Hi Jim
On (06 Aug 96) Jim Dunmyer wrote to Roy J. Tellason...
 JD> I use a couple of farily large UPSs on my computer equipment, bought 
ery
 JD> cheaply because of their internal batteries being shot. My procdure is 
o
 JD> remove those batteries, install binding posts on the rear, then connect 

 JD> pair of Group 27 RV/trolling batteries with welding cable. This gives me 
a
 JD> LOT of backup power; I can run 2 or 3 computers for over an hour if
 JD> necessary.
Help this stranger to your US terminolgy- are the trolling batteries gel type
or liquid type? Lead- acid type ie 2v per cell?
JD> However: I've been doing this for some time, and have experienced what I
JD> feel is very short life for these batteries. As in about 3 years.
On what basis do you decide to retire an aged battery? If you discharge test
it before condemning it, what test preparation do you first undertake?
                                               
(!) They
 JD> are seldom discharged to any degree (our power is pretty reliable), and
 JD> are maintained by highly-regulated chargers in the UPSs.
Highly- regulated *should* mean, that the output is exactly matched to the
needs of the battery ie fast recovery when flat. It seems though that yours 
s
regulated to a rather small current. One amp seems awfully inadequate for a
healthy recovery from discharged status. The fact that you have been 
atisfied
says a lot more for the quality of the battery, than it says for the
suitability of the recharge regime!
Said chargers are
 JD> capable of only about 1 amp of current, but that's sufficient to restore
 JD> the batteries after a use, albeit over a fairly long time. However, they
 JD> never equalize the charge, and some cells die eventually. Due to this, 
I'm
 JD> instituting a program to equalize the batteries periodically, probably
 JD> every other month. I set my home-made charge to 5 amps and the timer to 

 JD> hours and let 'er rip.
That's better. Is 5 amps enough? Assume that the battery is good for say 50 
amp
hours. BUT if you are ripping 5 amps into a 10 amp hour battery then this
might strip active material from the plates and also concentrate the
electrolyte, both are harmful results.
 JD> I have batteries in other applications that go much longer; the pair on
 JD> the sawmill engine went 10 years before needing replacement, the one in 
my
 JD> old forklift was 8+ years old when it finally croaked, and even my
 JD> seldom-used backhoe batteries last longer than 3 years. Interestingly, 
the
 JD> gel-cell on my COCO lasted about 6 years before rolling over. It has 
hat
 JD> silly constant-rate charge mentioned in my other message.
I wonder what a COCO is?  The other three starting batteries you mention as
having good lifetimes, are well matched to their duty ie momentary discharge
followed by brief vigorous recharge. Deep discharge [standby power] is very
wearing and such batteries are not expected to have long lifetimes.
As you have not used the same batteries as were provided with the UPS then 
he
volts- per- cell on standby duty may not now be optimum. Especially if the
batts you chucked, were nicads. Important that you keep your chosen trolling
battery, at the manufacturer's recommended "floating" voltage.  Cheers.ALEC
... FLASH! Energiser bunny arrested, charged with battery.
--- PPoint 1.92
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