Connect with us

UPS External Battery

Discussion in 'Electronic Design' started by BeeJ, May 15, 2013.

Scroll to continue with content
  1. BeeJ

    BeeJ Guest

    I have several UPS units. One has a connector for an external 12V
    battery. I am thinking of hooking up a deep discharge marine battery
    to the UPS. Is there any thing to watch out for? What current rating
    wiring should I use? The biggest UPS is 900VA.
    Also, can a connector mate be found or should I just solder or attach a
    lug to the contacts?
    Suggestions please.

    The UPS is signaling to the PC that I should replace the battery but
    running the built in test says it is still viable but probably not for
    a long power outage. I only want the UPS to fend off power line

  2. Yes. Many cheap UPS units are designed to run, when at maximum load,
    the switching transistors at the ragged edge of their peformance, or
    even above, knowing that the battery is going to die in a few minutes.
    If you put a battery tha can handle maximum load for much more time
    than was originally anticipated (e.g. replacing an internal 7Ah SLA
    with a large 100Ah flooded cell), then the transistors can easily cook
    themselves the first time you have an outage.
    If the output is 900VA, and we assume a terminal voltage of 12.5
    volts, then the current is going to be (900/12.5)*(1/efficiency).
    Your absolute BEST bet would be to hook up a "about the middle" load
    (say a few incandescent lamps) and measure the voltage and current
    from the actual battery, and get a good ballpark guess for the
    efficiency. Add a safe margin and engineer for that amount of
    current. My wild-ass-guess: you are unlikely to draw more than 100
    amps at 12V for the 900VA unit.
    A very common connector for that application is the Anderson
    "Power-Pole" series connector. Here's a web-page that shows them
    being used in an amateur radio context:

    A google-search will lead you to mail-order sites where you can get
    the connectors onesey-twosey.
    If you really do only need "few tens of seconds", I vigorously
    recommend just replacing the internal battery with the same
    size-and-chemistry. No power-connector or pass-transistor headaches.

    A guy at a local flea-market sells "dead battery" APC 600VA units for
    $40 bucks, and I can buy a brand-new battery at a jobber downtown for
    another $20. These just have a YUASA 7Ah SLA in them. The larger
    units often will go to a 14Ah or 25Ah battery, which will cost more.

    Here is a pic of one of the APC units that I have six of now:

    (just a random image I found off the web - no relation to Kaboodle)
  3. That’s probably the 5 year alarm for battery replacement. Which is about
    how long they last on a float charge.

    Measure up the battery and go to Mouser and get a CSB replacement. It's
    less expensive that what APC or triplite will
    charge you and will last just as long.

    And you don't have to worry about charging a larger battery which has
    its own set of problems.

  4. BeeJ

    BeeJ Guest

    After serious thinking Jeff Liebermann wrote :
    The two UPS units are:
    APC BX900
    APC XS1500 (label on this unit says battery pack BR24BP)
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day