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using computer UPS's

Discussion in 'Home Power and Microgeneration' started by Andy Baker, Dec 8, 2004.

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  1. Andy Baker

    Andy Baker Guest


    I was wondering if anybody had experience running much larger batteries on
    computer UPS (uninterruptible power supplies) I have a wood fired boiler
    that only uses small circulator pumps. An outage on a full load of wood
    means at the very least scaling hot water spraying out the relief valve and
    all over the garage, so I'd like to avoid that. The particular UPS I'm
    looking at is a beast that rates double what the circulator pumps draw (I
    have no blower as it's wood fired). It's also a damn good deal at a hundred
    bucks for true sine wave output. It's internal batteries are two 11 AH 12
    volts in series for 24 volts. I'd like to hook my two 12V deep cycles up to
    it (80 AH each) instead. Any thoughts? I have no idea how they determine
    battery life or when the battery needs replacing (I replaced a 7 AH 12V one
    here at work, and took the "bad" battery home where it continues to run like
    a champ)


  2. Steve Spence

    Steve Spence Guest

    I built my own with a motorcycle battery, a 300 watt inverter, and a 3
    stage charger. The whole thing came to less than $100, but much longer
    run time than a UPS. It's a true "online" unit, not a "backup" unit, in
    that the load is always powered by the inverter. I did this to cover the
    short switchover between our generator and house inverter. That was
    enough to cause the satellite to lose sync.

    Steve Spence
    Dir., Green Trust
  3. SQLit

    SQLit Guest

    I like this idea, thanks for sharing.
  4. Andy Baker

    Andy Baker Guest

    I know a furnace doesn't really care all that much, but I'm kind of worried
    about the crappy quality of the inverter's "modified sine wave" power which
    is just a crappy square wave and how induction motors deal with that (power
    factor issues I'm sure)

    Also is the fact that... say you're drawing a 300 watt load for your online
    system, your battery charger would need to put out 30 amps. I know they
    exist, but it's easy to get in to high amperage situations here where your
    charger just can't keep up.

    A recent setup I had used a 4 pole, double throw relay. It was actuated by
    the incoming line. When the coil was energized, it hooked the main up to the
    furnace and all was good. When power dropped out, the coil went dead, and
    the line connection went to normally open. Normally closed hooked the
    furnace to the inverter, and one of the un-used poles on the relay turned
    the inverter on.

    Worked great for the two times that I tested it, then the MOSFETS feeding
    the main transformers in the inverter EXPLODED, plus did evil things to the
    chip that provided their clock signal, soooo I couldn't simply replace the
    mosfets, as it would causee a shoot-thru situation and promptly blow them
    up. POOF!!

    Bought a new inverter. Praying for now that the power goes out when I'm home
    so I can manually switch it.

  5. Steve Spence

    Steve Spence Guest

    30 amp auto chargers are very available. If your load isn't a 24/7 load,
    then a smaller charger will suffice. These MSW inverters are fine for
    electronics and lighting, but motors and such would need something
    better. SW inverters are available as well, for more $$$.

    Steve Spence
    Dir., Green Trust
  6. Guest

    Will work just fine as long as you install an extra automatic battery
    charger - as the charger in the UPS is quite likely to have a problem
    with the big batteries after a sustained outage.
  7. Guest

    A Ferrups is extremely inefficient. The resonant core runs very warm,
    even without a load.
  8. SQLit

    SQLit Guest

    I suggest you use an latching relay. Check into the GE RR-9's and 7's.
    Originally designed for lighting relays they work on 24 vdc I believe that
    they are rated for 20 amps 120 or 277 v. I admit that you will need to have
    an slightly more complex control circuit but you do not have the coil
    holding for extended lengths of time. Also it is an good idea to have an
    timer in the circuit. Changing from one source to another instantly is an
    really bad idea with out synching the sources. Phase angles and all that.

    I watched a guy go from utility power to generator power on an 2000 ton
    chiller (5 kv) underload by pushing both transfer buttons at the same time.
    After the explosion we rebuilt the switch gear and I added an 2 minute timer
    in the circuit and mounted so it was un accessible if the switchgear was
    hot. No more midnight nonsense.
  9. Andy Baker

    Andy Baker Guest

  10. Rob

    Rob Guest

    Ignoramus23449, I have a ferrups 1Kw, I gather as long as it
    has 48v in the batts the inverter part will work? I'm thinking
    of getting some bigger batts for it (it takes 4 X 31 amp), and
    was wondering how the charger would fair, can you still use
    it, as per normal with out the charger working?
    Tanks Rob
  11. Guest

    Looks like a pretty high end unit - and a true sine wave output to
    It SHOULD work, given acceptable battery charging.
  12. Guest

    The Ferrups is a rather specialized unit and is/was expensive because
    of the massive resonant transformer used as a voltage regulator. With
    today's intelligent buck/boost Ferros are fast falling out of favor -
    particularly because of their low efficiency, and particularly at low
  13. John

    John Guest

    I have an APC 650 connected to a #27 115 AH marine/trolling battery. The
    original battery was 7AH. I has only been used once for about 45
    minutes. The case remained cool to the touch.

    It is supplying juice to a cable modem, d-link wireless router,
    a P-75 powered firewall PC, an AMD Barton 2600 PC and, one monitor.

    The assembly was simple:
    1. Drill a hole in the top of the plastic battery box,
    2. remove the battery cover from the UPS,
    3. fashion a patch cord with #10 wire with post connectors for the battery
    end and blade connectors for the UPS.
    4. Place the UPS on top of the battery box and secure with a
    ratcheting type cargo strap,
    5. Plug everything in,
    6. pay your homeowner's insurance premium.
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