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details</title></head><body>
<div>Hi Jamie,</div>
<div><br></div>
<div>Thanks for the link. I find the Rolls/Surrette instructions
puzzling. They suggest a bulk phase at I1 (presumably 0.25xC20
which is fine), followed by an absorb phase " The charger should
maintain the voltage U0 until the current tapers to I1"
This current I1 makes no sense to me in the second stage, but the
graph shows current dropping to 0.012xC20 which does make sense and
corresponds to the Fullriver instructions linked by Larry.</div>
<div><br>
The proper charging procedure clearly requires that the
charger/regulator measures the charging current (not just the PV
current and/or wind/hydro current, since there may be a load). </div>
<div><br></div>
<div>My questions to the Wrenches List is: "What hardware do
wrenches use to regulate the charge on an AGM battery?"
Does everyone use this Blue Sky Energy device? Is it possible to
use AGM batteries with a conventional diversion controller such as the
Morningstar Tristar, and if so how do you determine the transition
from 2.45 V/cell to 2.3 V/cell? Morningstar offer a timed
transition, but without knowledge of current or of SOC this is rather
less precise.</div>
<div><br></div>
<div>Both of the charging methods in the agm-faqs linked below (and in
the Fullriver document) require measurement of the charging current to
determine the correct transition from one stage to the next.
Measurement of dV/dt is also suggested in the case of constant current
charging. Who actually follows these guidelines, and can AGM
batteries operate successfully without?</div>
<div><br></div>
<div>thanks!</div>
<div><br></div>
<div>Hugh</div>
<div><br></div>
<div><br></div>
<div>At 18:41 -0300 25/4/11, James Surrette wrote:</div>
<blockquote type="cite" cite>Content-Type: text/html;
charset=US-ASCII<br>
Content-Description: HTML<br>
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<blockquote type="cite" cite><font face="Arial">Hi Hugh,</font><br>
</blockquote>
<blockquote type="cite" cite><br></blockquote>
<blockquote type="cite" cite><font face="Arial">Here is the charging
information for our AGMs.</font><br>
</blockquote>
<blockquote type="cite" cite><br></blockquote>
<blockquote type="cite" cite><font face="Arial">Please let us know if
you need anything else.</font><br>
</blockquote>
<blockquote type="cite" cite><br></blockquote>
<blockquote type="cite" cite><a
href="http://www.surrette.com/content/agm-faqs"><font face="Arial"
color="#0000FF"><u><i>http://www.surrette.com/content/agm-faqs</i></u></font
></a><br>
</blockquote>
<blockquote type="cite" cite><br></blockquote>
<blockquote type="cite" cite><font face="Arial">Regards,,</font><br>
</blockquote>
<blockquote type="cite" cite><br></blockquote>
<blockquote type="cite" cite><font face="Arial">Jamie</font><br>
<br>
>>> "Starlight Solar, Larry Crutcher"
<larry@starlightsolar.com> 4/25/2011 6:04 PM >>><br>
Hi Hugh,<br>
<br>
An AGM battery is considered full when the current drops below a
specified<br>
amount. Lifeline, for instance, is considered full when current is
less than</blockquote>
<blockquote type="cite" cite>0.5 amps per 100AH. The Blue Sky Energy
IPN Pro Remote<br>
<a
href="http://www.blueskyenergyinc.com/products/details/ipn_proremote/"
>http://www.blueskyenergyinc.com/products/details/ipn_proremote/</a
> will allow<br>
you to program the transition into float mode based on the amount of
current<br>
flowing through a shunt. This can be very useful for your project
that<br>
involves opportunity charging. Multiple charge sources can be
monitored by<br>
the IPN Pro simultaneously. For us, it is the most ideal charger for
VRLA<br>
batteries.<br>
<br>
Here's a link to some charging instructions for the Fullriver AGM:<br>
<a
href=
"http://www.fullriver.com/products/admin/upfile/Charginginstruction.pdf"
