Battery Meter
 

"Wayne.B" wrote in message
...
On 21 May 2004 15:07:58 GMT, (Gould 0738) wrote:

There is no logic at all in a position that says the battery is not
"fully
charged" until the reading declines .6 volt.

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

There is a great deal of logic however in saying that 12.6 is the
normal resting voltage of a fully charged battery. That is the
condition most people will be interested in. Evaluating the state of
charge of a battery still connected to a charger/eliminator makes very
little sense, and that is really what this whole discussion is all
about.


This is the point I was trying to politely make to Gould. If you listen to
his story half the newbie boaters will be filing into West Marine to buy new
batteries when the ones they have are likely to be perfectly fine.

Eisboch

Battery Meter
 

This is the point I was trying to politely make to Gould. If you listen to
his story half the newbie boaters will be filing into West Marine to buy new
batteries when the ones they have are likely to be perfectly fine.

Eisboch

Your point is accurate, merely incomplete and also misleading if considered
without
taking important variables into account.

If that "newbie" owns a battery that cannot be charged to a point above 12.6
volts on a functional charger he darn well just might be in need of a new one.

Do most boaters disconnect the battery from the boat, and set it on the dock
overnight, before evaluating the state of battery charge? If we are going to
discuss
testing a battery and the results that should be expected, it makes sense to
frame that discussion around actual boating conditions.

What happens when the "surface charge"
bleeds off a battery that can only absorb 1.1 volts per cell? Probably drops
down close to 12 volts in fairly short order- a marginal level that all of us
will agree is getting rather weak.

There's also a difference in the voltage one can expect if checking the
batteries on a trailer boat sitting in the backyard under a tarp vs a boat that
is connected to shorepower. But in either case, at the moment when the battery
has absorbed a full and healthy charge or recharge it will
read 2.2 volts per cell. I don't disagree with a statement that later on it may
read less.

Battery Meter
 

"Gould 0738" wrote in message
...


But in either case, at the moment when the battery
has absorbed a full and healthy charge or recharge it will
read 2.2 volts per cell. I don't disagree with a statement that later on
it may
read less.


Awesome! We agree.

Thanks

Eisboch

Battery Meter
 

"Gould 0738" wrote in message
...

Do most boaters disconnect the battery from the boat, and set it on the
dock
overnight, before evaluating the state of battery charge?

If you want to establish state of charge based on voltage alone then that is
what you should do. It doesn't have to be overnight, but an hour would be a
good idea.

If the battery is not at rest then you have to consider the current along
with the voltage, which makes things a lot harder. A battery at rest will
NOT be at 13.2 volts. A battery charger will "float" a battery at around
13.2 volts, and IF the battery is fully charged there will be little or no
current flow into the battery. If you measure the battery voltage when it
is connected to a charger then you need to verify that the current is near
zero before you can say that the battery is fully charged.

Rod

Battery Meter
 

"Gould 0738" wrote in message
...
This is the point I was trying to politely make to Gould. If you listen to
his story half the newbie boaters will be filing into West Marine to buy new
batteries when the ones they have are likely to be perfectly fine.

Eisboch

Your point is accurate, merely incomplete and also misleading if considered
without
taking important variables into account.

If that "newbie" owns a battery that cannot be charged to a point above 12.6
volts on a functional charger he darn well just might be in need of a new one.

A bad battery or a depleted battery may still read a high voltage when connected
to a charger, and even for a while after being removed. All your reading of
13.2 tells you is that your charger decided to go into float mode. This may be
a strong hint that the battery is fully charged, but it doesn't necessarily mean
that.


Do most boaters disconnect the battery from the boat, and set it on the dock
overnight, before evaluating the state of battery charge?

If you read the information I presented, you would know that a flooded battery
will settle most of the way rather quickly, and that the surface charge can be
removed by applying a load for a few minutes. Every boater should learn these
simple facts, it isn't rocket science.

If we are going to discuss
testing a battery and the results that should be expected, it makes sense to
frame that discussion around actual boating conditions.

What could be more of an "actual condition" than checking the state of charge
when you wake up after a night on the hook? Your scenario seems to be connected
to shore power. Further, if someone is interested in getting a reliable State
of Charge, they should use the methods described by all of the experts. It only
takes a few minutes to remove a surface charge; failure to do so gives a
meaningless answer.



What happens when the "surface charge"
bleeds off a battery that can only absorb 1.1 volts per cell? Probably drops
down close to 12 volts in fairly short order- a marginal level that all of us
will agree is getting rather weak.

I'm not sure what you mean by "absorb 1.1 volts" - batteries absorb Amps, not
Volts. But yes, if a battery is reading 12 Volts with no load, it is probably
either discharged or in poor health.


There's also a difference in the voltage one can expect if checking the
batteries on a trailer boat sitting in the backyard under a tarp vs a boat
that
is connected to shorepower. But in either case, at the moment when the battery
has absorbed a full and healthy charge or recharge it will
read 2.2 volts per cell. I don't disagree with a statement that later on it
may
read less.

This may be true with a given charge protocol, but it is not true in all cases.
Further, the opposite is not true at all: if you get a reading of 13.2 without
having any knowledge of the history, you can't say anything about the charge
state or the general health of the battery. This is the essential point in this
discussion. 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.

