How to disable charger circuit on APC UPS

Discussion in 'Electrical Engineering' started by Kaz, Nov 3, 2007.

  1. Kaz

    Kaz Guest

    Hello, I have this question posted in another group as well but I
    figured I'd give you folks a shot at it.

    I have two APC rackmount ups units. One is a 2200XL model which has a
    larger internal charger to support external battery packs. The other
    unit is a 2200 model that does not support external battery pack and
    thusly has a smaller charger. I want to disable the charger in the
    second unit while retaining all of the normal functionality of the UPS.
    I want to do this in order to have them share a large deep cycle battery
    pack where only the other unit will charge it.

    I have taken a few photos of the main board of the ups. I am curious if
    anyone is familiar with it or can recognize what I can do to disable its
    charger. Perhaps even removing a simple fuse would do the trick, I
    dunno. I can do the work, just not sure how to proceed. I do not have
    a schematic for this.

    http://www.webglider.com/APC/
     
    Kaz, Nov 3, 2007
    #1
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  2. Kaz

    Palindrome Guest

    Kaz wrote:
    > Hello, I have this question posted in another group as well but I
    > figured I'd give you folks a shot at it.
    >
    > I have two APC rackmount ups units. One is a 2200XL model which has a
    > larger internal charger to support external battery packs. The other
    > unit is a 2200 model that does not support external battery pack and
    > thusly has a smaller charger. I want to disable the charger in the
    > second unit while retaining all of the normal functionality of the UPS.
    > I want to do this in order to have them share a large deep cycle battery
    > pack where only the other unit will charge it.
    >
    > I have taken a few photos of the main board of the ups. I am curious if
    > anyone is familiar with it or can recognize what I can do to disable its
    > charger. Perhaps even removing a simple fuse would do the trick, I
    > dunno. I can do the work, just not sure how to proceed. I do not have
    > a schematic for this.
    >
    > http://www.webglider.com/APC/
    >


    My first thought would be to stick a suitable diode* in series with the
    wire going from the external battery pack to smaller UPS. Bingo - no
    charging current from the smaller unit.

    *Or a suitable FET circuit with a much lower voltage drop than a diode
    will give - either as a simple two terminal diode replacement, or a
    switch operated by sensing some parameter that indicates the other
    charger is operating, or mains supply is present, etc.

    --
    Sue
     
    Palindrome, Nov 3, 2007
    #2
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  3. Kaz

    Kaz Guest

    Perhaps I devised a problem where none exists. Let me step back and ask
    it this way; Is there anything wrong with running multiple chargers on
    a single battery pack? In my case, each charger will be onboard a 120V
    UPS system, and each system will be on opposite halves of a split 240 feed.

    The charging power for the batteries is obviously DC, but I wonder if
    there is any risk of some sort of "bad AC thing" happening with dual
    chargers where each charger is fed from a split 240 leg to shared neutral.



    Palindrome wrote:
    > Kaz wrote:
    >> Hello, I have this question posted in another group as well but I
    >> figured I'd give you folks a shot at it.
    >>
    >> I have two APC rackmount ups units. One is a 2200XL model which has a
    >> larger internal charger to support external battery packs. The other
    >> unit is a 2200 model that does not support external battery pack and
    >> thusly has a smaller charger. I want to disable the charger in the
    >> second unit while retaining all of the normal functionality of the
    >> UPS. I want to do this in order to have them share a large deep cycle
    >> battery pack where only the other unit will charge it.
    >>
    >> I have taken a few photos of the main board of the ups. I am curious
    >> if anyone is familiar with it or can recognize what I can do to
    >> disable its charger. Perhaps even removing a simple fuse would do the
    >> trick, I dunno. I can do the work, just not sure how to proceed. I
    >> do not have a schematic for this.
    >>
    >> http://www.webglider.com/APC/
    >>

    >
    > My first thought would be to stick a suitable diode* in series with the
    > wire going from the external battery pack to smaller UPS. Bingo - no
    > charging current from the smaller unit.
    >
    > *Or a suitable FET circuit with a much lower voltage drop than a diode
    > will give - either as a simple two terminal diode replacement, or a
    > switch operated by sensing some parameter that indicates the other
    > charger is operating, or mains supply is present, etc.
    >
     
    Kaz, Nov 5, 2007
    #3
  4. Kaz

    Palindrome Guest

    Kaz wrote:
    > Perhaps I devised a problem where none exists. Let me step back and ask
    > it this way; Is there anything wrong with running multiple chargers on
    > a single battery pack? In my case, each charger will be onboard a 120V
    > UPS system, and each system will be on opposite halves of a split 240 feed.
    >
    > The charging power for the batteries is obviously DC, but I wonder if
    > there is any risk of some sort of "bad AC thing" happening with dual
    > chargers where each charger is fed from a split 240 leg to shared neutral.
    >



    There is a problem of running some internal battery UPS designs with
    exteral (larger) battery packs - when they weren't designed to do so. eg
    the manufacturer may have relied on the battery discharge characteristic
    to keep certain components within their safe operating region. A device
    that won't get hot enough to fail in the 15 mins runtime that the
    standard batteries can provide could get heated to failure in the 30
    mins or more that an external pack can provide.

    Of course such a unit may also have protective trips - but these may be
    non-resetable.

    Some charger designs could give you problems - eg if they monitor the
    charging pattern of the battery and compare it to a standard pattern. Or
    monitor battery temperature and use that as a control parameter. A
    battery with a different charging pattern, with or without a second
    charger, can be interpreted as a faulty battery. This could lead to the
    charger disabling itself and alarms going off..

    So you need to check those factors and more before proceeding further -
    or take the risk that all will be well.


    --
    Sue
     
    Palindrome, Nov 5, 2007
    #4
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