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.

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.

On 22 May 2004 16:46:20 GMT, (Gould 0738) wrote:

Come to discover that my track record of never being stuck without
battery power is nothing but dumb luck.

===========================================

It's not dumb luck at all. You're keeping the boat at a dock and it
spends most of its time connected to shore power, with a decent
battery charger which is not overcharging or undercharging. You have
a power boat so that when you are underway the alternator is keeping
things topped off. Your battery bank is of an appropriate size that
time on the hook does not run the batteries down too much, and when
you motor back to the dock the alternator tops things off again. Your
batteries will last a long time under that scenario because they're
always being topped off and never get used very hard.

Change this scenario by keeping your boat on a mooring, anchoring out
a lot, and/or converting from power to sail, and your usage pattern
will change a great deal. Now the batteries work hard for a living,
rarely get recharged much past 80 to 90% of capacity, and are
frequently drawn down to the 50% level or below. You will definitely
need new batteries much more frequently and will ocassionally find
yourself with a bit less reserve power than you'd like. People who do
extended cruising away from shore power invariably have one or more
ways of recharging without the engine: auxiliary generator, wind
charger, or solar panels. Many have all three and are glad to have
the redundancy. My personal preference is for two generators, or one
generator combined with an engine mounted high capacity alternator.
That's because I have an above average number of electronic toys to
keep running and have gotten used to air conditioning, heat and hot
water on demand. It wasn't always like that and most of my sailboats
were lucky if they had a fresh pair of Sears Die Hards,

PS, when fully charged and left idle for a short time the batteries
will read about 12.6 volts under any of these scenarios. Been there,
done that.

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

"Wayne.B" wrote in message
...
On 22 May 2004 16:46:20 GMT, (Gould 0738) wrote:

Come to discover that my track record of never being stuck without
battery power is nothing but dumb luck.

===========================================

It's not dumb luck at all. You're keeping the boat at a dock and it
spends most of its time connected to shore power, with a decent
battery charger which is not overcharging or undercharging. You have
a power boat so that when you are underway the alternator is keeping
things topped off. Your battery bank is of an appropriate size that
time on the hook does not run the batteries down too much, and when
you motor back to the dock the alternator tops things off again. Your
batteries will last a long time under that scenario because they're
always being topped off and never get used very hard.

Change this scenario by keeping your boat on a mooring, anchoring out
a lot, and/or converting from power to sail, and your usage pattern
will change a great deal. Now the batteries work hard for a living,
rarely get recharged much past 80 to 90% of capacity, and are
frequently drawn down to the 50% level or below. You will definitely
need new batteries much more frequently and will ocassionally find
yourself with a bit less reserve power than you'd like. People who do
extended cruising away from shore power invariably have one or more
ways of recharging without the engine: auxiliary generator, wind
charger, or solar panels. Many have all three and are glad to have
the redundancy. My personal preference is for two generators, or one
generator combined with an engine mounted high capacity alternator.
That's because I have an above average number of electronic toys to
keep running and have gotten used to air conditioning, heat and hot
water on demand. It wasn't always like that and most of my sailboats
were lucky if they had a fresh pair of Sears Die Hards,

PS, when fully charged and left idle for a short time the batteries
will read about 12.6 volts under any of these scenarios. Been there,
done that.

"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.

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.

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.

On Sun, 23 May 2004 15:56:34 GMT, "Ernie"
wrote:
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?

========================================

Yes it's too high. Check you're batteries after you've been running
for a while. If there are gas bubbles around the battery plates
and/or low electrolyte levels you should be concerned. 14.8 volts
will cause a great deal of electrolyte loss and plate damage if
applied for an extended period of time. It can also damage other
electrical and electronic devices if they are sensitive to high
voltage. Several years ago I had an issue with failing electric fuel
pumps on my generator. The problem was eventually traced to a
defective voltage regulator which was causing the generator battery to
charge at 14.6 volts. It took 3 fuel pumps and a lot of aggravation
before the problem was fixed.

Let me clarify my 14.8 situation. I do have a new 90HP Merc outboard and
battery purchased last June and the battery was fully charged when I got
that reading. Does that justify that type of reading and is there anything
I can do without pulling the boat out water?

"Wayne.B" wrote in message
...
On Sun, 23 May 2004 15:56:34 GMT, "Ernie"
wrote:
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?

========================================

Yes it's too high. Check you're batteries after you've been running
for a while. If there are gas bubbles around the battery plates
and/or low electrolyte levels you should be concerned. 14.8 volts
will cause a great deal of electrolyte loss and plate damage if
applied for an extended period of time. It can also damage other
electrical and electronic devices if they are sensitive to high
voltage. Several years ago I had an issue with failing electric fuel
pumps on my generator. The problem was eventually traced to a
defective voltage regulator which was causing the generator battery to
charge at 14.6 volts. It took 3 fuel pumps and a lot of aggravation
before the problem was fixed.

"Ernie" wrote in message
...
Let me clarify my 14.8 situation. I do have a new 90HP Merc outboard and
battery purchased last June and the battery was fully charged when I got
that reading. Does that justify that type of reading and is there
anything
I can do without pulling the boat out water?



Ernie,

Did you measure 14.8 volts with the engine running or off? If off, for how
long did the battery sit without running the engine?

I suspect you are going to say you measured it with the engine running. If
so, that voltage would not surprise me. To put your fears at rest, call the
dealer or a qualified Merc tech and get an answer from them rather than
listening to us old farts argue about batteries.

Eisboch

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?

When does it read 14.8?

When the alternator is running?

Your voltmeter will read at a higher number
than the battery's state of charge when there is current from the alternator
present.
You won't get a reading that reflects only the battery voltage until you have
discoed the charger or alternator current.