Anyone interested in learning about this should read the links I've provided, or
google on: "surface charge" battery

Battery Meter
 

"Jeff Morris" wrote in message
...

A bad battery or a depleted battery may still read a high voltage when
connected
to a charger, and even for a while after being removed. All your reading
of
13.2 tells you is that your charger decided to go into float mode. This
may be
a strong hint that the battery is fully charged, but it doesn't
necessarily mean
that.


Exactly. The best way to tell (other than checking specific gravity of the
cells) is to also monitor the charger current delivered to the battery. If
it is at it's float voltage (13.2v - 13.5v) and is still indicating a small
current flow, then the battery voltage - which is a reflection of it's
apparent internal resistance - is less than the float voltage. A difference
of potential must exist in order for current to flow. If the battery charge
potential were the same as the charger float potential, the current meter
would read zero.

With due respect, I think this is where Gould's understanding is flawed.
The battery behaves like a variable resistance as it is charged, much like a
large capacitor. For a given charge voltage delivered by the charger, the
current will vary (decrease) as it is charged).

Not to start this debate all over again, but I think Gould might be
surprised that while his voltage meter is reading the float potential of the
charger, it is almost a certainty that there is still a small amount of
current flow - probably an amp or 2. This can only mean that the battery
has not come up to 13.2 volts.

Eisboch

Battery Meter
 

Just to maybe add more fuel to the fire, when I measure the current into the
battery (flooded lead acid) from my fixed voltage (13.3 volts) float
charger, and the float charger has been floating the battery for days on
end, the continuous unchanging current is around 20ma. I guess my battery
is fully charged. The current is not going up or down and the voltage is
not changing. I can then conclude the internal leakage current of the
battery (while on float charge for days) is 20ma.

Also, when I remove the float charger and wait 24 hours for the battery
voltage to settle, it measures around 12.65 - 12.72 volts (depending on
which battery I measure) This is as measured with a DVM.

Have a nice day.....

"Eisboch" wrote in message
. ..

"Jeff Morris" wrote in message
...

A bad battery or a depleted battery may still read a high voltage when
connected
to a charger, and even for a while after being removed. All your
reading
of
13.2 tells you is that your charger decided to go into float mode. This
may be
a strong hint that the battery is fully charged, but it doesn't
necessarily mean
that.


Exactly. The best way to tell (other than checking specific gravity of
the
cells) is to also monitor the charger current delivered to the battery.
If
it is at it's float voltage (13.2v - 13.5v) and is still indicating a
small
current flow, then the battery voltage - which is a reflection of it's
apparent internal resistance - is less than the float voltage. A
difference
of potential must exist in order for current to flow. If the battery
charge
potential were the same as the charger float potential, the current meter
would read zero.

With due respect, I think this is where Gould's understanding is flawed.
The battery behaves like a variable resistance as it is charged, much like
a
large capacitor. For a given charge voltage delivered by the charger, the
current will vary (decrease) as it is charged).

Not to start this debate all over again, but I think Gould might be
surprised that while his voltage meter is reading the float potential of
the
charger, it is almost a certainty that there is still a small amount of
current flow - probably an amp or 2. This can only mean that the battery
has not come up to 13.2 volts.

Eisboch

Battery Meter
 

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.

Battery Meter
 

Just to maybe add more fuel to the fire,


Here's yet another reference stating that
a battery cell has a capacity of 2.2 volts, not the 2.1 being trotted through
the NG by those on the other side of this question:

Illustrations to the text are available at:

http://www.allaboutcircuits.com/vol_1/chpt_11/2.html



Battery construction


All About Circuits Volume I - DC Chapter 11: BATTERIES AND POWER SYSTEMS
Battery construction

--------------------------------------------------------------------------
------

Battery construction
The word battery simply means a group of similar components. In military
vocabulary, a "battery" refers to a cluster of guns. In electricity, a
"battery" is a set of voltaic cells designed to provide greater voltage and/or
current than is possible with one cell alone.

The symbol for a cell is very simple, consisting of one long line and one short
line, parallel to each other, with connecting wires:



The symbol for a battery is nothing more than a couple of cell symbols stacked
in series:



As was stated before, the voltage produced by any particular kind of cell is
determined strictly by the chemistry of that cell type. The size of the cell is
irrelevant to its voltage. To obtain greater voltage than the output of a
single cell, multiple cells must be connected in series. The total voltage of a
battery is the sum of all cell voltages. A typical automotive lead-acid battery
has six cells, for a nominal voltage output of 6 x 2.2 or 13.2 volts:



The cells in an automotive battery are contained within the same hard rubber
housing, connected together with thick, lead bars instead of wires. The
electrodes and electrolyte solutions for each cell are contained in separate,
partitioned sections of the battery case. In large batteries, the electrodes
commonly take the shape of thin metal grids or plates, and are often referred
to as plates instead of electrodes.

For the sake of convenience, battery symbols are usually limited to four lines,
alternating long/short, although the real battery it represents may have many
more cells than that. On occasion, however, you might come across a symbol for
a battery with unusually high voltage, intentionally drawn with extra lines.
The lines, of course, are representative of the individual cell plates:



If the physical size of a cell has no impact on its voltage, then what does it
affect? The answer is resistance, which in turn affects the maximum amount of
current that a cell can provide. Every voltaic cell contains some amount of
internal resistance due to the electrodes and the electrolyte. The larger a
cell is constructed, the greater the electrode contact area with the
electrolyte, and thus the less internal resistance it will have.

