Horse electric fence
 

Hi all,
I want to remotely power a couple of electric fences for horses .
For many years I've powered them in the fields using rechareable batteries
I've also tried solar powering
Both have issues from damage and the hassle of bringing the batteries in to charge etc ( plus the hazard of the batteries bring nicked )
It looks like the pro company's use a very expensive mains powered unit ( £900 plus !) and then run a well insulated cable ( again expensive ) to the remote fields carrying the full 5000 volts !
The distance from mains supply to field is about 150 mtrs .
My immediate thoughts were to use say twin and Earth 2.5 mm mains cable
( cheap ) and generate say 15 volts to allow for the volt drop at the mains supply end ( simple transformer plus bridge rec etc ) .This would simply be connected to the normal battery powered energiser in the field ( 12 v )
The energiser use less than 1 amp and is a short pulse
This would have the advantage of no worries of leakage to earth using high volts ( 5000 ! ) and safe to anyone touching the cable should it be damaged
Has anyone done something similar ,or see a problem with my idea please ?
Cheers Pete

Re: Horse electric fence
 

Sounds electrically feasible to me. The only problem I have found when using plastic cable along fence lines through fields (we sometimes have to do this with temporary telephone wires at work) is the fact that every living thing with sharp teeth seems to want to chew it. This is a particular problem with livestock, but also with rabbits, deer, rats et al. The cable is usually destroyed within days if not routed carefully. The cable will also probably radiate interference, something to consider if you are a radio listener.
Alan.

Re: Horse electric fence
 

Good point Alan.i guess I could push the boat out and use amoured cable .

Re: Horse electric fence
 

Um, liability in a word. If anything goes wrong, or if anyone just thinks there is something wrong. It's a lot easier if you have a standard fence driver and nothing unusual for anyone to point at.

David

Re: Horse electric fence
 

@ 12 volts David ?

Re: Horse electric fence
 

I have a 12v fencer in my workshop, it was bought to protect the chickens from foxes and bagers but they had them all before I got round to fitting it.

I have run a mains cable to our well about 150 yards away inside 22mm blue plastic pipe, I didn't even use 2,5mm cable I got some very cheap high current flex from ebay, you get a bit of a voltage drop when the pump starts up but that's drawing about 5 amps, you will only be drawing milliamps.

You probably could run 2.5 mm with the charger at the house end, the fencer uses very little current and you could always up the voltage from the charger a bit but I'm sure that would be adequate.

Peter

Re: Horse electric fence
 

Reconsider the battery and fencer arrangement - can you use lithium in place of the (usual) lead-acid and, if so, convert the unit to take slide-in (or clip-on) batteries like power tools use?

You can then make recharging a much easier exercise.

Fit a timer to switch the device off at night (presumably the horses don't move around too much in the dark?) - lengthen the time between pulses etc. Any other power-saving methods?

Re: Horse electric fence
 

I did once come across a patent for an electric fence generator filed by a New Zealander where the invention was about energising the fence at random intervals rather than continuously (actually pseudorandom as he used a motor-driven metal disc with portions of the rim insulated to provide the OFF periods). He had found that cattle could withstand the pain of a continuously-energised electric fence for long enough to trample it down, but were afraid of a fence that might or might not give them a shock. Such intermittent operation would reduce power drain.

Re: Horse electric fence
 

Joe public doesn't understand much. If there's anything homebrew powering an electric fence and someone gets even a bog standard fence bite from it, you run the risk of someone exaggerating claims of 'frankenstein-like supercharged home-made electric fence electrocuted me' or someone decides you're doing it to torture animals. A nice maker's name prominent on the box can protect you from getting sucked into a logic-free zone.

Kelly, horses move around a lot at night. They can half doze off and still move around grazing. They're probably more likely to wander into a fence. During daylight, non-electric fences come under a lot of stress used as scratching posts, and with animals leaning over to munch anything reachable on the other side.

Those expensive mains powered fence chargers are usually intended to drive all the fences on an entire farm. Their failing is that their power has to be limited so they don't risk anything or anyone that contacts them, but if the wire or tape gets grounded, the whole system is ineffective. Less hassle than maintaining multiple battery ones, more hassle when something goes wrong.

At farm sale auctions, I notice that old rusty fence units sometimes sell for more than the new price :-)

David

Re: Horse electric fence
 

Thanks for the horsey insight David ;D

As you can gather I'm not a keeper or user of such but the information will be used at some future interval I'm sure.

I've repaired a few fence energisers locally in recent years and did at one time briefly consider developing my own version but have yet to explore any further down that track.

But powering a system over long cables could be achieved using inexpensive buck-boost converters to recharge the battery overnight. I'm thinking along the lines of the XL6009 (auction site purchase) to deliver a constant voltage to a charging circuit.

Re: Horse electric fence
 

Hi We use solar types with no problem, batteries and electrionics are all in lockable boxes, but I will concede that winter requires a couple of charge top ups and fence units should be the ones with auto shut down on low volts or you will kill your batteries. Rodents eating cables was a problem untill I ran all wires in thick walled garden hose.

