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back up battery for mains supply???

Discussion in 'Power Electronics' started by villageveg, Jul 29, 2011.

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  1. villageveg


    Jul 29, 2011
    Just wondering if such a thing exists?

    We run a pump in a rented commercial greenhouse which powers our irrigation system The greenhouse electronics is set up in such a way where it is easy to trip for safety reasons.

    Now and again the electric system at the greenhouse trips at weekend when nobody is there to turn it back on, and our crops dry out because the pump no longer works :(

    Is there a something that we can plug into the mains and the pump that has a battery that kicks in to run the pump if the mains trip? We only need about a day of power in the battery as there will be someone to reset the mains supply the next day.

    Hope somebody can help me.

  2. Alchymist


    Apr 16, 2011
    A battery bank and an inverter would do it,but would take a lot of battery to run the pump all day. How big is the pump, and how much $$$ do you want to invest?
  3. BobK


    Jan 5, 2010
  4. villageveg


    Jul 29, 2011
    do you have the names of some suppliers?:)
  5. daddles


    Jun 10, 2011
    It sounds like your pump should have its own circuit -- putting it on a circuit with a ground fault interrupter (which is what is probably causing your trips) is a mistake, precisely for the reason you're experiencing. Unfortunately, since you say it's a rented building, you might not be able to change the wiring.

    If your pump is, say, 1/4 horsepower or larger, you're going to find it prohibitively expensive to provide a backup battery system that will run it for a day -- it would likely cost many thousands of dollars. For a small fraction of that cost you can have the wiring redone. If there's room in the circuit breaker panel and the electrician doesn't have to run a lot of conduit, it's probably something that can be done easily in a morning of work.

    So the key questions are: what's the horsepower rating of your pump? What voltage does it run on? How long does the pump need to run on the battery assuming the power is out?
  6. duke37


    Jan 9, 2011
    Have you considered an engine/generator to automatically switch in?
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Another option is that when your pump is operating from backup power it could operate (say) on for one minute, off for ten. It may provide sufficient hydration to keep the plants alive (at the expense of growth) and significantly reduce the power requirements.
  8. jackorocko


    Apr 4, 2010
    I wouldn't waste my money. Unless this is some sort of illegal grow I would just talk to the owner about upgrading the electrical to your requirements, offer to pay for it in return for free rent.

    I don't know too many owners that will say NO when you offer to fix up their property.

    You could always set up a cheapo "alarm". A cheap cell phone, remove a key and expose the two conductors under the key. Solder a wire to each of these conductors. Now connect those two wires to a NC relay. Hook the relay up to mains and wait for the power to go out. The relay will drop out closing the relay which should speed dial whoever it is programmed to that number on the cell phone. Now just program the number in your cell phone and call it 'alarm'. Go flip the breaker... It is an idea
    Last edited: Jul 30, 2011
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Heh. Yeah.
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