Electric Fence Chargers
To energize the electric fence you need a fence charger. I prefer very powerful AC-powered energizers. The low wires are constantly shorting out against grass and weeds, and it takes a lot of power to keep their zap going. I think it's better to string thousands of feet of wire along the farm than to use battery-powered chargers, which just aren't powerful enough. I use 2x4's up on end to get the wire ten or twelve feet up in the air when it crosses gates. Otherwise, I just run the wires along the top of the posts of my farm's perimeter fence.
I prefer energizers with built-in voltmeters, so I can go check things out if the voltage falls into the red zone. In general, this means I buy Parmak units, because most of the others don't have meters. My favorite model is their "Super Energizer 3," which is very powerful indeed. That's what I use on the front pasture to protect the laying hens. (The newer Super Energizer 4 ought to be at least as good.) The "Maxi-Power" line is also good, though less powerful. (I've used the Mark 5, but they're up to Mark 7 these days).
If you insist on buying a battery-powered or solar charger, get a 12V unit. The 6V units have minimum zap, which means they can be shorted out by a few blades of grass. I was quite happy with Parmak's most powerful 12V charger. It only lasted about five years when exposed to the elements, so putting a a roof or a five-gallon bucket over it might be a good idea.
Premier also makes excellent chargers. Karen likes them better than Parmak, and that's what she's using on the back forty to protect the broilers (my super-long wire feeding the back forty from the barn has been mothballed). She uses a Premier Intellishock 50, which is a 12V battery-powered unit.
I'm not convinced that solar chargers are worth the extra cost, but then I'm in Western Oregon, which has a lot of cloud cover. The convenience of not having to monitor and lug around batteries is worth paying money for, but you get even more convenience by putting an AC-powered charger in the barn and stringing a hot wire all the way to the back forty.
The hardest part of installation is getting the ground connection good. I prefer pounding in ground rods along the drip line of my barn's roof.
It really helps to have the units placed so you can see the meters easily when you wander in and out of the barn.
And that's all I can think of to say about electric fences!
Fence Chargers on eBay