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

Feather River Solar Electric info at frenergy.net
Mon Nov 23 08:25:41 PST 2015


Dan, Larry,

         I just had a S-460 do exactly the same thing, bank of 8, good 
maintenance, light usage, one battery with 2 cells at 1.270, one at 
"zero"  Surrette was low hassle and prompt with free replacement.

         As someone notable once said "excrement occurs".

Bill



On 11/23/2015 6:42 AM, Starlight Solar Power Systems wrote:
> Dan,
>
> Last week I had a 3+ year old Trojan L16H-AC with one dead middle 
> cell, SG shows water. The bank has 8 batteries and the customer is 
> diligent about maintenance and charging. I wish I knew why this 
> happens but it seems over the last few years like there is a pattern 
> with Trojan L16’s.
>
>  Larry
>
>
> On Nov 22, 2015, at 7:49 AM, Dan Fink <danbob88 at gmail.com 
> <mailto:danbob88 at gmail.com>> 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>
>
>
>
>
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-- 
Feather River Solar Electric
Bill Battagin, Owner
4291 Nelson St.
Taylorsville, CA 95983
530.284.7849
CA Lic 874049
www.frenergy.net



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