Although we generally consider a cell or battery in a circuit to be a perfect
source of voltage (absolutely constant), the current through it dictated solely
by the external resistance of the circuit to which it is attached, this is not
entirely true in real life. Since every cell or battery contains some internal
resistance, that resistance must affect the current in any given circuit:



The real battery shown above within the dotted lines has an internal resistance
of 0.2 O, which affects its ability to supply current to the load resistance of
1 O. The ideal battery on the left has no internal resistance, and so our Ohm's
Law calculations for current (I=E/R) give us a perfect value of 10 amps for
current with the 1 ohm load and 10 volt supply. The real battery, with its
built-in resistance further impeding the flow of electrons, can only supply
8.333 amps to the same resistance load.

The ideal battery, in a short circuit with 0 O resistance, would be able to
supply an infinite amount of current. The real battery, on the other hand, can
only supply 50 amps (10 volts / 0.2 O) to a short circuit of 0 O resistance,
due to its internal resistance. The chemical reaction inside the cell may still
be providing exactly 10 volts, but voltage is dropped across that internal
resistance as electrons flow through the battery, which reduces the amount of
voltage available at the battery terminals to the load.

Since we live in an imperfect world, with imperfect batteries, we need to
understand the implications of factors such as internal resistance. Typically,
batteries are placed in applications where their internal resistance is
negligible compared to that of the circuit load (where their short-circuit
current far exceeds their usual load current), and so the performance is very
close to that of an ideal voltage source.

If we need to construct a battery with lower resistance than what one cell can
provide (for greater current capacity), we will have to connect the cells
together in parallel:



Essentially, what we have done here is determine the Thevenin equivalent of the
five cells in parallel (an equivalent network of one voltage source and one
series resistance). The equivalent network has the same source voltage but a
fraction of the resistance of any individual cell in the original network. The
overall effect of connecting cells in parallel is to decrease the equivalent
internal resistance, just as resistors in parallel diminish in total
resistance. The equivalent internal resistance of this battery of 5 cells is
1/5 that of each individual cell. The overall voltage stays the same: 2.2
volts. If this battery of cells were powering a circuit, the current through
each cell would be 1/5 of the total circuit current, due to the equal split of
current through equal-resistance parallel branches.

REVIEW:
A battery is a cluster of cells connected together for greater voltage and/or
current capacity.
Cells connected together in series (polarities aiding) results in greater total
voltage.
Physical cell size impacts cell resistance, which in turn impacts the ability
for the cell to supply current to a circuit. Generally, the larger the cell,
the less its internal resistance.
Cells connected together in parallel results in less total resistance, and
potentially greater total current.
Back
Forward

Battery Meter
 

Yet another irrelevant link. Why do you keep posting links to high school
physics experiments, rather than acknowledging the information from the leading
manufacturers and experts? The issue is not the voltage from an "ideal" cell
on a lab bench, it's how to measure the State of Charge for a real life battery,
which has a different chemistry.

The bottom line is that the method you're recommending is considered by all the
experts to be flawed.





"Gould 0738" wrote in message
...
Just to maybe add more fuel to the fire,


Here's yet another reference stating that
a battery cell has a capacity of 2.2 volts, not the 2.1 being trotted through
the NG by those on the other side of this question:

Illustrations to the text are available at:

http://www.allaboutcircuits.com/vol_1/chpt_11/2.html



Battery construction


All About Circuits Volume I - DC Chapter 11: BATTERIES AND POWER SYSTEMS
Battery construction

--------------------------------------------------------------------------
------

Battery construction
The word battery simply means a group of similar components. In military
vocabulary, a "battery" refers to a cluster of guns. In electricity, a
"battery" is a set of voltaic cells designed to provide greater voltage and/or
current than is possible with one cell alone.

The symbol for a cell is very simple, consisting of one long line and one
short
line, parallel to each other, with connecting wires:



The symbol for a battery is nothing more than a couple of cell symbols stacked
in series:



As was stated before, the voltage produced by any particular kind of cell is
determined strictly by the chemistry of that cell type. The size of the cell
is
irrelevant to its voltage. To obtain greater voltage than the output of a
single cell, multiple cells must be connected in series. The total voltage of
a
battery is the sum of all cell voltages. A typical automotive lead-acid
battery
has six cells, for a nominal voltage output of 6 x 2.2 or 13.2 volts:



The cells in an automotive battery are contained within the same hard rubber
housing, connected together with thick, lead bars instead of wires. The
electrodes and electrolyte solutions for each cell are contained in separate,
partitioned sections of the battery case. In large batteries, the electrodes
commonly take the shape of thin metal grids or plates, and are often referred
to as plates instead of electrodes.

For the sake of convenience, battery symbols are usually limited to four
lines,
alternating long/short, although the real battery it represents may have many
more cells than that. On occasion, however, you might come across a symbol for
a battery with unusually high voltage, intentionally drawn with extra lines.
The lines, of course, are representative of the individual cell plates:



If the physical size of a cell has no impact on its voltage, then what does it
affect? The answer is resistance, which in turn affects the maximum amount of
current that a cell can provide. Every voltaic cell contains some amount of
internal resistance due to the electrodes and the electrolyte. The larger a
cell is constructed, the greater the electrode contact area with the
electrolyte, and thus the less internal resistance it will have.

