[KYHAM] Battery Lesson Learned...help needed

[N4AOF]

> I've been running a 12VDC battery system for about a year. It powers
my
> ham radio equipment, my weather station and my home network (cable
modem,
> hubs, wireless routers, etc).  It ran off (2) two 12V Everstart Deep
Cycle
> Marine Trolling motors I purchased at Walmart.

All fine, except the choice of batteries was not quite perfect.

There are many different kinds of batteries -- each meant for different
purposes and different duty cycles.

Automotive batteries are meant to provide a short period of high current
(starting the car) then to be recharged and pretty much left alone to
wait for the next short period of high current.  Automotive batteries
don't do well in deep cycle operation.  They also don't do well in float
operation -- which is essentially what you were doing.

Deep Cycle batteries were developed largely to overcome the shortcomings
of automotive batteries in camping and boating where the battery is
meant to provide a low to moderate current until the entire charge is
used up (or nearly so), then to be recharged fully.  This kind of
service kills automotive batteries quickly but Deep Cycle batteries
thrive on it.   Deep Cycle batteries are not meant to serve as float
batteries but they do survive such use better than automotive batteries.

Float batteries were developed to do what you are doing -- they are live
in line with the real power source and the load.  They carry the peak
load when the real power supply can't handle it and carry the full load
in the event the regular power supply fails (which in your case would
happen if the AC power failed).  Real float batteries are large and
expensive.  In some places it used to be possible to get used float
batteries for free from local telephone company offices because most
telcos replaced their float batteries on a schedule rather than waiting
for individual batteries to fail.  This has pretty much dried up as the
telcos are unwilling to get involved with potential liability risks both
for accidents involving the used batteries and under present law they
could still be held responsible for the proper disposal of the hazardous
materials in the batteries.  I'm sure some people involved directly with
small local telcos still manage to get some old float batteries, but
most of us will never see any free ones that way.

In your case, one of the batteries developed a shorted cell internally.
If it is one of the better grade Walmart batteries, you can probably
return it under warranty for a free or partial replacement.

Considering that real float batteries are probably out of reach, the
deep cycle batteries are a decent choice.  Just be sure to actually
cycle them occasionally and to check the voltage of the individual
batteries every week or so.