Batteries will fail, 2 volt cells are easily replaced your, not so w/your 12 volt cell, thats the whole battery. What causes it? usually its a manufacture issue. bad weld on the plates, poor forming of the plates in the cell. I have seen this many times where there IS voltage but no Spg. You were correct to try and EQ (low input current / hi voltage for a few days until the other cells reach the manu's recommended specs)but as you saw there was no change... so its a bad battery. Keeping good records w/ a good refractomter is critical and quite helpful when confronting the manufacture for replacment. In your application I would not hesitate to install a single replacement battery. Non critical & certainly very little cycling. Tump On Nov 22, 2015, at 10:08 AM, Jay wrote:
> Hi dan > > Assuming all charge settings correct, it's a manufacturing fault. > I couldn't tell if the other lower SG readings were in the same battery or > not. > > I just replaced a 1 yr old HUP, cell. > > Now as to what, why, how it failed, that's a good mystery > > Jay > > > > > > On Nov 22, 2015, at 6:49 AM, Dan Fink <[email protected]> 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 >> >> >> _______________________________________________ >> 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 >> > _______________________________________________ > 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 > > [email protected] www.SWNL.net > Solarwinds Northernlights > Serving Mid Coast Maine & Northern California > 207-832-7574 Cl. 610-517-8401 > > Blair "TUMP" May > ******** MAINE'S CHARTER ******** > NABCEP "Certified PV Installer" > > ******** MAINE'S CHARTER ******** > Trace Xantrex "Certified" Dealer / Installer" >
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