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<DIV><FONT size=2 face=Arial>Hello Travis,</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I think that 2 days is not enough battery
autonomy in the Ozarks and many other locations unless you have a fossil
fuel generator to carry you through long cloudy periods. Battery autonomy
is site and load specific. I've done systems with as little as 1 day and as
much as 3 weeks at 80% depth of discharge. Lately, I've been generically specing
1.5 days of autonomy at 50% d.o.d. to get the dialogue started with the
customer.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I use to spec up to 4 parallel strings of
T-105s or L-16s in 2, 4, and 8 batteries in series, but now I keep the number of
strings down to 3 or less and prefer 1 or 2 strings of big 2-volt
cells to reduce the number of cells and connections.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Southern California urban and suburban grid-tie PV
systems are almost all non-battery although we still get asked about emergency
power - until they hear how much it adds to the cost of a grid-tie PV
system.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Joel Davidson</FONT></DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=tcreswell@ozarkenergyservices.com
href="mailto:tcreswell@ozarkenergyservices.com">Travis Creswell</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=re-wrenches@lists.re-wrenches.org
href="mailto:re-wrenches@lists.re-wrenches.org">'RE-wrenches'</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, December 01, 2009 2:15
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [RE-wrenches] Other's
thoughts on Autonomy? was concordbatteries, EQUALIZE Them!</DIV>
<DIV><BR></DIV>
<DIV class=Section1>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt">IMHO, one of the
worst design boo-boo’s is going past more then 2 days of autonomy.
Personally, I no longer size much over one day because it’s my anecdotal
observation that most batteries die of old age and being ignored long before
cycles get them. Speaking mostly about quality deep cycle
flooded.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt">Lots of good things
result;<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt">-50%-75% smaller
battery bank means a $20,000 battery bank just turned into $5,000 bank which
frees up a ton of money for more modules and now-a-days you can buy a lot more
PV with that money. More array mean far less reliance on autonomy.
I’ll take the trade all year long. In the summer we have 3 to 4 weeks of
sun and one day of clouds and in the winter we get 3 to 4 week stretches with
1 sunny day. Autonomy doesn’t really matter in either case from what
I’ve seen. The larger the bank means more self discharge losses, which
on large battery banks gets significant as they age. 5-15 years later
you’ll still have all that array but no matter what you’re looking at new
battery bank.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt">-If you study the
quality deep cycle manufacturers literature you’ll see that you’ll see that
anything over 1 day of autonomy is too much to allow the array to actually
charge the battery bank anywhere near the recommended amps and just like rust,
sulfation never sleeps.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt">-Less cells to
water<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt">-Less space
required<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt">-Given that a
surprisingly high percentage of off gridders totally screw up on their first
bank, no matter how much we all try we might as keep the stupid tax of
replacing a 2.5 yr old battery bank to a minimum.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt">-All of this
discussion about cross paralleling, buss bars, TLC with a gazillion
connections and multiple strings goes away.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt">-And the best part is
we don’t have to carry all of the lead into the basement and even better back
out of the basement!<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt">Just my .02.
