life expectancy of sealed & wet batteries [RE-wrenches]

[David Palumbo, Independent Power & Light]

Wrenches,
My experiences mirror Travis' on the sealed bats. But I have seen
significantly longer life spans with wet cell batteries over my 23 years
working with them. With L-16 size 10 to 13 years not that unusual in our
off-grid systems. Golf Cart size we have seen a few systems get 12 useful
years out of them which amazed me. We also have a number of systems with
large 2v cells with no problems yet in 12 years so far. Properly sized
systems with attentive homeowners is the common thread with all of these
long lived battery banks. But I do have a theory about battery temperature
also prolonging the life of these cells. Here in Vermont these batteries are
65 F in the summer and 55 F in the winter. We do know that higher battery
temperatures yield higher storage capacity but reduce life cycles. Please
note that we also have folks that use up an L-16 bank in 3 to 5 years.

I have kept a set of Hoppecke FNC's (Fibered NiCads) going in my off-grid
rental house for over 17 years now. Old timers will remember that our old
friend Rob Wills (Skyline Engineering back then) brought these in from
Germany as an improvement over the standard NiCads cells that many of us
were frustrated with in the early 90's. The FNC's do not require the mineral
oil float on the electrolyte's surface to reduce the onset of oxidation and
electrolyte contamination. It appears that claim may be true, I have not had
to recycle the potassium hydroxide electrolyte yet (in hard service since
1990). BUT the FNC's still had the same issues as the old technology Edison
Cell NiCads, mostly amp hour capacity related problems due to the fact it
was difficult charging them to 1.7 volts per cell and still operate an
inverter. If they did not reach the 1.7v they lost most of their rated
capacity. One or two cells would suddenly lose voltage and crash the
inverter when it was assumed that the bank was reasonably well charged. You
may remember trying 19 cells on a 24v system etc. trying to lick this
problem, it didn't help very much, all things considered. The FNC's were
very expensive and I had a lot of them that I removed from every one of the
dozen systems that I sold FNC's with. Add that to several more systems that
had the old reconditioned Edison NiCads (remember Pacific West, the NiCad
reconditioning company? Now there's a story for another day) where not a one
of them lasted more than a couple of years before I swapped them out for
lead acids. I slept better after biting that bullet. The FNC's in my rental
house are working really well for me after I figured out that you really
needed three times the amp hour capacity as Rob originally recommended and
have charged them to screaming high voltages. They are in a cold mudroom and
work well there, one of the advantages of NiCads being that they do not
loose as much storage capacity due to cold temps as lead acid cells do. I
water them once per year and use an OutBack FX2012 inverter that can
tolerate the 17+ volts input that they get when the sun is out.

Will I see any of you in Arizona for the AEE dealer conference in early
February? I'm looking forward to a change of scenery for a few days.
-Dave


<<We did about the same number of systems about the same time, many with
Concorde AGMS and only one set still remains.  The others all died at or
before 5 years.  Oddly, pretty much, the opposite of William's experience.
We learned that even using the manufacturer's specifications for charging
that grid tied systems (Trace SW's) are particularly hard on sealed
batteries.  Our assumption was that since they constantly are charging the
battery it dries the battery out.  One manufacturer essentially confirmed
this but would not admit that maybe they needed to publish different specs
for grid tied system.  It makes sense when you think about it...charging a
battery for years on end can't be good for it even if it's just a tiny
charge.  The one set of Concords that remains is probably still alive
because we turned down the float setting to just above 12.7v (per 12v) after
we started seeing all the other sets go.

In over 15 years in this business I've never seen a battery go anywhere near
its rated cycle life.  Of course it's not like there's a "cycle counter"
built into the battery so it's just the best I could estimate.  I've
personally never seen a battery bank that I've installed last more the 10
years.  We installed our first set of HUP's (a serious flooded battery)
about 5 years ago and have no problems with them to date.  We've got a few
sets of the big Surrettes out there on off grid systems.  While they are
still alive after 5 years they are very much in need of what most would
consider very high charge rates (over 200 amps) else they will quickly
become severely sulfated.

I've seen T105'a go over 7 years and I've seen them die in just a few.  Same
for L16's.  Owner involvement is absolutely critical to flooded batteries
while there's not much they can do with sealed other then pay a twice what a
flooded bank of the same capacity then watch it die sooner.

Travis Creswell
Ozark Energy Services >>


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