The Accidental Smallholder Forum
Smallholding => Techniques and skills => Topic started by: Squinky on August 29, 2010, 08:54:48 pm
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Hello, I'm wondering about the feasibility of using a solar panel to power fencing for pigs. Could I use a solar unit to charge a battery whilst that battery is running the fence? Or would I need two batteries and swap them around? Also would it be possible to run a small water pump from the same panel or again would it need a separate battery? The situation I have in mind would require water to be pumped up at least 10 feet and then laterally to the trough, distance undecided as yet, but anything between 10 an 150 yards. All helpful suggestions welcome.
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I believe Hot-Line fencing at Brunel Industrial Estate, Newton Abbot ,Devon may be able to help you.
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Rutland do solar fence energisers. Pretty sure they only use the solar panel to charge the battey though.
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hi .
basically , yes !
you need a charge controller ,as well as a panel .
an ability to understand watts /amps would be handy .
(ok ,so no one actually understands watts/amps ,but basic power in /power out )
remember , the world of 12v ,and lead acid is deceitful ! - a 110 amp battery should never be run below 50% 'full' , a '200 watt' solar panel is more likely 100 watt at 12 volt in the uk , and so on .
running a pump from a 12v battery will probably be a huge drain - if the pump is rated in watts or amps ,then you could tell . if it's only running the pump for a few mins ,then it's probably a case of whatever .
hope this helps .
plenty of info on off-grid sites . seem to remember REUK having some guides .
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Hi Squinky,
In few words, yes, you could run your fence off a battery that was being trickle charged from a solar panel but there are a few things to be aware of ( I'll try to explain it simply ).
If you look on the battery you're thinking of using, it will give you an Ah ( Amp hour ) figure. So if ( for example ) it says 140Ah, you could get 140 amps for one hour from it or, 1 amp for 140 hours.
Somewhere on your fence unit it will tell you the voltage ( 12v ) and wattage ( again, for example say 100w ).
Using the formula
P
I x V
( Don't know how that comes out but it should read P divided by I times V )
Where P is the power in Watts ( w ), I is the current in amps, and V is the voltage.
We need to know I, so covering the unknown quantity gives us the formula to calculate it - in this case
P
V
So,
100
12
Gives us an answer of 8.3A
If we use our battery above which has a capacity of 140Ah, we can calculate
140
8.3
Giving us a figure of 16.86 hours
I've set the wattage high so in normal use the battery wouldn't go flat in 16 hours but you can see how to do the calculations with your own unit.
You can use the same calculation for the output from your solar panel into the battery, but as Woodsman says, the output will be down slightly on the manufacturers quoted figures - I'd expect about 80% tbh, but maximise the output by orientating it so it faces south and isn't shadowed by anything.
A normal lead acid battery can be discharged to 20% of capacity and will recover fully when charged, a maintenance free gel cell battery can be discharged to 40% of capacity but once put on charge must be left until it is full.
I think you'd be asking a lot to run a pump off a battery, but you have the calculations now so you can do the maths and see if it will.
I hope that's helpful, and not too baffling! :D
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http://www.fearing.co.uk/Speedrite-S150-Energiser/Default.aspx