WO1993007735A1

WO1993007735A1 - A method for adapting the operation of an electric fence energiser to the type of battery

Info

Publication number: WO1993007735A1
Application number: PCT/SE1992/000671
Authority: WO
Inventors: Lars-Arne Eriksson
Original assignee: Alfa-Laval Agriculture International Ab
Priority date: 1991-10-03
Filing date: 1992-09-25
Publication date: 1993-04-15
Also published as: GB2275583B; GB2275583A; GB9405368D0; DE4293194T1; SE9401075L; SE9102866L; SE9401075D0; SE9102866D0; SE500486C2

Abstract

In a method for adapting the operation of a battery powered electric fence energising apparatus to type of battery the rate of decrease of the battery voltage is determined, and the power consumption from the apparatus is decreased if the rate of decrease exceeds a predetermined limit. Further, the energy required for charging a discharge capacitor (C3), arranged to produce output pulses, is determined, and an essentially constant current is drawn from the battery during the charging period of said capacitor.

Description

A method for adapting the operation of an electric fence energiser to the type of battery

The subject invention relates to a method for adapting the operation of a battery powered electric fence energiser to type of battery.

In battery powered apparatus for the production of pulses on electrical fences it is of the utmost importance that the battery achieves a service lifetime as long as possible.

The object of the present invention is to achieve maximum service lifetime of the battery at the use of dry batteries as well as alkaline batteries. This object is achieved by a method of the kind indicated by way of introduction by determining the rate of battery voltage decrease, decreasing the power consumption of the apparatus if the the rate of decrease exceeds a predetermined limit, and determining the energy required for charging a discharge capacitor arranged for the output pulse generation, an essentially constant current being drawn from the battery during the charging period for charging the capacitor.

At the method according to the invention the characteris¬ tic of the batteries is considered, the current consumption from the battery for charging the discharge capacitor for generating the output pulses being decreased at a to large decrease of the battery voltage. By this getting outside the range of operation recommended by the supplier of the battery is avoided, so that the battery is saved and its service lifetime is increased. By decreasing the output power from the electric fence energiser if the battery voltage is decreasing too rapidly one avoids that the battery is de¬ stroyed or is discharged too soon at the use of smaller types of batteries. By determining the energy required for charging the discharge capacitor arranged for generating the output pulses and in this connection drawing an essentially constant current from the battery during the charging period of the capacitor, one avoids a high top current consumption which is particularly harmful for dry batteries. An essentially constant current consumption is however also advantageous at the use of alkaline batteries as the inner resistance thereof reduces the efficiency at large curents.

According to yet another embodiment of the method accor¬ ding to the invention the outdoor temperature is measured where the apparatus is placed, and the output power from the apparatus is decreased when the temperature is decreasing below a limit value. This contributes further to saving the battery through a lower current consumption at a lower temperature with a longer service lifetime of the battery as a consequence. Preferably the output power can be decreased successively in several steps at decreasing temperature, the battery being completely cut off at a certain temperature.

The invention will now be described more in detail through the following description of one embodiment of an an electric fence energiser and of its operation with reference to the attached drawings, on which

Figure 1 shows a schematical circuit diagram of one embodiment of a battery operated electric fence energiser for implementing the method according to the invention.

Figure 2 shows voltage-time characteristics for different types of batteries and

Figure 3 illustrates the current drawn from the battery during the charging period for different modes of operation. In the battery operated electric fence energiser, shown in Figure 1, the battery, not shown, is intended to be connected to terminals Wl and W2. Sl is a switch for connec¬ ting and disconnecting the battery. The elctric fence apparatus is connected at terminals OUT and GND over the secondary side of a transformer Tl. The primary side of the transformer Tl is divided into two windings, coupled in two opposite directions, i.e. an energy recovery winding PI and a pulse winding P2.

