Arthur Britto wrote:
You likely want more than a minute. Most likely, you don't want your
system to crash when coming back up when power fails soon after it is
restored: your system could be in the middle of a fsck. Generally, you
want enough capacity to: power off, power on, and then power off safely.
I second this. If the system is busy, it might take a couple of minutes
before it really shuts down. Ten to fifteen minutes is the MINIMUM
runtime I'd suggest. As the battery ages, runtime will lessen, plus it
gives you more room to expand. Power usage does not scale linearly, if
200 watt usage lasts X amount of time, 400 watt usage lasts less than
X/2 and 100 watt is more than 2X. My personal experiences with power
outages is that they're rare and short, but when they do occur they
happen a few times during the day/night. This, of course, may vary from
your area. Another thing to consider is brownouts or volt dropages. The
ups will kick in if the volt level drops too low (or too high). If this
happens frequently enough, it will deplete the battery or wear it out
much more quickly.
I am very happy with the CyberPower Intelligent LCD Series: CP*AVRLCD
http://www.cyberpowersystems.com/
The series has:
NUT support:
You want something that works with NUT. Instead of a vendor specific
package. This way your acquired skills are portable and future proofed.
Network UPS Tools
http://eu1.networkupstools.org
NUT is great. It safely powers off my system when the UPS is low.
Additionally, I set it up to e-mail my cell phone when the power state
changes. If I go out during a power outage, I can stay out longer if I
know the power is not restored.
My personal experience has been with APC equipment, but CyberPower is
also a great maker. I also second NUT. It's a better, more flexible
framework that supports just about any decent ups.
USB interface:
* A USB port is more future proof: serial ports are becoming rare.
* Allows monitoring UPS state.
* Allows powering off the UPS.
USB is almost mandatory now. Serial ports are usually only on high-end
expensive models, and (almost) never on what you'll find in stores.
LCD Display:
At a touch know:
* power consumption (don't need to pull out a Kill-O-Watt)
* battery charge
* estimated minutes remaining
Before spending extra on anything with an LCD, google the model or lcd
errors first. I've seen reports that they tend to be inaccurate,
especially with APC. Mine under reports watt usage by a significant
amount, somewhere between 1/3 to 2/3 of actual usage(I forget what my
tests with various light bulbs showed). This was testing the ups with
only a small lamp plugged in, everything else UNPLUGGED (not just off).
I also used several light bulbs since they can vary a little.
One thing to be wary of is like most inexpensive UPSes it does not
provide a pure sine wave. This can damage a power supply that has
active power factor correction. Luckily for my Silencer 750 Quad
according to the manufacturer due to the short time in which the UPS is
in use it is not an issue.
-Arthur
PaulNM
--
gentoo-user@lists.gentoo.org mailing list
