Roger Long wrote:

If you want to charge your batteries faster and harder than they should be
charged, are willing to put up with crawling around on top of them sucking
acid out of them with a hydrometer and putting distilled water back in to
them to repair the damage you have done to them, and are willing to accept
the small but quite real danger of having carrying free acid around in your
boat, wet cells will give you more bang for the buck and faster charging.

If you can live with charging at reasonable charging rates, you'll have a
safer boat and get better performance with AGM's. Remember, the outfit that
made such a strong recommendation to me about AGM's builds many unattended
mission critical systems. That's a good description of how I would like my
battery bank to be. There are a lot of mechanical things I like fiddling
with on a boat but batteries are not one of them.

You are not correctly stating the case by using the phrases 'faster and
harder than they should be charged' and 'reasonable charging rates'.
But it all depends on your use. If you use a main engine or a generator
to charge then I think AGM or gel are out of the question. Unattended
operation may require specific requirements. But these are not
requirements for boat use. As you say, there are many mechanical (and
other) things on a boat to fiddle with, and I don't understand the logic
that batteries should not be one of them. You mention using a
hydrometer, the only way to find the real state of charge for a
lead-acid battery. What is the alternative procedure for AGM? There is
none: there simply is no way to find the real state of charge of an AGM!
I would say that simply rules them out for anything mission-cricial. Yes
it may not be fun but batteries SHOULD be one of the things to 'fiddle'
with, IMHO.
If you read the article then you will also have read that if you are
willing to use 'reasonable charging rates' (=slow charging), standard
lead-acid is 'maintenance free' just like AGM and gel.
But AGM and gel are much more expensive.
You definitely seem to be wrong when you say that AGM will give you
better performance - even when using 'reasonable' charging rates. From
what I read they will NEVER do that and will most likely fare a lot
worse than standard lead-acid, for ANY application.

So to quote the article, AGM is good if you want to put your boat upside
down for an hour or two. In all other cases, use standard lead-acid.

On Sun, 15 Jun 2008 11:22:35 -0400, "Roger Long"
wrote:

If you can live with charging at reasonable charging rates, you'll have a
safer boat and get better performance with AGM's.
What do you consider reasonable. One guy says 15% of capacity per
hour. If you run them for three hours that leaves time to charge them
at the twenty hour rate. One inland lake cocktail cruise per day. Two
of the biggest trolling motors made draw how much juice?

Casady

On Jun 15, 9:46 am, Salomon Fringe wrote:
...If you use a main engine or a generator
to charge then I think AGM or gel are out of the question.

And you believe this because...? I and many others have gotten many
years of outstanding service from AGMs used in exactly this way. I've
got nothing against regular old flooded batteries. They're certainly
the best in terms of capacity per monetary unit or capacity per weight
for lead acid. But the article you're quoting is being wildly, even
absurdly unfair in its comparison of the types of lead acid
batteries. He gives AGMs a particularly bad rap by asserting that
they are essentially the same thing as a "maintenance free" starting
battery. His argument seems to be "well, they've got thin plates and
you can't add water to them so they must outgas like mad if you charge
them fast and the plates must fail quickly because they are thin." Of
course, if that were true AGMs would die quickly in normal use. Yet,
I and many other folks, have AGMs that have lasted for 8+ years
despite being deep cycled and charged at significantly faster rates
than flooded cells. How can that be? The answer is that the author
of your article either doesn't know the differences between an AGM and
a cheap maintence free starting battery or is being intentionally
misleading.

As far as I know all AGMs are "valve regulated". Certainly all the
major players are. Under normal charging they recombine virtually all
gas. While massive overcharging will cause them to vent, modest
amounts of over voltage will not hurt them noticeably. Indeed, all of
the manufactures that I've looked at recommend periodically equalizing
them. Generally you can put all the amps you've go into them as long
as you regulate the voltage (max between 14.0 and 14.6 depending on
the temperature and the particular battery). Even so regulated their
acceptance rates are higher than deep cycle flooded batteries and
charge times are quicker.

AGMs do have thin plates. But, those plates are packed tightly into
the glass mat and physically very well supported. So, they are less
prone to physical failure than the thin plates in flooded starting
batteries that need to be largely self-supporting. And, at the same
time, they have more surface area than flooded deep cell batteries.
The net result is that AGMs have very low internal resistance compared
to other deep cycle batteries and are more durable. Low resistance
also reduces gassing.
....
If you read the article then you will also have read that if you are
willing to use 'reasonable charging rates' (=slow charging), standard
lead-acid is 'maintenance free' just like AGM and gel.
But AGM and gel are much more expensive.

