On Sun, 2 Jan 2011 10:01:46 -0600, Andrew Rossmann
wrote:
I have a battery I bought for an APC UPS about 4 years ago. I bought 2,
and used one immediately.
Model number please? I'm curious.
I kept the other on the side as I have several
UPS's that use basically the same battery. Of course, over time, it has
discharged itself.
If you let a gel cell battery run down for an extended period, it will
sulfate itself rather nicely. Once the terminal voltage drops below
about 11VDC, it's on it's way to the recyclers. I have to charge my
stock of SLA batteries every 6 months or I end up with dead batteries.
Sometimes, even with a 6 month recharge, my older used batteries die.
After 4 years, you have the added enjoyment of plate corrosion, which
is not reversable. For my amusement, I once tore apart a dead SLA
battery to see what's inside. To my surprise, both the lead
(positive) and lead dioxide (negative) plates looked like rather
corroded.
I measured about 4.3V instead of the normal 12-13V.
Yep, it's almost dead, but not quite. It might be possible to recover
by overcharging. See:
http://batteryuniversity.com/learn/article/how_to_restore_and_prolong_lead_acid_batteries
I
put it in a spare UPS, which immedialy complains if I try to turn it on.
Luckily, the UPS charges even when it is off, but slowly. I measured
about 15mA initially, and after about 36 hours, about 7.5mA. It is
currently up to about 10.7V.
I've often suspected that UPS charging circuits were a bit too
aggressive and have a detrimental effect on battery life. My
conspiracy theory is that most people don't bother to replace dead
batteries and will replace the entire UPS instead. So, premature
battery death will result in more UPS sales. However, the problem is
that UPS's are sold based on their run time and somewhat on how fast
they recharge after a power failure. So, the charging circuits are
designed to squeeze as much charge into the battery as possible, in as
short a time period, rather than for long life.
http://robots.freehostia.com/Batteries/Batteries.html
How much damage do you think was done to the battery? I know it will
lose some capacity.
Dunno. I've had zero luck with recovering an SLA battery that's been
run down that far.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558