29 March 1996



Planning on buying a new electric fence energiser for spring and summer strip grazing? Heres a round-up of whats available

THE advent of solid state electronics has done wonders for the reliability and performance of electric fence energisers.

But without the benefit of experience, choosing an energiser from the vast number on offer is a daunting task. Not least because of the varied situations in which this equipment might be used.

"It really is very difficult to provide a rule-of-thumb guide to, say, the power needed to run a particular fence length because there are so many factors that affect the answer, not least the type of wire and number of strands used," says Martin Armstrong of Rutland Electric Fencing. "The likelihood of contact with foliage is another consideration, given that this drains the fence of power and reduces its effectiveness."

Nonetheless, a few basic specification requirements should help point buyers in the right direction. In terms of voltage, a minimum of 3000v (the "pressure" behind the flow of electricity) is needed to hold stock.

This should not be confused with the "power" of an electric fence energiser, however, which is the amount of energy stored in the capacitor and is these days most frequently expressed in joules – the measure of the electrical energy released and thus the shock delivered.

The joule output figure provides a means of gauging which energiser from a particular range is needed for a particular fencing task, and allows models from different ranges to be compared like-with-like.

UK manufacturers Rutland and AEC Hotline offer a substantial range of energisers to cover a multitude of fencing situations and user preferences, with importers tending to be more selective and offering fewer options.

Rutlands range, for example, extends from the 0.07j ESB25, suitable for short length single wire fencing across a silage face or temporary paddock systems, to the 4.7j output ESB350 which is recommended for use in high power leakage situations as well as permanent fencing where it is not possible to connect a mains energiser.

"Within our particular range, the ESB200 and ESB250 wet battery energisers with outputs of 1.6j are probably most popular with farmers, giving plenty of output to contain difficult stock or cope with a certain amount of power loss through contact with vegetation," says Martin Armstrong.

Power and voltage output apart, battery life is a key factor of temporary electric fence systems, not only in terms of time between recharging but as regards overall battery life.

"In buying a new battery, I always recommend a leisure type rather than a tractive type for a car or tractor," says Martin Armstrong. "The internal structure of the two is slightly different, one consequence of which is that, while a completely discharged leisure type battery can be re-charged to give 90 to 95% of its original performance, some tractor batteries may regain barely 70%.

"This is particularly the case with old discarded tractor and combine batteries often used to power electric fences," Mr Armstrong adds. "These may have more than enough performance to provide the power needed initially but output will decline with repeated re-charging."

Energiser manufacturers have come up with some useful features to extend the period between charges. Most now offer two or more pulse speeds, for example. In some cases that includes a fast rate (typically one pulse per second) to train animals to respect the fence and a standard setting (say one pulse every 1.5-2sec) for regular use.

As the accompanying supplier listing shows, a number of manufacturers now include light sensors so that the energiser automatically switches to an economy mode (typically one pulse every three to four seconds) at dusk and the standard pulse rate at dawn.

Typically, they say, users can expect such a feature to add a week to charging intervals.

Solar panels are a more high-tech means of extending useful battery life and work well during the late spring and summer months. They are vulnerable to damage, though, and are only cost-effective on smaller output energisers.

In contrast, wind-powered chargers can successfully extend the life of batteries used with high-output systems if used in a sufficiently windy location.

Battery and fenceline condition indicators on energisers provide a useful quick check that, first, there is sufficient battery power (indicator lights blink when the charge is getting low); second, that the fence is still managing to do its job. Again, products differ in the extent and form of these devices.

The choice of whether to buy an energiser with integral battery case is down to personal choice. Clearly they afford useful weather protection as well as added convenience since the complete assembly can be moved as one.

But such designs do restrict battery size and if the inclination is to use a ready source of old combine or tractor batteries, then a non-cabinet design is probably the more appropriate choice.

&#8226 Remember that an electric fence energiser can work only as well as the earthing and insulation allows. Earthing, in particular, is often inadequate – a rusty 6in nail driven into the ground will provide very poor contact.

&#8226 A 1m (3ft 3in) earth stake, in clean condition, knocked well into the ground will do a far better job, ensuring the fence can do its job.

&#8226 Soil moisture is another factor; a poor earth contact driven into damp soil may work well enough but, as the soil dries, will become less effective. Last years very dry summer proved the point that earthing needs to be given more attention than it often is.

Olli range from Grene Agricessories.

A combination of a well charged battery and efficient energiser helps make an effective electric fence – and keeps livestock in the right place.