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Do-it-yourself UPS

Posted by michael on from the shocking-experience dept.

Giampiero writes "Over at dansdata.com some guy named Dan creates a UPS out of some spare parts. To sum it up, "if you're looking for an industrial-capacity UPS solution, and don't like the prices of the off-the-peg options, it might be easier than you think to roll your own."" Of course you can mentally substitute U.S. 110 volts for Australian 220 volts wherever necessary...

13 of 388 comments (clear)

  1. Why convert DC to AC to DC? by cyberformer · · Score: 4, Interesting
    A major part of the description on the site (and the cost of a "real" UPS) is how to convert the DC output of a UPS to the AC power required by most PCs.

    Of course, PCs don't actually use AC power: there's a big box in the back that converts all the AC input back to DC. So why not save some money and bypass this, by running the PC straight off the battery (like a laptop)?

    1. Re:Why convert DC to AC to DC? by steveha · · Score: 5, Interesting

      I have, for years, wished for a DC input on the PC's power supply, and a standard for UPSes that would plug in to that DC input.

      Taking DC, converting to AC so the PC power supply is happy, then the power supply converts to DC... it would be nice if it could just be DC all the way.

      The problem is that your monitor, modem, etc. all expect AC power. It's easiest just to make a UPS that provides standard AC power, and plug everything in.

      Someday, I think we will have "smart" plugs. Wall power outlets will not be live by default; they will only serve power when a proper coded request goes in over a smart plug. The device will be able to tell the wall outlet what kind of power it wants, and the outlet will be able to tell the device what kinds of power it can offer. Then little kids will stick butter knives into wall outlets and not get fried; PCs and monitors will ask for +5 and +12 volts DC and get it; and UPSes will be able to feed +5 and +12 volts DC to those PCs and monitors.

      Actually, if you have the complicated smart power system I envision, there will probably be a UPS integral to the system. When your home loses power, the smart power system would broadcast a "power interrupted" signal and devices like your refrigerator and your laser printer will power themselves down; your PC will run for about 5 minutes and then power itself down (unless you are there and override it) and medical devices will run indefinitely. Maybe only the DC devices in your home will be on the UPS by default?

      steveha

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      lf(1): it's like ls(1) but sorts filenames by extension, tersely
    2. Re:Why convert DC to AC to DC? by dr_db · · Score: 2, Interesting

      Friend of mine was a radio tech in the armed forces. To get the class to pay attention, the instructor loudly said "If you make a mistake and get in the beam, the first thing that will happen is your testicles will explode"

      Immediately have quiet and attentive students.

  2. Great solution... by Anonymous Coward · · Score: 1, Interesting

    But now you have 3 big boxes under your desk, instead of 1

  3. 220V by Anonymous Coward · · Score: 1, Interesting

    How the heck did 220V suddenly become Australian? :D. here i thought we used it over here in Europe too, just those wierd yanks that use 110v :)

  4. Lacking some features by BagOBones · · Score: 2, Interesting

    IMHO un attended shutdown is one of the best features of the higher end UPS systems.. It safely saves your work and turns the computer of in case of an extended outage.. also what kind of surge protection do you get from that getto unit? Remote battery status? I use a UPS to protect my self from bad wiring and surges.. Hooking up to a settup like that would just be to unstable IMHO.. To each thier own, I guess

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    EA David Gardner -"... but the consumers have proven that actually what they want is fun."
  5. UPS maintenance by PD · · Score: 3, Interesting

    These do-it-yourself UPS thingies are going to require maintenance. Car batteries are designed to deliver about 3400 amps directly into the alternator of a car, only during the time that you turn the key. They they trickle charge very slowly off the engine mains.

    By contrast, UPS batteries are designed to discharge at a slower rate, but charge very very quickly to be able to work if the power suddenly cuts out two or more times in a row.

    The problem with using one battery where another is required is that a memory effect can develop. That slow discharge on a car battery can cause it to lose capacity and in as little as 6 months it'll be useless for any power failures over about 5 seconds.

    How much does a car battery cost? about $50. But, you're going to need one every 6 months or so, making a home built UPS actually many times more expensive than one you buy at Comp USA.

    I know it's counter-intuitive, but many things about batteries are.

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    If tits were wings it'd be flying around.
    1. Re:UPS maintenance by Compuser · · Score: 3, Interesting

      As a physicist I had to design a portable
      experiment. Imagine an industrial table
      full of physics equipment. It drew more power
      than any desktop or small server but needed
      to run for hours. We bought a single AGM sealed
      valve regulated deep cycle battery for $80 and
      it has worked well. It provided power continuosly
      for more than 4 hrs and as far as we can tell
      has not lost much capacity yet (i.e. after a few dozen fairly deep discharge cycles). It has also
      worked for a couple of years now without a hickup.
      So from personal experience, this scheme works
      very well, but a quality setup will run you ~$300.
      Look at boating and RV sites and newsgroups for
      names of good battery manufacturers and compare
      prices. We have nothing but good things to say
      about Concorde's Chairman batteries.

  6. been there done that by Anonymous Coward · · Score: 1, Interesting

    A few years ago, the Solar Car team at MTU (www.sos.mtu.edu/solar) had to do the same thing while at a race. We were running a data collection system and the power kept failing. We just used some of the old batteries from the car, hooked up a car charger and a small inverter from best buy. It was pretty kicking, and worked very well, when all other teams were cursing the power supply in the pits, we were sitting high on life

    -Matt

  7. This is dumb and dangerous. by newerbob · · Score: 2, Interesting
    I would not recommend doing this. Batteries are dangerous and can overhead or explode.

    Also the cost for these components is *much* higher than a $59 APS UPS.

    However, if you wanted to roll your own you would ditch the inverter and simply regulate the gel-cel down to the +12, +5, +3.3, +2.2, etc that your computer needs, and use a DC-DC converter chip to get the -12 and -5volts.

    That's much more efficient and somewhat safer.

    You wouldn't want a person without a CS degree writing software; we shouldn't have folks without EE degrees designing power supplies.

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    Ask the Ya-Hoot Oracle Anything!
  8. Don't-do-it-yourself UPS by AlexA · · Score: 2, Interesting

    So, if I didn't want to build my own UPS, what are some good brands to get for affordable yet good quality UPSes (reliable, has computer interface that Linux supports, etc.)? I've heard not so great stories about APS...

  9. Re:Be Careful by threephaseboy · · Score: 2, Interesting

    YES! Putting a diode across an AC line is a GREAT way to rectify the power, and thus turn AC into pulsed DC. Oh wait, i'm sorry, i forgot you are a flaming idiot

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  10. Re:VA? Watts? by threephaseboy · · Score: 2, Interesting

    W=P=E*I ONLY for purely resistive loads.
    W == less then E*I for inductive loads, like computers, motors, etc... anything with a power factor less then 1. On the other hand, VA == E*I for any device, and gives the total amount of power required by the device, not how much it is using.
    (E == volts, I == amps)

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