Although we generally consider a cell or battery in a circuit to be a perfect
source of voltage (absolutely constant), the current through it dictated
solely
by the external resistance of the circuit to which it is attached, this is not
entirely true in real life. Since every cell or battery contains some internal
resistance, that resistance must affect the current in any given circuit:



The real battery shown above within the dotted lines has an internal
resistance
of 0.2 O, which affects its ability to supply current to the load resistance
of
1 O. The ideal battery on the left has no internal resistance, and so our
Ohm's
Law calculations for current (I=E/R) give us a perfect value of 10 amps for
current with the 1 ohm load and 10 volt supply. The real battery, with its
built-in resistance further impeding the flow of electrons, can only supply
8.333 amps to the same resistance load.

The ideal battery, in a short circuit with 0 O resistance, would be able to
supply an infinite amount of current. The real battery, on the other hand, can
only supply 50 amps (10 volts / 0.2 O) to a short circuit of 0 O resistance,
due to its internal resistance. The chemical reaction inside the cell may
still
be providing exactly 10 volts, but voltage is dropped across that internal
resistance as electrons flow through the battery, which reduces the amount of
voltage available at the battery terminals to the load.

Since we live in an imperfect world, with imperfect batteries, we need to
understand the implications of factors such as internal resistance. Typically,
batteries are placed in applications where their internal resistance is
negligible compared to that of the circuit load (where their short-circuit
current far exceeds their usual load current), and so the performance is very
close to that of an ideal voltage source.

If we need to construct a battery with lower resistance than what one cell can
provide (for greater current capacity), we will have to connect the cells
together in parallel:



Essentially, what we have done here is determine the Thevenin equivalent of
the
five cells in parallel (an equivalent network of one voltage source and one
series resistance). The equivalent network has the same source voltage but a
fraction of the resistance of any individual cell in the original network. The
overall effect of connecting cells in parallel is to decrease the equivalent
internal resistance, just as resistors in parallel diminish in total
resistance. The equivalent internal resistance of this battery of 5 cells is
1/5 that of each individual cell. The overall voltage stays the same: 2.2
volts. If this battery of cells were powering a circuit, the current through
each cell would be 1/5 of the total circuit current, due to the equal split of
current through equal-resistance parallel branches.

REVIEW:
A battery is a cluster of cells connected together for greater voltage and/or
current capacity.
Cells connected together in series (polarities aiding) results in greater
total
voltage.
Physical cell size impacts cell resistance, which in turn impacts the ability
for the cell to supply current to a circuit. Generally, the larger the cell,
the less its internal resistance.
Cells connected together in parallel results in less total resistance, and
potentially greater total current.
Back
Forward

Battery Meter
 

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.

Battery Meter
 

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.

Battery Meter
 

"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.

Battery Meter
 

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.

Battery Meter
 

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.

Battery Meter
 

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.

"Fully charged" is not "artificially high."

Do you dispute that the voltage of a battery
cell is 2.2 volts? Yes or no answer please.

Do you dispute that 6 x 2.2 = 13.2?
Yes or no answer please.

After the battery self discharges a bit, it will stabilize about 12.6 or so.
But it has
self discharged to get to that level, and while it may be "adequately" charged
or even "typically" charged, a battery cell is not fully charged until it gets
to 2.2 volts.

Nigel Calder not whithstanding.

It's basic physics.

Battery Meter
 

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.

Battery Meter
 

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.

Battery Meter
 

"Gould 0738" wrote in message
...

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.



Now wait a minute there Gould!

First of all - if the poster is talking about an outboard - particularly an
older outboard, and he is talking about voltage when the engine is running,
the 14.8 volts might be very typical. Not ideal, but common with outboard
charging systems. Voltage regulation is often very loosey -goosey on some
outboards.

But, my main question is:

Could you please elaborate on your comment, "Your voltmeter will read at a
higher number than the battery's state of charge when there is current from
the alternator present."

I hope you mean to the limit set by the voltage regulator. If for some
other reason, please explain.

Eisboch

Battery Meter
 

"Gould 0738" wrote in message
...
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.

"Fully charged" is not "artificially high."

Do you dispute that the voltage of a battery
cell is 2.2 volts? Yes or no answer please.

Sure, I'll dispute it. While the voltage of an ideal cell might be higher, the
"open circuit voltage" of a modern marine battery such as a Rolls (like you
have) or a Trojan (like I have) will be somewhat lower, perhaps 2.13 volts or a
tad less. If you have any doubt, you can look at the Rolls site or the Trojan
site.
http://www.rollsbattery.com/Bulletins/600.htm
http://www.trojanbattery.com/custome...erymaint4.html

Of course, to properly measure this, you have to wait a little while (at least
10 minutes, better after an hour or more) for the battery to stabilize
internally.

Now you can probably find 1000 sites oriented towards high school chemistry and
physics labs that say 2.2 volts, but I claim they are all trumped by the people
that build and maintain actual marine batteries, which are, after all, a
slightly different formulation than the traditional lead acid battery.



