On Wednesday, April 1, 2020 at 4:21:26 AM UTC-5, Paul wrote:
R.Wieser wrote:
Andy,

I did a search, but found conflicting formulas.

12 volt
18 Ah

Neither is a formule, just some numbers. Just for the record, next time
please include those formulas. They simply might include factors that are
outside of a quick calculation (which we could than point out to you).

But, onto the quick calculation:

12 volt times 18 Ah = 216 watt-hour.

216 watt-hour divided by 200 watts = a few minutes more than an hour

Than again, that ignores any kind of conversion losses, the fact that when
the battery goes near empty its voltage will drop (possibly causing the UPS
to cut out early), and that VA's are not the same as watts. YMMV.

Regards,
Rudy Wieser

With modern "Active PFC" ATX supplies, the power factor is around 0.99
or so. This means that roughly "VA equals Watts" on those.

With the older supplies, the PF was around 0.7 or 0.65 or so,
meaning a Kill-O-Watt meter might come in handy for characterizing
the load. The Kill-O-Watt meter is good enough at what it
does, to nail the "off" power (like when the PC sleeps).
Many other measurement methods can be off by a factor
of ten (when you believe them). For example, using the
Kill-O-Watt, my machine with 8 DIMMs draws 7.5W at S3 sleep,
and the machine with 4 DIMMs draws 5W at S3 sleep. If the
8 DIMM machine is in Soft Off state, power drops to 1.3W and
some of that is USB devices on 5VSB.

Some UPS do not behave well, when on battery and driving
extremely light loads. Throwing a couple 3W lights
onto the UPS, might keep it running with such a light load.
(Preferably 3W incandescent, or even power resistors, if
you have the skills to wire some of the correct value up.)
If your UPS continues to run down to zero load, then... great :-)

And some UPS, if you switch them off using the switch, then
switch them on, they won't go back onto battery. They're refuse
to do anything until the power comes back. If you were thinking
"I'll just switch this off so in an hours time I can do X",
they don't necessarily accept your request when asked. They
can be temperamental.

Paul

I installed software for my UPS as well as connected a cable from my computer to my UPS.

It said Time to Empty is 40 minutes.

I have periodic power outages, but they usually only last a few seconds to a few minutes.

Andy