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UPS Batteries...The Good, The Bad and The Ugly

Discussion in 'Electronic Equipment' started by Too_Many_Tools, Oct 19, 2005.

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  1. I just finished working on a number of UPSs.

    One thing I noticed was that many of the Sealed Lead Acid (SLA)
    batteries were swollen and hard to remove.

    Why do SLA batteries swell?

    I did notice that the UPS manufacturers apparently do not design for
    this problem. Many of the UPSs had to be partially disassembled to
    remove the batteries because of the tight quarters the battery
    containers presented. Very poor design in my opinion.

    Any suggestions for preventing a recurrence of this problem?

    Thanks

    TMT
     
  2. It's part of their failure mode. Likely a combination of excess
    gases at high pressure, high temperatures generated from shorted
    plates and decomposing plates making themselves into funny shapes.
    Sure, replace the batteries when they fail instead of waiting
    a few years. :)

    Anthony
     
  3. RoughRider

    RoughRider Guest

    This is an economic situation in consumer devices where the commodity is
    purchased, used, then chucked, never maintained, or fixed. UPS systems
    along with much of todays electronics are cheap enough to make that they
    become landfill at the moment something goes wrong. It can be cheaper to
    buy a new laser printer (c/w toner cartridge) than to buy a replacement
    toner cartridge. But I degress.

    People want small, so no space is spared to allow for a bulging battery.
    Mechanically, it is easier to fit the battery tight than to come up with a
    different restraining method with space buffer (read: shave every penny off
    that you can). Conversely, it is also about fitting the largest battery you
    can into the available space.

    The typical cheap gel cell UPS battery lasts about 5 years. There is also
    heat in that UPS which doesn't make things easier. In commercial
    applications, a battery is considered for replacement when it gets to 80% of
    its original capacity (IEEE guideline). In the small UPS, people will
    continue to use it until the load dies within seconds of a power failure,
    well beyond battery end-of-life. With bad cells internally, the battery
    created some additional heat during recharging.... which caused the battery
    to accept more charge current.... more heat...more charge.... leading to
    thermal runaway and the bulging plastic you see.

    There are methods available to detect thermal runaway: Smart CPU
    programming, temperature monitoring, etc... but it probably doesn't change
    the fact that the manufacturer wants you to buy a completely new unit when
    the battery fails. Or many consumers would do this anyway. You want a
    cheap UPS, the temperature sensor gets removed along with some other frills.

    For those that can switch the battery themselves, a new battery for a small
    UPS costs between $12 and $30 wholesale depending on size.

    The way they build things these days, next time you walk into a Walmart
    store, consider where much of the goods will end up in 5 or so years!
     
  4. Thanks for the responses so far....

    When I say that there is no extra room in these UPSs, I mean not even
    1/8" extra.

    The UPSs were all commercial units that were being serviced per the
    manufacturer's schedule.

    TMT
     
  5. George Ghio

    George Ghio Guest


    The most common reason is exceeding the allowed charge voltage. Have
    seen some that actually split their cases.
     
  6. Some of the batteries that I removed had split...no acid leakage but
    again I was surprised at the number and severity of the damage to the
    batteries.

    Shouldn't these batteries have vented before swelling and spliting?

    Maybe what I am asking is are SLA batteries TOTALLY sealed? I would
    expect a safety plug to vent before a rupture would occur.

    TMT
     
  7. Crystal growth between plates is the normal problem, related to sulphation,
    which is caused by the batteries being overdischarged / left flat for long
    periods.

    Gas vents pop at quite low pressure, it is unlikely to be gas pressure.

    Peter
     
  8. George Ghio

    George Ghio Guest

    They probably did. That's part of the trouble, anything lost cannot be
    replaced. But the charger keeps charging.
    No safety plug.
     
  9. George Ghio

    George Ghio Guest

    Yep, over charge the suckers and you lose material. It can't be put
    back, battery degrades, fails. Seen it often.
     
  10. Steve Spence

    Steve Spence Guest

    overheating, over charging. we had the ac fail in our data center over
    the weekend, and the telephone tattletale failed to call out. Room temp
    was 150F when we showed up for work on monday. batteries burst, acid on
    the floor, backup tapes destroyed by heat and acid fumes, servers dead,
    etc ......
     
  11. Ouch....my condolences to whoever had to clean that mess up..

    TMT
     
  12. Steve Spence

    Steve Spence Guest

    Thanks. The CTO and Dir. of IT were conspiciously absent .....

    It was left up to us net engineers and a couple of admins.

    we flushed the floor with lots of water to neutralize the acid, did lots
    of moping, and wiping, and cdw was happy to take our orders for
    replacements.
     