>http://www.fullriver.com/products/admin/upfile/Charginginstruction.p<span
></span>df</a><br>
<br>
Larry<br>
<br>
<br>
----- Original Message -----<br>
From: "Hugh" <hugh@scoraigwind.co.uk><br>
To: "RE-wrenches"
<re-wrenches@lists.re-wrenches.org><br>
Sent: Sunday, April 24, 2011 12:11 AM<br>
Subject: Re: [RE-wrenches] AGM battery charging, more details<br>
<br>
<br>
| Thanks, Larry for the detailed response<br>
| ><br>
| ><br>
| >Generally, the manufacturers charge recommendations should be
followed.<br>
|<br>
| Yes but the issue I have is to know when and how to switch from<br>
| absorption to float. The Tristar has its own decision process
but is<br>
| it correct? And if not then are the settings suitable.<br>
|<br>
| > If you take away the red paint, I believe the Rolls AGM
is the<br>
| >Fullriver DC series battery. We started selling Fullriver last
year<br>
| >and I was surprised to find the very high absorb voltage<br>
| >recommendation. For the DC400-6 (415AH) in cycle use they
recommend<br>
| >charging at 29 to 29.8 volts and float at 27.6 @25C! That is
the<br>
| >highest AGM voltage settings I have seen from any
manufacturer.<br>
|<br>
| That's my worry.<br>
|<br>
| ><br>
| >My thinking about AGM's is that the float voltage and
transition<br>
| >current are much more important factors than absorb voltage
and<br>
| >current.<br>
|<br>
| Transition current is not in the vocabulary of the
Tristar</blockquote>
<blockquote type="cite" cite>| controller. I am not aware of a
product that has this feature aside<br>
| from maybe some inverters. I have read in an Outback
manual that<br>
| you should program the absorb time based on charge current<br>
| measurements, but the logic of this depends on the battery being<br>
| 'flat' to the same degree at the start of each charge - whereas
wind<br>
| and solar charging is not like that.<br>
|<br>
| >For most AGM's, initial charge current is almost unlimited.
However,<br>
| >Fullriver recommends current limiting and constant voltage for
the<br>
| >bulk/absorb cycle. Their current limit is .15 to .35*C20 rate.
BTW,<br>
| >make sure to adjust the temp. comp to 3mV/C/C for float. That
is<br>
| >lower than most.<br>
|<br>
| Tristar default is 5 mV/C/C but can be modified by RS232 lead
and<br>
| software intervention.<br>
|<br>
| ><br>
| >Equipment in a 24 volt system should be fine up to 32 to 33
volts.<br>
| >Check the specs.<br>
|<br>
| It's not me that has the problem it's the telemetry engineers.
I<br>
| assume they read the manual. But reduced temp comp helps.<br>
|<br>
| ><br>
| >What I said about equalizing was that I had done it twice to
my<br>
| >personal AGM battery bank. After the battery is fully charged
(<0.2A<br>
| >per 100ah @ C20) I put each battery, not each string, on a
current<br>
| >controlled charger. The current setting is .05*C20.<br>
|<br>
| That is 5 amps for a 100Ah battery? Does this not make them
gas?<br>
|<br>
| >I don't use voltage regulation when I do this. Once the
battery<br>
| >reaches 2.58 V/Cell, I charge for about 4 more hours always<br>
| >monitoring battery temperature. I use this process to recover
AGM<br>
| >battery capacity and it has been mostly successful with all<br>
| >brands. No more puzzle.<br>
|<br>
| Thanks - AGMs are a puzzle to me but you make it sound pretty
simple.<br>
| I do still have an issue with controlling the charge rate using<br>
| existing technology on an opportunity charging system where the<br>
| battery may be in any state of charge when the wind starts
blowing,<br>
| or sun starts to shine.<br>
|<br>
| best wishes,<br>
| --<br>
| Hugh Piggott<br>
<br>
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<div><br></div>
<x-sigsep><pre>--
</pre></x-sigsep>
<div>Hugh Piggott<br>
<br>
Scoraig<br>
http://www.scoraigwind.co.uk</div>
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