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[Rob <becida AT comcast.net>]

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Date: Sat, 06 May 2000 18:06:42 -0400
From: tvoivozhd <tvoivozd AT roanoke.infi.net>
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Subject: Re: Powering up your fence was Re: Chickens
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Sojourner wrote:

> (1) What's a trigger coil?

Tvoivozhd---Years ago I did a lot of electronic work.  Can't remember 
what I was
going ti build, but the circuit needed a trigger coil.  I'd have to 
find it to be
sure, but I think it has a coil with a capacitor, the capacitor would 
charge up and
discharge through a tiny curved fluorescent tube, triggering heavier 
current flow in
another circuit.

>
> (2) What's the difference (besides the obvious) between a 6 and 12v
> charger?

Tvoivozhd---I have never gone inside a fence charger, but it will have either 
a
step-up transformer or a voltage multiplier circuit which bounces an 
increasing
charge along a series of capacitors.  It may have both.  In any event 
a six-volt
system costs less to build and puts out less voltage on your fence 
line than would a
twelve volt system.  Note the batteries are not interchangeable, you must use 
a
6-volt battery on a 6-volt system and a l2-volt battery on a 12-volt system.

>
> (3) how much fence line can you run off a marine battery as opposed to
> whatever your set up consists of?

Tvoivozhd---it doesn't make any difference whether your battery is a 
marine battery
or flashlight cells. as regards the length of line that can be 
charged.  The only
difference between a marine battery and your car battery is that a 
marine battery can
be run through a great many cycles of near-exhaustion and recharging 
before dying of
sulfation or reversal of polarity.  Your car battery can't do 
that---it is designed
to operate at near full-charge.  If you exhaust it the plates become 
sulfated (lose
the capacity for chemical reaction) and will reverse polarity, which 
is why your
battery charger goes berserk after a few minutes of charging, with 
the overload trip
cycling on and off, the needle swinging back and forth.  The 
ampere-hours rating of
any given battery dictates how long it will run under a known 
load.  650 ampere hours
will operate exactly twice as long as a 325 ampere-hour battery under 
the same load.

>
>
> I've been looking around, and it seems like I can buy a deep-cycle
> marine battery and charger for around $130.  Here's one I found, their
> web site is funky and with my Netscape (4.72) I have to minimize the
> browser window and then pop it back up to get it to draw properly:

Tvoivoxzhd---don't even think about it.  I have a flashlight that 
draws more than
this toy 18 ampere hour thingy would provide.  When people talk about 
deep-cycle
batteries, they are usually talking about those used in wind-generator storage
systems, cranking marine diesels at sea---these are really heavy metal jobs 
and
nobody spends that kind of money unless the application demands 
it---a fence charger
doesn't.

>
>
> http://www.shipstore.com/SS/HTML/SEV/SEVBTCII.html
>
> Maybe its the wrong kind of battery, I don't know.  They list "deep
> cycle marine batteries" from 90 amp to 225 amp.  I have no idea how much
> current you'd need to keep a fence charged.  Still don't know if I can
> use my Prestone JumpStart to charge a marine battery either, but if I
> can then I wouldn't think I'd need another charger.

Tvoivozhd---I am not sure whether a Prestone Junpstart is intended to 
start cars with
a dead battery, after which the alternator will provide the voltage a 
dead battery
lacks, and also will shove amperes into it to charge it back up.

Or is it also a 110 volt AC input, 6 or 12 volt DC output meant for charging
batteries, as opposed to a simple jumpstarter.  The latter puts out a 
lot of amperage
for a very short period---which if kept up for two or three minutes 
should cause a
thermal switch to kick off.  Look to see if a plate or literature 
mentions CONTINUOUS
amperage output.  Intermittent output is no good for charging 
batteries.  A very,
very small battery charger will put out 6 amperes continuosly.  Homeowner-type
chargers usually put out 10 amps at twelve-volts continuously.  Shop chargers
generally start at thirty to fifty amps continulus.


>
> I like the idea of a solar charger, though I'm not sure how practical it
> would really be here.

Tvoivozhd---solar chargers state on the label-plate and/or literature 
how many days
of cloudy weather the integral gel-type battery will carry 
through---a week or more.
They would probably be of little use in Portland, Oregon, but most 
places they work
fine.  The photoelectric cells in the plate above the fence-charger, 
charges the gel
battery. You replace them when the needle gage on the fence charger 
stays in the
yellow or red zone, even though there has been ample sunshine to keep 
the battery
charged.  Replace the gel battery  when this happens---usually about 
three years.
Caveat, the needle gives the same indication when there is a heavy weed load 
or
fencewire shorted for other reasons.  Solar fence-chargers are not 
"weedburners".
They are low-impedance, low amp-input, intermittent-demand 
machines.  Their output
power is generally rated in joules.  Some are a  lot hotter, eight to 
ten joules or
more, but four joules can provide you with a very interesting 
experience, and for
movable crossfences, cows become very wary of a 1.2 joule D-cell (six) 
operated
fence-charger sting.