life expectancy of sealed batteries [RE-wrenches]

[Travis Creswell]

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





-----Original Message-----
From: William Miller [mailto:wrmiller at charter.net] 
Sent: Sunday, January 06, 2008 7:35 PM
To: RE-wrenches at topica.com
Subject: Re: life expectancy of sealed batteries [RE-wrenches]


Davis:

My information is anecdotal:  In 1998/1999 we installed about a dozen 
grid-tie backup systems.  About half were AGM or Gel and half were 
vented.  All of the vetted systems experienced battery failure in 4 to 5 
years.  All of the sealed systems are using the original batteries.

William Miller


At 04:09 PM 1/6/2008, you wrote:

>Wrenches,
>
>Does anyone have some general ideas of the life expectancy of sealed 
>batteries in backup applications.  I have seen charts showing so many 
>cycles at such and such depth of discharge, but I am wondering how time 
>enters the equation.  If the manu says 600 cycles at 80% DOD and there are 
>10 cycles per year, does this mean the battery bank will last 60 years or 
>even close to that?  Thanks.
>
>--
>Davis Terrell
>Bright Earth Solar
>(802) 492-2273 / brightearthsolar.com


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