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Thread: What size power inverter?

  1. #1
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    Default What size power inverter?

    I have a 110 AC electric fence energizer that is listed at .2 amps. Now if I use a inverter and run off a 12 volt battery is this a 2.4 watt/hr consumption or is the watt consumption 110voltsx.2amps=22watts? I see that a similar sized fence energizer is listed for sale with a 80 watt panel. At any rate, what size power inverter would I require and how much power will the inverter use so I can figure out how big of panel to purchase?

  2. #2
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    Quote Originally Posted by hayray View Post
    I have a 110 AC electric fence energizer that is listed at .2 amps. Now if I use a inverter and run off a 12 volt battery is this a 2.4 watt/hr consumption or is the watt consumption 110voltsx.2amps=22watts? I see that a similar sized fence energizer is listed for sale with a 80 watt panel. At any rate, what size power inverter would I require and how much power will the inverter use so I can figure out how big of panel to purchase?
    Yes, 0.2 amps at 110 volts is 22 watts. But I would guess the actual consumption is somewhat less than 22 watts as 0.2 amps would be the absolute maximum. Those electric fencers also seem to draw more when tall grass shorts the wire out.

    If it really did draw the full 0.2 amps for 24 hours, then you would need 530 watt hours (0.5 KWH) of energy each day to run it.

    You would need your panels to produce 130 watts for 4 hours each day to produce 530 watt hours (and this wouldn't account for cloudy days or battery and inverter losses).

    It would be nice to check the actual current draw of the fencer in operation.

  3. #3
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    Thanks, that is what I was thinking. I can't see getting that kind of of solar array set up so I think some numbers may not be correct. I got the numbers by calling the manufacture. I also wonder if there is a difference once you swithc to DC. I believe all the output on a electric fence is DC regardless if the unit is a AC or DC unit. Do those Watt meters that I can buy at say Home Depot or Lowes work ok? Another thing that the repair guy at the manufactuer said is that they put out a constant power, I was pretty sure as you mentioned that power usage was dependent on fence load. This is a 15 stored joule energizer and he stated that when running with minimum load it may be putting out 5 joules and then kick in using the capacitors (low impedence technology) to get up close to 12 output joules.

  4. #4
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    I remember the day I learned aluminum carried electricity very well. I was crossing an electric fence carrying an armful on aluminum siphon tubes - not good when one of them touched the charged wire!

    Most of the tubes were plastic and no problem but this particular lot were new an aluminum. I think I was maybe 10 years old at the time.

    Russ

  5. #5
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    Quote Originally Posted by hayray View Post
    Do those Watt meters that I can buy at say Home Depot or Lowes work ok? A
    Never used one, but I think the Kill-o-watt thingie would be perfect. You could also check to see if the current draw increased if the wires are shorted out.

    I may be wrong, but I would have to believe the unit draws more power when shorted out. You are getting a pretty good spark when the unit is shorting and this spark takes energy to produce. If the unit is NOT shorted, where would this extra energy go?


    I use a small Agway electric fencer for my small garden that runs on a small square 6 V lantern battery. It usually takes me only 2 batteries to make it though the whole gardening season. When I use more fence, the battery life is definitely decreased.

  6. #6
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    You will need at least a 200 watt panel depending on where you live and a 200 AH 12 volt battery.
    MSEE, PE

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