Martin Brown wrote:
On 11/05/2012 06:59, The Natural Philosopher wrote:
Bill Wright wrote:
The Natural Philosopher wrote:
Bill Wright wrote:
The Natural Philosopher wrote:
Tim Lamb wrote:
Newish car battery employed to power pony field electric fence.

Car batteries aren't suitable. Use a deep discharge battery, as sold
for golf buggies, caravans, etc. ('Leisure' batteries).

Bill

they aren't suitable either.

Still die on deep discharge, they just go a BIT deeper that's all,
and its not that much.

Friend of mine had a canal boat,..tried em all. All failed.

It is bad practice to run them into the ground. I am sure you know that.

I'm speaking from considerable personal experience, not merely an
anecdote from a friend.

Bill

so you have run several deep discharge batteries totally flat, and they
have all survived?

No. It is a really bad idea to run any of them to totally flat.

Towards the end the weakest cell in the series chain gets wrecked by the
others and will never properly recover. Deep discharge will tolerate a
bit more cyclic abuse over its nominal Ah capacity though. Car batteries
are really only happy delivering very high output currents for shortish
periods of time. Run them flat into the ground and you are asking for
trouble with predictable results.

As someone else said protection circuits are offered to drop the load
when the battery voltage is getting too low and there is a risk of not
being able to start the engine.

That or a low charge indicator flashing led to warn or impending doom.

The only difference between deep discharge and standard is that standard
will survive going to half flat only but deliver more starting current
for a car. deep discharge go to about 75%-80% discharge without damage
but cant do starter motor currents so well.

In the end the real solution is to disconnect the battery when the
voltage gets low.

--
To people who know nothing, anything is possible.
To people who know too much, it is a sad fact
that they know how little is really possible -
and how hard it is to achieve it.