Do you dispute that 6 x 2.2 = 13.2?
Yes or no answer please.

Duh. Garbage In Garbage Out. You're really trying hard to be a horse's ass
here, aren't you?



After the battery self discharges a bit, it will stabilize about 12.6 or so.

It isn't self discharge. If you read the quote from Calder you would understand
that. The battery charger can induce a "surface charge" that is not
representative of the actual state of charge.



But it has
self discharged to get to that level, and while it may be "adequately" charged
or even "typically" charged, a battery cell is not fully charged until it gets
to 2.2 volts.

Actually, that's not the issue at all. The issue is that the cell can read 2.2
volts and NOT be fully charged. Any battery that has been charging for a while,
regardless of what state of charge it has reached, might read 13.2 volts
immediately after removing the charger. That's why its meaningless.

Are you claiming that if you can ever read 13.2 volts from a battery it must be
fully charged?
Yes or no answer please.



Nigel Calder not whithstanding.

Yes, we know that the opinion of experts and all of the other observers is not
good for your argument.



It's basic physics.

No. Its marine batteries. Sometimes real life is a bit different from what you
read in a high school textbook.

Battery Meter
 

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.

Battery Meter
 

"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

Battery Meter
 

On Sun, 23 May 2004 13:54:06 -0400, "Eisboch"
wrote:


"Gould 0738" wrote in message
...

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.



Now wait a minute there Gould!

First of all - if the poster is talking about an outboard - particularly an
older outboard, and he is talking about voltage when the engine is running,
the 14.8 volts might be very typical. Not ideal, but common with outboard
charging systems. Voltage regulation is often very loosey -goosey on some
outboards.

Not that this has anything to do with charging via a small outboard, but
if we change the topic to a battery charger or regulator with remote
sensing, it could be entirely fine and normal that a fish finder or the
boat's voltmeter reads 14.8. It all depends on where the readings are
taking place (closer in the circuit to the charger or to the battery)
and how much voltage drop there is betweent the charger/regulator and
the battery.

Steve

Battery Meter
 

Are you claiming that if you can ever read 13.2 volts from a battery it must
be
fully charged?
Yes or no answer please.

Must be?
No. You could get a false reading.

But you can get a 13.2 reading from a fully charged battery without it being a
false or artificial reading. That's the combined voltage of all six cells
before the battery self discharges to a lower voltage.

After a battery partially discharges, it will stabilize around 12.6. Partially
discharged is not the same as fully charged- although it will represent a
common state of charge for batteries that have been removed from
a float charer and allowed to self-discharge to that level.

Why do you suppose every battery charger mfg sets float voltage at 13.2 or
13.3?
Just an arbitrary number?

I'm amused to see that the laws of physics are suddenly suspended when they
don't support your tottering argument. :-)

Battery Meter
 

Now wait a minute there Gould!

First of all - if the poster is talking about an outboard - particularly an
older outboard, and he is talking about voltage when the engine is running,
the 14.8 volts might be very typical.

I saw nothing in the OP to indicate inboard, outboard, or otherwise.

Not ideal, but common with outboard
charging systems. Voltage regulation is often very loosey -goosey on some
outboards.



Could you please elaborate on your comment, "Your voltmeter will read at a
higher number than the battery's state of charge when there is current from
the alternator present."

I hope you mean to the limit set by the voltage regulator. If for some
other reason, please explain.

Eisboch

Yes, if the system is functioning properly up to the limit set by the voltage
regulator.
14.8 seems a tad high for the regulator....


but as you say we don't know about many things here.

when the voltage reads 14.8

type of battery....flooded, gel, or AGM

inboard vs outboard

etc.

Battery Meter
 

Yet another irrelevant link. Why do you keep posting links to high school
physics experiments, rather than acknowledging the information from the
leading
manufacturers and experts?

Way back at the beginning of this thread, the argument began when I commented
that a battery consists of 6 cells at 2.2 volts per cell, or 13.2 total volts.

Several geniuses corrected me, stating that the number is only 2.1 volts per
cell, not 2.2. Is the number no longer 2.2, as it has been since the invention
of the battery because a battery company and Nigel Calder say that's the case?

What other laws of physics are vetoed by
claims on a commercial web site? It would be handy to have a list.

The folks who believe that there is no
"actual charge" above 12.6 volts are free to manage their 12-volt systems
accordingly.
Perhaps Nigel Calder or the Trojan Battery guys will come tow them.

Battery Meter
 

"Gould 0738" wrote in message
...
Yet another irrelevant link. Why do you keep posting links to high school
physics experiments, rather than acknowledging the information from the
leading
manufacturers and experts?

Way back at the beginning of this thread, the argument began when I commented
that a battery consists of 6 cells at 2.2 volts per cell, or 13.2 total volts.

Several geniuses corrected me, stating that the number is only 2.1 volts per
cell, not 2.2. Is the number no longer 2.2, as it has been since the invention
of the battery because a battery company and Nigel Calder say that's the case?

What other laws of physics are vetoed by
claims on a commercial web site? It would be handy to have a list.

The folks who believe that there is no
"actual charge" above 12.6 volts are free to manage their 12-volt systems
accordingly.
Perhaps Nigel Calder or the Trojan Battery guys will come tow them.


