Solar electric fence

I was lucky to find fly killer in a shape of tennis racket like the one that you recommended. I took the circuit diagram.
I want to use it for project similar to fly killer. I want to connect it to our electric fence where we keep 4 sheep.
I connected the ground of the base of the transistor to a 555 timer that oscillate at 1 Hz. The current is only 10mA when I don't touch the fence. It is 30mA when there is ark. In normal operation we don't have ark.
If I use 4 Ni-Cad cells I think it will be enough for one day. I want to put also small solar panel to charge the battery.

I need advice please from somebody who knows about solar panel. How big it has to be to charge the battery average 30mA on cloudy day?

One house in our village paid 15000 Euros for 16 square meters of panels on his roof. They told him that on sunny day he will have 2KW and after 5 years the panels will pay for themselves. He had only 100W on sunny day and the company came to look and told him that it's because the panels are dirty with kacki of birds. He cleaned the panels and the output went up to 200W. Now he takes the company to court, his advocate say that he has to clean the panels of birds kacki every week until he is 135 years old until the panels pay for themselves.

The guy with the solar panels on his roof needs to continuously rotate and tip his house so that the panels face the sun all the time. But the panels do not last much longer than 10 or 20 years, so they will never pay for themselves.

10mA draw is 24h * 10mA = 240mAh per day (so AA NiCd or NiMH cells should be adequate for several days operation without charging).
You need to add about 150% of that per day to keep the batteries charged or 360mAh.
Assuming 8 hours of daylight, you need the panel to average (not peak) 360/8 = 45mA. (It could be less on a cloudy day as long as there aren't more than a few cloudy days in a row.)

hi mirel,
I would suggest you do a quick test of your fence circuit effectiveness with sheep, with all their wool and lanolin oil they are quite good body insulators.
You may need about 1.5 Joules of energy in each pulse if you are to deter sheep.

E

crutschow said:

10mA draw is 24h * 10mA = 240mAh per day (so AA NiCd or NiMH cells should be adequate for several days operation without charging).
You need to add about 150% of that per day to keep the batteries charged or 360mAh.
Assuming 8 hours of daylight, you need the panel to average (not peak) 360/8 = 45mA. (It could be less on a cloudy day as long as there aren't more than a few cloudy days in a row.)

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Hello,
When I search on the internet they always say how much current the panel gives on sunny day but they don't say what is the current on cloudy day. Here in north France they say we have 2 hours of sun every day, the people where I live think that they say it only because they want tourists to visit.
I can buy panel and try but to save me that maybe you can tell me about the current before I buy. Thank you.

ericgibbs said:

hi mirel,
I would suggest you do a quick test of your fence circuit effectiveness with sheep, with all their wool and lanolin oil they are quite good body insulators.
You may need about 1.5 Joules of energy in each pulse if you are to deter sheep.

E

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I use electric fence to stop my dogs to go to the road. I noticed that the dogs never touch the wire when it's on and they walk on it when it is off. I think the dogs can smell the HT. One student told us that he can smell the HT and it is the same smell that you have near ionizer. I think the sheep and the cows can smell it too.

Here's some info that indicates a solar panel can still output near 50% of its full-sunshine peak value on a heavy overcast day, which is encouraging.

mirel said:

I use electric fence to stop my dogs to go to the road. I noticed that the dogs never touch the wire when it's on and they walk on it when it is off. I think the dogs can smell the HT. One student told us that he can smell the HT and it is the same smell that you have near ionizer. I think the sheep and the cows can smell it too.

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I like cows but I don't understand them, how can they be scared of the smell of ionizer and not mind their own smell.

In your case solar panel will be ok because you need little power. Check maybe the man in your village will sell his panels in a reduced price.

I tried solar panels a few years ago, on cloudy days the output went down to 1 or 2 percent. In England you get clear sky for 2 hour a year. Solar panels convert energy with efficiency of 2% they are good only for the desert.
In Europe they use wind turbines or waterfalls.

hi mirel,
This is the electric fence we use on our farm, sheep, goats and pigs, works OK.
I have designed it so that you can set the pulse rate, dwell time to suit your fence.
In order to increase the 'jolt' the animal gets, run a thin ground return bare wire about 1 foot below the insulated HV wire, also a good grounding rod at the battery -Ve.
Tie red or orange ribbons every few metres along the HV wire, the animals will quickly associate the ribbons with a 'jolt'.
Other people who have built it with good results.

Uses a 2nd hand car battery, ignition coil, capacitor and ballast resistor.
Using a 12V car battery means its easier to charge with a regular battery charger and if required a 12V~ 17Vo/c solar panel will keep it topped up.

E

crutschow said:

Here's some info that indicates a solar panel can still output near 50% of its full-sunshine peak value on a heavy overcast day, which is encouraging.

Click to expand...

I would suggest 'optimistic' rather than 'encouraging'

A vehicle ignition coil run open ended will give a higher voltage than it was designed for, and might shorten its life, if you put a spark plug on the end of the coil it will limit the voltage from the coil, and you can adjust the voltage to the fence by setting the gap.
Probably not that critical if your using a near worn out battery.

hi dr,
If you look at the date of my posted drawing ie: 2008, thats been working for 6 years plus.
E

Just to add some more information ...

