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UPS for Computers

Discussion in 'Home Power and Microgeneration' started by John, Feb 10, 2007.

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  1. John

    John Guest

    I just have a couple of questions about the UPS devices you can get
    for your computer.

    How do you know how much power your computer and it's peripherals use?
    And how do you know what it uses on average? How do you go about
    calculating or measuring the typical power consumption of your system
    so you have a better idea of what capacity UPS device you need?

    I also wondered if it is possible to connect an external battery to a
    UPS device in some way to boost the amount of back up time you have?
    Do any of the devices on the market today allow external batteries to
    be added? I think it would be quite useful if you could add a small
    additional battery if your current UPS isn't giving you enough back up

    My system I would definitely want the computer and monitor as well as
    the ADSL/Router to be permanently connected to the UPS. I would also
    like the other device to be connected to like the printer and scanner
    even though these are not as critical. Do most UPS device today give
    you lots of different connection options e.g. computer power lead, 3
    pin plug (uk) etc? As far as my ADSL/router is concerned I would never
    want the power to go out on that, I would always want it to be

    Cheers for your advice.

  2. Get a portable watt-meter - like the Kill-A Watz or whatever.
    The old Powerware Prestige EXT allows for external battery. They are
    "obsolete" now, but available on the surplus market. The EXT runs60
    volts while the standard unit ran 48.
    I run my router and cable modem on a small UPS (350 va) and my main
    system on a 600va Prestige. This is a dual conversion system so I get
    100% clean power all the time.
  3. Eeyore

    Eeyore Guest

    You can measure it or estimate it. Some products especially monitors tell you
    how much power they consume.

    What you need to be aware of is that PCs use more power on start-up, although a
    good UPS may have an allowance for this.

    It's wise to be slightly generous in your UPS sizing btw. You never know what
    you might want to add later.

  4. Saul

    Saul Guest

    Not sure

    But how do you estimate the MPG of an auto or truck??


  5. Inkjets are OK on a UPS if necessary, but NEVER a laser. Any dual
    conversion UPS will work almost infinitely if enough DC power is
    available. They are DESIGNED to run full time. Only caveat is you will
    likely require an external charger to handle the extended run
    batteries if the unit was not built as extended run.
    I like the idea of a small IC engine powered generator for extended
    run, like the old BEST UBS system.
  6. They tell you the MAXIMUM they will draw, not necessarily the real
    running power. Many good UPS units will actually TELL you how much
    load they are running (as a percentage of full load)
    20% on a 600va unit is 120 va.
    They use only a moderately greater amount on startup - they use more
    when accessing hard drives or cds and more yet when writing to them.
    NEVER try to scrimp and use a marginal device. Slightly oversized buys
    you a lot of reliability.
  7. John

    John Guest

    Thanks for all the advice.

    I actually already had a current meter that you plug in so I have
    pulled it out the back of the wardrobe and tested it on my system and
    was quite surprised by the results.

    My system appears to only be using around 100 watts of power when
    switched on, give or take a fluctuation of 5 watts.

    I'm pretty sure that the power supply in my system was something like
    380 or 420 watts. I know it was higher than the power supply I have
    had in the past for previous systems. My system does have quite a few
    devices and drives in it so it was a surprised it is only drawing

    I have yet to test the power draw of the ADSL/router on it's own.

    As far as a ups device overheating is concerned, when these devices
    are connected to your computers it is constantly powered from the
    mains power supply to keep the battery topped up right?

    I am just trying to understand how it would overheat if it was still
    constantly connected to the mains power but with a 12v deep cycle
    battery in between?

    So you would have the mains keeping the 12v deep cycle battery topped
    up, and that would then be going via a 12/240v inverter providing say
    around 150w of power (which would be more than enough to cover my
    system) which would keep the UPS topped up and the computer in

    The only time the battery from the UPS would start to drain would be
    after the deep cycle battery had run out during a power cut. If I had
    a deep cycle battery with a capacity of about 100 amp hours, that
    would provide quite a few hours of use at 100 watts consumption before
    it would exhausts wouldn't it? And by that time the electric may be
    back on anyway.

    Can anyone see any flaws to this type of setup?

  8. Which does NOT change the FACT that a dual conversion UPS of ANY
    stripe is built to work 24/7, 365 days a year if enough DC power is
  9. If it is not a dual conversion UPS, the computer runs off mains power
    untill the mains power fails. The inverter then takes over. A dual
    conversion UPS is essentially a large battery charger, a battery, and
    an inverter.
    There are dual conversion, line interactive, and standby UPS systems.
  10. Mike

    Mike Guest

    That *might* be the original intention of the engineers, but, by the
    time the accountants and marketing people have had their say, then
    what the customer *actually* ends up with isn't capable by any stretch
    of the imagination of 24/7 365 operation.

    Heck some of them, and I'm talking about big names here, even after
    many years experience in the field don't even know how to properly
    float charge the batteries they fit in multi thousand dollar UPS's.

  11. You do not understand. A DUAL CONVERSION UPS DOES run 24/7, 365 days
    in NORMAL USE. The inverter runs ALL THE TIME, supplying the FULL
  12. Smart UPS RT series for all the APC fans out there is a Dual
    Conversion UPS. Tripplite SmartOnLine 5000 is also dual conversion.
  13. Mike

    Mike Guest

    Yes I do COMPLETELY understand the concept of a dual conversion UPS
    and I stand by my statement.

    The lack of fault tolerant design such as redundant cooling fans and
    restrictive particle filtration is a continuing design error in a
    significant number of dual conversion UPS's Site the equipment in an
    air conditioned environment and you might get away with it for a
    couple of years, fit it in the real dusty grimy world especially with
    temperatures approaching the upper end of its declared operating
    regime and you are extremely lucky to get much more than 365 days use.

  14. The same goes for ANY equipment. Abuse it and it WILL FAIL.
  15. Guest

    I have one of those - a low-end APS brand. If the mains power
    goes off, there is an audible "click," which I guess is a relay
    switching between the mains feed-though, and the inverter.

    There doesn't seem to be any provision for cooling at all.

    It's really just to get through very brief (say, two second)
    dips, and to give time to shut down, if the mains stays off
    longer than that.

  16. I'm assuming you mean APC, not APS, and you are right, their low end
    stuff SUCKS. Their midline stuff isn't much better from my 20+ years
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