Hi Dan,
No definitive suggestions, but kudos for making it a learning experience
for _all_. Great analytical technique. Hopefully you gain more
credibility with the kids as a result of your candor.
Bill Loesch
Solar 1 - Saint Louis Solar
314 631 1094
On 11/22/2015 8:49 AM, Dan Fink 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™ for:
~ PV Installation Professional
~ Small Wind Installer
Executive Director, Buckville Energy
NABCEP Accredited Continuing Education Providers™
970.672.4342 <tel:970.672.4342>
_______________________________________________
List sponsored by Redwood Alliance
List Address: [email protected]
Change listserver email address & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://www.mail-archive.com/[email protected]/maillist.html
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out or update participant bios:
www.members.re-wrenches.org
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
_______________________________________________
List sponsored by Redwood Alliance
List Address: [email protected]
Change listserver email address & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://www.mail-archive.com/[email protected]/maillist.html
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out or update participant bios:
www.members.re-wrenches.org