BWAHAHAHAHA! Now its a conspiracy! Trojan, Rolls, and Calder are ganging up
on poor Gould!

Battery Meter
 

"Gould 0738" wrote in message
...
Are you claiming that if you can ever read 13.2 volts from a battery it must
be
fully charged?
Yes or no answer please.

Must be?
No. You could get a false reading.

Exactly. You have no information. The battery could be at 60% or it might be
at 100%. You have to wait until the voltage stabilizes.



But you can get a 13.2 reading from a fully charged battery without it being a
false or artificial reading. That's the combined voltage of all six cells
before the battery self discharges to a lower voltage.

It isn't "self discharge."


After a battery partially discharges, it will stabilize around 12.6.
Partially
discharged is not the same as fully charged- although it will represent a
common state of charge for batteries that have been removed from
a float charer and allowed to self-discharge to that level.

Since this happens fairly quickly, are you now claiming that battery will loose
a sustantial part of its charge in the the first 10 minutes? It was at 100%
then it drops to what, 80% ten minutes later? Then magically it goes into a
mode where it only looses 5% a week? What color is the sky in your world?



Why do you suppose every battery charger mfg sets float voltage at 13.2 or
13.3?
Just an arbitrary number?

What does this have to do with anything?



I'm amused to see that the laws of physics are suddenly suspended when they
don't support your tottering argument. :-)

Tottering? You just admitted I was was right! Your words: "You could get a
false reading." You originally claimed that 13.2 meant the battery was fully
charged. Now you admit it could be a false reading. Your right. The only way
to tell what the true state of charge is to wait for the voltage to stabilise
(not self-discharge). If it stabilises at 12.6, its fully charged.

Battery Meter
 

"Eisboch" wrote in message
.. .

"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

You are right. The engine was running. As you suggested, I will call my
qualified Merc tech tomorrow morning to get the right stuff though I suspect
you might be right. Thanks for the information.

Battery Meter
 

On 24 May 2004 00:15:23 GMT, (Gould 0738) wrote:

Are you claiming that if you can ever read 13.2 volts from a battery it must
be
fully charged?
Yes or no answer please.

Must be?
No. You could get a false reading.

But you can get a 13.2 reading from a fully charged battery without it being a
false or artificial reading. That's the combined voltage of all six cells
before the battery self discharges to a lower voltage.

After a battery partially discharges, it will stabilize around 12.6. Partially
discharged is not the same as fully charged- although it will represent a
common state of charge for batteries that have been removed from
a float charer and allowed to self-discharge to that level.

Why do you suppose every battery charger mfg sets float voltage at 13.2 or
13.3?
Just an arbitrary number?

I'm amused to see that the laws of physics are suddenly suspended when they
don't support your tottering argument. :-)

If you want to talk laws of physics, you're all wrong.:) Sure, you can
find web sites that support just about any voltage of a lead acid cell
from about 2 volts to 2.2 volts with most of them supporting a claim of
around 2.1 to 2.15 volts. But if you want to talk physics, why not
write out the half-cell reactions that take place at the cathode and
anode of a lead-acid battery. Add them up and that is the potential of
the battery.

I'd write them here but the characters are hard to reproduce in ascii so
I'll just say that the anode reaction is about 0.36v and the cathode
reaction is 1.69v for a total of 2.05v. You can look them up yourself
by googling pbs04 half-cell reactions. Now, to see why 2.05v can really
be anything "around" there due to differences in the concentrations of
the chemicals as well as temperature, google the Nernst equation, which
tells you how the potential of the cell varies according to temperature
and concentration.

The Nernst equation also explains part of why a lead-acid cell will have
a higher voltage when it's just taken off a charger and then settle to a
full-charge voltage a little bit lower and still be considered to have a
100% charge. It has to do with 1) the concentrations of the chemicals
at the plates equalizing some time after removing the charging voltage
and 2) the cooling down after charging which lowers the potential. It
nothing to do with self discharge or internal resistance.

Steve

Battery Meter
 

BWAHAHAHAHA! Now its a conspiracy! Trojan, Rolls, and Calder are ganging
up
on poor Gould!

First characteristic of a losing argument, switch to personal attack.

Or, was that several posts back when you assumed I was a 'bozo" that ran a gen
set all night?

Damn, it's hard to keep the insults straight any more.

2.2 X 6 = 13.2.

Battery Meter
 

On Mon, 24 May 2004 02:34:50 GMT, (Steven
Shelikoff) wrote:
The Nernst equation also explains part of why a lead-acid cell will have
a higher voltage when it's just taken off a charger and then settle to a
full-charge voltage a little bit lower and still be considered to have a
100% charge. It has to do with 1) the concentrations of the chemicals
at the plates equalizing some time after removing the charging voltage
and 2) the cooling down after charging which lowers the potential. It
nothing to do with self discharge or internal resistance.

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

Thank you. It's good to see a little high quality science interject
itself into an otherwise degenerating discussion. :-)

All the better it supports what most of us have observed. Chuck's
electrons have become damp, slugish, and not a little bit stubborn,
having lived in the Pacific North West for so long.

