A grounding cable reel for grounding a vehicle of the type used to service electrical power lines includes a reel assembly incorporating a conductive slip ring capable of conducting very large, short term ground fault loads, i.e., on the order of 20,000 amps. A first cable connected at one end to the vehicle's frame is coupled at its second end to a copper rod which extends through a hollow shaft which supports the reel such as for mounting to the vehicle. The copper rod is coupled to a conductive inner hub of the slip ring which is mounted to an end of the hollow support shaft. Rotationally coupled to the inner hub is an outer conductive swivel to which a first end of a second cable is coupled, while the second end of the second cable may be coupled to a grounding post or other grounded object. The second cable is disposed about the reel which is coupled to the outer swivel and rotates therewith. A louvered circular conductive strip is disposed intermediate and in contact with the inner hub and the outer swivel for providing electrical continuity in the slip ring. The inner hub and outer swivel are preferably comprised of brass for conducting large currents and for serving as a heat sink, while the contact strip allows for rotation of the outer swivel on the inner hub and electrical current conduction therebetween and is preferably comprised of a silver alloy.

The invention provides an electric fence charger of the type that periodically provides high voltage electrical shock pulses through an electric fence wire. The fence charger has a low voltage power source that powers the fence charger and supplies a charging current. An energy converter converts the low voltage and charging current of the power source to high voltage for storage in a high voltage storage means. A timer emits pulse discharge control signals on a periodic basis and these control signals are used to control discharge of the stored high voltage for delivering shocking pulses into the fence wire. A regulator adjusts operation of the energy converter to provide a minimum high voltage energy level as long as the power source voltage exceeds an established power source voltage reference. In another embodiment of the invention, a fence charger employs a DC-DC flyback converter for charging a high voltage storage means to a discharge voltage level which provides a minimum shock energy pulse. This embodiment includes means for operating the flyback converter at a constant frequency and means responsive to battery voltage for changing the flyback converter duty cycle to regulate the discharge voltage level.

An electric fence controller and method of controlling the energization of an electric fence. The controller includes a digital timing circuit which generates a digital signal to control the activation of a switching circuit for applying energy from an external power source across the primary winding of a transformer. The power source may be an alternating current source, the cycles of which are located by the timing circuit which activates the switching circuit after a selected number of cycles are counted driving an off-time period. Alternatively, the power source may be a direct current source and the timing circuit may include an oscillator and a counter for counting the number of oscillations and generating a digital signal which activates the switching circuit during an on-time period corresponding to a first selected number of oscillations, the switching circuit being inactive during an off-time period corresponding to a second selected number of oscillations.