Paddocks & Fields Part 2: The heart of the electric fence: Which fence energiser is right for keeping horses?

A fence has to keep horses safe while deterring wildlife. To ensure both containment and deterrence functional optimally, the fences are usually electrified. The fence energiser forms the heart of the electric fence, around which this guide revolves: What energisers are available and which one is right for my horse’s fence?

What fence energisers are available? Technical terms & their definitions

There are various energisers on the market with different „drives“ and outputs, which are not equally suitable for every horse fence. Before we go into detail about the selection of electric devices, let’s first clarify a few terms.

Voltage (Volts):

Voltage indicates how much current is required to set electrons in motion. In this process, the current flows from the negative terminal (electron surplus) to the positive terminal (electron deficiency). It thus describes the gradient between the negative and positive terminals, while the current strength indicates how many electrons flow through in a given time. Current strength is measured in amperes, voltage in volts.

Crucial for assessing the electric fence unit is the voltage achieved under normal load conditions. Load in this context refers to the contact of vegetation or the horse with the electric fence.

For a horse fence, a minimum voltage of 2,000 to 2,500 volts is required. For horses with thick coats, which are less sensitive, a minimum voltage of 4,000 volts is recommended. However, the voltage should not exceed 12,000 volts. The voltage of most energisers ranges between 8,000 and 10,000 volts.

Pulse Energy (Joules):

The charging energy indicates how much the unit consumes for itself before it even delivers current to the electric fence. Thus, the charging energy is the component that makes the units most comparable with each other.

In practice, however, the discharge or pulse energy is decisive. This shows how much current the unit delivers to the electric fence. The higher the pulse energy, the stronger the shock effect of the fence, the more intense the electric shock, and adjacent grasses are better eradicated.

Electrical Resistance (Ohm):

Electrical resistance is important when assessing a fence energiser and its associated electric fence. It indicates how much voltage is required to allow current to flow through the conductors. The greater the resistance, the lower the conductivity, so the greater the voltage must be for electrons to flow. Conversely, if the resistance of the material is low, less voltage is needed to generate a high current strength.

Now that we have a grasp of the terminology, we can now move on to selecting the right fence energiser. There are various energisers with different voltages and power sources:

• 9V energisers are battery-operated. Once the battery is discharged, it must be disposed of professionally.
• 12V energisers are operated with a rechargeable battery.
• Solar-powered 12V energisers use solar energy to recharge the integrated battery.
• 230V mains energisers are connected directly to the mains via a power socket.

How electric fence energisers work

The basic principle of an electric fence is simple: In a closed circuit, the energiser sends short current pulses through the conductor material (fence wire). For the circuit to be closed and function, the current must be sent back to the power device. This is done via earthing using an iron stake. Without an earth stake, no voltage would be sent back to the device, rendering the electric fence ineffective.

Similar to the earth stake, the circuit functions when the horse touches the electric fence: The current is conducted through the horse into the ground, back to the earth stakes and the energiser – the horse then receives an electric shock.

Any contact with the ground results in a diversion of the current into the ground. The more plants or defective insulators that touch the conductor material, the more current is diverted and the greater the drop in voltage, making it harder to achieve the desired fence voltage.

How do I choose the right electric fence energiser for my paddock or field?

Comparing individual energisers is often not enough when making a decision. In practice, there are other factors that need to be taken into account, which we will address below:

Which animals will be fenced in?

Horses generally belong to the easy-to-keep group of animals, as they are accustomed to electric fences from a young age, usually have short hair and thus feel the electric current clearly. Therefore, it is not necessary to construct a „high-security wing“. However, one should still keep in mind that native breeds with dense, long coat like some ponies or cobs are less sensitive to the electric current than other horse breeds. A higher voltage and pulse energy are then required.

Growth – How quickly will the fence become overgrown?

