Newish car battery employed to power pony field electric fence. Likely
to have been left connected well beyond the fully discharged state and
possibly exposed to overnight frost.
Won't take a charge! Yes, I know, throw it away. However, horse person
has gone off with my sound spare. Is *over* discharging an issue>?
Car batteries are designed to deliver lots of cranking amps. They are
generally destroyed by a deep discharge, or the very least have their
capacity severely reduced.
Use a leisure battery which is more rugged and can cope with deep
discharge, or should I say are less damaged by a deep discharge. I'm
pretty certain you can get devices which switches off a load once
battery volts get below 11V.
There is a thought that leisure batteries can be part recovered by
charging at 15V or so to reverse sulphation, but I don't have any
experience of this or if applies to car batteries. My experience of car
batteries is that unless they stay fully charged, they are relatively
Or a mains energizer! Actually these seem to *tick* on medium wave radio
Escaping ponies only an issue with a stranger as the regulars avoid the
tape whether it is energised or not. Hence the probably flat for weeks
I used a Rutland windcharger for years with an electric fence, but
they're not cheap and a fair bit of hassle to install - a PV panel would
probably be the best bet. Having said that, electric fences don't draw
too much current - and if the batteries are swopped over every week or
so and then recharged they should be fine.
Can anyone think of any other application where the presence of
electricity rather than its consumption is the primary function? After
all, apart from inefficiency the device should have zero consumption
unless something puts its nose on the wire.
You might as well say that about a burglar alarm. The fence unit does
its 'useful work' by generating a high voltage from a 12 volt source,
and providing a barrier. The animals don't have to keep touching it,
having touch it once and got a shock from it they will keep away - and
be contained. That is its job, and it generally does it very efficiently.
I suspect that more energy goes into the conduction to ground via blades of
grass and other foliage than is used shocking the stock. Thankfully now I'm
down to only one electric fence (keeping my sows in) but it's still a daily
check to make sure that the green light is flashing when I feed them. I
think a solar panel of the sort intended to top up a long standing car is
probably the best way to keep the battery ok, but I managed to run over mine
in the last snow with my tractor. They tend not to work after that!
Umm.. Can't quite get my brain round that one. Assuming perfect
insulation for the fence and no radio transmission, I can see your
There must be losses in the induction coil primary and the timing/switch
circuitry but not much.
Anyway, the plan is to retrieve my battery after a couple of weeks when
the new horse will have learned to avoid white tape:-)
On Thu, 10 May 2012 22:33:04 +0100, Rick Hughes wrote:
Any half decent boat doesn't use the engine battery for general
"house" electricals. But such a device is still a good idea with deep
As for Mr Lamb's battery it's dead, it's not worth the faffing about
trying to resurect and even if it can be brought back it will still
be unreliable. Weigh it in.
Provided you don't overheat it and keep it topped up, an extended charge
at a few amps might recover it, although I wouldn't be that hopeful.
It is *really* worth using leisure (deep discharge)rather than car
batteries for electric fencers. It just isn't worth the trouble trying
to manage with ex-car batteries, in my experience.
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