Feel free to strongly disagree but let’s be polite about
it.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt">Travis
Creswell<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt">Ozark Energy
Services<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT color=navy size=2 face=Arial><SPAN
style="FONT-FAMILY: Arial; COLOR: navy; FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<DIV>
<DIV style="TEXT-ALIGN: center" class=MsoNormal align=center><FONT size=3
face="Times New Roman"><SPAN style="FONT-SIZE: 12pt">
<HR tabIndex=-1 align=center SIZE=2 width="100%">
</SPAN></FONT></DIV>
<P class=MsoNormal><B><FONT size=2 face=Tahoma><SPAN
style="FONT-FAMILY: Tahoma; FONT-SIZE: 10pt; FONT-WEIGHT: bold">From:</SPAN></FONT></B><FONT
size=2 face=Tahoma><SPAN style="FONT-FAMILY: Tahoma; FONT-SIZE: 10pt">
re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <B><SPAN
style="FONT-WEIGHT: bold">On Behalf Of </SPAN></B>R Ray Walters<BR><B><SPAN
style="FONT-WEIGHT: bold">Sent:</SPAN></B> Tuesday, December 01, 2009 12:44
PM<BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B>
RE-wrenches<BR><B><SPAN style="FONT-WEIGHT: bold">Subject:</SPAN></B> Re:
[RE-wrenches] concord batteries, EQUALIZE
Them!</SPAN></FONT><o:p></o:p></P></DIV>
<P class=MsoNormal><FONT size=3 face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT size=3 face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P>
<DIV><SPAN
style="WIDOWS: 2; BORDER-SPACING: 0px 0px; ORPHANS: 2; WORD-SPACING: 0px; -khtml-text-decorations-in-effect: none; -apple-text-size-adjust: auto">
<DIV>
<P class=MsoNormal><FONT color=black size=5 face=Helvetica><SPAN
style="FONT-FAMILY: Helvetica; COLOR: black; FONT-SIZE: 16pt">I used to think
that one string was optimal; until I had a single cell failure take out an
entire system for weeks. (try operating a 24 v system at 22v!
)<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT color=black size=5 face=Helvetica><SPAN
style="FONT-FAMILY: Helvetica; COLOR: black; FONT-SIZE: 16pt">I now think that
2 parallel strings is optimum, 3 is OK, and 4 is
max.<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><SPAN class=apple-style-span><FONT color=black size=4
face=Helvetica><SPAN
style="FONT-FAMILY: Helvetica; COLOR: black; FONT-SIZE: 13.5pt">At 4 parallel
strings, we start spending more time looking to make sure all connectors are
the same exact length etc. to insure equal
operation.</SPAN></FONT></SPAN><FONT color=black size=5 face=Helvetica><SPAN
style="FONT-FAMILY: Helvetica; COLOR: black; FONT-SIZE: 16pt"><o:p></o:p></SPAN></FONT></P></DIV></DIV>
<DIV>
<P class=MsoNormal><FONT size=3 face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt"></SPAN>But of course how do you account for varying
internal resistance of the
batteries......??<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT size=3 face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt">I've done 4 parallel strings at 144 DC of sealed
batteries on an electric vehicle, but we were very careful with our
resistances, I even switched to smaller wire, on closer strings, and
calculated out the exact resistance, so all strings were theoretically equal.
This set actually just died, but achieved its manufacturer's predicted cycle
life. (B&B battery, 350 cycles to 80%
DOD)<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT size=3 face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt">So if you're careful, 4 strings can work
well.<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT size=3 face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt">Worst I've seen was 20 golf carts paralleled in a 12 v
system, (10 strings) and they didn't pull the main connections from across the
set, just connected to one end.<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT size=3 face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt">The results were very predictable, with the furthest
batteries being chronically under charged, and the closest ones being over
cycled to a premature death.<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT size=3 face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT size=3 face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt">Ray Walters<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT size=3 face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P></DIV>
<P class=MsoNormal><FONT size=3 face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P>
<DIV>
<DIV>
<P class=MsoNormal><FONT size=3 face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt">On Dec 1, 2009, at 11:28 AM, <A
href="mailto:Windsun@wind-sun.com">Windsun@wind-sun.com</A>
wrote:<o:p></o:p></SPAN></FONT></P></DIV>
<P class=MsoNormal><FONT size=3 face="Times New Roman"><SPAN
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<P class=MsoNormal><FONT size=2 face=Calibri><SPAN
style="FONT-FAMILY: Calibri; FONT-SIZE: 10pt">You gotta wonder about why the
customer bought such a battery layout, or why the installer sold that kind of
configuration (which ever it was) with so many small batteries. We would
never recommend going over 2 parallel banks, but sometimes the "customer knows
best...".</SPAN></FONT><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><FONT size=3 face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt"> <o:p></o:p></SPAN></FONT></P></DIV></DIV></DIV>
<P class=MsoNormal><FONT size=3 face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P></DIV>
<P>
<HR>
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