When I repaired my solar powered fence, I was surprised at how simple the solar section is. A sealed lead acid (SLA) battery (12V) is connected to a solar panel through a diode. That was it. I think the key is to choose the right solar panel which creates a reasonable charging profile for the battery and shuts off when the battery is fully charged. The SLA battery can last a long time, so powering through the night or through a couple days of rain was never a problem with a powerful electric fence circuit.

steveB said:

I think the key is to choose the right solar panel which creates a reasonable charging profile for the battery and shuts off when the battery is fully charged.

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You're over thinking it

It's simply that the panel is too small to overcharge the battery, so no 'controller' is required.

You only need a controller when the panel is big enough to actually overcharge the battery - or I suppose if the battery is so tiny as to be capable of overcharging from a small panel

The AA Ni-MH cell in my solar garden lights is overcharged every sunny day so that they still light up following a cloudy day. I do not know if the sun's heat or the overcharging causes the battery cell to get hot, probably both. But luckily the cell is not made of chocolate so the heat does not melt it.

Nigel Goodwin said:

You're over thinking it

It's simply that the panel is too small to overcharge the battery, so no 'controller' is required.

You only need a controller when the panel is big enough to actually overcharge the battery - or I suppose if the battery is so tiny as to be capable of overcharging from a small panel

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My concern would be if the solar cell puts out too much voltage, then it will damage the battery. There is only a diode in series, so too much voltage would not be good for the battery.

This cell I tested puts out almost 18 V (if I remember correctly) in full direct sunlight with no load. Then with loading, and diode drop, the voltage goes down and does not seem to be able to overvoltage/overcharge the battery with any significant current.

When the battery is depleted, then the solar panel voltage will drop under the loading and provide current for charging.

This is all I meant about creating a charging profile and automatically shutting off.

My point is that it is simple and effective, and the OP could use the same basic idea.

Nigel Goodwin said:

I would suggest 'optimistic' rather than 'encouraging'

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crutschow said:

some info that indicates a solar panel can still output near 50% of its full-sunshine peak value on a heavy overcast day, which is encouraging.

Click to expand...

I put in my report:

L.A. clouds (crutschow) = 50% output
English clouds (Nigel Goodwin) = less optimistic, 2% (moty22)

Nigel Goodwin, do you know how much output you get with your clouds?

ericgibbs said:

hi mirel,
This is the electric fence we use on our farm, sheep, goats and pigs, works OK.

Click to expand...

This circuit is very similar to the one we have now, the 555 drives a relay directly. I had to repair it 2 years ago, it was only the relay. We have it in a box with a small battery like they have in motorcycle.
I don't have another transformer of old car, the one I had I use for the fly killer. I think because I need 1 spark every 1 second it is 100 times less energy than sport car ignition, so the small coil from the zapper I have now is good enough.
My new circuit takes only 10mA and the one with the relay takes current of 120mA.

steveB said:

When I repaired my solar powered fence, I was surprised at how simple the solar section is. A sealed lead acid (SLA) battery (12V) is connected to a solar panel through a diode. That was it. I think the key is to choose the right solar panel which creates a reasonable charging profile for the battery and shuts off when the battery is fully charged. The SLA battery can last a long time, so powering through the night or through a couple days of rain was never a problem with a powerful electric fence circuit.

Click to expand...

steveB
What is the size of your solar panel?
I'm unhappy to hear that you have solar electric fence, I thought mine is the first in the world. You write in your page that you are happily married, Frenchmen say that when a man say that he is happily married he is telling a lie.

moty22
I don't think the cows in France like your joke.

I don't have another transformer of old car, the one I had I use for the fly killer. I think because I need 1 spark every 1 second it is 100 times less energy than sport car ignition, so the small coil from the zapper I have now is good enough.
My new circuit takes only 10mA and the one with the relay takes current of 120mA.

Click to expand...

hi,
Using 10mA at 1 sec rate, what do you expect the energy in Joules to be.???
As I said in an earlier post you need at least 1.5 Joules to zap a sheep.

E

Nigel Goodwin said:

I would suggest 'optimistic' rather than 'encouraging'

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Well, those were measured values by the poster, so I though "encouraging" was the appropriate word.

steveB said:

My concern would be if the solar cell puts out too much voltage, then it will damage the battery. There is only a diode in series, so too much voltage would not be good for the battery.

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The voltage doesn't really matter - it's how much current it can feed in to the battery - a battery is very much like a zener diode, and will regulate the voltage fed to it.

For this particular application, where it's a fairly light (and constant) load on the battery, a correctly sized panel would easily do the job with no regulation needed.

ericgibbs said:

As I said in an earlier post you need at least 1.5 Joules to zap a sheep.

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As a young teenager I used to go 'beating' on a local estate for pheasant shooting - one of the fields we used to beat through was a field of kale, used as cattle food. The farmer moved the electric fence back a couple of yards every day, and let the cattle eat their way gradually across the field.

Now apparently cattle love kale (horrible smelly stuff if you ask me), and the normal electric fence didn't hold them back - so he ran a 240V live lead from the farmhouse directly to the fence

Bear in mind we had to get over this fence, in the pouring rain!.