Repurposing Solar Lamps for Slug Protection

[Rive]

TL;DR Summary

There is a permanent slug infestation in our garden.
Just collecting/disposing them is futile: they have several 'endless' sources of reinforcements nearby.
Needs some means to protect some key areas.

There is a permanent slug infestation in our garden and collecting/disposing them is just not a solution: thus, I need some means to protect at least some important areas.

After some deliberation I've decided to give a try to these electric 'snail fences'.

Something for long term, 7/24 maintenance-free operation, with as much DIY as convenient => it'll be some repurposed PV+battery system providing some 6-9V voltage for the wires.
I don't know the current yet. It's just an experiment at this point.

After some further deliberation these solar lamps (not the decorative type) come to my attention. It has the PV, the charge circuitry, battery, some kind of output and an water-resistant casing in one go.

What's lacking is my experience. For example - can these be modified to provide output while still charging? Any chance to set the output voltage?

Any thoughts, ideas?
Thanks in advance.

 

[BillTre]

Is there a voltage that for sure repels them?
What is the nature of the area you want to protect?

 

[Tom.G]

I expect the electric field strength (Volts per unit distance) would be the important parameter.

With your unlimited number of test subjects, try a flashlight battery and different electrode spacings in a controlled environment.

Or maybe AC would be more effective using a doorbell transformer. Come to think of it, AC may be preferable anyhow to avoid or slow electrolysis of the electrodes.

Cheers,
Tom

 

[Rive]

I expect the electric field strength (Volts per unit distance) would be the important parameter.

Actually, no. It's about the slug touching the second wire as it bridges the wires. So: current at the point of contact.
I'm relying on available 'resources' like youtube and gardening blogs at this point (), so it's kind of uncertain but the usual voltage is 9V and around due the available battery. 12V often mentioned as already deadly. I've seen only a few mentions about 5V, but none below.

AC might be OK, but I don't want to bother with bringing the line to the garden.

What is the nature of the area you want to protect?

There are some sensitive plant beds those slugs often completely ruin. Salads, some type of flowers...

I've checked some of those solar lamps and as it seems the electronics is terrible. No protection for the battery, no protection for the output...
Maybe I should check the solar USB batteries instead? Will they supply 5V all the time?
Might be a bit on the low side but at least something barely decent...

 

[Tom.G]

continued:
Having experienced both AC and DC hand-grip muscle contraction, the AC seemed more annoying. (Also once from an electric fence, which is a pulse every 2 - 4 seconds, that gives you a chance to break contact!)

And this from:
https://www.asc.ohio-state.edu/physics/p616/safety/more_current.html

A.C. is More Dangerous than D.C.

A.C. is said to be four to five times more dangerous than D.C. For one thing, A.C. causes more severe muscular contractions. For another, it stimulates sweating, which lowers the skin resistance. Along those lines, it is important to note that resistance goes down rapidly with continued contact. The sweating and the burning away of the skin oils and even the skin itself account for this. That is why it's extremely important to free the victim from contact with the current as quickly as possible (but without endangering yourself) before the climbing current reaches the fibrillation-inducing level.

The frequency of the AC has a lot to do with the effect on the human body. Unfortunately, 60 cycles is in the most harmful range. At this frequency, as little as 25 volts can kill. On the other hand, people have with stood 40,000 volts at a frequency of a million cycles/sec or so without fatal effects(above found with:
https://www.google.com/search?hl=en&q=is+ac+or+dc+more+dangerous)

Cheers,
Tom

 

[Rive]

... I just want the job done (with minimal fuss). Being optimal (in this sense) is no concern at all

 

[renormalize]

How about simple battery power? Take a look at: Electric Garden Slug Fence

The author claims to get around-the-clock slug protection for a raised bed (area unspecified) over a full growing season, all from just one 9V battery.

 

[Rive]

Yep. I hate to waste batteries but if nothing practical comes out at the end then it'll be about that, indeed...

 

[Tom.G]

... I just want the job done (with minimal fuss). Being optimal (in this sense) is no concern at all

OK!
The Electric Fence referenced in your first post seems the most straight forward.

I don't know what the battery voltage is in those solar powered lights. You will likely need at least 6V to power the fence, obviously 9V works.
(I test 9V batteries by touching them on my tongue. If new, I sorta wish I hadn't! After some practice, you get an idea of how much charge is left. Chemical taste when they are leaking.)

To get continuous power from those solar lights, open them up and connect directly to the battery. You will likely need several of them wired in series to get enough voltage.
Keep in mind that when the fence gets wet there will be some leakage current flowing and slightly draining the battery.

Or use a doorbell transformer if you are near a power outlet. If you can find it, you could even use your existing doorbell transformer. Or connect the fence across the doorbell button. That will power the fence except while the button is pushed.

You might wire a light in series with the fence that comes on if the fence is shorted. This gives you a visual indicator and also won't short-out and damage the power source.

Please keep us updated on your progress/effectiveness.

Cheers,
Tom

 

[Flyboy]

Half joking, half serious suggestions:
-Get some runner ducks. Apparently they love slugs.
-Put up some nesting spots for wrens. Apparently they too love slugs. Benefits the neighbors, too, helping thin out the reinforcements.

That said, I'm in the camp of the electric fence. It's simple, relatively cheap, and some designs are solar powered, so you can set it and forget it.

Although... what about the little ones? Shorter than the gap between the contacts? Is the slime conductive enough to zap them, or will they just gleefully slime across them one at a time?

 

[Rive]

-Get some runner ducks. Apparently they love slugs.

They have been considered

Sadly, they love flowers and plants too. Fencing them off would be easier, but that would undermine the effectiveness...
Also, these slugs are mostly active at night.
There are only a few visible/available at day.

-Put up some nesting spots for wrens. Apparently they too love slugs.

A bit hard to believe, given their weight... But we had some wrens in the garden and they did not made an impact.

Although... what about the little ones?

That's a really good question I'll need to consider properly By the way I've discovered the battery protection parts in these cheap solar lamps. Solar USB bricks dropped, back to lamps. I'll get a sample soon, I think.
I'll need some small boost (battery to 7-9V) converters too.

 

[Tom.G]

Might be cheaper to get more lamps and wire them in series.

 

[Rive]

Not really: a low power boost converter is around 1 EUR, a cheap solar lamp is around 4-5 EUR.

But indeed, it would work. At the end I guess it'll depend on the (continuous, idle) consumption of the converter. If it does not fit with the (quite crappy) solar cell, then I'll do so (and deal with balancing later).