is - there are little losses everywhere and it's hard enough to judge how efficient even the collection process is (solar radiance, wind kinetic energy, hydro kinetic energy) from minute to minute.  No, people judge mostly on the basis of whether the lights come on when they need them (or pump motor, or dish washer, etc.)  When that criteria is met, it is very hard not to be satisfied and go on with all the other things in life.  It would takes a major effort to evaluate every efficiency and loss and reliability factor of even a simple system, and few people are trained to do so knowledgeably.

[Simen]

Just to get a bit back OT (without me winding back to read everything), i'd think it's safe to say that it's mechanical impractical to wind a 17' for 12V? One would struggle to get all the needed copper onto the stator unless one made the diameter of the stator and rotors much larger, which would reduce efficiency, and the wires down from the tower would have to be rather thick.

I myself run a 12V system, and really enjoy the newest led-lights for 12V and other 12V equipments, but i got only 300W of solar and soon an 7' windgen. But i see that if i build a larger windgen (which i will), it's more practical (yes; also more expensive) to opt for a higher system voltage; 24V or 48V...
But there are also some dc-dc converters that are both cheap and efficient in the 15-20A range that would let you run your favourite 12V equipment even when running at 24V or 48V...

Just my thoughts (without the intention to start another pissing contest... )

[ChrisOlson]

Just to get a bit back OT (without me winding back to read everything), i'd think it's safe to say that it's mechanical impractical to wind a 17' for 12V?

Way impractical.  But not impossible.  I built one for 16 foot PowerMax blades by stacking four generator rotors for my 13's on the output shaft and winding two stators.  When I tested it it put out well over 200 amps at only 250 rpm.  I stood there and scratched my head for awhile, then went and did some figuring.

There's no way on God's Green Earth I can handle 200 amps from the turbine when the solar is putting out 75.  My 3,000 amp-hour battery bank just can't take 275 amps.  It would've put out tremendous power in lower winds but I would've had to have it pretty much shut down by the time the wind was blowing more than 18-20 mph to prevent damage to all my stuff.

I did some more figuring, and I figured out I can get more usable power from a 10 and 12 footer, and that's what I got now.  So I never flew it.  Still got the blades brand new in the box.

To my way of thinking, at 17 feet you're getting to the practical limit of battery charging turbines at any voltage.  At 20 feet and larger you're over the practical limit and you should be looking at something else besides battery charging.  But that's just my opinion.

I'll add some more comments, just my opinion, on max size with low voltage turbines.

I've flown 13 foot 12 volts for quite awhile.  I just, not too long ago, built a geared 12 footer - actually I've built two of them now and got the second one ready to go up when I get decent weather.  That new geared machine makes the direct drive 13's look downright anemic.  That thing pushes a good solid 65 amps @ 18 mph, 80 amps @ 20 and it's got the ammeter so far pegged at 24 mph that I don't even care to know what it is.

I like it because it puts out tremendous power at only 12 mph.  But IMHO that machine is over the practical limit for a 12 volt turbine.
--
Chris

[Fused]

I build little Axial flux and a few conversion mills.
I do it only for fun. (and 24/7 yard LED lights)
I started off at 12v, but when I wanted more power to batteries and I figured the cost of replacing my wire to batteries....it was obvious that I could bump up battery voltage to 24v and use the existing wires to battery.
For me, the savings was in the extra cost of copper of that 100 foot run to batteries. More watts into the battery through the same wire "more efficiently" and my watts to battery could be increased through the same wire I used at 12v (there is the amp limit of the wire). Seemed only sensible to me.
I have a good quality controller that only required changing the setting from 12V to 24V.
I am already using two 12V batteries so only needed to put them in series.
My existing dump load was reconfigurable from 12V to 24V.
My gas back-up charger works better and more efficiently at 24V than it did at 12V.
24v equipment is out there, more and more. I bought a Pure sine 1500 watt inverter from japan $350

Its just as easy to build a 24v mill as a 12v. There's just less copper at 24v needed to move the watts to battery, where 12v and the required wire is a waste of money for me.

Fused

[ChrisOlson]

Its just as easy to build a 24v mill as a 12v. There's just less copper at 24v needed to move the watts to battery, where 12v and the required wire is a waste of money for me.

Yep.  If you have any length of run, then higher voltage is definitely the way to go.  For me, I originally had 12 volt, then went to 48.  When I had the 12 volt I had put in 12 volt stuff in the house.  Lights, power jacks so we can use mobile 12V->19V converters for our laptops, etc..

Unlike DanB, I was not about to give up my 12 volt stuff, because I like it.  Those 12 volt -> 19 volt converters for our laptops, for instance, are way more efficient than the common transformer outfits that most people use plugged into the wall outlet for a laptop.

