Electric Fence Chargers
Without even thinking about the technical basics of fence chargers, one can say that there are three general classes–AC-powered, battery-powered, and solar-powered chargers; that there are vast differences in strength, even among the chargers in each of these three classes; and that most chargers suited to powering an electric horse fence, including all of the ones that we offer, put out a pulsed charge about once a second and are known as “low impedance” chargers. Before selecting an electric fence charger from among our products, it may help those unfamiliar with how chargers work to go over some basic points about volts, joules, and “low impedance.” Those who are already familiar with these terms should skip the next three headings and go on to other matters relating to selection.
The Technical Basics: Why Are Volts Important? Volts measure electrical pressure, the urge electrons have to get off the charged wire and go elsewhere, just as pounds per square inch measure water pressure, the urge water molecules have to burst out of a hose or faucet. The higher the voltage, the greater the charged wire’s ability to shock some target creature that happens to touch the wire. In the case of horses, a voltage potential of 2,000 volts will reliably do this job.
Such very high voltages are not dangerous unless they involve a large flow of electrons or are associated with a more or less continuous current. Today’s “low impedance” chargers (see below) tend to be relatively safe because they produce very short bursts of electric output, typically around one per second; and so, during the interval between pulses, a shocked creature or person has no difficulty letting go the wire.
More Basics: Why Are Joules Important? Joules are important because they indicate the power of an electric fence charger’s shock. Specifically, they measure how much heat would be generated if an electric fence charger administered its maximum potential shock. That doesn’t mean that a horse contacting a conductor powered by a 6-joule charger would actually receive a 6-joule shock, it just means that it is theoretically possible if the horse received the charger’s full output.
This says something about effectiveness, because some of the electric energy that a charger puts on the electric fence line is dissipated by resistance on the line and also by electricity leaving the line through weeds and brush–all of which diminishes the remaining joules and also diminishes the voltage available to shock target animals. At some point the voltage dips below the 2 kilovolts needed to reliably shock a horse through its hair and skin.
All other things being equal, the more joules one has the better. For example, a mild electric fence charger like the Zareba Yellow Jacket (product 01-23), with its rating of 0.28 stored joules, can be rendered powerless to shock horses by a few weeds leaning on the fence. In contrast, the Parmak Super Energizer 4 (product 01-11A), with its rating of 9 stored joules, can charge many miles of electric horse fence, and can reliably shock horses despite heavy loads of weeds and brush.
But joules also relate to the size of the jolt administered, which can panic horses, and to safety. That stands to reason. A shock that generates a small amount of heat while passing through a target animal is going to be safer and less likely to send the animal into a panic than one that generates ten times that heat. Thus, the Zareba Yellow Jacket, while generating high line voltages, administers shocks so small that they probably won’t harm a kitten; while shocks from the vastly more powerful Parmak Range Master (product 01-22) can harm small animals and demand respect.
Some experts claim that too much stress has been placed on joule ratings, because joules = volts x amperes x time; and so a weak electric fence charger generating a continuous output may have a higher theoretical joule rating than a powerful electric fence charger whose pulses only last a thousandth of a second. That’s perfectly true. But the electric fence chargers best suited to controlling horses, and all the chargers that we offer, are so-called “low impedance” chargers (see below) that put out very brief pulses measured in thousandths or even ten-thousandths of a second. That being the case, their relative joule ratings do give a rough idea of their relative shocking power, potential hazard, ability to charge long electric fence lines, and ability to cope with weeds and brush.