I've read the article. It is total BS. AGMs are not gels or cheap
sealed starting batteries. All his conclusions follow from a false
assumption and no evidence for the conclusions is provided.

-- Tom.

Richard Casady wrote:

On Sun, 15 Jun 2008 11:22:35 -0400, "Roger Long"
wrote:


If you can live with charging at reasonable charging rates, you'll have a
safer boat and get better performance with AGM's.

What do you consider reasonable. One guy says 15% of capacity per
hour. If you run them for three hours that leaves time to charge them
at the twenty hour rate. One inland lake cocktail cruise per day. Two
of the biggest trolling motors made draw how much juice?

Casady

There's really A LOT to say about batteries and charging, especially
because everybody has a different charging and usage situation. One
excellent document that has just about all info is this one:
http://www.victronenergy.com/upload/...yUnlimited.pdf

wrote:

On Jun 15, 9:46 am, Salomon Fringe wrote:

...If you use a main engine or a generator
to charge then I think AGM or gel are out of the question.


And you believe this because...? I and many others have gotten many
years of outstanding service from AGMs used in exactly this way. I've
got nothing against regular old flooded batteries. They're certainly
the best in terms of capacity per monetary unit or capacity per weight
for lead acid. But the article you're quoting is being wildly, even
absurdly unfair in its comparison of the types of lead acid
batteries. He gives AGMs a particularly bad rap by asserting that
they are essentially the same thing as a "maintenance free" starting
battery. His argument seems to be "well, they've got thin plates and
you can't add water to them so they must outgas like mad if you charge
them fast and the plates must fail quickly because they are thin." Of
course, if that were true AGMs would die quickly in normal use. Yet,
I and many other folks, have AGMs that have lasted for 8+ years
despite being deep cycled and charged at significantly faster rates
than flooded cells. How can that be? The answer is that the author
of your article either doesn't know the differences between an AGM and
a cheap maintence free starting battery or is being intentionally
misleading.

As far as I know all AGMs are "valve regulated". Certainly all the
major players are. Under normal charging they recombine virtually all
gas. While massive overcharging will cause them to vent, modest
amounts of over voltage will not hurt them noticeably. Indeed, all of
the manufactures that I've looked at recommend periodically equalizing
them. Generally you can put all the amps you've go into them as long
as you regulate the voltage (max between 14.0 and 14.6 depending on
the temperature and the particular battery). Even so regulated their
acceptance rates are higher than deep cycle flooded batteries and
charge times are quicker.

AGMs do have thin plates. But, those plates are packed tightly into
the glass mat and physically very well supported. So, they are less
prone to physical failure than the thin plates in flooded starting
batteries that need to be largely self-supporting. And, at the same
time, they have more surface area than flooded deep cell batteries.
The net result is that AGMs have very low internal resistance compared
to other deep cycle batteries and are more durable. Low resistance
also reduces gassing.
...

If you read the article then you will also have read that if you are
willing to use 'reasonable charging rates' (=slow charging), standard
lead-acid is 'maintenance free' just like AGM and gel.
But AGM and gel are much more expensive.


I've read the article. It is total BS. AGMs are not gels or cheap
sealed starting batteries. All his conclusions follow from a false
assumption and no evidence for the conclusions is provided.

-- Tom.

That's interesting. Do you have the actual manufacturers discharge
graphs that the author says they -for some reason- don't seem to supply?
Personally I would not make a decision on hearing that so-and-so
deep-cycled AGM's for 8+ years without any problems. How often and how
deeply have these really been cycled, how quickly were they charged, at
what temperature. Plenty of unknowns. Myself, I heard of people that
have definitely NOT been able to deep cycle their AGM's 8+ years. Far
from it, actually. The author claims that a Dutch magazine got 500
responses confifming his stance though.
Before I would agree that the author was talking nonsense, I'd like to
see hard (manufacturers) data that would really prove this. If the AGM
manufacturers have nothing to hide then that info will be advertised on
their websites.

On Jun 15, 12:32 pm, Salomon Fringe wrote:
....
That's interesting. Do you have the actual manufacturers discharge
graphs that the author says they -for some reason- don't seem to supply?

