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'[OT]: DOA Sealed Lead Acid Batteries'
2000\07\17@014621 by James Cameron

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Bought a new 6V 5AH sealed lead acid battery, and when it arrived it
had no apparent capacity.  Not quite as dead as an open circuit,
though.  It seems that applying a constant current charge simply
results in the terminal voltage soaring to whatever voltage limit my
charger has.  Remove that and the voltage via DMM drops to 1.3V.
Battery is dated in 1999 some time.

Is this a "normal" behaviour, and is it fixable?  Any references?

Or is it a "return"?  [bought it via a friend; problematic]

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2000\07\17@022228 by Robert Rolf

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It's called SULFATION. Permanent and fatal, and the number one cause of
lead acid battery failure. (number 2 is plate shorts from shedding).

The battery was left in a discharged state for too long (many weeks)
and the lead pentoxide on the plates was converted to lead sulfide
(which is very inert).
The sulfation process is not easily reversed although some references
suggest that charging at 1/100C can undo the damage. I have tried
this on numerous batteries (mostly UPS's that weren't turned off
correctly), without success. There are also a number of products
that claim that they can 'fix sulfation' but I rather doubt their
efficacy, given the tenacity of the chemical bonding that occurs.

If this were a commercial battery I would return the battery to the
supplier with a strongly worded letter of complaint about their poor
storage practices and sale of 'dated' batteries. Since this was a
'friend' you have to tell him that he sold you a bad battery because it
had been left uncharged for too long. You thought you were buying a
'good' battery. It wasn't, so your friend should make-good on the deal.
If he sold you a case of beer and it was sour, would he replace it?

James Cameron wrote:
{Quote hidden}

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2000\07\17@024340 by David VanHorn

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>
>Is this a "normal" behaviour, and is it fixable?  Any references?
>
>Or is it a "return"?  [bought it via a friend; problematic]


Feed it some AC current, limited by a lightbulb.
If you can get it to flow 1-2A, then you're probably ok.
Despite claims that it's permanent, it isn't always.

My home station uses a "sulphated" 38AH gell that had zero capacity when I
got it.
It would run my electric lawnmower now..

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2000\07\17@043021 by McMeikan, Andrew

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Just thought I would comment.

I have recovered some batteries from this, majority stay open and are
useless, but sometimes you can get a current flowing by briefly reverse
charging or by applying 70-80v for a few seconds, you can then try and
charge them normally.

I would also note that sometimes they end up spitting acid or melting the
case, so this is a last resort.  I have saved 4 batteries out of 20 and had
2 'melt' during charging.  The 4 that came good stayed good.

       cya,    Andrew...

> {Original Message removed}

2000\07\18@162941 by Peter L. Peres

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>DOA Pb battery

The symptoms indicate a battery that was stored improperly (in a hot
place) and has dried up or discharged completely. Try to charge slowly for
14 hours at 1/20 C. If by then the Ri and voltage are not nearly
reasonable then return the hulk imho.

A new sealed lead acid should have nearly nominal voltage (slightly less
is ok) and be able to give 0.5C current without noticeable voltage drop
(drop < ~20% of open voltage) for 10 seconds or more. It should be cycled
once before use (slow charge -> slow discharge -> slow charge -> use) for
best results, unless the manufacturer says otherwise.

Peter

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2000\07\18@170530 by l.allen

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> >DOA Pb battery
>
> The symptoms indicate a battery that was stored improperly (in a hot
> place) and has dried up or discharged completely. Try to charge slowly for
> 14 hours at 1/20 C. If by then the Ri and voltage are not nearly
> reasonable then return the hulk imho.
>
> A new sealed lead acid should have nearly nominal voltage (slightly less
> is ok) and be able to give 0.5C current without noticeable voltage drop
> (drop < ~20% of open voltage) for 10 seconds or more. It should be cycled
> once before use (slow charge -> slow discharge -> slow charge -> use) for
> best results, unless the manufacturer says otherwise.
>

Just to restate what we should all know....

Lead Acid Batteries (SLA included) really really really hate going
totally flat. They prefer to stay at full charge.
For a 12 volt battery for example...
Flat is 10.8 volts, below this it starts to become damaged (they
lose capacity to hold charge).
Fully charged is 12.6 volts.
Quarter full capacity when 12 volts across terminals.

You can fast charge at 14.2 volts initially (but current limited to
0.33C) dropping to 13.8 volts to finish.
The battery can remain happily on 13.8 volts charge pretty much
permanently.
_____________________________

Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand

http://www.psych.auckland.ac.nz

_____________________________

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2000\07\18@171749 by David VanHorn

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>
>You can fast charge at 14.2 volts initially (but current limited to
>0.33C) dropping to 13.8 volts to finish.
>The battery can remain happily on 13.8 volts charge pretty much
>permanently.

The data I have from Yuasa, Gates, and a couple others, state that at
2.55V/cell you can charge at an unlimited rate, till the charge current
drops below 0.1C, then you should drop to a float voltage around 2.25/cell
but that varies with temperature.

I had to confirm this in person on one project, due to the small cell
(0.5AH) and the large supply it would be connected to.
The conversation went like this:

I see in the data sheet you don't specify a max charging current.
Nope.
How fast can I charge it?
As fast as you want.
100A? (I was looking for the hidden limit)
Just don't exceed 2.55 volts per cell, and you can put in as much current
as you can deliver.

Apparently, the cell chemistry limits the current at high rates.
This sort of makes sense, as jump-starting a dead battery would otherwise
act like a dead short for a while.




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2000\07\18@230217 by Dale Botkin

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On Tue, 18 Jul 2000, David VanHorn wrote:

> I had to confirm this in person on one project, due to the small cell
> (0.5AH) and the large supply it would be connected to.
> The conversation went like this:
>
> I see in the data sheet you don't specify a max charging current.
> Nope.
> How fast can I charge it?
> As fast as you want.
> 100A? (I was looking for the hidden limit)
> Just don't exceed 2.55 volts per cell, and you can put in as much current
> as you can deliver.
>
> Apparently, the cell chemistry limits the current at high rates.
> This sort of makes sense, as jump-starting a dead battery would otherwise
> act like a dead short for a while.

The current will be limited, I think, by the cell's internal resistance.
That will limit the drain current in the event of a short, too, just not
to a really useful figure...  <grin>

Dale
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