A discharge capacitor C3 is connected over the pulse winding P2. During the charging interval of the capacitor C3 a transistor Trl included in a DC-DC converter 2, is control¬ led by short pulses from a micro processor, not shown, included a control unit 4. This results in a short current from the battery through the transistor Trl and an inductance LI, connected in serie with said transistor. When the trans¬ istor Trl subsequently is cut off a voltage will be produced over the the inductance LI, which results in a current to the capacitor C3 through a diode D3 coupled to the inductance LI. The voltage over the capacitor C3 will thus increase somewhat for each such current impulse.

The voltage over the capacitor C3 is sensed by a measu¬ ring unit 6 over a resistor R2 and when a predetermined maximum voltage has been obtained the charging process is interrupted.

During a subsequent discharge process a thyristor TYR1, connected in serie with the diode D3, the winding P2 and an inductance L2, is ignited from the micro processor in the control unit 4. Normally the micro processor is programmed to ignite the thyristor TYR1 after a predetermined time from the preceding pulse. A current will then start flowing from the capacitor C3 through the winding P2, the inductance L2 and the thyristor TYR1. In this connection the inductance L2 has the function of limiting the increase rate of the current. After a certain time, when the voltage over the primary side of the transformer Tl has reached its value, the micro processor in the control unit 4 will ignite a thyristor TYR2, connected in parallell with the inductance L2 and the thyris¬ tor TYR1, whereby the energy in the capacitor C3 will be drained through the winding P2 of the transformer Tl and the thyristor TYR2.

The pulse through the winding P2 will be stept up by the transformer so as to obtain an output pulse of typically 4-8 kv on the secondary side of the transformer Tl, to which the electrical fence is connected.

The operating voltage of the battery is typically in the range 5-9 V and the charging energy amounts to 100-350 mJ. The pulse length is normally 1,4 seconds.

The voltage over the capacitor C3 is continously measured through the resistor R2 for security reasons. If the voltage does not develop in a predescribed manner the charging from the micro processor of the control unit 4 is interrupted.

During the subsequent energy recovery process the side of the energy recovery winding PI connected to the energy storing capacitor Cl goes positive and a current will flow through the diode D2 and the storing capacitor Cl will be charged, i.e. energy recovered from the fence is restored in the storing capacitor Cl. A diode Dl arranged between the terminal Wl and the switch Sl prevents the recovered energy from going into the battery. This is because as soon as the voltage over the capacitor Cl rises over the battery voltage the diode Dl will be blocked. The diode Dl is conveniently a Schottky diode.

The current which is recovered in the energy recovery winding also tends to charge the discharge capacitor C3 negatively. Through a diode D4 connected over the thyristor TYR1 this charge is later discharged through the transformer and is turned to a positive charge in C3 through the induc¬ tance of the transformer.

During the subsequent discharge phase for the discharge capacitor C3 the recovery energy stored in the storing capacitor Cl is first consumed, since the diode Dl is block¬ ing as long as the voltage over the capacitor Cl is larger than the battery voltage. Not until the energy of the storing capacitor Cl has been drained so that the voltage has decrea¬ sed below the battery voltage, current is beginning to be drawn from the battery for charging of the capacitor C3.

Preferably the voltage of the discharge capacitor C3 is measured when the energi of the storing capacitor Cl has been drained, and the remaining voltage over the discharge capaci¬ tor C3 is calculated. From this the average current required for reaching the correct capacitor voltage at the end of the discharge period is determined and this average current is drawn from the battery. Such a constant current consumption without heavy current top values is advantagous for the battery.

A switch S2 connected to the measuring unit as shown

?9 makes possible switching between two operational modes. One 5 of this, called "training", means that full output voltage is used all the time and is intended to be used during the learning time of the animals. During the other operational mode, called "normal", each full power pulse is followed by a number of pulses of lower power, which reduces the energy

10 consumption and thus increases the lifetime of the battery. In order for the rise time of the outout pulse not to be too short, e.e. in order not to make the rate of the dis¬ charge of the discharge capacitor too high, the transformer Tl is designed to achieve a high coupling inductance. A

15 filter is arranged on the primary side of the transformer, which attenuates high frequency components, above 150 kHz. The filter consists, on the one hand, of the capacitor C2 connected over the windings PI and P2 of the transformer Tl and the inductance L2 connected between the primary winding

20 P2 and ground, and, on the other hand, of the leakage induc¬ tance of the transformer Tl. By connecting the capacitor C2 over the two oppositely connected windings PI and P2, the effect of the capacitor in the filter is reinforced.

