<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<div class="moz-cite-prefix">Wrenches,<br>
I forwarded Brian's post on to Robin at Midnite, as I thought it
was an interesting idea. Below is his response, as well as boB's.<br>
Allan<br>
<br>
<div class="moz-signature">
<meta http-equiv="content-type" content="text/html;
charset=ISO-8859-1">
<title></title>
<font face="Times New Roman, Times, serif"><b>Allan Sindelar</b></font><br>
<small><a href="mailto:Allan@positiveenergysolar.com"><font
color="#000099" face="Times New Roman, Times, serif"><u>Allan@positiveenergysolar.com</u></font></a></small><font
face="Times New Roman, Times, serif"><br>
<span style="font-size: 10pt;">NABCEP Certified Photovoltaic
Installer<br>
NABCEP Certified Technical Sales Professional<br>
New Mexico EE98J Journeyman Electrician<br>
Founder and Chief Technology Officer<br>
<b>Positive Energy, Inc.</b><br>
3209 Richards Lane (note new address)<br>
Santa Fe, New Mexico 87507<br>
<b>505 424-1112</b><br>
<a href="http://www.positiveenergysolar.com/"
target="_blank"><u>www.positiveenergysolar.com</u></a><br>
<br>
</span></font>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Allan,
It is simpler than what is being suggested. The reason they
want to limit to 20 amps is because the battery doesn’t need
anymore than that. The controller will automatically limit
the charge current as the battery gets full. If a large load
is turned on, the controller will try to refill the battery
up to its capacity. The 80 amps will quickly be reduced
because the voltage will rise to the point where the charge
tapers off.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">There
is nothing else that needs to be done. If the problem is
that the battery bank is too small for a big controller, the
best answer is to get more batteries. A 80 amp charger into
a 200 amp hour battery is going to raise the battery voltage
so quick, it will not affect the battery at all. By the way,
discharging a battery at 60 or 80 amps is probably going to
do damage to a small battery also. We do have an input on
the Classic that could probably be programmed to do as
requested. That input feature has yet to be implemented. I’m
sure we will have discussions about this when the time comes
to write the input code. Maybe this feature will be designed
in, but it doesn’t sound like it is a very good feature to
spend a bunch of time on. After all, the main problem is
that the battery bank is just too darned small. <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Bob,
Tom and Ryan do you have any comments on the subject?<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Thanks,<o:p></o:p></span></p>
<span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Robin</span>
<p class="MsoNormal" style="margin-right: 722.25pt;"><span
style="font-size: 10pt;"><font face="Times New Roman, Times,
serif"><st1:place w:st="on"><st1:city w:st="on"></st1:city><st1:state
w:st="on"></st1:state><st1:postalcode w:st="on"></st1:postalcode></st1:place></font><b
style=""><br>
</b></span></p>
<br>
One idea I had in mind was to have an option, in software, to
limit the current into the battery,<br>
when the charging current goes above some set threshold. The
controller would have to get its information from<br>
the battery monitor over the network.<br>
<br>
If it is a grid tie system and grid is there and GT inverter is
selling, then no problem... The controller<br>
can work at its full output. If grid or loads go away, then the
CC will know and it can throttle back at<br>
that time.<br>
<br>
We don't have a battery monitor yet, but we will have one. This
will be one of the settings as well as<br>
Re-Bulk based on state of charge, ending amps and those types of
things.<br>
<br>
boB<br>
<br>
</div>
On 7/19/2012 8:34 PM, <a class="moz-txt-link-abbreviated" href="mailto:maverick@mavericksolar.com">maverick@mavericksolar.com</a> wrote:<br>
</div>
<blockquote
cite="mid:8E7291AE-7BB4-4677-81C2-66250F555B0A@mavericksolar.com"
type="cite">
<div>I say it is waste of time. </div>
<div><br>
</div>
<div>1. AGM batteries can take the high current and you are right,
the absorb voltage is reached and the absorb current is tapered
rather quickly. Current generation charge controllers are rather
fast at the transitions. I have a bunch of data from a system
with a PentaMetric that shows the battery bank going to absorb
voltage at grid tie, during cloud events, but only for a few
seconds at a time.</div>
<div><br>
</div>
<div>2. A properly designed GTBB system should cover the connected
loads for 24 hours of each sunny day, at a minimum. Keep in
mind, off grid systems are designed for that, and 3 days + of
backup, etc.</div>
<div><br>
</div>
<div>3. I would say, based on my experience, the minimum battery
bank should be 400Ah. I personally try to set it at 600Ah (48V).
