No I wasn't duped. I didn't get the AGM's because I expect any better
electrical performance. Quite the opposite. I know that standard wet
cells carefully tended by a knowledgeable person equipped with
hydrometers, thermometers, bottles of distilled water, flashlight,
face shield, and internet connection will give better performance and
cost less than anything out there.

I just don't want to muck around with all that stuff (if you could see
where my batteries are, you would know why. I also don't want free
liquid acid and batteries with a space that gas can mix with oxygen
above the acid in my boat. I know that I'm paying a price in both
money (lots) and performance (slight) for the convenience and safety.

One of the compromises, as you have pointed out, is that the wet cells
are much better at cooling themselves because the liquid electrolyte
can convect around and carry heat to the surface. If a long run under
power with a crude voltage regulator overcharges the wet cells, they
will tolerate it better. If they do boil off some electrolyte, I
would discover it and correct it the next time I wanted to get warm
and fuzzy with my batteries. With AGM's, I'll just be moving the next
expensive replacement a bit closer. Thus, I want to be sure that I am
charging them very carefully.

--

Roger Long



"Larry" wrote in message
...
"Roger Long" wrote in news:2GAQf.7687$Zs1.7219
@twister.nyroc.rr.com:

When running for long periods under power
however, my expensive AGM's are being driven by the alternator
which
isn't significantly different from the ones on the Model T.
Retrofitting my larger spare with an expensive, 3 stage,
temperature
compensated regulator is on my wish list.


Like most boaters who've been sold amazingly overpriced AGM
batteries,
you've been duped into thinking they are some amazingly different
technology than the cheap $89 golf cart batteries from Sam's Club.

The AGM battery is not. It's simply a cheaper way of rolling up
thin lead
plates with glass mats soaked in the same electrolyte used in all
the other
lead-acid batteries. These plates cannot be as thick as the ones in
the
golf cart batteries because the big thick plates are very hard to
bend.
With so limited an amount of electrolyte, that cannot flow in the
gauze and
cool the cell while moving fresh acid in contact with the plates as
the
solution of lead sulphate moves away, it matters little how thin the
plates
are. To get capacity, the plates rolled up are huge!

BOTH these archaic lead-acid batteries are charged just fine with
any
standard alternator with a voltage regulator. They've been working
fine
since way before the Model T was produced....(c;