To get a large filtering effect, i.e. a long rise time of

25 the pulse and yet low losses, the inductance L2 of the filter is only connected into circuit during the first part of the pulse. During the second part of the pulse the thyristor TYR2 is conducting and is conducts the current past the inductance L2. Otherwise an undesired voltage drop should appear over

30 the inductance L2 due to its resistance, with consequent losses.

The battery voltage is measured regularly, e.g. once an hour, and if the battery voltage is decreasing below a predertermined threshold or if the battery voltage is decrea-

35 sing too rapidly, the power consumption is decreased by the energy stored in the capacitor decreasing.

After this a new measurement is made each 24 hours and a new admissable threshold is decided, which is somewhat below the battery voltage and if the voltage during the operation of the apparatus is later decreasing below this threshold, the current consumption from the battery is decreased so that the voltage again increases above this level.

To supervise the condition of the battery and to resolve when it should be changed a permissable threshold is set for the battery voltage. At the use of a battery with a decrea¬ sing voltage-time charecteristic the threshold is set at a comparatively low level, while for batteries with an essenti¬ ally constant voltage level during the operational time, i.e. for alkaline batteries, the permissable threshold is set comparatively high, as the voltage is decreasing rapidly when the battery no longer maintains its voltage level. This is illustrated in Figure 2 which shows the voltage-time charac- teristic for two different types of batteries. To the battery a light emitting diode LED1 is also connected, which is normally twinkling at each output pulse to the fence, until the battery voltage has decreased below the predetermined level. This light emitting diode LED1 serves thus as an indication of "poor battery". Absence of twinkles from the light emitting diode LED1 indicates that the battery needs to be changed.

To save the battery and thus further increase its service lifetime the apparatus is made to reduce the power at a decreasing temperature. For the measurement of the temperatu¬ re a temperature dependent resistance R3 connected to the measuring unit 6 is used. For example, at an environmental temperature of +5 degrees C the output power can be decreased to 50% and at -5 degrees C it can be cut to almost zero.

As has been mentioned above the average current that must be drawn from the battery for charging of the discharge capacitor C3 to the predetermined level during the charging period is calculated and an essentially constant current equal to this average current is drawn from the battery.

Further, if the battery voltage is decreasing in an unsui¬ table way, the output power and thus the current consumption from the battery is decreased, to save the battery. This is illustrated in Figure 3 which shows the current consumption at three different battery designs.

Case I illustrates the current consumption according to prior art having no possibility to preset the magnitude of the charging current drawn from the battery, while the cases II and III show the preset, essentially constant current which is drawn during the charging process according to the present invention at two differently sized batteries. As is appearent from Figure 3 an essentially constant current is drawn from the battery during the charging process.

Claims

1. A method for adapting the operation of a battery powered electric fence energising apparatus to type of battery, characterised by determining the rate of decrease of the battery voltage and decresing the power consumption from the apparatus if the decrease rate exceeds a predetermined limit, and by determining the energy required for charging a discharge capacitor arranged for generating output pulses, and drawing an essentially constant current from the battery during the charging period of said capacitor.

2. A method according to claim 1, charaterised by decrea- sing the power consumption by decreasing the pulse voltage.

3. A method according to claims l and 2, characterised by measuring the outdoor temperature and decreasing the output power of the apparatus when the temperature is decreasing below a predetermined limit value.

4. A method according to claim 3, characterised by decreasing the output power in several steps at the passage of subsequently lower limits values.

5. A method according to any of claims 1-4, characterised by, in order to decide when the battery is used up and need to be changed, measuring the battery voltage a first time after a relatively short time of operation of the apparatus, and deciding a lower threshold for permissable battery voltage which is considerably below said measured battery voltage.