"aurgathor" wrote:

I have a 650VA APC UPS (Back-UPS Pro 650)
that has worn batteries (occasionally, it starts to
beep and the red battery light comes ON) .
The UPS is there to ride through brownouts and
outages lasting usually less than 10 seconds (have
quite a few of those) so if the batteries are less
than perfect, I don't care as long as it can last for
10 - 20 seconds.

So, how does the UPS's circuitry determines if
the battery is going bad? Is it simply a voltage
measurement, or something more sophisticated?
How difficult would be to modify the UPS to
lower the treshold for a bad battery?

Alternatively, how would the unit work if I were
to connect a marine or car battery instead of
the manufacturer supplied battery?

It will probably work. Beware though with the sealed batteries. An APC
UPS will shut down when the batteries are completely worn out.

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