So I ran my 12 volt stuff off one string of 12 volt in the bank.  That worked, but it was what *I* would call "clunky".  When everything was said and done, I was not happy with the efficiency of the inverter (which was supposed to be a top-of-the-line unit), I wasn't happy with the turbines having to deal with such a wide operating voltage range, and when I wanted to add batteries or solar panels I had to add them in groups which put the crimp on the cash flow because I couldn't do it a little at a time.

It's only 17 feet from the base of the main Power Tower to my battery bank.  And one day I said screw it - this is not working for me.  I sold the inverter on eBay (and ended up trying various 12 volt ones until I got the ones I got now, which I'm very happy with), I pulled out the underground and buried 2/0 the 6 feet to the tower from the outside of the house to the tower base.  I got the 2/0 for free, changed the stator in the turbine and rewired my solar in parallel and ran 4 gauge from the solar junction to the batteries.

My "downgrade" from 48 back to 12 ended up being an "upgrade".  My inverters I got now are more efficient and I got less than half the cost in them.  I never had a gas charger before.  I built one for free out of stuff I already had.  I invented a different system for "dumping" power using the inverters to heat water - built it for mostly free out of stuff I had using only two $8.99 water heating elements that I had to buy.  Sold all my expensive 48 volt elements on eBay.  All my 12 volt stuff now blends right in with the system and no more dealing with the bank being unbalanced.

Today, I got no solar power again because those damned panels are just about worthless in the winter time here, but the wind is blowing.  I got WAAY more power than I can use already - I'm heating water with one inverter at 1,100 watts steady and the other one is kicking on and off in the bigger gusts.  It works.

Could I have done it better, or more efficient, with 24 volt?  I don't think so.  A few tenths of a percentage difference in efficiency of my power transmission losses on the wire run will never make up for the convenience and cost of putting the system together out of low cost, good quality, readily available stuff.

So my point is, for anybody who's putting in an off-grid power system, just don't automatically assume that you have to have 48 volt.  Sit down and figure it out first.  It's not hard to figure voltage drop in wire runs and such.  Put together a plan - don't do it based on what somebody says you HAVE to have to make it work.  Put it together based on what YOU need to make it work, and can afford.  If you can only afford $5 Grand for a "lowly" 12 volt system, but it will power your house, that's way better than spending $10 Grand on a top-of-line 48 volt system that only gets you halfway to where you want to be, even if the 48 volt is 5% more efficient.
--
Chris

[ghurd]

There is a 7.5% difference in the turbine rectifiers alone (2.5% loss in 48V to 10% loss in 12V).
Laptop power supplies have not been transformer based in a LONG time.

I can see what you are saying about total cost sometimes being lower in a low efficiency system that does what needs done.
I built a off grid solar dedicated wheelchair charger.  12V solar to 12V battery to inverter to 24V battery charger to 24V wheelchair.  Horrible efficiency, but it does the job (year round, in the snow belt with <0.5H worst case insolation), and was the cheapest route available at the time.  That was a very strange situation.
The numbers just do not line up for a large 12V system.
G-

[ChrisOlson]

well you do as you have done, start a genset and bring up the batteries

this is probably the only circumstance that i can make a better case for 24volts than 12, (still working on 48 so i will not comment
on that voltage yet) 

Bob, generators are a non-issue in my mind because there's none of them that are efficient at all, no matter what you do.  Right off the bat you're dealing with the thermal and mechanical efficiency limitations of internal combustion engines that send the vast majority of the heat in the fuel right up the exhaust stack.

That being said, I get more kWh per gallon of fuel out of my gas charger than I do from the AC generator, unless the AC generator can be run at close to full load, where it slightly beats the gas charger in fuel burned per kWh.  Since the gas charger runs at 12 volt and the AC generator runs at 120/240, it's kind of hard to arrive at a conclusion that voltage really makes all that much difference when you're only talking like 10 feet from the generator to the load.
--
Chris

[bob g]

Chris:

thanks for making this a more constructive discussion,  while i might disagree on certain aspects i will
concede your point that one ought to do his homework and setup his system according to his needs
balanced with his abilities and finances.

i pretty much took this approach, however i started my design from what is likely the least efficient component
of a system and worked backwards from that,  along the way i happened across both 24 and 48volt subsystem components
that i felt i could not pass up,,, that in hindsight was a mistake.

i passed along a 14kwatt 24volt outback rack system, four 3500watt inverters, 2 mx60, the distribution stuff and the backplane
all for a princely sum of 3 grand, it was off a boat and was only 2 years old,, there was over 14grand worth of stuff there.