Just go look them up. There's no secret. I don't know why the author
seems to think there is. Indeed, the article you posted in reply to
Roger down the thread has some good info on this. Did you read it?
In any case, the author of your first link doesn't provide a single
test or citation to support his views, so why should we believe him?

... If the AGM
manufacturers have nothing to hide then that info will be advertised on
their websites.

It is.

--Tom.

wrote:

On Jun 15, 12:32 pm, Salomon Fringe wrote:
...

That's interesting. Do you have the actual manufacturers discharge
graphs that the author says they -for some reason- don't seem to supply?



Just go look them up. There's no secret. I don't know why the author
seems to think there is. Indeed, the article you posted in reply to
Roger down the thread has some good info on this. Did you read it?


Yes I actually have the printed version of that doc, but I don't think
there is even a hint of being able to use a AGM for 8+ years while
deep-cycling... ?

In any case, the author of your first link doesn't provide a single
test or citation to support his views, so why should we believe him?


... If the AGM
manufacturers have nothing to hide then that info will be advertised on
their websites.



Err, I was hoping you would have the links handy... ;-)


It is.

--Tom.

On Jun 15, 1:23 pm, Salomon Fringe wrote:
....
Yes I actually have the printed version of that doc, but I don't think
there is even a hint of being able to use a AGM for 8+ years while
deep-cycling... ?

Well, I don't think I said that. What I was trying to say is that the
author doesn't seem to have had any trouble coming up with published
data. For instance he notes that deep cycle flooded cells ("semi-
traction") get 350 cycles at 60% DOD (which is deep cycling) while
AGMs get 650-800 depending on construction and chemistry. Service
life depends on how you use them but the AGMs look much better than
the semi-traction batteries for deep cycle use. His service life
numbers suggest that some AGMs will be expected to last 10 years.
AGMs have only been popular in marine use for less than a decade so it
may be hard to get real numbers. My experience has been fantastic.
YMMV... I think some of the very negative responses in the "Dutch
magazine" (if they exist, got a citation?) might have been for gel
cels. AGMs are not gel cells and linking them is bogus (or maybe even
dishonest). AGMs have really good cycling numbers and they are
published and you've even posted a link to them. So the Sterling
guy's conclusion that you should avoid AGMs because they have "poor
cycling numbers" is hard to figure. The rest of his arguments seem to
be based on straw men and thin air, too. Who is this guy?

Although it's a little off topic http://www.proboat-digital.com/proboat/20080203/
is interesting and has some insight into usage issues.

....
Err, I was hoping you would have the links handy... ;-)

I was hoping you'd do your own. If you can't google I'll do it for
you, but last time I looked both Full River and Lifeline (Concord) had
graphs and spec sheets on-line for their AGMs. You may have to plot
data from your favorite flooded deep cycle battery for comparison but
if the flooded guys have nothing to hide their data will be on-line,
too... ;-)

I'm not trying to sell AGMs. There are good reasons that they don't
use them in golf carts, for instance. But the guy at Sterling seems
to have decided that he hates AGMs and then gone off to figure out
why.

--Tom.

On Sun, 15 Jun 2008 15:20:55 -0700 (PDT), "
wrote:

His service life
numbers suggest that some AGMs will be expected to last 10 years.
AGMs have only been popular in marine use for less than a decade so it
may be hard to get real numbers. My experience has been fantastic.

I have heard the same from others whom I respect. I will probably
convert one of my house banks to AGMs in the future.

"Wayne.B" wrote in message
...
On Sun, 15 Jun 2008 15:20:55 -0700 (PDT), "
wrote:

His service life
numbers suggest that some AGMs will be expected to last 10 years.
AGMs have only been popular in marine use for less than a decade so it
may be hard to get real numbers. My experience has been fantastic.

I have heard the same from others whom I respect. I will probably
convert one of my house banks to AGMs in the future.

While I cannot comment on AGM batteries, my experience with gel batteries
may be of interest.
In 2005 I imported a boat from Florida to Norway. The survey was carried out
in mid March and the batteries were Ok and powered up all auxiliaries
properly.
Three months later she arrived in Norway and the batteries were flat
because, as recommended by the makers, the refrigerator was connected
directly to the batteries rather than going through the panel and nobody had
thought to disconnect it.
I tried to charge the batteries with a powerful charger and it could get no
current at all to pass through the batteries-they blocked the current
completely..
I found that very surprising although I had half expected them to accept,
but not retain, a charge.