It is a backup system after all. But the key is the customer's
expectations...who are they going to call after the lights go
out?<br>
<br>
<div><br>
</div>
<div>Thank you,</div>
<div><br>
</div>
<div>Maverick</div>
<div><br>
</div>
<div><br>
</div>
<div>Maverick Brown</div>
<div>BSEET, NABCEP Certified Solar PV Installer ®</div>
<div>President & CEO</div>
<div>Maverick Solar Enterprises, Inc.</div>
<div>Office: 512-919-4493</div>
<div>Cell: 512-460-9825</div>
<div><br>
</div>
Sent from my HondaJet!</div>
<div><br>
On Jul 19, 2012, at 6:35 PM, Brian Teitelbaum <<a
moz-do-not-send="true" href="mailto:bteitelbaum@aeesolar.com">bteitelbaum@aeesolar.com</a>>
wrote:<br>
<br>
</div>
<blockquote type="cite">
<div>
<meta http-equiv="Content-Type" content="text/html;
charset=ISO-8859-1">
<meta name="Generator" content="Microsoft Word 12 (filtered
medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
<div class="WordSection1">
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Drake,<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I’ve
been hounding a couple of the charge controller
manufactures about this issue, but so far I just haven’t
seen a light bulb go off in their heads, but I’ll keep
trying, and maybe this is a better forum to do it.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">MPPT
controllers can be adjusted to current limit at amperage
values below their rating, but if you do that, you are
also limiting the output of the array in general, and
the amount of PV power available to run the loads
directly from the array (through the inverter). Not the
best use of available PV power.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Say
you have an 80A controller and a 200AH battery. With
current technology, you have two choices:<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Let
the controller operate at 80A. If you have loads to draw
off some of the current (or sell to the grid), great,
but if not you could be seeing a charge rate of C/2.5,
which would be pretty hard on a sealed 200AH battery, to
say the least. Granted, the battery voltage would rise
pretty quickly, and the controller would start to taper
off, but it would still see high currents especially if
the absorption time is set long. Not a happy scenario.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Or,
you can set the current limiting on the controller to
20A for a C/10 charge rate. But if you had loads drawing
60A, you would be pulling that additional 40A from the
battery and not using the array’s full power. Also not a
happy scenario.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">What
we need is a controller that can read the signal from a
shunt at the battery, and use that as the basis of
current limiting control. <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">For
example, if we have an array that can produce 80A of
current, but we want to limit the battery to 20A of
charge, there would be 60A of potential current there to
run loads without drawing on the battery. If there are
no loads running, the controller should current limit at
20A (reading from a shunt), but if loads are turned on,
the controller should be able to let more current
through while still limiting the battery to 20A. When
loads are shut off, the controller should go back to a
20A limit.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">This
doesn’t all have to happen very quickly as a battery can
take a heavier charge for a short period of time, but I
think that this would be a major improvement of
controller function.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Of
course, if you are grid-tied you can sell all the excess
power, but if the grid goes down, or you are off-grid….?<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Because
of the low cost of PV and the high cost of batteries
these days, I’m seeing more and more requests for large
arrays with smaller batteries. I also think that PV is
now cheap enough to allow for oversizing of arrays for
better battery charging on cloudy days, which can reduce
generator run times. We need smarter controllers.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">What
say ye, charge controller gurus?<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Brian
Teitelbaum<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">AEE
Solar<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">
<a moz-do-not-send="true"
href="mailto:re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a>
[<a class="moz-txt-link-freetext" href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>] <b>On
Behalf Of </b>Drake<br>
<b>Sent:</b> Thursday, July 19, 2012 2:21 PM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> [RE-wrenches] Small battery bank vs
too large array<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hello Wrenches,<br>
<br>
Where can I get a device that will measure current through
a shunt and create a signal to trigger a relay? <br>
<br>
We want to be able to use a 2 kW array with four, 200 AH
sealed batteries on an Outback system. 2 kW of PV would
be too much amperage for the batteries. The idea is to
open relays to disengage strings in conditions of high
current to the batteries.<br>
<br>
The reason for this is to create backup systems where
power will be abundantly available when the sun shines.
The system will normally connect to the grid, except
during outages. In normal charging conditions the power
will go straight to the grid. When the grid is down,
power will be available for loads and battery charging,
but batteries will be protected from overcharge?<br>
<br>
Any suggestions on ways to accomplish this are welcome!<br>
<br>
Thanks<br>
<br>
Drake <br>
<br>
<br>
Drake Chamberlin<br>
<i>Athens Electric LLC<br>
OH License 44810<br>
CO License 3773<br>
NABCEP Certified Solar PV Installer<br>
740-448-7328<br>
</i><a moz-do-not-send="true"
href="http://athens-electric.com/">http://athens-electric.com/</a>
<o:p></o:p></p>
</div>
</div>
</blockquote>
<blockquote type="cite">
<div><span>_______________________________________________</span><br>
<span>List sponsored by Home Power magazine</span><br>
<span></span><br>
<span>List Address: <a moz-do-not-send="true"
href="mailto:RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a></span><br>
<span></span><br>
<span>Options & settings:</span><br>
<span><a moz-do-not-send="true"
href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org">http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a></span><br>
<span></span><br>
<span>List-Archive: <a moz-do-not-send="true"
href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org">http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a></span><br>
<span></span><br>
<span>List rules & etiquette:</span><br>
<span><a moz-do-not-send="true"
href="http://www.re-wrenches.org/etiquette.htm">www.re-wrenches.org/etiquette.htm</a></span><br>
<span></span><br>
<span>Check out participant bios:</span><br>
<span><a moz-do-not-send="true"
href="http://www.members.re-wrenches.org">www.members.re-wrenches.org</a></span><br>
<span></span><br>
</div>
</blockquote>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
List sponsored by Home Power magazine
List Address: <a class="moz-txt-link-abbreviated" href="mailto:RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a>
Options & settings:
<a class="moz-txt-link-freetext" href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org">http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a>
List-Archive: <a class="moz-txt-link-freetext" href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org">http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a>
List rules & etiquette:
<a class="moz-txt-link-abbreviated" href="http://www.re-wrenches.org/etiquette.htm">www.re-wrenches.org/etiquette.htm</a>
Check out participant bios:
<a class="moz-txt-link-abbreviated" href="http://www.members.re-wrenches.org">www.members.re-wrenches.org</a>
</pre>
</blockquote>
<br>
<br>
</body>
</html>