On Wed, 19 May 2004 17:09:07 -0400, "Eisboch"
wrote:
This is an often debated subject, because it depends on the type of battery,
temperature, aging, etc. In general for lead acid batteries:

Open circuit voltage Charge in %
12.6V and higher 100%
12.4 - 12.6V 75 - 100%
12.2 - 12.4V 50 - 75%
12.0 - 12.2V 25 - 50%
11.7 - 12.0V 0 - 25%
11.7V and less 0%

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

Debated indeed, but that seems a wee bit harsh to me on the low end.
I routinely run my deep cycles down to 11.5 under moderate load and
they still have lots of juice left at that level, more than enough to
start the engines for example. I've always regarded 11.5 volts as the
50% mark where you really should recharge but don't necessarily need
to. A battery discharged to that level should be recharged ASAP of
course.

Regarging Chuck's 13.2 volts, that is about the right voltage for
"floating" a fully charged battery, but the battery will soon drop
back to 12.6 or 12.7 once the float charger/battery eliminator is
turned off.

"Gould 0738" wrote in message
...
A fully charged 12 volt battery is
12.6 volts.

13.2

2.2 volts X 6 cells equals 13.2

Nonsense. You obviously have never actually used a voltmeter on a boat. The
"open circuit voltage" varies a bit with the technology, but will generally be
between 12.6 and 12.8. It may read a tad higher after charging, but settles in
a few hours.

http://www.trojanbattery.com/custome...erymaint4.html

Gould, it's 2.1 x 6, you get 12.6.


"Gould 0738" wrote in message
...
A fully charged 12 volt battery is
12.6 volts.

13.2

2.2 volts X 6 cells equals 13.2

Gould, it's 2.1 x 6, you get 12.6.

If it were 2.1, you'd get 12.6. Corect.

However, the potential capacity of a cell is
2.2 volts.

Consider the "Ideal Charge Curve" described by Rick Proctor of Cruising
Equipment Co:

Bulk phase: Chare at a rate up to 20-40% of amp-hour capacity to a voltage of
about 14.4 volts. (Gel: 14.1). For example, a 200 amp-hour battery would be
charged at 40-80 amperes. This will bring the battery to about 75% of full
charge.

Aceptance phase: Maintain battery at 14.4 volts (Gel, 14.1) while the amperage
is steadily reduced. This restores the next 25% of capacity at a declining
rate. Your battery can be considered fully charged if it will accept current
equal to 2% of cpacity at 14.4 volts. Example: A 200 amp hour battery accepts
only 4 amps at 14.4 volts.

Float phase: The voltage is reduced to 13.3 volts, (gel 13.7 volts) to maintain
the battery without losing electrolyte from the cells. *THIS IS A MAINTENANCE
PHASE, NOT A CHARGING PHASE*

If you test a battery aboard a boat and it reads only 12.6, it is not fully
charged.
Fully charged to "float phase" is over 13 volts for flooded batteries and 13.7
for gel cells.

"Gould 0738" wrote in message
...

If you test a battery aboard a boat and it reads only 12.6, it is not
fully
charged.
Fully charged to "float phase" is over 13 volts for flooded batteries and
13.7
for gel cells.

With the float charger attached, agreed.
Remove the float charger for an hour or so and the voltage for a fully
charged flooded battery will be 12.6 volts.

Been that way for many, many years.

Eisboch

Where do you get this nonsense? "Open Circuit Voltage" is not the same thing as
"Float Voltage." Did you even look at the link I provided, or are you claiming
to know more about batteries than Trojan?

http://www.trojanbattery.com/custome...erymaint4.html




"Gould 0738" wrote in message
...
Gould, it's 2.1 x 6, you get 12.6.

If it were 2.1, you'd get 12.6. Corect.

However, the potential capacity of a cell is
2.2 volts.

Consider the "Ideal Charge Curve" described by Rick Proctor of Cruising
Equipment Co:

Bulk phase: Chare at a rate up to 20-40% of amp-hour capacity to a voltage of
about 14.4 volts. (Gel: 14.1). For example, a 200 amp-hour battery would be
charged at 40-80 amperes. This will bring the battery to about 75% of full
charge.

Aceptance phase: Maintain battery at 14.4 volts (Gel, 14.1) while the amperage
is steadily reduced. This restores the next 25% of capacity at a declining
rate. Your battery can be considered fully charged if it will accept current
equal to 2% of cpacity at 14.4 volts. Example: A 200 amp hour battery accepts
only 4 amps at 14.4 volts.

Float phase: The voltage is reduced to 13.3 volts, (gel 13.7 volts) to
maintain
the battery without losing electrolyte from the cells. *THIS IS A MAINTENANCE
PHASE, NOT A CHARGING PHASE*

If you test a battery aboard a boat and it reads only 12.6, it is not fully
charged.
Fully charged to "float phase" is over 13 volts for flooded batteries and 13.7
for gel cells.

Ernie, the best way to test a batter is with a load tester that uses a
carbon pile, but only shops would have that equipment. Autozone used to test
your battery for free with one, maybe they still do.

The voltmeter test is a good one to use on a battery, without the engine
running. Another poster said that the "voltage will settle down" after a
while....this is called a surface charge, what you get from a battery just
after it has been fully charged. It'll throw the VM test off. To remove the
surface charge, crank the motor for 15-30 seconds.

Another good test for a regular lead-acid battery is the electrolyte test.
It's a glass eye-dropper, you check each cell individually, and that way you
can tell if you have any bad cells. I can't remember the pass/fail,
something like if there are two cells that are bad, then the battery is
trash, or if two adjacent cells are bad....I can't remember. But the
electolyte test will tell you if your battery is bad.

Drew


"Ernie" wrote in message
. ..
Is it normal for the battery gauge to read 16 when the boat is in
operation? The gauge only goes up to 18. The battery will be a year old
next month. Should I be concerned?