Lead Battery Seems To Have Expired Suddenly

Chris Hedges said:

I recently pulled out my sla-powered light and discovered that I was
missing the manufacturer supplied charger. So, I plugged the battery
(6V 3.2Ah) into a 6V 500 mA AC to DC power supply. The battery seemed
to charge just fine, and the light (actually two bulbs) was nice and
bright for over an hour. Charged it again, and the light worked great
on a 20 minute ride. Tried to charge it again and . . . nearly
nothing. A mere glow. Even after a couple days on the charger, the
light when used with the battery remains dim, though with the charger
connected, the light is at least as bright as before.

A voltmeter shows the charger is producing 6 volts. It also shows
the battery is producing only 4 volts. (Unfortunately, I don't know
what the fully charged battery was producing when the light was
working well.)

I haven't dropped anything or done any obvious crimping.

Have I done something stupid by using the 500mA power supply? Any
ideas about what I should check?

That sounds typical of a shorted cell. A 6 volt lead acid battery is
made of three cells in series, each of which produces just over 2
volts. One shorted cell would explain the 4 volt reading. If the
battery sits around discharged lead sulfate crystals can form. These
crystals can then push the lead plates in a cell together shorting it
out. If the case of the battery looks to be bulging you can be pretty
sure this is what has happened. Even if it isn't bulging the story
you tell sounds like a shorted cell. Time for a new battery.

Chris Hedges said:

I recently pulled out my sla-powered light and discovered that I was
missing the manufacturer supplied charger. So, I plugged the battery
(6V 3.2Ah) into a 6V 500 mA AC to DC power supply. The battery seemed
to charge just fine, and the light (actually two bulbs) was nice and
bright for over an hour. Charged it again, and the light worked great
on a 20 minute ride. Tried to charge it again and . . . nearly nothing.
A mere glow. Even after a couple days on the charger, the light when
used with the battery remains dim, though with the charger connected,
the light is at least as bright as before.

A voltmeter shows the charger is producing 6 volts. It also shows the
battery is producing only 4 volts. (Unfortunately, I don't know what
the fully charged battery was producing when the light was working well.)

I haven't dropped anything or done any obvious crimping.

Have I done something stupid by using the 500mA power supply? Any ideas
about what I should check?

I agree with Jim Smith. Sounds like your battery has one shorted cell.
While cells shorted by sulferous dendrites can sometimes be brought back
to life by applying overvoltage during charge while monitoring cell
temperature and interrupting charge when temp. goes too high, the
process is dangerous - risk of explosion - and definitely is not for the
faint of heart. Your battery should be disposed of properly and
replaced.

Probably the 500mA charger did no damage. However!.... charging a lead
acid battery of that capacity is kinda hard on it. A 3Ah lead/acid
battery can draw a lot of current while charging; the lower the state of
its charge, the more current it can draw. Depending on how well made -
read "over-designed" - the charger is, it could die prematurely.

Michael

Michael wrote:

[snip]

Quoted message said:

Probably the 500mA charger did no damage. However!.... charging a lead
acid battery of that capacity is kinda hard on it. A 3Ah lead/acid
battery can draw a lot of current while charging; the lower the state of
its charge, the more current it can draw. Depending on how well made -
read "over-designed" - the charger is, it could die prematurely.

Yikes! Your comment about ruining the charger is alarming. Since I use
the charger for other things, and it cost around $12 - about the price
of a new SLA battery - I would like to avoid damaging it.

What sort of charger would be properly "over-designed"? One with a
lower mA rating, a higher mA rating, or something else entirely?

Chris Hedges said:

Michael wrote:

[snip]

Quoted message said:

Probably the 500mA charger did no damage. However!.... charging a lead
acid battery of that capacity is kinda hard on it. A 3Ah lead/acid
battery can draw a lot of current while charging; the lower the state of
its charge, the more current it can draw. Depending on how well made -
read "over-designed" - the charger is, it could die prematurely.

Yikes! Your comment about ruining the charger is alarming. Since I use
the charger for other things, and it cost around $12 - about the price
of a new SLA battery - I would like to avoid damaging it.

What sort of charger would be properly "over-designed"? One with a
lower mA rating, a higher mA rating, or something else entirely?

There are a multitude of specialty chargers for SLA batteries. The 2-7 Amp hour batteries are commonly used in radio controlled hobbies for engine starting etc and quality peak chargers are available at most hobby shops, mail order and on line. I have a universal charger that does SLA, NiCd, NiMH and LiPoly but that would be overkill for your application.

