hi very good point, many older units will not startup w/o
running from a/c power first.

Some newer APC models you can 'fool' it into
startup by pressing the test button with it offline.

Another factor, many of these older units like
the Exide, Best, Liebert and Trip Lite are
full sine wave units, a real bargian at today prices.

There was an article in QST on adapting a smaller
ups to run on an external battery. Very easy to to,
just use good fuses MaxiFuse on the leads.

Some of these newer units use microprocessors
to run the thing so if the don't power on without
batteries, they are useless except for the transformers.

73 dude




Beware that some UPSes refuse to start without A/C voltage
present. Kind of stupid, but it's reality. That could hinder their use
for emergency.