Hi Doug:
A battery is never "off." The best you can do is disconnect
it from the circuit. Whether or not the battery is disconnected,
if the separator is damaged, the resulting chemical reaction
will heat and produce gas which will cause the battery to swell.
(Some batteries have pressure-relief vents -- which then spill
electrolyte).
As far as I know, even if the UPS is "off," the battery is
trickle-charged to keep it at 100% charge. Like a laptop.
A battery can be damaged by over-charging or over-discharging.
Both will cause the battery to overheat. Once the separator
is damaged, there is nothing that can be done electrically to
halt the resulting chemical reaction.
Battery circuits are designed to prevent over-charging and
over-discharging. Such circuits should allow hundreds of
charge-discharge cycles before a battery needs to be replaced.
Batteries are also have a process known as self-discharge. If
allowed to sit unused for a long period of time, they will self-
discharge to the point of damage with no or little chance of
recovery.
Best wishes for the New Year,
Rich
On 1/5/2014 7:44 PM, Douglas Smith wrote:
Hi Everyone,
I seem to have a continuing experience with UPS equipment overheating
the batteries. Most all of my UPSs have done this at one time or
another. Here is an example:
At the office, I was to be away for a week and if the power went out,
some of my UPSs sound an alarm which can annoy people in hotel rooms
directly above the office. So I turned that UPS off. Light out, output
off. No sign of life so I thought it was really off. A few weeks later
I tried to turn on that UPS (we don't use that computer every day) and
it immediately switched off with a bad battery alarm. A coincidence I
thought that would happen just then when it worked fine last time. I
went to pull the UPS out from under the desk and found it very warm,
even though it was off. The battery was red hot, so hot I could not
hold it and it was beginning to swell up, but I was able to remove it.
The interesting thing was that APC had replaced this unit a few years
ago when the original one swelled the battery so much it would not
come out! I was able to replace the battery and the unit works OK now.
I replaced the battery on a second identical unit just in case.
How can this happen when I turned the unit off by the button on the
front and the unit seemed off, no indication any power was on at all?
And why do I keep having these problems. I spent two hours taking
apart another APC unit (this one had a metal case, which I like) to
remover a very swollen battery with a cracked case due to the
swelling. I have another of the same model which has the same problem.
Not sure I want to spend two hours again on that one.
All my units are APC, and I like them for their features and
reliability (except for battery problems) and will likely buy APC in
the future. I suspect this problem may occur on other brands as well,
a general industry problem.
I could probably avoid problems by replacing batteries every year, but
I still think the failure mode should be more friendly. Seems like
there is a safety problem here both from overheating, spilling of the
battery contents from a hot cracked case, and lack of performance
suddenly when not expected.
Any thoughts? Has anyone else experienced this?
Doug
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