anyway i digress,

the way i see it is the most expensive power i can generate is that which comes from a gas/diesel generator, and as much as we all hate it they are a fact of life for many offgrid folks, especially in smaller installations where the needs are greater than the capacity of a system.

so i started my R&D on the generator side of things first, i wanted to see if i could improve the efficiency of converting a gallon of diesel to electricity, over that which is typically a gas drive generator feeding an inverter charger, or over that of an engine driven
alternator charging 12 volts

the added conversion of an inverter charger didn't make sense, except that it is a simple system, using off the shelf stuff

the use of a car alternator turned out to be a non starter, as the efficiency is horrible,, it wasn't until i started to develop
or rather repurpose a hd 12volt alternator for use in charging a 24 volt battery... and that proved to not only be a measureable
increase in efficiency but a very significant one that i at least could not ignore.

going from the typical 54% of a hd alternator charging 14.4volts at 140amps (temp stabilized) and driving it in such a way that it can produce 28.8 volts at 100amps (temp stabilized) at an efficiency of approx 80% (including belt drive losses of 2%) was  a very significant improvement. so much so that the decision to leave 12volts behind was an easy decision.

the difference comes down to producing with 1 gallon of fuel at 24volts nominal is equivalent to the same power at 12volts nominal
that would take approx 1.5 gallons to accomplish.

if i would have stopped here i would have had my system sorted out, but i have decided to push forward to  48volts, and work out
the increased efficiency of the alternator at that level, so far i am about 3% under but i am not done,,, i should be about 3% better in efficiency at the 48volt level.  this is where i have to go now because i prematurely bought my exeltech inverter system
(48volt) before i had done the required research and testing to perfect the charging system at that level.

comments  have been made that generally folks don't have a way to accurately measure efficiency anyway, that i take exception to.

one can buy a precision shunt and amp meter fairly reasonably, and the accuracy is adequate for testing these sorts of systems
the difference in efficiencies going from one voltage to another exceeds the error of the shunt and meter, and because this is dc
we have no power factor issues to cloud the calculations.

all one has to do is measure how much power is going in and how much is coming out, do some simple math and and you got efficiency of the subsystem you are testing. as long as the test is run long enough for the system to stabilize your accuracy is plenty
acceptable, because generally the difference between 12 and 24 and between 12 and 48 is enough to get a very good
and relative if not exact indication of efficiencies.

you don't have to have an EE degree, be a research scientist, or have thousands of dollars of in test equipment. there are some
very good pieces of test equipment available that are common and really inexpensive.

going back to your system, and again i too spent a lot of years perfecting a 12volt design. these systems can be pretty good provided you can keep all the related components very close to each other. the problem arises when folks have to put the windgen
up on a hill a few hundred feet a way, or the batteries have to be housed a large distance away from the batteries, or solar panels
are up on the top of a barn that is better oriented toward the sun but 200 ft from the batteries, etc.

i still think a person can do a lot with 12 volts, but you have to design very carefully and make some compromises

going with 48volts allows one to build with far few compromises in my opinion.

at the end of the day, if it does the job that needs to be done, thats all that is important.

the lessen here for a newbie or someone just starting to think about a system, is this sometimes spending a bit more up front
to go with the higher voltage system will make the design and installation of your system less expensive overall, and likely return
more kw/hrs over its useful life.  how much less expensive overall or how many less kw/hrs over its useful life will depend largely
on your ability to design and build your system (talking about 12volts)

then there is the whole thing about UL or CE listing, most of the 12volt stuff doesn't qualify for either, so that must also be considered. most of the inverter manufactures seem to be moving to the 48volt stuff, and most of that stuff carries certification.
this may or may not be an issue for everyone, but likely will either be an issue for most or require another level of design to separate
the total system from any structure that is habitated.

in conclusion, yes i know anyone that has read this so far is wondering when will this A#$hole shutup!

i moved to 48volts because of the ability to get a superior grade inverter system at a price that msw sell for. and because of my interest and development of the base generation system that makes for the core of a trigeneration system (power, heat and cold)

i now have a system that can compete with the electric company, and i can now add in solar and possibly later windpower to further decrease the system runtime, in the end the system is measurably and significantly more efficient than it would be at 12volts.  the biggest reason for this is one of careful design, testing and verification via measurement.

it is possible that one might do very well with such a system with careful design using 12volts, its just doubtful that at the end of the day it will come close to overall efficiency.  (keyword "overall")

my opinions based on what i can observe and actually measure, not what i feel or find intuitive.

bob g

[bob g]

Chris

my test bed is 3 ft from alternator to battery bank, and i run large cables to the load bank

there is an enormous difference engine driving a 12volt alternator into a 12volt battery/load vs driving a 12volt alternator
into a 24volt battery/load

the difference is on the order of going from ~54% and 80% with the latter

its so significant that you really don't have to have much of any kind of accurate test equipment to see it.

