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Posted by Ulysses on February 24, 2009, 8:23 pm
 


Let's say you had some kind of giant supercapacitor that could store enough
to power your inverter.  I don't know anything about giant capacitors but I
suspect they would cost more than batteries.  Plus you would not have a
constant, reliable voltage so that would need to be regulated.  Voltage
regulators for wind generators are available but there is a specific range
of voltages that they will accept.  My guess is that this would be a big
problem.  With a battery it might be difficult to exceed the maximum input
voltage of an inverter unless you had no loads on the batteries and the wind
was always blowing like hell.


I paid about $000 for my twentyfour 6 volt golf cart batteries.  They are a
lesser known brand but I got very good customer support from the
manufacturer.  When I requested the specific float, absorb, and equalize
voltages they sent me all the information and then some.  One reason that
batteries can be expensive is undercharging--many people who have solar
panels seem to think that 96% of full charge is good.  One year later their
$0,000 battery bank is sulfated and possibly ruined.  The key to long
battery life seems to be making sure they reach full charge at regular
intervals and are not too deeply discharged between charging cycles.
Equalizing the batteries periodically helps to equalize the cells and reduce
sulfates.

I've read about some people getting used forklift batteries for next to
nothing and swear about how great they are for their off-grid power.
Supposedly once the forklift batteries are no longer good enough for
forklifts they still can be used for several years for home power
applications.  If you are interested you can probably find some information
by using Google search.

Batteries work.  If you want to experiment and come up with a better,
cheaper, more reliable way to store power I and many others would love to
know about it.  I talked to someone who had a reservoir and 120 volt
generator on a water turbine who got very good results but once the water
ran out there was no more power.  Using that same power to charge the
batteries would give him electricity 24/7.



Posted by Curbie on February 24, 2009, 10:07 pm
 
Ulysses,

Sound like you got a great deal on T-105 type batteries.

Model            T-105
Make            Trojan
Voltage            6
20 hour amps        225
20 hour watts        1,350
Serial Connections    8
Parallel Connections    3
Bank Voltage        48
Bank Amperage        675
Bank Wattage        32,400
Weight            62 Lbs.(28Kg.)
Length            10.3/8" (264mm)
Width            7.1/8" (181mm)
Height            10.7/8" (276mm)
Replacement        12 Months
Pro-rated        36 Months
Life Expectancy        3 to 6 years
Cycles (20% DOD)    2800
Cycles (50% DOD)    1300
Cost    $25.00
Cost per watt        $.00007
Bank Cost        $,000.00
3 year monthly cost    $3.00
6 year monthly cost    $2.00
Web    http://www.trojan-battery.com


My problem with batteries is that they're consumable see 3 to 6-year
monthly cost above (based life expectancy), The net effect of
consuming the batteries for a sort of power conditioner for the
inverter, instead of an source of backup energy ONLY when needed,
seems so wasteful on an expensive line item. This is reason for this
line of questions; to see if there is say a more expensive (up front)
way to greatly lower consumable costs in perpetuate.

But, it seems base on your explanation that this isn't being done, and
I'm sure it's been thought of, so there has to be reason why it
doesn't. I'll see if I can kick it up the using a spreadsheet, they
usually turn up the problem.


I'm sure to start out with batteries which should allow for time to
experiment.

Thanks for the reply.

Curbie
On Tue, 24 Feb 2009 12:23:25 -0800, "Ulysses"



Posted by Ulysses on February 25, 2009, 4:11 pm
 

I think it was Bruce In Alaska (regular poster here) who has been getting 10
years from a set of batteries.  I've read of others getting that many years
too.  With proper care I'm seeing more like 6-10 years.  At it's best that's
still $00/year but that's not too bad.

I am all for doing everything as cheaply as possible.  I charge my batteries
(right now) with a $89 generator.  I was using (and will be again as soon
as I find a cheap enough pulley) a $0 car alternator and a $9 engine to
charge my 48 volt battery bank.

