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Observations on a UPS - follow up to a previous post



 
 
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  #11  
Old August 13th 07, 11:40 AM posted to comp.sys.ibm.pc.hardware.misc,alt.comp.hardware,rec.audio.pro,rec.video.desktop,sci.electronics.repair
Joseph Ashwood
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Posts: 2
Default Observations on a UPS - follow up to a previous post

"Doc" wrote in message
oups.com...
On Aug 12, 10:24 pm, "James Sweet" wrote:
A test to find out how long it will actually run the computer sounds
like a good idea.


That's a good way to kill the battery, these things tend to really punish
batteries, after a few complete cycles they're often pretty well toast.
You
should be fine to try it for a bit, say 5 minutes without issues.



Seems I've heard an occasional complete drain-down and recharge will
extend the life of a rechargeable battery, that being constantly
partially discharged and recharged is what shortens their life. Not
so? Does it depend what kind of rechargeable it is?



It does depend on the battery. Early Lithium-Ion batteries benefitted from
the occassional full discharge, and Nickel-Metal Hydride batteries may
benefit from it. Lead-Acid batteries (like is in your car) have major issues
if they are completely drained, these are also the common battery in cheap,
well, just about everything. Newer Lithium-Ion batteries and Nickel-Metal
Hydride batteries have the controls in place so they don't benefit from a
complete drain. The Lithium-Polymer batteries that are beginning to appear
in some places do not benefit from complete drains, nor do they have
problems with overcharging, and now that they've gotten the self-ignition
problems eliminated look to replace just about everything but lead-acid.

So know your batteries, and you know the necessary behaviors, but really the
only problem ones are Lithium (non-rechargable) and Lead-Acid (damaged by
full drain).
Joe

  #12  
Old August 13th 07, 12:32 PM posted to comp.sys.ibm.pc.hardware.misc,alt.comp.hardware,rec.audio.pro,rec.video.desktop,sci.electronics.repair
Arno Wagner
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Posts: 2,796
Default Observations on a UPS - follow up to a previous post

In comp.sys.ibm.pc.hardware.misc James Sweet wrote:


A test to find out how long it will actually run the computer sounds
like a good idea.



That's a good way to kill the battery, these things tend to really punish
batteries, after a few complete cycles they're often pretty well toast. You
should be fine to try it for a bit, say 5 minutes without issues.






Maybe, but a lot of people seem to swear by the Kill-A-Watt meter,
which can be had all day for around $25 online, eBay etc.



EE friend of mine compared one to a $2500 power analyzer at work, found that
the Kill A Watt performance is pretty much inline with the specs printed for
it. It's not as good as the professional equipment, but it's really very
impressive for what it is and certainly adequate for consumer use. The
wonders of modern microelectronics, it's amazing what they can do with one
inexpensive chip and a handfull of passive components. I still remember when
a pocket calculator was $300, then a few years later $50 would buy one just
as effective, and not long after that they were under $20 and those are all
more capable than large machines costing many thousands just a few decades
earlier.


Hmm. Interesting. I trust he did this right and tested non-ohmic
loads such as a PC PSU as well?

Arno
  #13  
Old August 13th 07, 12:36 PM posted to comp.sys.ibm.pc.hardware.misc,alt.comp.hardware,rec.audio.pro,rec.video.desktop,sci.electronics.repair
William Sommerwerck
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Posts: 39
Default Observations on a UPS - follow up to a previous post

Seems I've heard an occasional complete drain-down and recharge
will extend the life of a rechargeable battery, that being constantly
partially discharged and recharged is what shortens their life. Not
so? Does it depend what kind of rechargeable it is?


You're thinking of nickel-cadmium batteries. The lead-acid batteries used in
these power supplies can be crippled or destroyed by a "full" discharge. Try
to avoid it.


  #14  
Old August 13th 07, 12:38 PM posted to comp.sys.ibm.pc.hardware.misc,alt.comp.hardware,rec.audio.pro,rec.video.desktop,sci.electronics.repair
Arno Wagner
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Posts: 2,796
Default Observations on a UPS - follow up to a previous post

In comp.sys.ibm.pc.hardware.misc Doc wrote:
On Aug 12, 8:45 pm, "William Sommerwerck"
wrote:


My experience -- at least where I live -- is that the power is off for a
fraction of a second, or hours. There's rarely anything in-between.



In general, I'd say that's my seat of the pants impression too, though
not always. I also notice they'll often come in clusters.


The transformer - if that's the correct term for it - big gray
basically cylindrical unit on top of a power pole - near my house blew
once.


