Hi!

I'll also put
in a fan that will turn ON if it the UPS is running on battery
power, or charging the batteries.

http://greyghost.dyndns.org/ups.jpg (62.8KB / 1024x768)

I need to consider adding that to my modified APC UPS. I have found that it
gets a little warm to the touch over the transistors inside, which don't
seem to have that great of a heatsink anyway. I also have plans for a fuse
holder very close to the battery, just in case. (The UPS itself is
internally fused...)

If you have too much time on your hands, adding an ammeter makes for a nice
touch. I used a small automotive one that shows how much is being pulled off
the battery. It doesn't really have a small enough scale for charging
though.

BTW, how do these sealed batteries degrade? Is it sulfating,
or something else?

I suppose many of them just sulfate, but a lot (maybe even an equal number)
seem to just "boil dry" from the heat at some point. I don't recommend you
do so unless you really know what you're doing and have tools you don't care
about--but I took one such dead battery apart recently. It had basically
turned totally dry inside. There was no liquid to be found anywhere.

If you do that with an old battery, wear eye protection, wash thoroughly
when you're done and safely dispose of the remains. I think it goes without
saying that any open flame or spark is not a good idea.

Those that are run often may just wear out over time. Lead-Acid batteries
aren't really fond of being deeply discharged and then run up again.

Is there any way to reverse it to some
degree, like charging it with a slightly higher current and/or
voltage, or pulsing it?

For sulfated batteries I have heard that a very *slow* charge can at least
get the batteries to limp along for a little while. I have never tried that.

up in the middle of the night because my UPS is beeping
can be highly irritating. :-(

Take the beeper out. With the unit unpowered and the battery removed, just
find the beeper and desolder it or just yank it out. All my UPS units are
now the strong silent type. :-)

William