Temperature is the enemy of fast charging at rates over C/10 (for your 3.2 A*H, that would be 320 mA). While you can charge your 3.2 at 500 mA, you should not charge it more than about 6 hours at that rate. 5 hours would be better but you should check the end voltage to be sure. Your 6 volt is fully charged at 6.9 volts, AFTER you remove the charger (and wait a few minutes after removing the charger).

"Chris Hedges" wrote: Yikes! Your comment about ruining the charger is
alarming. (clip)
^^^^^^^^^^^^^
Since you say the light seems to have normal brightness with the charger on,
chances are it is still working. However, it seems to me that 500 ma (1/2
amp) is not enough capacity to be sure you're not going to hurt the charger
if you continue to use it this way. Does your meter measure current?
That's what you need to measure to be sure you are not overloading the
charger. Especially with only 4 volts at the battery terminals, the charger
is able to push way more than the rated current into the battery, and could
have sustained damage.

"Chris Hedges" wrote ...
(snip)

Quoted message said:

Have I done something stupid by using the 500mA power supply?

(snkp)

Maybe ... to properly charge a SLA battery you need a charger specifically
designed for the task (or, an adjustable voltage supply that you must
monitor continuously so as not to overcharge the battery)

A *very* good third party SLA battery charger are made by the POWER-SONIC
company. The one best suited for your battery would likely be the 6 v 300
ma model PSC-6300A (see:
http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=296707&e_categoryid=342&e_pcodeid=54702
and the pdf fact sheet listed on that page)

The Power-Sonic charges will change from a "fast" charge to a "float" charge
mode when the battery is fully charged, so you can leave it connected
without worry of overcharging and damaging the battery. MOUSER sells this
model for about $36 ... a bit pricey, but well worth it. (I own four
Power-Sonic chargers .. two 6 volt models, and two 12 volt models)

Richard in Boston, MA, USA

Thanks very much for the help, but I think I am too thick-witted to
decide what to do.

Weisse Luft said:

[snip]

Temperature is the enemy of fast charging at rates over C/10 (for your
3.2 A*H, that would be 320 mA). While you can charge your 3.2 at 500
mA, you should not charge it more than about 6 hours at that rate. 5
hours would be better but you should check the end voltage to be sure.
Your 6 volt is fully charged at 6.9 volts, AFTER you remove the charger
(and wait a few minutes after removing the charger).

Weisse, I think this means that if I were to purchase a battery rated at
5 Ah, I could leave it on the charger longer (which would be better.)
Is that right? Is the danger that if I exceed C/10 I risk damaging the
battery?

Since reading your post and having a better idea what I was looking for,
I ran across a this [pdf]: ttp://www.web-ee.com/primers/files/fsect5.pdf

I don't know what credence to give it, but its table 5.7 seems to
indicate that I can "slow" charge an SLA at .25C. That would mean I
could charge a 3.2 Ah battery at 800 mA and a 5 Ah battery at 1250 mA
without worries.

Or does it? Another interpretation of the chart might be that I would
hit full charge at 24 hours and then need to worry. Again, I don't
really know what I am reading so I might be completely wrong.

(BTW, the same table lists V/cell for the SLA battery at 2.27. That's
why you said that my 6V battery is fully charged at 6.9V, right?)

Leo Lichtman said:

"Chris Hedges" wrote: Yikes! Your comment about ruining the charger is
alarming. (clip)
^^^^^^^^^^^^^
Since you say the light seems to have normal brightness with the charger on,
chances are it is still working. However, it seems to me that 500 ma (1/2
amp) is not enough capacity to be sure you're not going to hurt the charger
if you continue to use it this way. Does your meter measure current?
That's what you need to measure to be sure you are not overloading the
charger. Especially with only 4 volts at the battery terminals, the charger
is able to push way more than the rated current into the battery, and could
have sustained damage.

Leo & Michael, I am afraid that I just don't understand how I can figure
out whether the charger has enough capacity. Is it the voltage of the
battery that determines the risk of harm to the charger or the current
rating? Or something else entirely? Would there be any indications
that I am in danger of screwing up the charger? (Short of smoke rising
from it!?)

"Chris Hedges" wrote: (clip) I am afraid that I just don't understand how I
can figure out whether the charger has enough capacity.(clip)
^^^^^^^^^^^^^
Chris, it is the DIFFERENCE in voltage between the battery and the charger.
The person who designed the charger intended it to be used on a battery with
a certain voltage--say 6 volts, in this case. So the charger is made to
produce enough, maybe 7 or 7 1/2 volts, so the difference of 1 or 1 l/2
volts drives an acceptable current through the battery. Then, as the
battery gets charged, its voltage rises, reducing the driving voltage,
causing the current to taper off.

