I shall try again.
My boat's gauge and my garmin 220 fishfinder both read 14.8. Is this too
high and should I be concerned?

"Ed" wrote in message
. ..
I use two very unscientific methods to get a rough idea of my battery
capacity....
-Turn off the charger for a couple days (No DC fridge or other high
current devices left on) and check to see if the engines will start. (I
do this once a year before the main cruising season)
-Watch the voltage drop when I start the engines cold. This is a
relative measurement so you have to have tried this when the batteries
were new. Another one is to watch the V drop when using the windlass
under a standard load (Free lift-no pull).



Jeff Morris wrote:
"Gould 0738" wrote in message
...

If a battery is discharged to 80%, and then you put it on a float
charger at 13.2, you won't add much (if anything) to the charge state,
but
because of the surface charge you will get a reading of 13.2.

If a battery has discharged to 80% and
you put it on a charger that brings it up to
13.2, nothing really happened. OK. Whatever you say. Guess one has to
wait for
the battery gods to bless the charger before there's any "real" change
in the
voltage.



You keep missing the point. The fact that the Voltage reads 13.2 while
the
charger is running is completely meaningless. It does not mean that the
battery
has "been brought up" to 13.2 Volts, it only means that the charger can
sustain
that Voltage. Immediately after removing the charger, the Voltage will
still be
artificially high. As Calder says: "... the surface areas of the plates
in a
discharged battery are the first to be recharged, but thereafter it
takes time
for the charge to diffuse into the inner plate areas. The surface
voltage must
build up on the accessible plate areas before the inner areas begin to
receive a
charge. Surface voltage is what is measured by a voltmeter ... if
charging
ceases, the voltage differential inside a battery will slowly equalize
until the
battery reaches an internal equilibrium, known as an open circuit
state."

The point is, if you read the voltage immediately after removing the
charger,
all you're reading is an artifact of the recent charge; you learn
nothing about
the state of charge.


I should have been buying lotto tickets all these years. With frequent
checks
of battery electrolyte level, quarterly checks of specific gravity with
a
hydrometer, and periodic terminal cleaning I thought I could trust my
voltmeter. Come to discover that my track record of never being stuck
without
battery power is nothing but dumb luck.


No, it sounds like you;ve been doing all the right things. However,
reading the
voltage immediately after turning off the charger has been a waste of
time.