Bob said:
I've never got round to an UPS, and they took them out of our systems we
used to have at work because they caused more trouble than they saved -
they failed more often than any computer. However, I'm sure that modern
ones are much better, and as you describe yours, much more sophisticated -
there were no data connections on our old ones, for example. Capacity, as
you rightly say, is usually the problem - anything big enough to be much
use is prohibitively expensive and prohibitively large too.
I got excellent life from the battery in my UPS. I changed
out the battery for the first time this year (Jan 2013).
The unit was purchased Feb 2002, according to the receipt.
That's nothing short of amazing. It should not have
lasted that long.
When buying a UPS, stay away from the "lowest tier" of
products. We bought on price at work, and 10% of the
units received, were malfunctioning one way or another,
out of the box. Just to give some idea how bad they
can be. We bought a batch of 100 or so at the time.
There is a backgrounder here, if you want to know something
about the various types you can buy. The one in Figure 4, is
the type used in our server room. It has a cooling fan that
runs all the time. The one in Figure 1, is my
home UPS. It's the standby type, which remains cool to the
touch when utility power is available. No fan needed
in one of those. And remaining cool, likely helps extend the
life of the battery.
Another thing that helps the battery, is not running it flat
a lot. While the UPS cuts off current flow before the battery
is damaged, charge-discharge cycles can shorten the life.
http://web.archive.org/web/20090521041358/http://www.apcmedia.com/salestools/SADE-5TNM3Y_R5_EN.pdf
You know the battery is done, when the unit makes random
beeps around once every five hours or so. Apparently,
the unit does some kind of test, to see if the
battery has available capacity or not. At first,
I couldn't figure out where the beeping was
coming from. I thought it was my smoke alarm
Paul