[TenTec] Hercules II Power Source

[M. Clark]

[Snip]

>All in all,  sounds as if I do not want a marine battery,
>but a regular auto,  wet or floated cell battery.  And not,
>by definition,  a deep cycle battery,  whatever that is
>supposed to connote.

Some points:

You do not want an automotive battery for your application.  Auto batteries
are optimized for starting (occasional very heavy current draw for very
brief periods).  Deep cycle batteries are optimized for a low or moderate
draw for long periods.  They can be deeply discharged numerous times
without compromising their service life.  Do that with a car battery and it
will die a quick death.

Of course any battery will last longer if you minimize how deeply you
discharge it.  This includes deep cycle batteries.

The finish voltage and the maintenance (float) voltage differ with battery
construction and temperature.  The generally available deep cycle types
include flooded cell, starved electrolyte, and gel cell.  Each type has its
advantages and disadvantages.  

I have no personal experience with the starved electrolyte type, so I can't
really comment on them.

Flooded cells require venting to the outside atmosphere.  They must be
maintained, and topped up with distilled water.  Periodically, they should
be equalized (deliberately overcharged to about 16 volts for a short
period) to obtain full service life.

Gel cells have the advantage of being safe for use indoors without special
venting arrangements, and can be mounted in any position.  They MUST,
however, be charged with a charger designed specifically for them (or one
where the user can set the voltage).  Charging them to too high a finish
voltage will destroy them.  Generally, their charging voltage should not
exceed 14.1 to 14.2 volts (temperature dependent of course).  Gel cells
must NEVER be equalized.

Both gel and flooded cell batteries in communications site float service
have service lives of twenty years or more.  In this application they float
across a supply that can accommodate the equipment's total power draw.  The
batteries are only drawn down if the commercial power goes down.
Frequently, backup generators minimize this time to only minutes.

Cruising sailboaters (many of whom are hams themselves) typically get five
years out of their deep cycle batteries if maintained correctly.  Their
usage is more severe than that proposed here, so a longer service life
should be expected.  I would estimate that quality flooded or gel batteries
floated across a quality supply would last 10 to 15 years in a hamshack
application.

One of the popular choices among cruising sailors is the use of six volt
golf cart batteries in series.  Because of the demand, they are readily
available most places at reasonable prices.  Two of them have as much
capacity as a really large 12 volt battery that is too much for one person
to handle.  One person can pick up a golf cart battery, even though it is
not exactly fun.

Golf cart batteries are designed to be run nearly flat while supplying
fairly heavy loads.  The best golf cart battery is generally considered to
be the Trojan T105.  I don't know a single person that has gone to them and
has not been satisfied.  Note:  I have run across a number of low cost
battery places selling other Trojan models.  They always say that the so
and so model (usually the T2200) is the same as the T105.  According to the
battery technical expert at the Trojan plant in Santa Fe Springs, that
isn't so.

I've known a number of people who bought WalMart and Sam's Club marine and
golf cart deep cycle batteries.  With exceptions, most only lasted a year
or two.  One couple bought four Sam's Club golf cart batteries, one of
which swelled up like a balloon.

One last point:  Again with exceptions, most of the people I have come
across selling batteries at retail were selling pizza the day before.  Be
very careful.

Hope this helps.

73, Malcolm WX4YZ


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