Does anybody have any direct experience with the AGM (Absorbed Glass
Mat) batteries? One manufacturer claims that these batteries are
completely sealed against fumes and don't require venting. Does
anybody have these on their boat?

Bob Whitaker
"Free Spirit"

I put in two to replace my starting batteries. They appear to have survived the
winter. In my research I couldn't find a downside, other than the cost, and the
possibility of overcharging. I'm thinking of replacing my house bank with them
when the need arises.



"Bob Whitaker" wrote in message
om...
Does anybody have any direct experience with the AGM (Absorbed Glass
Mat) batteries? One manufacturer claims that these batteries are
completely sealed against fumes and don't require venting. Does
anybody have these on their boat?

Bob Whitaker
"Free Spirit"

The possability of overcharging is not unique to AGM. It will
quickly destroy most any battery.

Doug
s/v Callista

"Jeff Morris" wrote in message
...
I put in two to replace my starting batteries. They appear to have
survived the
winter. In my research I couldn't find a downside, other than the cost,
and the
possibility of overcharging. I'm thinking of replacing my house bank
with them
when the need arises.



"Bob Whitaker" wrote in message
om...
Does anybody have any direct experience with the AGM (Absorbed Glass
Mat) batteries? One manufacturer claims that these batteries are
completely sealed against fumes and don't require venting. Does
anybody have these on their boat?

Bob Whitaker
"Free Spirit"

I seem to recall that the "margin of safety" WRT overcharging is smaller with
AGMs. Heavy duty flooded batteries can handle considerable abuse as long as you
add water when needed. In fact, periodic controlled overcharging is useful for
keeping them healthy.

I've gathered that this is not true for AGMs.



"Doug Dotson" wrote in message
...
The possability of overcharging is not unique to AGM. It will
quickly destroy most any battery.

Doug
s/v Callista

"Jeff Morris" wrote in message
...
I put in two to replace my starting batteries. They appear to have
survived the
winter. In my research I couldn't find a downside, other than the cost,
and the
possibility of overcharging. I'm thinking of replacing my house bank
with them
when the need arises.



"Bob Whitaker" wrote in message
om...
Does anybody have any direct experience with the AGM (Absorbed Glass
Mat) batteries? One manufacturer claims that these batteries are
completely sealed against fumes and don't require venting. Does
anybody have these on their boat?

Bob Whitaker
"Free Spirit"

Liquid LA batteries should be charged at a max current equal
to 25% of the AH capacity (100AH bat, 25A max charge).
For gels it is 50%, for AGM it is 100% or even greater under certain
conditions. The deal with overcharging has to do with overvoltage.
If you charge/float at a voltage higher than recommended, the
lifetime of the battery can be severely reduced very quickly. They
are unforgiving in this sense.

Doug
s/v Callista

"Jeff Morris" wrote in message
...
I seem to recall that the "margin of safety" WRT overcharging is smaller
with
AGMs. Heavy duty flooded batteries can handle considerable abuse as long
as you
add water when needed. In fact, periodic controlled overcharging is
useful for
keeping them healthy.

I've gathered that this is not true for AGMs.



"Doug Dotson" wrote in message
...
The possability of overcharging is not unique to AGM. It will
quickly destroy most any battery.

Doug
s/v Callista

"Jeff Morris" wrote in message
...
I put in two to replace my starting batteries. They appear to have
survived the
winter. In my research I couldn't find a downside, other than the
cost,
and the
possibility of overcharging. I'm thinking of replacing my house bank
with them
when the need arises.



"Bob Whitaker" wrote in message
om...
Does anybody have any direct experience with the AGM (Absorbed Glass
Mat) batteries? One manufacturer claims that these batteries are
completely sealed against fumes and don't require venting. Does
anybody have these on their boat?

Bob Whitaker
"Free Spirit"

Liquid LA batteries should be charged at a max current equal
to 25% of the AH capacity (100AH bat, 25A max charge).
For gels it is 50%, for AGM it is 100% or even greater under certain
conditions. The deal with overcharging has to do with overvoltage.
If you charge/float at a voltage higher than recommended, the
lifetime of the battery can be severely reduced very quickly. They
are unforgiving in this sense.

Doug
s/v Callista

"Jeff Morris" wrote in message
...
I seem to recall that the "margin of safety" WRT overcharging is smaller
with
AGMs. Heavy duty flooded batteries can handle considerable abuse as long
as you
add water when needed. In fact, periodic controlled overcharging is
useful for
keeping them healthy.

I've gathered that this is not true for AGMs.