Ugh. Putting them up for each individual hous is a very, very
historic way to do it.

Powerful **BOOM** and a huge column of flame. Not sure what the
fuel for the flame was, do they have oil in them?


Yes, for cooling. If it was an old transformer, you might have
giotten a nice load of Dioxins for free there...

Also a bit
disconcerting since anyone nearby surely would have been in jeopardy
from flaming debris.


The right way to do this is to use bigger transformesr for 10-100 houese
and to bury 3-phase AC lines. A lot more expensive, but pays off
in the long run, since you have less problems. And all these ugly
poles and transformers will vanish.

Needless to say, power was out for a while on that one.


I can believe that.

Arno
  #15  
Old August 13th 07, 12:42 PM posted to comp.sys.ibm.pc.hardware.misc,alt.comp.hardware,rec.audio.pro,rec.video.desktop,sci.electronics.repair
William Sommerwerck
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Posts: 39
Default Observations on a UPS - follow up to a previous post

Lead-acid batteries (like is [sic!] in your car) have major issues
if they are completely drained, these are also the common battery
in cheap, well, just about everything.


The _only_ consumer products I've owned that used lead-acid batteries were
an early Sony Discman, and two APC SPSs. They are not common in consumer
products. They provide relatively high capacity at a low cost (which is why
they're used in SPSs and UPSs), but they are too-easily damaged by a full
discarge. I accidentally ruined a $45 batter for the Sony D-T10.


  #16  
Old August 13th 07, 12:44 PM posted to comp.sys.ibm.pc.hardware.misc,alt.comp.hardware,rec.audio.pro,rec.video.desktop,sci.electronics.repair
William Sommerwerck
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Posts: 39
Default Observations on a UPS - follow up to a previous post

My experience -- at least where I live -- is that the power is off for a
fraction of a second, or hours. There's rarely anything in-between.


In general, I'd say that's my seat of the pants impression too,
though not always. I also notice they'll often come in clusters.


Yes. The glitches are rarely isolated events.

Around my area, wind storms often cause sustained outages in areas where the
lines are above ground.


  #17  
Old August 13th 07, 01:49 PM posted to comp.sys.ibm.pc.hardware.misc,alt.comp.hardware,rec.audio.pro,rec.video.desktop,sci.electronics.repair
David
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Posts: 7
Default Observations on a UPS - follow up to a previous post


But be aware that in general, these cheap 'power' meters
are expecting
'traditional' sine-draw loads. I have seen wildly
inaccurate standby figures being given for equipment, by
eco-campaigners that have been let loose with one. A lot
of modern equipment that makes use of switch mode power
supplies, handles standby mode by brief bursts of full
draw operation. This can confuse a simple power
calculating algorithm that's expecting continuous draw.
Also, the draw by many cheapo switchers is very asymmetric
and 'dirty', and may also not produce a true reading.

I wouldn't connect a UPS to a fridge. These things are
notorious for pulling a short-term startup current of tens
of amps, as they get the compressor turning over. The UPS
would probably fall over before being able to supply this,
and might, as someone else suggested, even sustain damage.

Arfa

I have a "Kill-A-Watt" and it appears to display true RMS
for voltage and current readings. The voltage reading for a
modified sine wave from a standard UPS displays the actual
RMS voltage. I do not know what crest factor it can handle
but displays power factors of considerably less than unity
for most consumer electronics with DC rectifiers off of the
line voltage. It is a very nice unit for the price.

David

  #18  
Old August 13th 07, 02:09 PM posted to comp.sys.ibm.pc.hardware.misc,alt.comp.hardware,rec.audio.pro,rec.video.desktop,sci.electronics.repair
Arfa Daily
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Posts: 49
Default Observations on a UPS - follow up to a previous post


"David" wrote in message
et...

But be aware that in general, these cheap 'power' meters are expecting
'traditional' sine-draw loads. I have seen wildly inaccurate standby
figures being given for equipment, by eco-campaigners that have been let
loose with one. A lot of modern equipment that makes use of switch mode
power supplies, handles standby mode by brief bursts of full draw
operation. This can confuse a simple power calculating algorithm that's
expecting continuous draw. Also, the draw by many cheapo switchers is
very asymmetric and 'dirty', and may also not produce a true reading.

I wouldn't connect a UPS to a fridge. These things are notorious for
pulling a short-term startup current of tens of amps, as they get the
compressor turning over. The UPS would probably fall over before being
able to supply this, and might, as someone else suggested, even sustain
damage.

