Larry wrote in news:Xns9939C87A94F33noonehomecom@
208.49.80.253:
whats the minimum voltage you would expect on a new battery ?
Over 12.5
Let me rephrase that, after thinking it over. The voltage on all 6 cells
of a lead-acid battery that has "some acid" in it is around 2V/cell. It
means NOTHING, except that all 6 cells have some lead and some acid in
it.
Voltage, in lead acid batteries, isn't important. SPECIFIC GRAVITY is.
Now, in a gelcell or AGM battery, there's no way to measure the condition
of the acid that puts the POW in POWer. This is precisely why I don't
like them. There's no way of telling what the chemical condition of an
AGM battery is unless you do a load test over hours to find out when dead
is dead. I'm kind of attached to my trusty TEMPERATURE COMPENSATED
hydrometer, myself, the ONLY way to tell what the condition of a wetcell
is. Why??
When a lead-acid battery is new, the new electrolyte specific gravity, an
indication of the amount of acid, knowing the quantity of electrolyte and
plate area, is around 1.260 to 1.270. (Take some electrolyte out of the
dry cell charger container and measure it with a hydrometer.) The design
of the cell is that a certain quantity of acid is available that will
produce the maximum electrons (AH capacity), without the acid eating the
lead to the point it has unrecoverable holes in it that cannot be
replated/recharged. The acid is converted to lead sulphate first. This
is measured by measuring the specific gravity of the liquid electrolyte.
Ok, a new battery is loaded with electrolyte and just sits there. From
that point on, impurities in the plates, mainly iron, form little shorted
batteries on the surface of the plates...lead-iron-acid. This eats a
tiny spot on the plate...if enough impurities exist, you not the specific
gravity of the worst offender drops below 1.26-1.27 further than the
others. They all drop a little as there are no pure lead plates,
especially at these prices and profit margins. It's ok to recharge a new
battery to restore the plating, raising the gravity back up to 1.27 as we
recover the acid.
"Dead cell" isn't dead. It has just run out of RECOVERABLE acid. The
cells in this "dead" AGM battery are in this condition if the cell has
been discharged over a week or two because the acid has been
unrecoverably converted to stable salts, like lead sulphate crystals.
You'll get the gravity (you can't measure in AGM) to rise some....but not
back to 1.27 because before that happens, we've run out of ionic lead
sulphate that electrical current can split to lead and H2SO4. As there's
not enough SO4 to use, charging the hell out of it only results in
"gassing", splitting the H2O in the electrolyte into H2, which bonds into
hydrogen gas if you do it hard enough, and rises out through the cell's
vent....the electrolyte drops as the water is split. (Your boat cells
been topped off, lately??)...just a thought...(c;
The only way I know of to "test" the condition of gelcell and AGM
CAPACITY is to watch how LONG it takes them before their charging voltage
gets to 14.2 or 14.3V. If the acid has been eaten up and cannot be
recovered, every boaters smiles away because he saw the "meter" rise
QUICKLY to 14.2V "in the GREEN" in 20 minutes at 10A. 10A x .33 hours =
3.3AH, the remaining capacity of these hosed AGM babies all sulphated to
hell. A "good" dead AGM battery won't come up for HOURS at 10A....10A
for 13 hours = 130AH, for instance.....NOT 20 MINUTES. If the dead AGMs
rise quickly, they're HOSED and need replacing.
Larry
--
AGM separator factory in China on Youtube!
http://youtube.com/watch?v=jNHR24Gi6A0