Battery Genius Question: What is the tradeoff for higher 20h capacity L16 batteries?

Re: Battery Genius Question: What is the tradeoff for higher 20h capacity L16 batteries?

Hi benthere,

Generally, L-16 are good for at least 5 years. 8 years is great. You appear to have a single string at 48 V. Good decision on not having multiple strings! In my opinion, more than 5 years is all gravy. And since you have 5 years service from them, you appear to be doing things correctly in caring for them.

Generally batteries in cyclic use have one failure mode that is a shorted cell, and another that is a high impedance cell. In my limited experience with L-16s, high Z is more common than a shorted cell, or one that has high self discharge.

IN my personal experience with Surrette Flooded batteries, they do NOT require high charge voltages. The ONLY exceptions that I have read about was one chap that said that he had Lead Calcium Flooded Surrettesc that required 64 V Absorbs. This is 5.5 volts higher than ANY of the Surrette Flooded batteries in use here require. AND, some folks who are Grid Tied/Grid Interactive may have screwy Absorb or Float voltage settings. This high Absorb voltage requirement appear to be some sort of myth, based on what I have seen here.

Am just speaking of the Surrette S-530s and 4KS25sFLAs that have been in service for nine years here.

Bottom line, it appears that all that you are doing is working well. Would just recommend that you continue to monitor SGs and continue what you are doing.

Simply my observations from actually USING Surrette Flooded batteries in off-grid cyclic applications. YMMV Good Luck, Vic

Re: Battery Genius Question: What is the tradeoff for higher 20h capacity L16 batteries?

I'm also a Surrette user and agree with both Vic and vtmaps.
One difference I found in the failure mode however (in my last bank which were not surrette) was that they simply lost capacity. SG and no load voltage remained good to the end, but they could no longer sustain any useful load. Another thing of interest is that I had 3 parallel strings, and I later realized that when one string failed, the other two did a good job of covering for the bad string, until finally the last string said good bye. They were by the way, 11 years old when they earned their retirement. They had an easy life, probably never drained more than 10% below full charge. And yes, I'm aware that some say they should at least once in a while be taken down to the 50% state to extend their lives, I never once did that, nor, right or wrong, am I doing it now with the Surrettes.
I made sure the new bank was one single string and chose Surrette because being made here, I could pick them up at the factory door, but also they are among the very few, or only two volt L16 batteries that are manufactured as a single cell, instead of a 3 cell, six volt battery (L16) rewired internally for 2 volts. Thus each Surrette 2 volt L16 has only one single fill cap for checking electrolyte level and SG, instead of three.

Re: Battery Genius Question: What is the tradeoff for higher 20h capacity L16 batteries?

Vic wrote: »

Generally batteries in cyclic use have one failure mode that is a shorted cell, and another that is a high impedance cell. In my limited experience with L-16s, high Z is more common than a shorted cell, or one that has high self discharge.

Based on my experience over 23 years with a total of 16 L-16 batteries, the only failure I have observed is the specific gravity of the electrolyte decreasing and charging being unable to restore it. Cell 2 is dying because my rely switched charge controller malfunctioned, and I did not catch it before the battery was over-charged.

... date .... | time|temp|volt| density (g/cm^3)
... (MST) ...|(24hr)|(F) | (V)|cell 0 |cell 1 |cell 2
2013-10-03| 13:00| 71|6.79| 1.260| 1.265| 1.265
2013-12-22| 15:30| 42|6.90| 1.240| 1.245| 1.200
2014-01-05| 15:25| 43|7.05| 1.245| 1.265| 1.200
2014-03-12| 12:15| 53|6.82| 1.275| 1.280| 1.160