* navti wrote, On 5/30/2007 2:29 AM:
UPDATE UPDATE UPDATE

Both Batteries were charged on full last night for 3 hours .
I put some lights on them for 2-3mins before checking voltage to
remove the surface charge (as advised by Ken Heaton).
They showed 12.69V and are sitting steady. Will leave them to settle
until till tomorrow evening then start using them and try and figure
out their performance over the next few days.

This means they are not totally dead. Only a load test (which could
simply be running a bright light for a while) will tell if the
capacity is seriously diminished. Unfortunately, the capacity could
be well below 50% and they would still behave like yours. With
traditional wet cells, the electrolyte can be sampled, making this a
bit easier. With AGM's you really have to measure how much they can
deliver before the voltage gets too low. Each battery is a bit
different, so there's no formula that says if "10 Amp hours drops the
voltage 0.1V, you have X capacity." You should get guidance from the
factory - they may be able to give a procedure that would be far more
accurate than the guesses you get on this board.

navti wrote in news:1180506549.946816.47150
@g4g2000hsf.googlegroups.com:

They showed 12.69V

Dead cell. 13.6 to 13.8V is "normal" on a fully charged battery....



Larry
--
Grade School Physics Factoid:
A building cannot freefall into its own footprint without
skilled demolition.

"Larry" wrote in message
...
navti wrote in news:1180506549.946816.47150
@g4g2000hsf.googlegroups.com:

They showed 12.69V

Dead cell. 13.6 to 13.8V is "normal" on a fully charged battery....



Larry
--
Grade School Physics Factoid:
A building cannot freefall into its own footprint without
skilled demolition.

If the battery was dead when you got it and you charged it for 3 hours I
would suspect that that it is about 50% charged. 12.69V seems reasonable.
I would suggest you continue charging.

* Larry wrote, On 5/30/2007 4:50 PM:
navti wrote in news:1180506549.946816.47150
@g4g2000hsf.googlegroups.com:

They showed 12.69V

Dead cell. 13.6 to 13.8V is "normal" on a fully charged battery....

This is total nonsense and mis-information. Once the charger is
turned off, and the surface charge is "burned off" the voltage will
drop to around 12.7V, give or take a tenth. This is the norm for
flooded batteries, but there is more variation for gel (which is often
a tad higher) and AGM. The float voltage used for AGMs is usually
rather low, around 13.2, so claiming that it has to be at 13.6 to be
fully charged is nonsense.

Here's a data sheet for Lifeline AGM batteries, one of the major
brands in the USA. You can clearly see the "Open Circuit Charge" for
100% charge is 12.8 Volts.

Note also, that as I mentioned in a previous post, AGMs can be
equalized to restore some lost potency.

http://www.lifelinebatteries.com/mch...procedures.php

On May 30, 1:22 pm, Jeff wrote:
* navti wrote, On 5/30/2007 2:29 AM: UPDATE UPDATE UPDATE

Both Batteries were charged on full last night for 3 hours .
I put some lights on them for 2-3mins before checking voltage to
remove the surface charge (as advised by Ken Heaton).
They showed 12.69V and are sitting steady. Will leave them to settle
until till tomorrow evening then start using them and try and figure
out their performance over the next few days.

This means they are not totally dead. Only a load test (which could
simply be running a bright light for a while) will tell if the
capacity is seriously diminished. Unfortunately, the capacity could
be well below 50% and they would still behave like yours. With
traditional wet cells, the electrolyte can be sampled, making this a
bit easier. With AGM's you really have to measure how much they can
deliver before the voltage gets too low.

Jeff

I am curious as to how the battery capacity can be 50 % diminished and
still deliver 12.6 volts (or thereabouts.

Are the individual cells in the battery wired in series or parallel ?

If I had four 12 volt cells wired in parrallel each with a capacity of
10 amp hours then I would have 40 amp hours at 12 volts,

If one cell went dead then I would have 30 amp hours at 12 volts,

If I had four 3 volt cells wired in series each with a capacity of 10
amp hours then I would have 10 amp hours at 12 volts,

If one cell went dead then I would have 10 amp hours at 9 volts,

How does it go with my battery ? Is it a combination of series and
parallel ?

* navti wrote, On 5/31/2007 4:31 AM:

I am curious as to how the battery capacity can be 50 % diminished and
still deliver 12.6 volts (or thereabouts.

Are the individual cells in the battery wired in series or parallel ?

series


If I had four 12 volt cells wired in parrallel each with a capacity of
10 amp hours then I would have 40 amp hours at 12 volts,

yup


If one cell went dead then I would have 30 amp hours at 12 volts,

Actually, in this case the dead cell might kill the whole bank. If
one cell of a parallel setup is shorted, then all are shorted.


If I had four 3 volt cells wired in series each with a capacity of 10
amp hours then I would have 10 amp hours at 12 volts,

yup



If one cell went dead then I would have 10 amp hours at 9 volts,

only if it died "shorted," which is often the case.


How does it go with my battery ? Is it a combination of series and
parallel ?


You have 6 2.1 Volt cells in series. This is the case with all "12
Volt" lead acid batteries. If you had a catastrophic failure of one
cell, the battery is trash. This is most often an internal short,
sometimes its a cracked case. There are some high end batteries that
have replaceable cells, but they are expensive and heavy.

The issue you have is probably simply deep discharge, which can cause
several problems. One is a loss of lead or "shedding" - the lead
comes loose from the substrate that holds it. In a flooded cell, this
tends to fall to the bottom. The battery acts the same but with
diminished capacity, until the debris builds up and shorts the plates.
Most of us have encountered this if we tend to leave the lights on
in the car every now and then - with each episode some of the lead
falls off and after a dozen or so times, its toast. This is
particularly the case in starting batteries, because the the plates
are so thin. Slow shedding is a normal process, which is why a car
battery often dies the month after the warranty expires.