Battery Meter
 

Thank you. It's good to see a little high quality science interject
itself into an otherwise degenerating discussion. :-)

All the better it supports what most of us have observed. Chuck's
electrons have become damp, slugish, and not a little bit stubborn,
having lived in the Pacific North West for so long.


Steve's hypothesis states that once the battery has achieved a full charge of
2.2 volts per cell, the decrease to 2.1
is due to an a change in the chemical concentration within the cell. Very
probable scenario.

Doesn't support any sort of position that the battery was never charged to
13.2, though, does it?

Merely explains with greater technical clarity than the term "self discharge"
why the voltage will eventually drop.

And that's the Pacific North WET, thank you very much. :-)

Battery Meter
 

On 24 May 2004 06:11:19 GMT, (Gould 0738) wrote:

Thank you. It's good to see a little high quality science interject
itself into an otherwise degenerating discussion. :-)

All the better it supports what most of us have observed. Chuck's
electrons have become damp, slugish, and not a little bit stubborn,
having lived in the Pacific North West for so long.


Steve's hypothesis states that once the battery has achieved a full charge of
2.2 volts per cell, the decrease to 2.1
is due to an a change in the chemical concentration within the cell. Very
probable scenario.

Doesn't support any sort of position that the battery was never charged to
13.2, though, does it?

It may have been charged at 13.2, to 13.2, or whatever you want to call
it. But if you're taking the measurement right after charging, you're
reading an artificially high voltage. When the battery cools down and
the chemicals reach a constant concentration over the space inside the
battery, the voltage will drop to it's steady state full charge of well
less then 13.2 volts. The actual chemical voltage potential of the sum
of the half reactions of a lead-acid cell is between 2.05 and 2.06
volts.

The condition of a battery being fully charged is actually a chemical
condition and not a specific voltage. The battery is fully charged when
the negative plate is made fully of lead, the positive plate fully of
lead dioxide and there is no lead sulfate on either plate. The
electrolyte is sulfuric acid (around 25-35%) and the rest water. The
temperature and the concentration of the sulfuric acid can affect the
voltage of the fully charged battery. The maker of the battery will be
the one who knows what their designed full charge voltage is. They'll
also have to tell you how to measure it, i.e., what temperature, how
long to wait after charging, etc.

The voltage of the battery will drop as it discharges either through
self discharge or by being used because the electrolyte becomes diluted,
i.e., the concentration changes, when it breaks down into hydrogen and
sulfate and the hydrogen combines with oxygen to form more water. The
sulfate combines with the lead in both plates to form lead sulfate.

When the battery is fully discharged, both plates are covered in lead
sulfate and the electrolyte is almost all water. You don't want your
battery to get in that condition.:)

Merely explains with greater technical clarity than the term "self discharge"
why the voltage will eventually drop.

The voltage will drop eventually due to self discharge. But that's
something different then what happens in the few hours after removing
the charging voltage. The self discharge rate of lead acid batteries is
very variable. Sealed lead acid batteries lose maybe 3% of their
capacity per month. That also depends on temperature and the rate can
double if you increase the temp by like 20 degrees F.

However, you won't notice any self discharge in the few hours it takes
for the voltage to settle down after you remove the charger. I.e., if
the battery is fully charged and the float charger was at 13.2 volts and
you remove it and immediately measure the voltage as 13.2 volts, the
battery will still be fully charged (virtually no lead sulfate on the
plates and the same concentration of sulfuric acid in the electrolyte) a
few hours later when the voltage settles to a lower value.

Steve

Battery Meter
 

"Steven Shelikoff" wrote in message
... a bunch of good stuff related to
batteries...

I guess that's why they call them 12 volt batteries instead of 13 volt
batteries, huh?

Eisboch

Battery Meter
 

"Gould 0738" wrote in message
...
BWAHAHAHAHA! Now its a conspiracy! Trojan, Rolls, and Calder are ganging
up
on poor Gould!

First characteristic of a losing argument, switch to personal attack.

First characteristic of a losing argument: claiming all of the experts are
wrong, all of the manufacturers have a hidden agenda, and everyone is ignoring
the "science."


Or, was that several posts back when you assumed I was a 'bozo" that ran a gen
set all night?

No - you seemed to imply that not running a charging system was unnatural for a
boater. You called a "working environment" one that has a charger running.



Damn, it's hard to keep the insults straight any more.

2.2 X 6 = 13.2.


The first sign of dementia is mumbling the same nonsense over and over.

Battery Meter
 

It may have been charged at 13.2, to 13.2, or whatever you want to call
it. But if you're taking the measurement right after charging, you're
reading an artificially high voltage.

No, there's nothing "artificial" about it.
That's the voltage reading at the time a battery finishes charging. As others
have said, (quoting various time periods from
"almost right away" to "overnight") the voltage eventually drops to a lower
point.

If you've got a $3000 paycheck, spend $200 on the way home from work and only
have $2800 with which to pay your bills, would that mean that you *never* had
$3000?

If you put the battery to work as soon as it has recharged to full capacity and
before it undergoes the internal changes that lower the voltage, you can take
advantage of (some of) the additional voltage.

A battery that cannot be brought to a point above 12.6 when charging,
considering the benefits of the internal heat and the concentration of
chemicals on the plates,
is not in good shape. What would happen to the battery that barely charges to
12.6?
It will also cool down, the chemicals will also equalize, etc.......leaving you
with
what? 12.1? 12.2?