I have only played around with wind charging in a small way but from what I
have read it sounds like once the voltage gets up to the Absorb rate most
wind charge controllers "dump" the power to an alternative source.  The way
I see is that means the batteries never get to be fully, properly charged
and would still need another charging source (such as a generator or car
alternator) to complete the charging cycles, at least periodically.  Maybe
someone who does it will jump in here and straighten me out.


Just because nobody does it doesn't mean it can't be done.  I have ideas
that go through my brain like a pinball bouncing around until they finally
fall into the hole.  In this case the hole would be the conclusion as to
*why* it won't work.  But it is pretty difficult to come up with something
that many people haven't already thought of or tried.  Fortunately those who
do seem to be the type that also explain the shortcomings which can either
prevent others from wasting their time OR give others something to build on.





Posted by Curbie on February 25, 2009, 8:02 pm
 Ulysses,

I read a saying from a battery rep (or somewhere) that "most batteries
don't die from old age, they're murdered". Good maintenance is
mandatory to get the most (or even a reasonable) life out of your
batteries. But given good maintenance procedures, cycles and their
energy usage seem to be the next determining factor. I'm still trying
to figure how to relate DOD to cycles, is a battery discharged to DOD
of 50% 1/2 (or to DOD of 20% 1/5) of one cycle. I don't know how it's
calculated, I'll search groups and if the answer is not there, I'll
start a thread on it.


The way I read the process was that the wind turbine's generator was
to (or to be designed to) "Cut In" slightly below the battery's normal
discharge level so that battery wouldn't present a load on the
generator until the turbine blades got through "stall" and up to speed
at which point the battery's load would eat all the generator charge.
As the battery charge goes up and get close to full (more charge
coming in from the generator than what the battery could store) the
controller would start to receive the overflow which it would then
dump.


charged

My reading is that a properly designed system should handle all but
quarterly equalization charges. Still, you may require I.C.E.
generator for back-ups (no/low wind) and equalization.

You got a great deal on batteries, one which I won't be able to get
due to the rising cost of lead, so I'm still bound to the reality of
the spreadsheet. As I said I will probably start by buying my first
bank, but subsequent banks I'm looking at building. I bought a book on
battery building that so far has passed the scrutiny of the
spreadsheet.

If I understand your comments correctly your main source of energy is
that which you store in batteries, charged from a generator powered by
I.C.E? I looked at that method with interest and if so, would have a
pile of questions about your experience with it.

As always thanks for the light.

Curbie

On Wed, 25 Feb 2009 08:11:42 -0800, "Ulysses"



Posted by daestrom on February 25, 2009, 11:09 pm
 

Discharge to 50% and recharge, that is 0.5 cycles.  Discharge to 20% and
recharge, that is 0.2 cycles.  Discharge to 70% and that is 0.7 cycles.  (so
far we've 'used' 1.4 cycles of battery life).

The 'trick' is that just how many cycles you can get out of a battery is a
function of what you do for average DOD.  Say a battery is quoted as '1000
cycles at 50% DOD'  That means you can discharge it to 50% and recharge it
2000 times (0.5 cycles per charge/discharge).  But that same battery may
also be rated as '900 cycles at 70% DOD'.  So you could discharge it to 70%
and recharge it 1286 times.  While these two numbers *seem* quite a bit
apart (2000 vs 1286), they aren't really.  If a cycle is 500 amp-hours, in
one you got 250 amp-hours * 2000 times for 500,000 amp-hours of storage life
and in the other you got 350 amp-hours * 1286 = 450,000 amp-hours total
storage life.

You do get more life if you use a smaller DOD.  But you would need a bigger
battery to store the same amount of energy and only operate to 50% DOD.  (to
reduce typical DOD from 70% to 50% you need 70/50 = 1.4 times larger
battery).  So it may not be worth it compared to just replacing the smaller
battery slightly sooner.

Of course, probably each time you use it you won't discharge it to exactly
the same DOD, so you have to make a bit of a guesstimate of your average
DOD.

And if you *don't* get them fully recharged right away, that shortens their
life.  So it may often be prudent to charge with a gas generator if the wind
isn't available for a day or two.

daestrom


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