> Did you open them up and see if you could get a substitute battery 
> locally that would

It turns out that almost all UPSes use one or more 12 volt deep-cycle
sealed batteries.  If you don't mind doing the wiring yourself, you
can substitute 12V marine batteries (about $65) for the batteries in
your UPS.  The trickle-charger will charge the marine battery in the
same way it charged the original UPS battery.

Be careful that you get the right number of volts that the UPS uses.
The APC Smart-UPS 700, for instance, uses two 12 volt batteries in
series for its 24-volt system.  To replace its batteries, you would 
need two 12 volt marine batteries also wired in series.

The added benefit of using large marine batteries is that you get
much more Ampere-Hours out of the big battery than you would get
out of the small batteries that the UPSes usually ship with.  The
drawback is that the UPS assembly now has two or more parts since
the batteries won't fit in the case, and it also becomes EXTREMELY
heavy and unwieldy.

You can't use automotive 12V batteries in a UPS because the auto-
motive batteries do not tolerate being fully drained of charge very 
well.  The marine deep-cycle batteries are designed to work even if 
they get fully drained of charge.

In terms of extended run-time, an APC Smart-UPS with the OEM batt-
eries might run for 15-35 minutes under full load, but might run
for 2-3 hours under full load with the large marine batteries.

Hope this helps.

--
Jim Ockers (ockers@ockers.net)                     Ask me about Linux!
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