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.