AC> 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
 JD> a LOT of backup power; I can run 2 or 3 computers for over an 
 JD> hour if necessary.
 AC> Help this stranger to your US terminolgy- are the trolling 
 AC> batteries gel type or liquid type? 
I've seen them both ways,  though the liquid type is far more common (they're 
cheaper,  too).  That's what I've got here.  RV/Trolling refers to what we 
used to call in the store any "deep cycle" battery (I've also seen them 
called "High Cycle".)
 AC> Lead- acid type ie 2v per cell?
Yup.
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.
 AC> On what basis do you decide to retire an aged battery? If you 
 AC> discharge test it before condemning it, what test preparation 
 AC> do you first undertake?
I would not get rid of one unless there were a shorted cell,  or a bad 
connection inside the battery which prevented any power drain (a condition 
I've encountered more and more frequently over the years).
 JD> (!) They  JD> are seldom discharged to any degree (our power is 
 JD> pretty reliable), and are maintained by highly-regulated 
 JD> chargers in the UPSs.
 AC> Highly- regulated *should* mean, that the output is exactly 
 AC> matched to the needs of the battery ie fast recovery when flat.
One would hope so.  I wonder how you'd get a charger to determine whether a 
battery was either severely discharged or had a shorted cell,  though?
 AC> It seems though that yours is regulated to a rather small 
 AC> current. One amp seems awfully inadequate for a healthy 
 AC> recovery from discharged status. The fact that you have been 
 AC> satisfied says a lot more for the quality of the battery, than 
 AC> it says for the suitability of the recharge regime!
I wonder about that,  though.  I can't quite see the sense of really pushing 
a battery quite hard.  It would appear that a long,  slow charge would tend 
to let things happen in there a lot more evenly,  too.
 JD> Said chargers are capable of only about 1 amp of current, but 
 JD> that's sufficient to restore the batteries after a use, albeit 
 JD> over a fairly long time. However, they never equalize the 
 JD> 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.
 AC> That's better. Is 5 amps enough? Assume that the battery is 
 AC> good for say 50 amp hours. 
One of the things that makes it hard to figure some of this stuff is that a 
lot of the batteries sold for RV/Trolling use aren't rated in amp-hours,  but 
rather in "reserve minutes",  which is how long you'd get to run it at a 
specified temperature (usually 80 F) and with a specified draw (most often 25 
amps).  That's fine to have for a spec for an automotive battery,  but I 
can't see the sense in rating deep cycle stuff that way.  Of course,  what's 
worse is that when someone would come into what used to be my store to get a 
battery for a trolling motor they'd tell me how many pounds of thrust it was 
rated for, and this had nothing whatever to do with the current it drew,  
except very indirectly.  
 AC> BUT if you are ripping 5 amps into a 10 amp hour battery then 
 AC> this might strip active material from the plates and also 
 AC> concentrate the electrolyte, both are harmful results.
Removing active material from the plates?  Isn't that a normal part of the 
process,  that some material is going to flake off the plates over the life 
of a battery?  And I don't understand your comment here about concentrating 
the electrolyte,  as that's one of the usual things that happens when you 
charge a lead-acid battery!
 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
 JD> my old forklift was 8+ years old when it finally croaked, and 
 JD> even my seldom-used backhoe batteries last longer than 3 years. 
 JD> Interestingly, the gel-cell on my COCO lasted about 6 years 
 JD> before rolling over. It has that silly constant-rate charge 
 JD> mentioned in my other message.
 AC> I wonder what a COCO is? 
Short for a radio shack "color computer"...
 AC> The other three starting batteries you mention as having good 
 AC> lifetimes, are well matched to their duty ie momentary 
 AC> discharge followed by brief vigorous recharge. 
Yeah,  the big problem with most of that kind of equipment is how much of the 
time it sits as compared with how often it's run.  Or how over-rated the 
battery is for what's needed in the situation.
 AC> Deep discharge [standby power] is very wearing and such 
 AC> batteries are not expected to have long lifetimes.
Actually,  it's not the discharge that does it but the leaving of a battery 
in a discharged condition -- when you do so,  you end up with lead sulfate 
crystals on the positive plates,  and those don't usually dissolve with a 
charge put back in.  You've therefore lost significant plate area.
This is why letting a battery sit around for a real long time and then 
charging it up doesn't usually work,  you end up with a charge but no real 
power behind it for starting applications.
I used to sell a *lot* of lawn&garden and motorcycle (and boat, jet-ski,  
etc.) batteries every spring,  and told each and every customer that the best 
way to avoid that situation again was to put a charger on the battery once a 
month or so over the winter or however long it was sitting for,  and then a 
full charge before they went to use it.  This actually cost me some sales,  
but I think that those people were happy enough that I ended up with more 
customers...
 AC> As you have not used the same batteries as were provided with 
 AC> the UPS then the volts- per- cell on standby duty may not now 
 AC> be optimum. 
Depends on what came in it in the first place.  The UPS I've got here uses a 
pair of lead-acid gel cells.  I've not connected anything heavier-duty to it 
because they told me at the mfr. that I'd "burn up the inverter" trying to 
run it for longer periods of time.  I'm not sure if this is really the case 
or not,  but I'm not willing to risk it until I can either get a schematic 
for this unit or get another one to _use_ if I trash this one.
 AC> Especially if the batts you chucked, were nicads. 
I haven't seen any UPS units that used nicads.
 AC> Important that you keep your chosen trolling battery, at the 
 AC> manufacturer's recommended "floating" voltage.
Maybe one of these days I'll call the mfr. and ask them about it...
 AC> ... FLASH! Energiser bunny arrested, charged with battery.
And I'm sure that this tagline came up here at random...    
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