However if you go with the remote power option, which opinion appears to be guarding against, do be aware that if the earth comes adrift at the remote fence energiser end the return path will be via your remote supply. ( in my experiece you will get some high voltage on the earth side anyway due to ground resistance)


Pete

Re: Horse electric fence
 

That's a very good point that Pete has made and remember that the primary/secondary insulation on the mains transformer that you are using should be guaranteed to handle the 5 to 7 KV the fence is producing. An ordinary wallwart or battery charger wont do, as potentially under the right conditions the output of the fence could be placed across the primary/secondary of the mains transformer.

Frank

Re: Horse electric fence
 

All my problems with BT Broadband & Openreach are well documented in another forum thread. However, recently, one of their engineers discovered a valid problem with a neighbour's paddock's electric fencing. Discharge through neglected encroaching gorse, weeds & long grass, particularly during wet & windy conditions, have been causing signal to noise problems. All 8 of us on a remote o/h rural supply(including the equine enthusiast) have been experiencing chronic S/N problems which are resulting in low speeds on ADSL1.
Frequency channels in the Download spectrum near 600KHz are electric-fence susceptible according to the O/R guy, and I also managed to locate noise problems(using my portable BEME LOOP DF Rx) near 785KHz.
The O/R guy seemingly has been investigating other fencing related problems in recent years & has found that broadband customers up to 1/2 a mile from a dodgy fence can be affected. Apparently, BT & OFCOM can come down on irresponsible fence owners like a ton of bricks.

Regards, David

Re: Horse electric fence
 

frank has made a very important point. The 'ground' point of the fencer often floats a few hundred volts above ground due to leakage paths between the HT output and earth. Using a battery fencer and a wall wart could mean HT voltage trying to get to earth (mains neutral) through the wall wart/LV supply and at 5-7kV, little will stop it. A switchmode 12V supply's primary/secondary insulation might easily break down with lethal consequences under repeated 'flash tests'.

Mains fencers work by having a capacitive/zener dropper that supplies a small DC current to an inverter that charges a film capacitor through a high value resistor that is then intermittently dumped across the primary of an HT transformer, the flyback creating the HV pulse on the output. The split-bobbin HT transformer is usually (though not always) encapsulated and highly insulated so at no point can anything (including damp) provide a path of any sort between mains and fence. The circuits are often protected at various points by MOVS and/or spark gaps to prevent the fence acting as a lightning conductor during a storm.
I would persist with power to a commercial mains fencer solution or think more about an independent 12V battery supply.

The principle is illustrated by the old die-cast bodied fencers which could suddenly become live if the fence went down to earth somewhere; usually when you'd just reached over to turn them off and discovered the insulated rubber boot on the dolly switch had perished!

Re: Horse electric fence
 

Thanks everybody for your inputs
I spoke to two well known fence manufactures today asking why they thought their idea of send 10k through an non armoured cable underground was a good idea !
Their tech guy said that's the way they have always done it !
I think it's a very valid point about the earth becoming disconnected etc
I will prob use a commercial mains powered unit but run the wire in plastic pipe for protection
I still think it's bonkers to run 10 k through this sort of cable underground ! Leakage problems etc
If I were to market such a system I would still run low volts in an amoured cable and build the appropriate power supply to cope with 10k insulation
Just a thought ,could the low volt feed be protected with high voltage zeneers or similar connected to earth ?
Cheers Pete

Re: Horse electric fence
 

Why not keep the battery at the unit in the field as a standard setup, and just supply a constant trickle charge?

Re: Horse electric fence
 

The amount of fence which can be driven by a given driver is a function of both the capacitance and the leakage of the fence. An underground section is thus equivalent to a significant amount of above-ground fence.But to link across a gate, the only alternative is some sort of gantry carrying a wire high enough over the top to clear whatever machinery needs to use the gate.

I rebuilt a fence unit in the early 70s. It used an output transformer from a Wolseley fencer. This had a well insulated secondary with separate connections, so y ground stake and the fence were both isolated from the aluminium box it was built in. The business part was a capacitor discharge system using HT from a small inverter, and the whole thing was powered from 12v so a battery and charger allowed the machine to keep on going through a power cut. Industrial unrest guaranteed plenty of those in the early 70s!

The fence kept pigs from grubbing their way into a banking carrying the drive to a farm. Once they did that the far was cut off. Pigs are smart enough to spot when the thing was out of action.

David

Re: Horse electric fence
 

I made one fencer unit using a car ignition coil,a 556 and a mosfet. The 556 was setup up to give a 5mS long pulse to "charge" the coil and then switch "off" every second resulting in a nice "whack" if you touched the fence. I ran it on an old alarm battery, lasted ages. A good earth for the unit is essential.

A duty time of 5:1000, all fitted in a tupperware box.