In your case, if we assume that a cell is shorted, producing a battery
voltage of only 4 volts, the voltage difference becomes 3 to 3 1/2 volts, so
the charging current is proportionately higher. If your meter has a current
range, you can check this by hooking the meter in series with one of the
charger leads. You do not want to see the current go above 500 ma.

quote='Jim Smith'Chris Hedges said:

I recently pulled out my sla-powered light and discovered that I was
missing the manufacturer supplied charger. So, I plugged the battery
(6V 3.2Ah) into a 6V 500 mA AC to DC power supply. The battery seemed
to charge just fine, and the light (actually two bulbs) was nice and
bright for over an hour. Charged it again, and the light worked great
on a 20 minute ride. Tried to charge it again and . . . nearly
nothing. A mere glow. Even after a couple days on the charger, the
light when used with the battery remains dim, though with the charger
connected, the light is at least as bright as before.

A voltmeter shows the charger is producing 6 volts. It also shows
the battery is producing only 4 volts. (Unfortunately, I don't know
what the fully charged battery was producing when the light was
working well.)

I haven't dropped anything or done any obvious crimping.

Have I done something stupid by using the 500mA power supply? Any
ideas about what I should check?

That sounds typical of a shorted cell. A 6 volt lead acid battery is
made of three cells in series, each of which produces just over 2
volts. One shorted cell would explain the 4 volt reading. If the
battery sits around discharged lead sulfate crystals can form. These
crystals can then push the lead plates in a cell together shorting it
out. If the case of the battery looks to be bulging you can be pretty
sure this is what has happened. Even if it isn't bulging the story
you tell sounds like a shorted cell. Time for a new battery.[/QUOTE]

Could you explain the possible SLA bulging?
Is that a sympton unique to SLA that wet cells don't have?

meb said:

Jim Smith said:

Chris Hedges said:

I recently pulled out my sla-powered light and discovered that I was
missing the manufacturer supplied charger. So, I plugged the

battery

Quoted message said:

(6V 3.2Ah) into a 6V 500 mA AC to DC power supply. The battery

seemed

Quoted message said:

to charge just fine, and the light (actually two bulbs) was nice and
bright for over an hour. Charged it again, and the light worked

great

Quoted message said:

on a 20 minute ride. Tried to charge it again and . . . nearly
nothing. A mere glow. Even after a couple days on the charger, the
light when used with the battery remains dim, though with the

charger

Quoted message said:

connected, the light is at least as bright as before.

A voltmeter shows the charger is producing 6 volts. It also shows
the battery is producing only 4 volts. (Unfortunately, I don't know
what the fully charged battery was producing when the light was
working well.)

I haven't dropped anything or done any obvious crimping.

Have I done something stupid by using the 500mA power supply? Any
ideas about what I should check?

That sounds typical of a shorted cell. A 6 volt lead acid battery is
made of three cells in series, each of which produces just over 2
volts. One shorted cell would explain the 4 volt reading. If the
battery sits around discharged lead sulfate crystals can form. These
crystals can then push the lead plates in a cell together shorting it
out. If the case of the battery looks to be bulging you can be pretty
sure this is what has happened. Even if it isn't bulging the story
you tell sounds like a shorted cell. Time for a new battery.

Could you explain the possible SLA bulging?
Is that a sympton unique to SLA that wet cells don't have?

Lead acid batteries have a stack of thin lead sheets inside that are
converted between lead, lead oxide, and lead sulfate as the battery
goes through its chare/discharge cycle. Bulging is due to the different
densities of these materials. Lead sulfate building up on the surface
of the plates pushes them apart, not unlike what happens when a book
gets wet.

Leo Lichtman said:

"Chris Hedges" wrote: (clip) I am afraid that I just don't understand how I
can figure out whether the charger has enough capacity.(clip)
^^^^^^^^^^^^^
Chris, it is the DIFFERENCE in voltage between the battery and the charger.
The person who designed the charger intended it to be used on a battery with
a certain voltage--say 6 volts, in this case. So the charger is made to
produce enough, maybe 7 or 7 1/2 volts, so the difference of 1 or 1 l/2
volts drives an acceptable current through the battery. Then, as the
battery gets charged, its voltage rises, reducing the driving voltage,
causing the current to taper off.

In your case, if we assume that a cell is shorted, producing a battery
voltage of only 4 volts, the voltage difference becomes 3 to 3 1/2 volts, so
the charging current is proportionately higher. If your meter has a current
range, you can check this by hooking the meter in series with one of the
charger leads. You do not want to see the current go above 500 ma.

So, using a power supply rated at 6 or 7 volts and which produces 500mA,
my charger and battery should both be fine. Is that right?

