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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Dan et al,</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Thanks for all the input. The 1 mA per A-hr
capacity (20 hr) for AGMS was very important to know. Our AGMs are 250 A-hr, so
that equates to 0.25 A. This is exactly what we are getting right now in float
mode. </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The problem that I was having arose from
the Blue Sky 3024 DiL CC only staying in acceptance mode for 2 hours each day
(this is the factory default). So it took quite a few days to really top off
the battery bank.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>In order to program the scenario I want, I
will have shell out a few hundred bucks for an “IPN-ProRemote” to
access and adjust the acceptance mode parameters on the 3024. </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<div>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>- Peter</span></font></p>
<p><font size=2 color=navy face=Arial><span style='font-size:10.0pt'>Peter T.
Parrish, Ph.D., President<br>
California Solar Engineering, Inc.<br>
820 Cynthia Ave., Los Angeles, CA 90065<br>
CA Lic. 854779, NABCEP Cert. 031806-26<br>
<a href="mailto:peter.parrish@calsolareng.com">peter.parrish@calsolareng.com</a>
<br>
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885 </span></font><font
size=1><span style='font-size:9.0pt'> </span></font></p>
<p><font size=2 color=navy face=Arial><span style='font-size:10.0pt'> </span></font></p>
</div>
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face="Times New Roman"><span style='font-size:12.0pt'>
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</span></font></div>
<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
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>Exeltech<br>
<b><span style='font-weight:bold'>Sent:</span></b> Monday, February 01, 2010
6:11 AM<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] Couple
of Qustions about AGM batteries</span></font></p>
</div>
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12.0pt'> </span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>AGM batteries in good condition and fully charged
will consume approximately 1 milliamp per rated amp-hour in "float"
mode at 25C. Thus, your 250 amp-hour battery will require 250 milliamps
at the manufacturer's rated float voltage (including temperature
compensation).<br>
<br>
Discussion now turns to whether or not it's preferable to leave AGM batteries
connected to a source of current in float mode. Continuous float
current flow with the battery at 100% state of charge, and supplied over a
long period of time (typically months to years), leads to a condition called
"positive plate corrosion" (PPC). In this process, material in each
positive plate is gradually diminished, being leached into the electrolyte
and/or deposited on the negative plate. Once PPC has occurred, the lost
material cannot be recovered and re-deposited back. Reduction of
positive plate material leads to a decreased ampere-hour rating for the
battery suffering from PPC, which then tends to aggravate the corrosion
situation over time.<br>
<br>
The rate of PPC can in of itself be reduced by a *slight* reduction in float
voltage at 100% SOC, and of a value to reduce the float current from 1 mA per
rated battery A-H to 0.5 mA per A-H.<br>
<br>
The problem in doing so: most equipment on the market isn't designed to nor
is capable of monitoring battery float voltage and current sufficiently
accurately to be of benefit.<br>
<br>
You didn't say at what temperature the batteries are kept. Cold
batteries have a self-discharge rate lower than when hot. AGM batteries
lose less than 1% per month at 25C (77F) through self-discharge. Thus
if your batteries are new/healthy, you'll be down less than 2% in six weeks
if charged to 100%, then disconnected.<br>
<br>
If your batteries are consuming 2 amps at 26.4 Vdc and 21C, either they're
not 100% fully charged .. or something else is amiss. Incidentally,
battery "float" current increases with age from the 1 m-A per A-H
stated above.<br>
<br>
That being the case, I'd agree with Warren. At 2 amps, either you have
unknown load(s) consuming power .. or something else is wrong (could be as
simple as the batteries not being at 100% SOC).<br>
<br>
My recommendation: First determine why the batteries are consuming 2
amps. Once you resolve that issue .. six weeks of current under proper
float conditions (as defined by the manufacturer) won't significantly help or
hurt the batteries. If the batteries are truly drawing 2 A at 26.4 V
(presuming that's the proper temperature-compensated voltage for those
