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On 6/2/2011 6:44 PM, <a class="moz-txt-link-abbreviated" href="mailto:dan@foxfire-energy.com">dan@foxfire-energy.com</a> wrote:
<blockquote
cite="mid:20110602184417.720a661d8db719b1f2ad39509c9edaa3.5de8cf490d.wbe@email14.secureserver.net"
type="cite"><span style="font-family: Verdana; color: rgb(0, 0,
0); font-size: 10pt;">
<div>What I like best about Mark's set up (the retired phone co.
dude w/ half a hand), is that he can select individual strings
at random. he can eq an individual string, or top off a few
strings and park them. he can even run strings of T 105s, or
even nicad (individually of course) in the same system as
L-16s and the like.. he just reprograms the chargers (and logs
it). I think he got the design from his days in the Navy.</div>
<div><br>
</div>
<div>So boB, how about a controller that can be user programed
to charge multiple battery configurations with a soft switch?
i.e. Bank A, Bank B...? and while you're at it, maybe a
multiple string DC box? Something with a shunt and a breaker
for each string? A four string set up would be nice.<br>
</div>
<div><br>
</div>
<div>I could use 2% of your first million.</div>
<div><br>
</div>
<div>db<br>
</div>
</span></blockquote>
<br>
<br>
Well, It's not a bad idea ! I'll forward that question off to
Robin.<br>
I have ran into several that use separate and independent battery
banks<br>
and switch between them. I'm not sure why they don't just use those
L-16 size<br>
2V cells though instead.<br>
<br>
But as I mentioned before, I think that a battery balancer device
would take<br>
care of problems with single strings but maybe even parallel
strings,<br>
as well as the pesky problem of AGM batteries that like to plump
when<br>
you cook 'em ! (I hate when that happens and one battery gets real
hot)<br>
<br>
Say, maybe a gizmo that goes across each battery (no 2V cells
though) to keep each<br>
battery in the string at the same voltage. It would have to be
cheap, maybe $30.<br>
<br>
Great discussion.<br>
<br>
boB<br>
<br>
<br>
<br>
<blockquote
cite="mid:20110602184417.720a661d8db719b1f2ad39509c9edaa3.5de8cf490d.wbe@email14.secureserver.net"
type="cite">
<div><br>
Dan Brown<br>
Foxfire Energy Corp.<br>
Renewable Energy Systems<br>
(802)-483-2564<br>
<a moz-do-not-send="true" href="http://www.Foxfire-Energy.com">www.Foxfire-Energy.com</a><br>
NABCEP #092907-44</div>
<div><br>
</div>
<br>
<span style="font-family: Verdana; color: rgb(0, 0, 0); font-size:
10pt;"><br>
<div><br>
</div>
<blockquote id="replyBlockquote" webmail="1" style="border-left:
2px solid blue; margin-left: 8px; padding-left: 8px;
font-size: 10pt; color: black; font-family: verdana;">
<div id="wmQuoteWrapper">
-------- Original Message --------<br>
Subject: Re: [RE-wrenches] 24 volt Battery Bank comparison<br>
From: boB Gudgel <<a moz-do-not-send="true"
href="mailto:boB@midnitesolar.com">boB@midnitesolar.com</a>><br>
Date: Thu, June 02, 2011 8:56 pm<br>
To: RE-wrenches <<a moz-do-not-send="true"
href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a>><br>
<br>
<br>
<br>
Nobody mentioned this in this thread, but it occurs to me
that the answer may be made clearer<br>
by looking at the Voc of each battery string after so many
Amp-Hours (years) of service.<br>
<br>
i.e., disconnect the strings' parallel connection and
measure the individual string voltage after charging them
all the best that can be done.<br>
<br>
This would be making the assumption that the batteries
themselves were fairly equal capacity and voltage at
installation time. <br>
<br>
And for whatever reasons, connections, temperatures and
everything else discussed here, the strings degrade
differently.<br>
<br>
The older and more worn out batteries should have a lower
voltage (Voc) than the less worn out strings. Thus, the
better strings<br>
may be tending to hold up the worse strings by dumping
charge into them when the whole bank is discharging,<br>
and wasting energy and battery efficiency.<br>
<br>
I guess that just large 2V cells are the answer in this
case, if at all possible.<br>
<br>
Thanks for the help on this question !<br>
<br>
boB<br>
<br>
<br>
<br>
On 6/2/2011 10:42 AM, Tom Elliot wrote:
<blockquote
cite="mid:A4EB2F42564C42A996084E6F44A4610E@Haikulaptop"
type="cite">
<div dir="ltr">
<div style="font-family: 'Arial'; color: rgb(0, 0, 0);
font-size: 10pt;">
<div>Not surprised at all about the phone company
guy. It was a phone company guy who read me the
riot act that no one in their right minds would ever
parallel battery banks the way PV off-grid systems
did and got me to set up my system with separate
strings connected independently to buss bars. The
battery engineer I talked to years ago at Dynasty
not only said the same thing but also said keeping
strings separate meant individual string distance
from the bars became irrelevant (given correctly
sized wire for each string’s parallel connectors).