Arfa

I have a "Kill-A-Watt" and it appears to display true RMS for voltage and
current readings. The voltage reading for a modified sine wave from a
standard UPS displays the actual RMS voltage. I do not know what crest
factor it can handle but displays power factors of considerably less than
unity for most consumer electronics with DC rectifiers off of the line
voltage. It is a very nice unit for the price.

David


But that's my point. You can't have a 'true' sine-based RMS figure for power
consumers that draw a pulsed current. Just because it is a sine wave that's
*available*, it doesn't mean that the load will draw anything like a
sinusoidal current, from it. The only items that will are those that are
totally 'passive' in nature, such as light bulbs. Even power supplies that
are transformer based, are likely to draw current in pulses from the
available sinusoidal supply, and switch mode power supplies, on which most
modern consumer electronics are based, most certainly won't draw a
sinusoidal current from the supply.

Arfa


  #19  
Old August 13th 07, 02:35 PM posted to comp.sys.ibm.pc.hardware.misc,alt.comp.hardware,rec.audio.pro,rec.video.desktop,sci.electronics.repair
Scott Dorsey
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Posts: 28
Default Observations on a UPS - follow up to a previous post

Doc wrote:
On Aug 12, 10:24 pm, "James Sweet" wrote:
A test to find out how long it will actually run the computer sounds
like a good idea.


That's a good way to kill the battery, these things tend to really punish
batteries, after a few complete cycles they're often pretty well toast. You
should be fine to try it for a bit, say 5 minutes without issues.


Seems I've heard an occasional complete drain-down and recharge will
extend the life of a rechargeable battery, that being constantly
partially discharged and recharged is what shortens their life. Not
so? Does it depend what kind of rechargeable it is?


It does not extend the life. Back in the seventies when NiCd packs had
memory effect, folks were recommending deep discharge. But today, you
are more likely to wreck a NiCd pack by reverse-charging a cell that way.

The cheap UPSes use gel-cells, which are gelled-electrolyte lead-acid
batteries. They are better at surviving deep discharge than NiCd packs,
but they still don't like it. Consequently, most equipment that uses
them will shut off when the battery voltage drops too low, to prevent
damage. Electronics are cheaper than batteries. Bigger UPS units use
liquid-electrolyte cells so you can check the battery condition with a
hydrometer periodically, and they also have a pulsed charging system that
prevents sulfates from building up on the plates. The Wal-Mart cheapies
probably do not.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #20  
Old August 13th 07, 03:01 PM posted to comp.sys.ibm.pc.hardware.misc,alt.comp.hardware,rec.audio.pro,rec.video.desktop,sci.electronics.repair
David
external usenet poster
 
Posts: 7
Default Observations on a UPS - follow up to a previous post


"Arfa Daily" wrote in message
...

"David" wrote in message
et...

But be aware that in general, these cheap 'power' meters
are expecting
'traditional' sine-draw loads. I have seen wildly
inaccurate standby figures being given for equipment, by
eco-campaigners that have been let loose with one. A lot
of modern equipment that makes use of switch mode power
supplies, handles standby mode by brief bursts of full
draw operation. This can confuse a simple power
calculating algorithm that's expecting continuous draw.
Also, the draw by many cheapo switchers is very
asymmetric and 'dirty', and may also not produce a true
reading.

I wouldn't connect a UPS to a fridge. These things are
notorious for pulling a short-term startup current of
tens of amps, as they get the compressor turning over.
The UPS would probably fall over before being able to
supply this, and might, as someone else suggested, even
sustain damage.

Arfa

I have a "Kill-A-Watt" and it appears to display true RMS
for voltage and current readings. The voltage reading for
a modified sine wave from a standard UPS displays the
actual RMS voltage. I do not know what crest factor it
can handle but displays power factors of considerably
less than unity for most consumer electronics with DC
rectifiers off of the line voltage. It is a very nice
unit for the price.

David


But that's my point. You can't have a 'true' sine-based
RMS figure for power consumers that draw a pulsed current.
Just because it is a sine wave that's *available*, it
doesn't mean that the load will draw anything like a
sinusoidal current, from it. The only items that will are
those that are totally 'passive' in nature, such as light
bulbs. Even power supplies that are transformer based, are
likely to draw current in pulses from the available
sinusoidal supply, and switch mode power supplies, on
which most modern consumer electronics are based, most
certainly won't draw a sinusoidal current from the supply.

Arfa

Arfa,
I know that the current draw on these things is anything but
sinusoidal. My point was that the "Kill-A-Watt" seems to
actually compute the RMS value for that complex current
waveform as well as non-sinusoidal voltage waveforms.

David

 




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