• An electric fence is powered by an energizer, which runs on a 12-volt
battery or mains current. The energizer converts the electricity into a
high-voltage and low-amperage DC pulse at about 1 pulse per second
and a pulse width (duration of pulse) of a few thousandths of a
second. Fences used for elephants usually carry a voltage between
6,000 and 9,000 volts and a current of about 5 milliamperes
Consider the case of a 100 µs duration pulse, for example.
Since the dura-tion is defined as 1.5 time constants, the
maximum allowable capacitance is seen to be 0.133 µF. Using
the energy limit of 5 J we have a peak voltage of 8660 volts,
since Energy = ½ CV2. The product of that voltage and the
capaci-tance gives a stored charge of 1155 µC. Based on the
dura-tion being 1.5 time constants, the delivered charge is then
897 µC. Note that the actual delivered charge could end up
being a value between these 2 charges if there is no trunca-tion
of the pulse. The net impact of this is minimally materi-al and
so we will use the delivered charge estimate of the last column.
Discharge curve of an ideal
energizer
Calculating the Joule
needed for a fence length
• Theoretically it would not be possible to
calculate the strength required to power a
fence, since we would not be able to
predict the factors given as a diagram on
the right.
• However we can take the guidelines
issued by some of the established
Energizer manufactures.
Estimating the power required by a energizer
• Measured Crown Energizer
• Required 500 milliamps of current
The pulse rate was 50 cycles per minute
Actual use of current half of it 250 milliamps
24hours 250 x 24 = 6000 milliamps or 6 Ah
This power has be delivered by the battery for a day. There is a loss of
20% power converting from chemical energy to electrical energy at the
battery which 1.2 Ah to 7.2 Ah
Battery requirement
• The energizer is requiring 7.2 Ah of power every day
A lead acid battery has a theoretical life of 1000 cycles. This would
drastically drop down to 300 if the battery is discharged completely
every day. The ideal discharge of battery should be less then 30 %.
Which would be 10.3 Ah which would ensure that the battery lasts for
3 years.
Due to rain if we can say there would be very little solar energy for 6
days
The capacity of the battery should be around 60 Ah. Depending upon
the locations rainy days it could be increased or decreased.
Sizing a solar cell
Bopal
Sunshine
• One hour of full sun provides 1000 Wh per m² = 1 kWh/m² as far as
Assam goes it gets 4.68 KWh/ m² per day annual average and this dips
to 4 during the monsoon
Formula
for converting is Ah to watts for calculating
.
the panel size
(Ah)*(V) = (Wh).
For example, ifwe have a requirement of 2 Ah
battery rated at 5 V, the power is
10Ah * 12V = 120 Wh
The efficiency of the solar panel is only 17 to 18 % 120*.18 which increase the panel 141.8 watts,
We get only 4.68 kWh of solar energy as an average
and during monsoon it drops down to 4.
Lowest energy produced is 4 KWh/m sq/per day 6
hours of energy producing sunlight 4/6 =0.66
141.5 * 0.66= 93 watts panel
KWh/m.sq /day
7
6
5
4
3
2
1
0
January
Feb
March
April
May
June
July
Agust
Sept
Oct
Nov
Dec
Conclusion
The assumption is that we are having a energizer which draws 500
milliamps of current
Battery size required 60 Ah at 12 volt a deep discharge battery
Solar panel required is minimum is 100 watts at 18% efficient (a higher
watts panel would be an insurance against failure)
A charge controller (with a display if possible) which could handle 20
am current at 17 volts.
The wiring used should as thick as possible and short in length as
possible to reduce losses due to transmission.