What does low impedance mean? In the old days, electric fence chargers were high-impedance. The output from a high-impedance fence charger is high voltage, but low current. Because of this, poor insulators or grass and weeds touching the fence drain much of the shock.
The new electric fence chargers we sell are mostly all low-impedance output. The output from a low-and impedance fence charger is, medium to high voltage, but at much greater currents. Low-impedance fence chargers have a large reserve of current and are able to power (in other words, charge) very long fences or fences that are overgrown by green growth.
The following diagram shows the difference in voltage outputs between high and low-impedance fence chargers.