On 8/21/2015 6:09 AM, micky wrote:
I have 2 UPSes, both used, and one was marked Working when I bought it
for $7, and the other I might have gotten for free. I can't remember.

Batteries are not cheap of course. A couple webpages gave me the
impression that some people just buy a new UPS instead of replacing the
battery. That's not a sound plan financially, is it???? Surely a UPS
should outlive several batteries, unless there's a lightning strike.

In general, you should be able to replace the batteries and extend
the "life" of the UPS. The UPS manufacturer would like you to
purchase the batteries from *them* -- at a highly inflated price!

Most batteries are standard case sizes (sometimes there are ~0.1" differences).
Virtually all used in UPS's are 12V -- though some UPS's will use 1, 2 or
4 such batteries (12, 24 or 48V).

If yours uses more than one battery, it is usually wise to replace
ALL at the same time; a "weak" battery will alter the way the charge is
shared among the batteries, typically shortening life.

If you opt to replace batteries, be sure to salvage any wiring harness
that is present. For a single battery, sometimes there is just a "fancy
connector" that transitions from the battery to the UPS. Other times,
there are wires (possibly including fusible links) interconnecting
the batteries within the "battery pack" (the batteries are sometimes
fastened together -- tape? -- to form a single unit).

Almost all UPS batteries (at least SOHO units) have "spade"/faston
terminals. These come in two typical sizes -- 0.25 and 0.187 (IIRC).
Obviously, you don't want a battery that has a larger terminal than
the mating cable can accommodate (it won't fit on!). But, you also
don't want a battery with a smaller terminal (you'll end up with
a tenuous fit that could end up being a high resistance connection).

For battery "packs", you can also fabricate your own from discrete
batteries held together with 2" cellophane packing tape.

It is often tedious to extract the battery pack from many UPS's.
They are designed for a tight fit -- don't want the battery
flopping around in there as it represents a significant mass.

Often, failed batteries will "bloat" -- you will actually see
that they have EXPANDED/bulged during use. In this case, it
is often hard to extract the batteries ("tight fit"). Rather
than dismantling the UPS itself (which will leave you with
a bunch of DANGLING parts as they are "fitted" into the plastic
case; not held with fasteners!), try to loosen the appropriate
screws as if you were going to disassemble the case. This extra
"slop" usually makes it easier to remove the battery -- esp if
it has "bulged".

Of course, don't short the battery (new or used) as they are capable
of delivering a fair bit of current (e.g., hold your wedding band
across the battery terminals and feel it get HOT! : )

Dispose of defective batteries responsibly. They contain lead so
represent hazardous waste. There are usually places in town where
these can be recycled -- the lead is extracted, "cleaned up" and
then reused (to make NEW batteries).

The second question is, I've read the instructions but still not sure if
the second one works. The instructions are short and don't address my
issue

APC XS 900 .

Does there have to be a load for the Online light to go on? It's off.

A 60 watt lightbulb is as good a load as any, right?

Typically, you size the test load at 1/3 the nameplate rating of the
UPS. Too small and you aren't really checking to see that it can
handle a *reasonable* load. Too large and you'll probably get
failures from "old batteries".

Some UPS's will not turn on unless AC mains power is available.

Many (esp APC units) UPS's will do a battery test on startup
(and then periodically, thereafter). If the UPS complains
after/during this test, chances are your battery (or battery
connections) are faulty. (it's looking to see how much and how
quickly the battery voltage "sags" under that known test load)

Some UPS's will omit the test cycle if they detect a *missing*
battery pack -- but will perform the test if they detect a
present but "dead" battery pack! The former is useful: it
allows you to use the UPS as an "outlet strip/surge protector"
even if the backup function is not available (because the
battery is missing).

[I have a dozen UPS's here that primarily serve as "outlet
strips" -- I can turn off a computer and its monitor plus
any peripherals with that one button/switch -- instead of having
to turn off the individual items]

For UPS's that test batteries periodically, a failing battery can
screw you unexpectedly: the UPS goes to test the battery at some
"random" time by essentially switching to backup power. If the
battery is toast, your computer will now crash! (i.e., when the
battery is known to be dying/dead, just remove it until you
get a replacement)

OTOH, the Building Wiring Fault light is on, probably because somewhere
I lost the ground connection, but It's only plugged in for testing. Do
I have to plug it in somewhere with a ground to get the Online light to
go on?