Help with UPS backup problem

  • Thread starter Thread starter Al
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Al

My Mac Mini is plugged into a power strip which in turn is plugged
into an APC Back-UPS 400 backup power supply.

We've had a few storms that knocked power out briefly, and when
that happened, the Mac Mini shut down. Shouldn't it keep going
while the APC unit switches to backup power in the event of such
an outage?

Could it be that the APC unit is not functioning? If so, how can
I check? So many questions...
 
My Mac Mini is plugged into a power strip which in turn is plugged
into an APC Back-UPS 400 backup power supply.
Click to expand...

My UPS maker, TrippLite, says not to put a power strip with any surge
protection in either side of the circuit. Does that power strip of
yours have surge suppression? If so, take it out of the circuit.

--

"The scientist is possessed by a rapturous amazement at the
harmony of natural law, which reveals an intelligence of such
superiority that, compared with it, all the systematic thinking
and acting of human beings is an utterly insignificant reflection.

"This feeling is the guiding principle of his life and work,
in so far as he succeeds in keeping himself from the shackles
of selfish desire. It is beyond question closely akin to that
which has possessed the religious geniuses of all ages."

--Albert Einstein
 
Al said:
My Mac Mini is plugged into a power strip which in turn is plugged
into an APC Back-UPS 400 backup power supply.

We've had a few storms that knocked power out briefly, and when
that happened, the Mac Mini shut down. Shouldn't it keep going
while the APC unit switches to backup power in the event of such
an outage?

Could it be that the APC unit is not functioning? If so, how can
I check? So many questions...
Click to expand...

I use the same UPS, but on a windoze server. Somewhere in the
configuration software there is an option to shutdown the machine
within x minutes of the power going low. I have this set to about
five minutes as I'd rather have the machine shutdown safely than the
battery run out and the system die. You do need the serial
connection for this to work though, at least in doze you do, I don't
know anything about macs (except you eat them when there's nothing
better about ;-)

Try checking that setting and increasing the time before it shuts
down the machine, also use the test button and /or kill the power to
it to check the unit functions. Download the manual from APC and
have a look through it.
 
My Mac Mini is plugged into a power strip which in turn is plugged
into an APC Back-UPS 400 backup power supply.
Click to expand...


Is that the only thing plugged in, or do you have the UPS
powering other more power hungry things too like a laser
printer or CRT monitor?
We've had a few storms that knocked power out briefly, and when
that happened, the Mac Mini shut down. Shouldn't it keep going
while the APC unit switches to backup power in the event of such
an outage?

Could it be that the APC unit is not functioning? If so, how can
I check? So many questions...
Click to expand...

Is it old, possibly the battery is now worn out?

Unplug everything from it and plug in 200 watts worth of
light bulbs. For example, 4 x 75W bulbs in lamps. Unplug
the UPS from AC and see if it powers them.

I suppose this is a silly question, but, have you connected
the battery to the UPS?
 
"Al" said:
My Mac Mini is plugged into a power strip which in turn is plugged
into an APC Back-UPS 400 backup power supply.

We've had a few storms that knocked power out briefly, and when
that happened, the Mac Mini shut down. Shouldn't it keep going
while the APC unit switches to backup power in the event of such
an outage?

Could it be that the APC unit is not functioning? If so, how can
I check? So many questions...
Click to expand...

The way a lot of UPSes work, is they are actually an SPS -
standby power supply. When the AC is lost, it takes a finite
time for the UPS to switch from the line to the battery.
This is why the UPS doesn't get hot in normal use - when
AC is present, it is wired straight through to the load,
and no power conversion is happening. When the AC is lost,
the UPS switches over to the battery, and a switching circuit
makes 120V for the load.

The critical parameter is "transfer time". This is the datasheet
for my home UPS:

http://sturgeon.apcc.com/techref.nsf/partnum/990-2004E/$FILE/2004E-eng.pdf

The "transfer time" is listed as 8 milliseconds (basically a half
cycle at 60Hz). Computer power supplies have a spec called
"holdup time", which is the amount of time the power supply
can continue to power the load, when the AC power is
interrupted. The longer the holdup time, the better the
chances that the computer will not be affected by the switchover
time of the UPS.

This $220 supply has a holdup of 20 milliseconds:
http://www.newegg.com/Product/Product.asp?Item=N82E16817703001

This $29 supply has a holdup time of 10 milliseconds, and might
occasionally "blip" when the UPS switches over. Its spec,
after all, is pretty close to the 8 millisecond figure of my
UPS, and the 8 millisecond figure might be a lie.

http://www.newegg.com/Product/Product.asp?Item=N82E16817104933

Since most cheap UPSes are not in fact uninterruptable, they
should have been called SPS instead. This is an example of
a true UPS that is doing power conversion all the time. The
search term you want, to find one of these is "zero transfer time".

http://www.excaliberpc.com/OPTI-UPS_DS2000B_SINEWAVE_ONLINE/DS2000B/partinfo-id-552418.html

With zero transfer time, it doesn't matter how crappy the holdup
time spec is on the computer power supply.

HTH,
Paul
 
The UPS manufacturer suggests no power strip protector on
output of a UPS because some of the larger transients are
output by that UPS when in battery backup mode. They sort of
forget to mention when transients are largest and other
embarrassing facts. They are marketing to those who, for
example, will also believe what Rush Limbaugh proclaims:
without numbers nor any reasons why. Instead we provide facts
with numbers.

Batteries for serious UPS systems tend to last something less
than 20 years. Even automobile batteries are good for seven
to nine years. But cheap plug-in UPS systems rarely get more
than 3 years from a battery. How old is that Tripplite?

Is that UPS battery defective? Run computer while plugged
into that UPS. Then disconnect that UPS from wall
receptacle. Computer should work just fine for more than 5
minutes if Tripplite is OK Now we have a fact you can post -
to learn what to do next.

Meanwhile, Bob has posted an accurate fact leads to other
damning facts beyond current scope of this discussion.
 
You could have a weak battery. Don't trust the battery monitor in the UPS software. Connect a voltmeter to the battery while the UPS is plugged in. If you have a single 12 volt battery it should between 13 volts and 14 volts. With the computer plugged into the UPS and turned on, unplug the UPS from the wall outlet. If the battery voltage drops below 9 volts you need a new battery.
 
unplug the UPS from the wall outlet.
Click to expand...

According to Tripp Lite, it is not good practice to unplug a UPS from
the wall socket because then you do not have a ground reference and
the entire system could float above ground which could cause damage to
networked computers that do have a ground reference.

The approved way to remove utility power from a UPS is to trip the
circuit breaker. That way the UPS has a ground reference.
 
I use an APC Back-UPS LS 500 and it stays on to shut down the computer
properly when interupted like yours was. Mine came with a test button and
has instructions on troubleshooting in the manual. I would suggest you start
there if available-- I have also found their people helpful when I have
called them.

Pflu
 
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