The other common problem is sulphation. During the normal discharge,
the lead and lead oxide plates are converted to lead sulphate.
Charging reverses this. If the cells are left discharged, the
sulphate can harden and resist reverting back. This can sometimes be
reversed by "equalizing" which is charging at a higher rate which
"loosens" the sulphate. The problem with AGMs is that you have to be
careful not to overcharge, since you can't add water. Severe
sulphation creates a thick layer and cannot be reversed.

In both of the situations, the only definitive test is a load test -
it will be difficult to determine the health simply by charging. Each
manufacturer has a different construction and formulation of the
plates, so detailed experience gained in one brand does not
necessarily apply in another. I've been using the same batteries
(Trojan T105) for my house banks for the last dozen years, and I check
the load, voltage, and amp-hours several times a day, so if they're
off by a tenth of a Volt I start to get suspicious. But on a
different boat, the normal reading could be a tad higher or lower.

Frankly, my experience with AGMs is limited to a pair of starting
batteries that have worked flawlessly for several years, including one
severe winter that killed the flooded house bank. But the basic
chemistry and issues are the same. However, AGM's are able to
withstand long periods of inattention. The Optima site, for example,
claims theirs can sit for a year and still start a car. There is
reason to hope that yours have survived, but only a load test will
tell for sure. You may be able to resurrect them with an equalization
cycle, but I would only try that if its impossible to return them.

On May 31, 2:55 pm, Jeff wrote:
* navti wrote, On 5/31/2007 4:31 AM:



I am curious as to how the battery capacity can be 50 % diminished and
still deliver 12.6 volts (or thereabouts.

Are the individual cells in the battery wired in series or parallel ?

series



If I had four 12 volt cells wired in parrallel each with a capacity of
10 amp hours then I would have 40 amp hours at 12 volts,

yup



If one cell went dead then I would have 30 amp hours at 12 volts,

Actually, in this case the dead cell might kill the whole bank. If
one cell of a parallel setup is shorted, then all are shorted.



If I had four 3 volt cells wired in series each with a capacity of 10
amp hours then I would have 10 amp hours at 12 volts,

yup



If one cell went dead then I would have 10 amp hours at 9 volts,

only if it died "shorted," which is often the case.



How does it go with my battery ? Is it a combination of series and
parallel ?

You have 6 2.1 Volt cells in series. This is the case with all "12
Volt" lead acid batteries. If you had a catastrophic failure of one
cell, the battery is trash. This is most often an internal short,
sometimes its a cracked case. There are some high end batteries that
have replaceable cells, but they are expensive and heavy.

The issue you have is probably simply deep discharge, which can cause
several problems. One is a loss of lead or "shedding" - the lead
comes loose from the substrate that holds it. In a flooded cell, this
tends to fall to the bottom. The battery acts the same but with
diminished capacity, until the debris builds up and shorts the plates.
Most of us have encountered this if we tend to leave the lights on
in the car every now and then - with each episode some of the lead
falls off and after a dozen or so times, its toast. This is
particularly the case in starting batteries, because the the plates
are so thin. Slow shedding is a normal process, which is why a car
battery often dies the month after the warranty expires.

The other common problem is sulphation. During the normal discharge,
the lead and lead oxide plates are converted to lead sulphate.
Charging reverses this. If the cells are left discharged, the
sulphate can harden and resist reverting back. This can sometimes be
reversed by "equalizing" which is charging at a higher rate which
"loosens" the sulphate. The problem with AGMs is that you have to be
careful not to overcharge, since you can't add water. Severe
sulphation creates a thick layer and cannot be reversed.

In both of the situations, the only definitive test is a load test -
it will be difficult to determine the health simply by charging. Each
manufacturer has a different construction and formulation of the
plates, so detailed experience gained in one brand does not
necessarily apply in another. I've been using the same batteries
(Trojan T105) for my house banks for the last dozen years, and I check
the load, voltage, and amp-hours several times a day, so if they're
off by a tenth of a Volt I start to get suspicious. But on a
different boat, the normal reading could be a tad higher or lower.

Jeff

Lets ASSUME I have a brand new 100 ah battery and its sitting at 12.6
volts.

I run it through a 3A DC lamp for 10 hours = 30ah.

According to my chart 70 per cent charged (30 per cent discharged )
is
12.3 volts,

If they were only 50 amp hour batteries then 30 ah would be a 60 per
cent discharge and my chart shows 40 per cent charged is 12 volts.

Is this the correct methodolgy ?

* navti wrote, On 5/31/2007 4:12 PM:

Lets ASSUME I have a brand new 100 ah battery and its sitting at 12.6
volts.

I run it through a 3A DC lamp for 10 hours = 30ah.

According to my chart 70 per cent charged (30 per cent discharged )
is
12.3 volts,

If they were only 50 amp hour batteries then 30 ah would be a 60 per
cent discharge and my chart shows 40 per cent charged is 12 volts.

Is this the correct methodolgy ?


Yes, this is the way to do it. The problem you have is that there's a
lot of guesswork in the discharge curve. Once you've used a battery
type for a while, it becomes predictable, but the first time through
you don't know if 12.3 volts is 30%, or maybe 20% or 40%. Thus the
first time you have to take it fairly deep to have any confidence.

The good news is that the battery will possibly get a bit stronger in
the near term as its exercised because some of the sulphation is
removed. So if you're able to get 50 Ah out of it and it still over
12 volts, you probably have some useful life left in them. But if
your 30 Ah test takes it under 12V, you have a problem.

One more thing - while under the load the Voltage will show lower, and
then it will jump up a tad when the load is removed. The higher
Voltage is the "Open Circuit" measurement.