Tall grass, leaves and branches that touch the electric fence divert the current and thus reduce the fence voltage. How quickly the grass grows must be considered when deciding on an energiser and its voltage. Overgrown electric fences are a sign of neglected monitoring and maintenance duties. However, since one cannot always keep up with the sprouting grass, especially in spring, an energiser with sufficient voltage and pulse energy should be chosen. This will destroy the emerging growth as soon as it comes into contact with the electric fence.

Length and condition of the fence material

To ensure that the electric fence is sufficiently effective, the fencing material should have good conductivity and low electrical resistance. Conductivity determines whether the shock effect is lost before the electrical impulse even reaches the horse.

The electric conductors are usually made of stainless steel, also called Niro conductor, or tinned copper conductors. Stainless steel or Niro is inexpensive but usually has poorer conductivity than copper conductors. Copper conductors conduct better but are more susceptible than stainless steel conductors. Therefore, stainless steel and copper conductors are often combined in electric fence tapes and poly-wire.

Conductivity is significantly influenced by the electrical resistance of the material. This can be read from the packaging of the fence material and is given in ohms per metre (Ohm/m). The range varies from very good conductivity to poor conductivity:

• Poor conductivity: up to 15 Ohm/m
• Medium conductivity: up to 5 Ohm/m
• Good conductivity: up to 0.5 Ohm/m
• Very good conductivity: up to 0.05 Ohm/m

The better the conductivity of the fence material, the longer the fence can be. Conductivity can be further increased by using multiple fence conductors – for horses, three fence tapes or poly-wires are recommended. These should then be coupled with line connector cables or fence connectors to avoid obstructing the current flow with knotted ropes.

Power sources – Which energiser is right for you?

Now that you have analysed all the requirements and options, it is time to choose the right fence energiser:

Installation, useful accessories and maintenance

Connecting the fence energiser correctly

1. Find a suitable place for the energiser

The energiser should be well protected from rain, wind, and theft, and placed on level ground. An ideal option is a battery & energiser case, which keeps both the battery and the energiser dry.

2. Connect the energiser to the fence

The energiser has a red and a black terminal nut, corresponding to the fence connection cable (red) and earth connection cable (black). The red fence connection cable is attached to the bottom fence wire using a heart clamp.

3. Install the earth stake

The earth stake should be driven as deeply as possible near the energiser. Now, connect the black earth connection cable to the energiser (black terminal nut).

4. Connect the energiser to the battery/rechargeable battery

Attach the red (positive) and black (negative) clamps to the matching poles of the power source. The energiser can now be switched on, and the current flow checked.

Earth stake: How to properly earth your energiser

The effectiveness of the circuit depends entirely on proper earthing. Therefore, the better the earthing, the more powerful the energiser. Poor earthing results in insufficient voltage returning to the energiser, causing high resistance and low fence voltage.

The length and number of earth stakes depend on the energiser. For 9-volt energisers, the supplied earth spike is sufficient. For 12-volt energisers, the earth stake should be at least 1 metre long, while powerful mains energisers require multiple one-metre earth stakes. These must maintain a minimum distance of 3 metres from each other.

As moist soil conducts electricity better than dry, sandy, or stony ground, the earth stake should be thoroughly watered regularly during prolonged dry periods. Additionally, only use earth stakes made from non-corrosive materials, as rust acts as an insulator.

Fence tester: Properly testing your electric fence energiser

In the final step, a fence tester is used to check if the circuit has been successfully established and current flows throughout. Fence testers measure the voltage of the electrical pulse by inserting a small earth stake into the (moist) ground, connected to the fence tester’s display. Current flow should be checked at various points.

Lightning protection: Does every fence need it?

If a lightning strike causes the circuit to become overloaded, the electric fence energiser will be damaged and the safety of the livestock will no longer be guaranteed. A lightning arrester is then installed between the energiser and the fence system. However, the use of a lightning arrester outside buildings is only recommended, not mandatory. It is, however, recommended for 230V mains units.