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UPS Batteries...The Good, The Bad and The Ugly - Page 6

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Posted by Steve Spence on October 19, 2005, 10:32 pm

Too_Many_Tools wrote:

You had to be there, listening to him stop down the halls yelling
"Where's my damn carrots, I want my carrots ....."

Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net

Posted by nospam on October 19, 2005, 3:09 pm

On 18 Oct 2005 20:02:51 -0700, "Too_Many_Tools"

Personal experience with APC UPSs in the 500VA to 1400 VA range is
they charge hard and selftest too often.   The latter was really bad
for the batteries.   As recieved and installed with they will self
test every two weeks,  Selftest runs the batteries well down the
curve and failure was often around 13months.  Extended selftest to
every 4 weeks and the batteries were still solid at 25 months at
which point they were replaced with new for reliability reasons.  The
old batteries were still 80% good or better likely due to the fewer
number of discharge and hard charge cycles.

Another thing that will kill batteries fast is using the UPS to run
the system or printer till exhaustion.  I tried it to see what happens
and the usual 7a gell cell in a 300VA unit expired after 20 cycles
of that.     Lesson, it's momentary backup, not aux power.

UPSs fall into two classes from what I see.  Those big enough to
bridge many hours of power failure (really big batts and lightly
loaded) and those really intended to allow enough time to do a quick
finish and shutdown or bridge those annoying under 1 minute outages
and severe but momentary line voltage fluctuations.   Most of those
consumer units sold  are for the latter and really work well for that.


Posted by LawsonHuntley@aol.com on October 19, 2005, 8:37 pm

Too_Many_Tools wrote:

You've already got a lot of good replys in regard to the swelling of
the plastic cases being due to higher than normal temperatures and
pressures; and even much higher, such as happens in thermal runaway.

In addition, as the batteries age and lose capacity, a portion of the
active materials in both the anode and cathode are slowly forming
molecules of lead sulfate that are not being reversed in the charging
process. The lead sulfate molecule may become tribasic in nature, or
even tetrabasic (at higher temperatures), either of which is a larger
molecule than the original active material.

Even flooded cells in tight confinement will swell enough to become
very difficult to remove.

Posted by Too_Many_Tools on October 19, 2005, 10:00 pm

Good comments...

If cells will swell and it is a known condition, then why do UPS
manufactures not allow for it in their battery case designs?

It would seem to be a common complaint from users and you would think
sooner or later the products would have space dedicated to this


Posted by Ian Stirling on October 19, 2005, 10:25 pm

You think that they want you to replace the batteries?

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