If we are going to apply the "battery cools down and chemicals equalize after
charging" caveat to the battery charged to
2.2 volts per cell, it must also be applied to
batteries charged to only 2.1.

Battery Meter
 

First characteristic of a losing argument: claiming all of the experts are
wrong,

Your experts disagree with my experts.
Surely you noticed that?

No - you seemed to imply that not running a charging system was unnatural for
a
boater. You called a "working environment" one that has a charger running.

Normally a battery works in an environment where there is a charger, or an
alternator. Neither the charger nor the alternator runs all the time, but one
or the other will be running when the battery is being charged, which has a
direct bearing on a question regarding the voltage reading of a battery that
has reached a full charge state.

From your perspective, on a sailboat, that may not be true. If you don't have
an auxiliary and you're charging the battery at home in your garage, you're
probably never going to see anything above 12.6 on the boat.

Battery Meter
 

On 24 May 2004 16:14:56 GMT, (Gould 0738) wrote:

It may have been charged at 13.2, to 13.2, or whatever you want to call
it. But if you're taking the measurement right after charging, you're
reading an artificially high voltage.

No, there's nothing "artificial" about it.
That's the voltage reading at the time a battery finishes charging. As others
have said, (quoting various time periods from
"almost right away" to "overnight") the voltage eventually drops to a lower
point.

If you've got a $3000 paycheck, spend $200 on the way home from work and only
have $2800 with which to pay your bills, would that mean that you *never* had
$3000?

Actually, that's not quite the way to think about it because you're
assuming something got spent. The way to think about it is, you got a
paycheck, you don't spend any and take it home. A few hours later look
at it and it says it's worth $2800. You can spend that $2800 or let it
sit under your mattress where inflation will mean that it's worth 3%
less every month (self discharge). It doesn't matter that it said $3000
when it was given to you a few hours earlier because the penalty for
spending even a single dollar is that it immediately becomes worth only
$2799. That's because even though the battery may read 13.2 volts
immediately after charging, it won't have hardly any more capacity then
it does after it settles.

If you put the battery to work as soon as it has recharged to full capacity and
before it undergoes the internal changes that lower the voltage, you can take
advantage of (some of) the additional voltage.

No, not really. There are only a fixed number of moles of molecules
available to be converted to electric power. If you put it to work as
soon as it has recharged and is still at 13.2 volts, by the time it
reaches say a 90% charge, you won't get measurably more power out of it
then if you waited a few hours.

A battery that cannot be brought to a point above 12.6 when charging,
considering the benefits of the internal heat and the concentration of
chemicals on the plates,

You can bring a battery to as high as you want when charging. You can
charge it at 100 volts and measure that across the terminals. There
will be current flowing with the battery acting as a resister. It won't
last long though. It will probably boil off so much flammable gas and
get so hot that it'll explode. But that doesn't mean you can't get 100
volts to appear across the terminals beforhand.

is not in good shape. What would happen to the battery that barely charges to
12.6?
It will also cool down, the chemicals will also equalize, etc.......leaving you
with
what? 12.1? 12.2?

If we are going to apply the "battery cools down and chemicals equalize after
charging" caveat to the battery charged to
2.2 volts per cell, it must also be applied to
batteries charged to only 2.1.

It applies to everything. But the problem is that now you're looking at
a battery that is not in good shape. Big lead sulfate crystals may have
formed that can't be broken down by normal charging. They may have even
broken loose from the lead plate and settled on the bottom of the
battery. That locks up some of the sulfate which would be converted
into sulfuric acid when charging and so the concentration of sulfuric
acid in the electrolyte never gets very high. It also takes away some
of the sponge lead on the plate that's available to be converted into
lead sulfate when discharging, reducing the capacity of the battery.

This is a different case again then looking at the settling voltage of a
fully charged battery in good condition.

Steve

Battery Meter
 

Actually, I'm not sure they disagreed. All of my experts were talking about
marine batteries in a practical environment. Two are the manufacturers of the
batteries we each happen to use, the other is the acknowledged expert in
cruising boat systems. None of your "experts" ever mentioned marine batteries;
in fact, I don't think they mentioned production batteries hardly at all.
Several weren't even talking about flooded cells. One actually gave numbers
closer to mine than yours.

Also, your "experts" mention an approximate value in passing, without a
discussion of charging, measuring state of charge, and surface charge. My
experts were all talking specifically about these subjects, and were unequivocal
that your approach to measuring state of charge is flawed.



"Gould 0738" wrote in message
...
First characteristic of a losing argument: claiming all of the experts are
wrong,

Your experts disagree with my experts.
Surely you noticed that?

No - you seemed to imply that not running a charging system was unnatural for
a
boater. You called a "working environment" one that has a charger running.

Normally a battery works in an environment where there is a charger, or an
alternator. Neither the charger nor the alternator runs all the time, but one
or the other will be running when the battery is being charged, which has a
direct bearing on a question regarding the voltage reading of a battery that
has reached a full charge state.

From your perspective, on a sailboat, that may not be true. If you don't have
an auxiliary and you're charging the battery at home in your garage, you're
probably never going to see anything above 12.6 on the boat.