  13. Ecnerwal

    Ecnerwal Guest

    Bad design. Batteries, computers and tapes all in the same room? Common,
    but not good design. Any offsite backups? Servers and their on-site
    backup tapes should be separated by enough distance that a minor fire
    won't get both, and fully offsite backups should be far enough away that
    major fire, flood, tornado, etc won't get both (unless it's a tornado
    with a flight plan to make your life miserable). A serious computer
    center UPS should be down in some nice isolated basement room...
     
  14. [ snip ]

    err, you're much better off with it
    above any flood level...

    which reminds me of what may, or may not, be a true
    story back during the 1965 blackout.

    (like all good urban legends, there's enough
    plausability here, but I've been unable
    to directly verify it).

    In the Good Old Days before all the blackouts,
    (and before modern day computers and such)
    emergency power and lighting was in very few places.

    One place usually equipped with something or another
    was the local hospital.

    NYC had (and has...) a very large municipal
    facility called Bellevue. Well known (no) thanks
    to generations of tv and movies as a psych place,
    it's actually a fully capable (and nowadays
    very highly regarded) institution.

    Anyway, back in 1965 it had, by 1965 standards,
    a pretty good emergency generator setup.

    (In fact, in the early 1970s I saw the physical
    power plant which had been installed Way Back When
    We Built Things Right).

    So... when the Sir Adam Beck substation did
    its thing and plunged the northeast US (including NYC)
    into darkness in 1965, Bellevue went out as well. But
    a few minutes later, the generators came on and things
    were back to (by 1965 standards) normal.

    Except for one little problem.

    Generators, especially back then, were big and ugly
    and heavy. So... would be in a basement. (Additional
    reason for this is it made getting the fuel to them
    quite a bit simpler and more reliable).

    ok... you know where I'm going...

    Guess how high above sea level Bellevue is...

    That's right, it's only a couple of dozen feet.

    Now guess how high above sea level the
    sub, sub, basement... where the generators
    were located... is.

    Eyup.

    Now guess what critical part of the Bellevue plant
    was _not_ hooked up to emergency power?

    Eyup... the sump pumps.

    So a couple of hours after the power went out,
    the generators were underwater.

    The end.
     
  15. Steve Spence

    Steve Spence Guest

    The tapes were in the backup drives. 7 tape dlt loaders. These were
    current tapes, not storage. no seperate liebert unit, these were
    rackmounted apc units in the same racks as the servers. This company
    wasn't serious about anything except the ceo's morning plate of carrots
    ......
     
  16. Windsun

    Windsun Guest

    A few years ago we did a check on a bunch of UPS systems installed locally
    for computer backup in some local city and company offices - about 30 total.

    Of those, about 1/2 had batteries good enough to even fire up the UPS, and
    about 1/2 of those that did were very marginal, such as only having enough
    capacity for 10 minutes instead of the rated 30 minutes or so.

    Going by that, I would bet that nearly half of the UPS systems in the
    country don't work.
     
  17. Me

    Me Guest

    Should have dumped a couple of boxes of Arm & Hammer Baking Soda
    in the water before you flushed the floor, and moped it up.......

    Me
     
  18. Guest

    You've already got a lot of good replys in regard to the swelling of
    the plastic cases being due to higher than normal temperatures and
    pressures; and even much higher, such as happens in thermal runaway.

    In addition, as the batteries age and lose capacity, a portion of the
    active materials in both the anode and cathode are slowly forming
    molecules of lead sulfate that are not being reversed in the charging
    process. The lead sulfate molecule may become tribasic in nature, or
    even tetrabasic (at higher temperatures), either of which is a larger
    molecule than the original active material.

    Even flooded cells in tight confinement will swell enough to become
    very difficult to remove.
     
  19. Steve Thomas

    Steve Thomas Guest

    Baking soda can be dangerous if there is any significant quantity of acid.
    We had a material handling accident with a full pallet of new car
    batteries once. A large sack of sodium bicarbonate was on hand for the
    purpose of neutralizing small spills. Several pounds were dumped on the
    resulting pool of acid. That was a big mistake. The fizzing release of CO2
    in the pool of acid created an aerosol cloud of corrosive, choking, stinging
    acid mist. It was not an experience I would care to repeat, and it was not
    popular with the other people working in the area.
    Based on this experience, we concluded that baking soda should only be
    used to neutralize what remains after the primary cleanup has been
    completed, or for very small spills.
     
  20. "The CTO and Dir. of IT were conspiciously absent ..... "

    They are always are when there is work to do.

    TMT
     
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