[RE-wrenches] Odd battery problem - very low SG in only one cell

[Drake]

Having one cell die seems to be an emerging pattern.


At 09:49 AM 11/22/2015, you wrote:
>Esteemed Wrenches;
>
>I'm looking for input on what could be going on 
>with a battery bank at the college I teach for. 
>It's a stand-alone system with 4 Trojan 12v 
>T-1275 in series / parallel for 24v, 660w of PV, 
>running only a drainback solar hot water system 
>for space heating. So, 3 pumps and 3 DTCs, max 
>load 100 watts and doesn't run all that often, 
>outback CC is usually in float. The batteries 
>are only 2.5 years old and are regularly maintained.
>
>My lab class tested and maintained the battery 
>bank last week, and on one battery there was one 
>cell, in the middle of the battery, with a SG so 
>low it wouldn't even register on our 
>refractometer or midnite hydrometer. That 
>battery reads about 0.2v lower than the others. 
>All the other cells in that battery read 
>reasonable SG, with 2 cells on the downstream 
>side reading SG slightly low, but still in 
>reasonable range. This was of course all before 
>topping up the electrolyte with distilled water.
>
>Our troubleshooting exercise looked at:
>~ Measurement error? Nope, I was right there 
>supervising and 2 different lab classes got the 
>same results with 2 different instruments;
>~ Stratification? A suspicion especially since 
>the system is usually in float. We equalized 
>twice, no change in SG. I DID hear that likely 
>this was the first time the batteries had ever 
>been equalized, but no way to know for sure.
>~ Spilled electrolyte from tipped battery 
>replaced with water by a previous instructor's 
>class? Can't see this, all the other cells would have lost electrolyte too;
>~ A student accidentally discharged electrolyte 
>into the bucket instead of back in the cell, 
>then was replaced by distilled water when 
>topping up? I can't see that either, the midnite 
>hydrometer needs only a small sample.
>
>So, I'm left with "likely we have a cell that is 
>failing for some reason" and students secretly 
>smug that the professor is also stumped.
>
>Any ideas?
>
>
>Dan Fink
>Adjunct Professor, Ecotech Institute
>IREC Certified Instructor™ forr:Â
>~ PV Installation Professional
>~ Small Wind Installer
>Executive Director, Buckville Energy
>NABCEP Accredited Continuing Education Providers™
><tel:970..672.4342>970.672.4342
>
>Â
>_______________________________________________
>List sponsored by Redwood Alliance
>
>List Address: RE-wrenches at lists.re-wrenches.org
>
>Change listserver email address & settings:
>http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
>List-Archive: 
>http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html
>
>List rules & etiquette:
>www.re-wrenches.org/etiquette.htm
>
>Check out or update participant bios:
>www.members.re-wrenches.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20151124/cd746366/attachment-0002.html>