"Doug Dotson" wrote in message
...
The possability of overcharging is not unique to AGM. It will
quickly destroy most any battery.

Doug
s/v Callista

"Jeff Morris" wrote in message
...
I put in two to replace my starting batteries. They appear to have
survived the
winter. In my research I couldn't find a downside, other than the
cost,
and the
possibility of overcharging. I'm thinking of replacing my house bank
with them
when the need arises.



"Bob Whitaker" wrote in message
om...
Does anybody have any direct experience with the AGM (Absorbed Glass
Mat) batteries? One manufacturer claims that these batteries are
completely sealed against fumes and don't require venting. Does
anybody have these on their boat?

Bob Whitaker
"Free Spirit"

I seem to recall that the "margin of safety" WRT overcharging is smaller with
AGMs. Heavy duty flooded batteries can handle considerable abuse as long as you
add water when needed. In fact, periodic controlled overcharging is useful for
keeping them healthy.

I've gathered that this is not true for AGMs.



"Doug Dotson" wrote in message
...
The possability of overcharging is not unique to AGM. It will
quickly destroy most any battery.

Doug
s/v Callista

"Jeff Morris" wrote in message
...
I put in two to replace my starting batteries. They appear to have
survived the
winter. In my research I couldn't find a downside, other than the cost,
and the
possibility of overcharging. I'm thinking of replacing my house bank
with them
when the need arises.



"Bob Whitaker" wrote in message
om...
Does anybody have any direct experience with the AGM (Absorbed Glass
Mat) batteries? One manufacturer claims that these batteries are
completely sealed against fumes and don't require venting. Does
anybody have these on their boat?

Bob Whitaker
"Free Spirit"

The possability of overcharging is not unique to AGM. It will
quickly destroy most any battery.

Doug
s/v Callista

"Jeff Morris" wrote in message
...
I put in two to replace my starting batteries. They appear to have
survived the
winter. In my research I couldn't find a downside, other than the cost,
and the
possibility of overcharging. I'm thinking of replacing my house bank
with them
when the need arises.



"Bob Whitaker" wrote in message
om...
Does anybody have any direct experience with the AGM (Absorbed Glass
Mat) batteries? One manufacturer claims that these batteries are
completely sealed against fumes and don't require venting. Does
anybody have these on their boat?

Bob Whitaker
"Free Spirit"

Bob,

We installed 2 8D Concord Lifeline AGM batteries about 4 years
ago. They are still going strong. That includes 8 months of full time
cruising where they were cycled twice a day and only occationally
fully charged. They absolutely will vent a little from time to time.
One of the problems with the early AGMs was that the valves were
sometime defective and resulted in damage or explosion. Haven't
heard anything lately in that regard. If you are going to use them,
make sure that the charging system is set properly for AGMs.
They are capable of quite a bit of abuse in regard to discharge
and high charge rates, but don't live very long if improperly
charged. Much of the bad rep they got when first introduced to the
marine market was due to improper charging. Also, the discharge
behavior is different than a liquid lead acid so folks would think
they were defective when in fact they were performing normally.

Hope this helps.

Doug
s/v Callista

"Bob Whitaker" wrote in message
om...
Does anybody have any direct experience with the AGM (Absorbed Glass
Mat) batteries? One manufacturer claims that these batteries are
completely sealed against fumes and don't require venting. Does
anybody have these on their boat?

Bob Whitaker
"Free Spirit"

Wasn't there something about mixing different types of batts on the same
charger? Something to do with charging rates?
"Doug Dotson" wrote in message
...
Bob,

We installed 2 8D Concord Lifeline AGM batteries about 4 years
ago. They are still going strong. That includes 8 months of full time
cruising where they were cycled twice a day and only occationally
fully charged. They absolutely will vent a little from time to time.
One of the problems with the early AGMs was that the valves were
sometime defective and resulted in damage or explosion. Haven't
heard anything lately in that regard. If you are going to use them,
make sure that the charging system is set properly for AGMs.
They are capable of quite a bit of abuse in regard to discharge
and high charge rates, but don't live very long if improperly
charged. Much of the bad rep they got when first introduced to the
marine market was due to improper charging. Also, the discharge
behavior is different than a liquid lead acid so folks would think
they were defective when in fact they were performing normally.

Hope this helps.

Doug
s/v Callista

"Bob Whitaker" wrote in message
om...
Does anybody have any direct experience with the AGM (Absorbed Glass
Mat) batteries? One manufacturer claims that these batteries are
completely sealed against fumes and don't require venting. Does
anybody have these on their boat?

Bob Whitaker
"Free Spirit"