Weisse Luft wrote:
(snip)

Quoted message said:

There are a multitude of specialty chargers for SLA batteries. The 2-7
Amp hour batteries are commonly used in radio controlled hobbies for
engine starting etc and quality peak chargers are available at most
hobby shops, mail order and on line. I have a universal charger that
does SLA, NiCd, NiMH and LiPoly but that would be overkill for your
application.

I agree. However, grabbing an r/c battery charger is a no-fuss
solution.
OP should consider it.

Quoted message said:

Temperature is the enemy of fast charging at rates over C/10 (for your
3.2 A*H, that would be 320 mA). While you can charge your 3.2 at 500
mA, you should not charge it more than about 6 hours at that rate. 5
hours would be better but you should check the end voltage to be sure.
Your 6 volt is fully charged at 6.9 volts, AFTER you remove the charger
(and wait a few minutes after removing the charger).

--
Weisse Luft

The rating, 500ma, is either the current at which the voltage rating
applies or the max. that the charger can deliver. It could be that what
the charger actually delivers is less than 500 ma. Also, O.P.'s charger
probably is not regulated. Therefore it's output voltage will drop
under load, and the current it delivers to battery could very well be
less than C/10.

("White Air"? Interesting.)

"Chris Hedges" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Leo Lichtman said:

"Chris Hedges" wrote: (clip) I am afraid that I just don't understand

how I

Quoted message said:

Quoted message said:

can figure out whether the charger has enough capacity.(clip)
^^^^^^^^^^^^^
Chris, it is the DIFFERENCE in voltage between the battery and the

charger.

Quoted message said:

Quoted message said:

The person who designed the charger intended it to be used on a battery

with

Quoted message said:

Quoted message said:

a certain voltage--say 6 volts, in this case. So the charger is made to
produce enough, maybe 7 or 7 1/2 volts, so the difference of 1 or 1 l/2
volts drives an acceptable current through the battery. Then, as the
battery gets charged, its voltage rises, reducing the driving voltage,
causing the current to taper off.

In your case, if we assume that a cell is shorted, producing a battery
voltage of only 4 volts, the voltage difference becomes 3 to 3 1/2

volts, so

Quoted message said:

Quoted message said:

the charging current is proportionately higher. If your meter has a

current

Quoted message said:

Quoted message said:

range, you can check this by hooking the meter in series with one of the
charger leads. You do not want to see the current go above 500 ma.

So, using a power supply rated at 6 or 7 volts and which produces 500mA,
my charger and battery should both be fine. Is that right?

The best thing to do is use an intelligent charger. Any charger that uses a
UC3906 chip will take good care of your batterys.

Marty

Chris Hedges said:

I recently pulled out my sla-powered light and discovered that I was
missing the manufacturer supplied charger. So, I plugged the battery
(6V 3.2Ah) into a 6V 500 mA AC to DC power supply. The battery seemed
to charge just fine, and the light (actually two bulbs) was nice and
bright for over an hour. Charged it again, and the light worked great
on a 20 minute ride. Tried to charge it again and . . . nearly nothing.
A mere glow. Even after a couple days on the charger, the light when
used with the battery remains dim, though with the charger connected,
the light is at least as bright as before.

A voltmeter shows the charger is producing 6 volts. It also shows the
battery is producing only 4 volts. (Unfortunately, I don't know what
the fully charged battery was producing when the light was working well.)

I haven't dropped anything or done any obvious crimping.

Have I done something stupid by using the 500mA power supply? Any ideas
about what I should check?

Hello,
I think the problem has something to do with the charging voltage instead of
the current. You mentioned that the power supply has an output of six volts. In
order to charge a six volt sla battery, you will need to apply a voltage higher
than that. You need about 7.35 volts for overnight charging or 6.9 volts for
float or trickle charging.

On Fri, 01 Oct 2004 11:47:28 GMT, Chris Hedges <[email hidden]>

Quoted message said:

I recently pulled out my sla-powered light and discovered that I was
missing the manufacturer supplied charger. So, I plugged the battery
(6V 3.2Ah) into a 6V 500 mA AC to DC power supply. <snip>

A voltmeter shows the charger is producing 6 volts.

A 6-volt lead-acid battery typically requires 6.9 to 7.2 volts to
fully charge. That power converter should not have been able to
charge the battery beyond a low charge.

Quoted message said:

It also shows the
battery is producing only 4 volts. (Unfortunately, I don't know what
the fully charged battery was producing when the light was working well.)

The battery is discharged, and may or may not be damaged.

Quoted message said:

I haven't dropped anything or done any obvious crimping.

Have I done something stupid by using the 500mA power supply? Any ideas
about what I should check?

Find the correct charger and try it. Chances are good that the
battery will still take a charge.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.