I had a system with 12 100 amphour strings of paired
12v Dynasty AGMs which was rock solid until the day
I sold the house. The last time I checked the
system before the sale no single battery varied from
any other in the system by more than 1/10 volt and
the majority were still holding identical voltages.</div>
<div style="font-style: normal; display: inline;
font-family: 'Calibri'; color: rgb(0, 0, 0);
font-size: small; font-weight: normal;
text-decoration: none;">
<div style="font: 10pt tahoma;">
<div> </div>
<div style="background: none repeat scroll 0% 0%
rgb(245, 245, 245);">
<div style=""><b>From:</b> <a target="_blank"
moz-do-not-send="true"
title="dan@foxfire-energy.com"
href="mailto:dan@foxfire-energy.com">dan@foxfire-energy.com</a>
</div>
<div><b>Sent:</b> Wednesday, June 01, 2011 4:14
PM</div>
<div><b>To:</b> <a target="_blank"
moz-do-not-send="true"
title="re-wrenches@lists.re-wrenches.org"
href="mailto:re-wrenches@lists.re-wrenches.org">RE-wrenches</a>
</div>
<div><b>Subject:</b> Re: [RE-wrenches] 24 volt
Battery Bank comparison</div>
</div>
</div>
<div> </div>
</div>
<div style="font-style: normal; display: inline;
font-family: 'Calibri'; color: rgb(0, 0, 0);
font-size: small; font-weight: normal;
text-decoration: none;"><span style="font-family:
verdana; color: rgb(0, 0, 0); font-size: 10pt;">
<div>Good thread. Thanks. </div>
<div>In my experience, it all boils down to the
customer. I've seen one temp. set up with like
12 strings (for a concert). but they were
recharged and sold individually within a few
weeks.. I've also seen a single string (Teledyne
aircraft batteries) fail in less than a year..
they were in a brand new airplane tug that was
never charged -- ever. (the guy said "I dunno,
it just stopped working").</div>
<div> </div>
<div>I have one customer who (last I knew) was
running 6 strings of mixed aged L-16s going on 8
years. Thing is, he's a retired phone company
dude (Who's missing half of his right hand from
using one of those pocket pal screwdriver
thingys on a key chain in a hot DC rack.. like
he'd done hundreds of times before.. but that's
another tale). But I do like his set up.. he has
each string set up with it's own fused Disco and
Trimetric.. Gives him random control over each
string. And yes, he keeps a very detailed log,
and you can bet that when he takes a battery out
of service, it's done.<br>
</div>
<div> </div>
<div>Me? for an average bullet proof off grid
system, I shoot for a max of two strings for 24V
systems (for the redundancy), and manually
reconfigure them every few years. for 48V
systems, I shoot for <span>one string of two
Volt cells<span id="GD__CURSOR"></span></span>..
thinking that if I loose a cell I can still
operate a 46V system until I get a replacement.</div>
<div> </div>
<div>And Yes, as we all know, there are folks out
there that really shouldn't be allowed to
operate a popsicle stick. </div>
<div> </div>
<div>db<br>
</div>
<div> </div>
<div><br>
Dan Brown<br>
Foxfire Energy Corp.<br>
Renewable Energy Systems<br>
(802)-483-2564<br>
<a target="_blank" moz-do-not-send="true"
href="http://www.Foxfire-Energy.com">www.Foxfire-Energy.com</a><br>
NABCEP #092907-44</div>
<div><br>
<br>
</div>
<blockquote style="border-left: 2px solid blue;
padding-left: 8px; font-family: verdana; color:
black; margin-left: 8px; font-size: 10pt;"
id="replyBlockquote" webmail="1">
<div id="wmQuoteWrapper">-------- Original
Message --------<br>
Subject: Re: [RE-wrenches] 24 volt Battery
Bank comparison<br>
From: Michael Welch <<a target="_blank"
moz-do-not-send="true"
href="mailto:michael.welch@re-wrenches.org">michael.welch@re-wrenches.org</a>><br>
Date: Wed, June 01, 2011 1:43 pm<br>
To: RE-wrenches <<a target="_blank"
moz-do-not-send="true"
href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a>><br>
<br>
Every now and then I see reference on this
list to the need for thermal detection. Here
is an interesting, inexpensive piece of
equipment that could be used for finding hot
(loose or corroded) connections, hot
batteries, hot PV cells in modules, and even
poorly insulated spots, its original intended
purpose:<br>
<br>
<a target="_blank" moz-do-not-send="true"
href="http://www.blackanddecker.com/power-tools/TLD100.aspx">http://www.blackanddecker.com/power-tools/TLD100.aspx</a><br>
<br>
I have one and used it for finding uninsulated
spaces, but cannot attest to its durability or
suitability for the other uses mentioned
above.<br>
<br>
<br>
boB Gudgel wrote at 01:00 AM 6/1/2011:<br>
<br>
>This might be a good reason for an
installer to have one of those FLIR (or
similar) thermal imager cameras.  They're a
bit on the expensive side, but could<br>
>really be helpful for so many things. Â
Even just to know if you have left a nut loose
(under load of course)<br>
><br>
>boB<br>
<br>
<br>
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