I'm setting up an electric fence for "cell", "intensive rotational", "mob" grazing, or whatever you want to call it. Basically, I'll have about 20 paddocks across 7 acres for cows, pigs, sheep and chickens.
I'm trying to size the charger now, which will be an AC powered unit, and I can't say I understand what size I need. Some of my perimeter fencing will be a 6-wire fence to keep all livestock in and all predators out. The rest of the perimeter will probably be a single wire because I already have a physical wood and wire mesh fence that should mostly do the job. Additionally I'll have 2-3 wires across several contour lines to set up the north/south boundaries of the paddocks, then I'll have movable fences on the east/west lines to define the individual cells that hold specific livestock in specific cells for a day or two.
But as I size up the charger requirements, I can't seem to understand the concept. They seem to vary in acreage perimeter length, and it's not at all consistent with the joules output. Sometimes 2 joules = 20 acres and 50 miles, other times I see manufactures say 1 joule does the same. Is there a reason, or do they just define what's acceptable output to them?
Also, I saw that a 6 wire fence across 100 feet would be the equivalent of 600 feet of load on the charger. But from a resistance perspective, this makes no sense to me. 6 wires in parallel should be 1/6th the resistance, thus decrease the voltage drop to the load, yet they act like it's the opposite. Am I missing something? Are they talking about a capacitive load, or something else?
Along the same lines as my last question, if I also have the horizontal wires that I mentioned in the second paragraph going across from one perimeter fence to the next, that would add conductors thus reducing resistance to the end load (the animal touching the fence) so it would increase the zap. But the specifications imply it does the opposite?
I can understand more wires is worse if they are all touching wet grass, but is that what they are referring to?
One last question, since I still have your attention: Is 2 joules to much for a chicken? How about 5? 5-6 joules doesn't cost much more for me, so I'd rather oversize unless I'm gonna start killing my smaller livestock.
It is the capacitive/inductive load that limits the line length. Part of the difference between brands is the pulse length makes the energy travel different, part of it is just what they are comfortable marketing.
Go as big as you can afford. And put limiters and cut outs on any wires that may have a heavy weed load. And most importantly, don't skimp on ground rods.
For your 6 wire perimeter, you don't have to charge every wire. Often every other works better. It depends on the spacing and the animals of concern.
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