batteries), it's a troubling sign - and I'd leave the batteries connected to
your current source, as it indicates a high rate of self-discharge. If
you're able to reduce the float current to the 250 mA range at the
manufacturer recommended float voltage .. once you reach that current level,
I'd disconnect them for the six week period.<br>
<br>
Finally .. I also agree with Warren. Sealed AGM are not intended in the
sense of the word for "equalization". The manufacturers often
call their equivalent to this a "freshening" charge. It's not
as rigorous as a flooded-cell equalization due to the sealed nature of AGM
batteries. A true "equalize" would likely over-gas the cells,
potentially opening the safety vent on the batteries. When this
happens, if it's a self-sealing vent, you'll have lost some of the available
H2O. If it's not a self-sealing vent .. you'll have destroyed the
battery.<br>
<br>
<br>
Batteries are a chemical and mechanical complexity that often defy easy
answers, particularly in a forum such as this.<br>
<br>
Hope this helps.<br>
<br>
(By the way - I'm on the road, and if you post any reply/questions, I won't
be able to answer for at least a week or more.)</span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>Dan<br>
<br>
<br>
<br>
<br>
--- On <b><span style='font-weight:bold'>Mon, 2/1/10, Warren Lauzon <i><span
style='font-style:italic'><windsun@wind-sun.com></span></i></span></b>
wrote:<u1:p></u1:p></span></font></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><br>
From: Warren Lauzon <windsun@wind-sun.com><br>
Subject: Re: [RE-wrenches] Couple of Qustions about AGM batteries<br>
To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org><br>
Date: Monday, February 1, 2010, 5:05 AM<u1:p></u1:p></span></font></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>The answer to systems
not being used is nearly always leave them on float. <br>
However, 2 amps seems a bit high for AGM batteries unless you have some kind <br>
of phantom load.<br>
<br>
Equalization for AGM's is different and for a different purpose than with <br>
flooded. The current should be quite a bit less than you would need for a <br>
flooded, since the purpose is not to stir the liquid up but simply to get <br>
all cells in the series up to the same state of charge. AGM's don't usually <br>
need much equalization.<br>
<br>
..................................................................................................<br>
Northern Arizona Wind & Sun - Electricity From The Sun Since 1979<br>
Solar Discussion Forum: <a href="http://www.wind-sun.com/ForumVB/"
target="_blank">http://www.wind-sun.com/ForumVB/</a><br>
..................................................................................................<br>
----- Original Message ----- <br>
From: "Peter Parrish" <<a
href="about://mc/compose?to=peter.parrish@calsolareng.com">peter.parrish@calsolareng.com</a>><br>
To: <<a href="about://mc/compose?to=re-wrenches@re-wrenches.org">re-wrenches@re-wrenches.org</a>><br>
Sent: Sunday, January 31, 2010 4:19 PM<br>
Subject: [RE-wrenches] Couple of Qustions about AGM batteries<br>
<br>
<br>
> We have put together a 850 Wdc portable stand-alone PV system. It uses<br>
> a Blue Sky 3024DiL charge controller, a pair of SunXtender 250 A-hr AGM<br>
> batteries (24 volt configuration), and a Xantrex Prosine 1000 inverter.<br>
><br>
> We have been using this system for powering "events" and
getting some<br>
> good marketing from the activities. Everything has worked out well, and<br>
> the system is not being used now and probably won't until March or April<br>
> sometime.<br>
><br>
> We have let the system fully charge the batteries through
bulk/absorption<br>
> and now float. The float conditions are 26.4 V and 2.0 A at a battery<br>
> temperature of 21 deg-C.<br>
><br>
> My first question: is it alright to let the batteries float every day
for<br>
> the next 6 to 8 weeks, or should I disconnect them from the rest of the<br>
> system until we are ready to use the system again?<br>
><br>
> My second question: since the 3024iL can perform an equalization,<br>
> is there a safe equalization procedure for these AGM batteries?<br>
><br>
> - Peter<br>
><br>
> Peter T. Parrish, Ph.D., President<br>
> California Solar Engineering, Inc.<br>
> 820 Cynthia Ave., Los Angeles, CA 90065<br>
> CA Lic. 854779, NABCEP Cert. 031806-26<br>
> <a href="about://mc/compose?to=peter.parrish@calsolareng.com">peter.parrish@calsolareng.com</a><br>
> Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885<u1:p></u1:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'><u1:p> </u1:p></span></font></p>
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