my diesel is advertised as 32% thermal efficiency, and yes i have confirmed this in testing
32%  with an alternator efficiency of 80% equates to an overall conversion of 25.6% this competes
with utility generated electricity very well (in overall efficiency)

it is doubtful that you can attain half that efficiency using a 12volt alternator driven by what i assume to be
a small gasoline engine.

hopefully you don't have to run that engine/alternator very much, over time the cost of fuel would likely buy
a much better system.

bob g

[ChrisOlson]

there is an enormous difference engine driving a 12volt alternator into a 12volt battery/load vs driving a 12volt alternator
into a 24volt battery/load
the difference is on the order of going from ~54% and 80% with the latter

Oh, I'm sure this is very true, Bob.  I've never really tested it because the first gas charger I built was for our 5th wheel RV, which seemed to be more efficient than the Onan generator it had in it before.

The second one I built was for my house power system, and I was also pretty happy with it.

I consider the generator a "necessary evil" to generate off-grid power in emergency situations.  Like last night, I wouldn't have HAD to run that gas charger.  But I did it just so the batteries would stay above 12.5 all night.  I really hate to pull my batteries below 12.5 at any time, although it won't hurt them to go down to 12 once in awhile as long as they get charged up again right away.

As it turned out, I could've just hammered on the batteries last night and not run the thing because we got pretty decent wind today.  If my dang solar panels would work, they easily make 5 kwh on a partly sunny day in the winter.  But when they're covered with a solid inch of ice that's tougher than tungsten carbide, that's what the gas charger is for - to get you thru to better times.

So for me, it boils down to being happy to make the tradeoff for what I might be able to get for better efficiency with a higher voltage unit, vs considering it only a standby and living with what it is.  If it was a prime power source, then I'd look at something different.  But my mode of operation is, if I consistently don't have enough power, I'll spend the money on another solar panel or throw up another turbine before I'll get too worried about a few percent efficiency gains in one component of the system.

I decided to modify my post and explain one of the changes I made to my gas charger too:
The first one had a 10SI on a 6 horse Tecumseh snowblower engine.  That was not a good match - not near enough generating power for the engine horsepower and I burned it up running it full-fielded all the time.

I got what I think is a 90 amp 12SI on it now, which seems to be a better match.  It puts out more power than the 10SI at the same engine speed, and the engine can still handle it at full output.  I usually run it at only about 50 amps with the engine barely idling and have not had any problems with it.
--
Chris

[kenl]

swaro

 Did you decide on which voltage you are going for? How large of a system are you building watt wise? Sorry your post got hijacked, never saw this happen before.

kenny

seemed like a good idea at the time

[TomW]

swaro

 Did you decide on which voltage you are going for? How large of a system are you building watt wise? Sorry your post got hijacked, never saw this happen before.

swaro;

If you are still following this..

Yeah, please repost this in a fresh thread and I will try to keep the thread on topic. I dropped the ball on this one by not stopping the hijacking earlier and I apologize for that.

Probably time for some on topic requirement for postings?? It is a shame when this happens between supposed adults.

Tom

[scoraigwind]

There is a reasonably simple solution for using a big wind machine and keeping a low battery voltage that we use here a lot.  Generate at around 200 volts and then step down for battery charging.  So long as the frequency is reasonably high (plenty of poles in the alternator) then the cost of adequate transformers is not too bad at all.

The other thing is that if the windmill is really big then most of it is going to go for heat anyway, and it makes more sense to wire that heating at higher voltage around 200 volts.   

Say you want 5 or 10 kWh per day.  Most of the time you only need to charge battery/inverter system at about 200-500 watts.  So why not install a charger around this size and put the rest into heat?   That's what we tend to do.  Put a heater in series with the transformer so as to get a good power curve (variable voltage a bit like 'adding resistance to the line') and then throw in a load more heaters as the wind gets stronger.  In low winds the blades turns slow and kick out all the (modest) power that you need.

That's how we deal with bigger windmills in a lot of systems here on Scoraig.  The batteries may often be at 12 or 24 volts.  The pros and cons of a 48 volt system have already been discussed here.  So I am not going to even start on any of that.  Maybe another day.

[electrondady1]

it may not produce 200 volts as Hugh has suggested but  if swaro could dig into his stator a bit and run his two in hand 14 gauge  59 turn coils as a single 14 gauge conductor with 118 turns it would lift the voltage up enough to  be useful for heat and could still use this step down transformer idea.
if i am not mistaken, within transformers there are often used something called " taps" that can be utilized to access different voltage levels.