Battery Experience/Suggestions for Grid Tie? [RE-wrenches]

[Doug Pratt]

Hey Travis. Grid tie and wet-cell batteries are not usually a happy combo.
Two primary problems. 1. Customers forget to service (water) them. I've
never visited a grid-tied wet-cell battery pack without finding exposed
plates. It's just too easy to forget them. 2. All the common deep-cycle
wet-cell batteries on the market (T-105's, L-16's, Rolls-Surrette, and
Hawker) expect to be used and cycled regularly. Their chemistry isn't built
for long, long periods of float charging. Think of them like the muscles of
your body. They need modest amounts of regular exercise to stay healthy.
Don't go to wet cells with grid-tie unless they're specially constructed for
emergency backup service, and you do some kind of automatic (or very easy
semi-automatic) watering system.

Sealed batteries are usually expected to go into emergency backup service,
their chemistry is tweaked a bit so they're happier doing long stretches of
float service without becoming hopeless weaklings. AGM sealed types are
easier to build (and therefore usually cheaper...Concorde's excepted,
especially the past couple years!), but they're fluid starved so have little
tolerance for even the least overcharging. Gel sealed types are trickier to
build, but start out with greater fluid reserves, so they're a bit more
tolerant of the occasional overcharge. Gels will usually last 10% to 15%
longer than AGMs.

I've been selling the MK Gels (made by Deka I believe) for over a decade.
Service life is roughly 5 to 10 years. It depends a lot on the customer's
use and charging patterns. Set your charging voltages no higher than 2.35
volts per cell with sealed batteries. NO equalizing! 

Oh God! I've ventured into BATTERIES! A world with no black or white but
plenty of gray areas. Let the flames begin... (got my nomex shorts on).

Cheers,
Doug Pratt
DC Power Systems


-----Original Message-----
From: Travis Creswell [mailto:tcreswell at ozarkenergyservices.com] 
Sent: Wednesday, May 23, 2007 7:23 AM

Hello All,

We've got several grid tie customers with aging or dead Concorde AGM battery
banks.  They feel that they got pretty poor calendar (4-6 years) life from
these batteries and the customers are not that excited about going back with
another ~5 year battery bank.  We did about 20 systems in 1999 with
Concordes and only one of them is still alive.  All in all we weren't that
impressed with Concordes.  How have MK AGMS been doing for folks?  We've got
a few really small sets out there

Both of these customers have budgets and I think would tolerate paying more
for batteries in exchange for getting a longed life battery bank.  Both
banks are in the basement but with some construction we could construct a
venting system so flooded batteries are not out of the question.  But I'm
not sure either of these customers would properly maintain flooded
batteries.

So what batteries should I be looking at?  I'm pretty sure we need to just
skip right past T-105 and L-16.  What about the HUP or similar in float
service?  One customer has several multi day power outages annually.  The
other rarely looses power for more then a few hours a year.

I'll look forward to suggestions.

Regards,

Travis Creswell

Ozark Energy Services

 


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