choosing a UPS

Mike Tancsa mike at
Fri Feb 3 18:10:00 PST 2006

On Fri, 3 Feb 2006 17:44:57 -0500 (EST), in
sentex.lists.freebsd.questions you wrote:

>I am in the market for a UPS to effect automatic shutdown (via DB9) of a
>file server (which will run FreeBSD 6.0).  I have noticed some large price
>fluctuations and I don't understand why.  I am comparing units of equal
>strength, say 750 VA.  Any comments on what I should be looking for?

The APC RS series work pretty well with /usr/ports/sysutils/apcupsd
and are a decent price.  Most use USB, but it works well with FreeBSD.

Not all UPSes are created equal.  In the "low end" consumer grade
stuff, they are essentially fast "switches".  The UPS detects power
loss, and it will quickly switch to the battery.  On higher end ones,
the utility power will feed the battery and you will get power
directly from the battery.  AC - DC - AC.  They can also clean up
noisy power and put out a constant voltage.  These are much more
expensive and are not really found in units under $750.  Some  units
provide a middle ground by providing some voltage regulation /
adjustment. APC calls it AVR and the UPS can kick in a few extra volts
when street power drops below a certain point.  The RS series does
that to a limited degree but provide decent value and protection for
the price.

Also check to see what the max watts it can put out.  If you have a
big power supply, the draw might be too big.  Another nice thing about
the RS, you can slap on an external battery pack to get longer

Here is some sample output.  For this box, it will shutdown
automatically when there is 5% charge left in the battery.  At that
point, it initiates a system shutdown and after 60 seconds cuts power
to all the outlets on the UPS and stays off until street power comes

# apcaccess 
APC      : 001,039,1002
DATE     : Fri Feb 03 20:59:34 EST 2006
RELEASE  : 3.10.18
VERSION  : 3.10.18 (21 July 2005) freebsd
CABLE    : USB Cable
MODEL    : Smart-UPS 1500 RM
UPSMODE  : Stand Alone
STARTTIME: Mon Dec 12 11:07:43 EST 2005
LINEV    : 123.1 Volts
LOADPCT  :  43.5 Percent Load Capacity
BCHARGE  : 100.0 Percent
TIMELEFT :  28.0 Minutes
MBATTCHG : 5 Percent
MINTIMEL : -1 Minutes
MAXTIME  : 0 Seconds
OUTPUTV  : 123.1 Volts
DWAKE    : -01 Seconds
DSHUTD   : 090 Seconds
LOTRANS  : 106.0 Volts
HITRANS  : 127.0 Volts
ITEMP    : 24.7 C Internal
BATTV    : 27.4 Volts
LINEFREQ : 60.0 Hz
XONBATT  : Thu Jan 19 12:03:03 EST 2006
TONBATT  : 0 seconds
CUMONBATT: 15 seconds
XOFFBATT : Thu Jan 19 12:03:04 EST 2006
STATFLAG : 0x02000008 Status Flag
SERIALNO : AS0308210854
BATTDATE : 1980-01-01
NOMBATTV :  24.0
FIRMWARE : 17.3.D USB FW:1.5
APCMODEL : Smart-UPS 1500 RM
END APC  : Fri Feb 03 20:59:35 EST 2006

Mike Tancsa, Sentex communications
Providing Internet Access since 1994
mike at, (

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