To prevent data corruption during a pull-the-AC-plug test, just
interrupt the bootup process so that you're sitting at a pre-Windows
screen. Or boot from a DOS floppy. All components will be consuming
power (though read/writes) take a bit more power) and you can accurately
gauge how much reserve time you've got. The problem with an
incandescent bulb test is that it is not your computer. Yes, it is
standardized, unlike the computer, but equating its results to computer
backup time is difficult.


Warren Post wrote:
I just replaced the battery in my UPS, and notice that the old one was
swollen and hard to remove. Searching this NG and elsewhere on the net, I
see this means that the battery had reached the end of its life some time
ago and should have been replaced sooner. Okay, replacing the battery
when it reaches the end of its life cycle instead of waiting until it
obviously fails is fine by me.

So how do I know when to replace a UPS battery? This particular UPS has
no self test feature and no com port with which to communicate with the
computer, and I don't want to toss perfectly working equipment into the
landfill just because it lacks bells and whistles to make my life a
little easier.