| ELECTRIC FENCES:
Electric fencing can be a cost effective and practical method
of fencing for a wide variety of animals.
There are several brands and models available from rural
agricultural stores which are battery powered as opposed
to being powered by the 240V grid. The battery type units
can then be powered by solar modules.
Due to the wide selection of energizers and accessories
on the market, we no longer sell the energizers. However,
we can supply you with a suitable solar panel and battery.
When you buy the energizer, only buy one as big as you require,
eg, if a 3 km unit will do the job, don’t purchase one
for 20 km, as they will need a solar panel several times
larger and more expensive than you’d otherwise require.
A 3 km energizer can be typically powered by a 2W solar module.
Several months ago one of our readers, Jules, submitted
some hints about using electric fences which is reproduced
below:
“I have used a number of different electric fence units,
from small to medium large, to power up to several kilometres
of fence, and I believe that they are an almost essential
part of fencing. In theory, smaller units are fine for shorter
fences, but in practice, shorting out from long grass/plants
is an unavoidable drain in most situations. Medium and large
units are available using 12V power and either an attached
solar panel or a separate panel. The units with a built in
solar panel are rather costly for what you get and the logical
conclusion might be to run your fence off your 12V home battery
bank/solar system. Provided all the connections are good,
and the unit is operating properly, this causes no more trouble
than a pulse across your TV screen with each fence discharge.
There are however two major problems that inevitably crop
up over a longer (several year) period:
a) As mentioned in your book (Energy From Nature), lightning
is a hazard to electric fence units. Even if you do not have
any direct strikes of lightning, a farm fence is a custom
designed electricity catcher. It is of course possible to
use diverters to earth (most) of a lightning strike and it
is sometimes possible to detach a fence during a storm (though
this could be dangerous in itself). The problem with lightning
is that the voltages generated are just so huge that any
form of protection has its limits.
b) Electric fence units are subject to more failure than
most other electrical equipment. I’m not sure why this
is, but I’d guess that the mixture of low voltage with
strong pulses of high voltage is problematic. It is quite
common to get some sort of feedback of high voltage from
the output side of the circuit to the input. Some units seem
to do this when in perfect working order and others can develop
it as a fault where transformer insulation breaks down.
Both of the above failures can be very serious for sensitive
electronic equipment like computers and solar regulators.
The best and safest way to power an electric fence is from
a separate panel/battery/earth system preferably housed in
a shed away from your house. A reasonably cheap and very
functional system can be put together with a second hand
solar panel (and if you’ve been using solar for a while
you might well have a spare), a decent car battery (or that
size of deep cycle battery), and the highest output 12V fence
unit you can stretch to.”
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