[RE-wrenches] Bulk Chrging Rate for AGM Batteries

[Starlight Solar, Larry Crutcher]

Peter,

AGM batteries account for over 50% of our battery sales. One of the
beautiful aspects of AGM's is that you can hammer them very hard during the
initial bulk charge stage. Their low impedance makes this easy to do. More
than likely you can't make enough current to come close to the maximum
in-rush this battery can handle. As long as you control voltage, hit with
ALL you can! Don't try this with flooded batteries, though.

For complete details, download the technical manual from the Sun Xtender
website and see section 5.4:
http://www.sunxtender.com/pdfs/Sun_Xtender_Battery_Technical_Manual.pdf

Man I love AGM's.

Larry Crutcher
Starlight Solar Power Systems
www.starlightsolar.com
928-342-9103

Store and Shipping Address:
2998 Shari Ave.
Yuma, AZ 85365

Mailing Address:
11881 S Fortuna Road, #210
Yuma, AZ 85367




----- Original Message ----- 
From: "Peter Parrish" <peter.parrish at calsolareng.com>
To: <Allan at positiveenergysolar.com>; "'RE-wrenches'"
<re-wrenches at lists.re-wrenches.org>
Sent: Sunday, February 27, 2011 1:35 PM
Subject: [RE-wrenches] Bulk Chrging Rate for AGM Batteries



We have a portable "demo-off grid" system (24 Vdc, 120 Vac, 1kW-ac) and
occasionally we end the day with a fairly deep discharge 11.6-11.7 V (80%
DoD).

I like to get a deeply discharged battery back up to 100% capacity as soon
as possible (as opposed to letting the 850 W PV / charge controller system
charge it up over a several days) and I have a AC battery chargers with
"20A', "10A" and "2A" bulk settings along with being able to choose, "wet",
"gel" and "AGM" settings.

Our battery of choice is a SunXtender AGM battery (PVX-2120L, 12V 253 amp-hr
(C/120).

My question: Starting with this battery at say 11.6 volts (open circuit), is
it safe to begin the bulk charge at ~8% of its C/120 capacity (i.e. 20A),
and let the charger go into absorption at 14.4 V (with temperature
correction of course) and finish at 2A? How high could I safely start the
bulk charge?


Peter T. Parrish, Ph.D., President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parrish at calsolareng.com
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885



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