wet-cell battery gravity test

M

Mike

Guest
A while back, I had a brand new battery that sat for a long time, eventually
loosing its charge. It was slow-charged for several hours until the battery
voltage read ~ 12/12.5 volts. I was actually having problems with the
battery handling a load; cranking for 4-5 seconds revealed a slow-down on
the starter. I proceeded to do a gravity test, which the battery failed. I
brought the battery into Sears where they put the battery on some
cutting-edge technology machine that didn't use gravity testing. I was
actually arguing with the manager because he was telling me that gravity
tests are very inaccurate. How can this be? Battery acid has greater gravity
than plain water, which makes up most of the fluid in a dead battery, thus
causing the "balls" to drop in the tube. This was a while ago, but the
thought just popped in my head...

Thanks
 
Mike posted:

<< A while back, I had a brand new battery that sat for a long time, eventually
loosing its charge. It was slow-charged for several hours until the battery
voltage read ~ 12/12.5 volts. I was actually having problems with the
battery handling a load; cranking for 4-5 seconds revealed a slow-down on
the starter. I proceeded to do a gravity test, which the battery failed. I
brought the battery into Sears where they put the battery on some
cutting-edge technology machine that didn't use gravity testing. I was
actually arguing with the manager because he was telling me that gravity
tests are very inaccurate. How can this be? Battery acid has greater gravity
than plain water, which makes up most of the fluid in a dead battery, thus
causing the "balls" to drop in the tube. This was a while ago, but the
thought just popped in my head... >>

I'm not certain what thought just popped into your head, but specific
gravityreadings are a good indication of lead/acid cell condition.

When you measured 12.5V you should have kept charging the battery. When a
battery is badly discharged you will probably need to charge it at about 13.2
Volts; that's 2.2 Volts per cell. During the heavy charge it is a good idea to
monitor it's temperature, voltage, and cell specific gravity periodically.

If your charger cannot reach 13.2 Volts you will need to charge it for more
time. Or have a garage do a quick charge on it.

Don
 
Hi Don,

"~" meant approximate, so I don't remember exactly what it read. Could have
been well over 13 volts, but the question in my post was whether that Sears
manager was BS'in me.

Thanks for your feedback.
Mike

"Dbowey" <dbowey@aol.com> wrote in message
news:20041217134032.08215.00002166@mb-m05.aol.com...
Mike posted:

A while back, I had a brand new battery that sat for a long time,
eventually
loosing its charge. It was slow-charged for several hours until the
battery
voltage read ~ 12/12.5 volts. I was actually having problems with the
battery handling a load; cranking for 4-5 seconds revealed a slow-down on
the starter. I proceeded to do a gravity test, which the battery failed. I
brought the battery into Sears where they put the battery on some
cutting-edge technology machine that didn't use gravity testing. I was
actually arguing with the manager because he was telling me that gravity
tests are very inaccurate. How can this be? Battery acid has greater
gravity
than plain water, which makes up most of the fluid in a dead battery, thus
causing the "balls" to drop in the tube. This was a while ago, but the
thought just popped in my head...

I'm not certain what thought just popped into your head, but specific
gravityreadings are a good indication of lead/acid cell condition.

When you measured 12.5V you should have kept charging the battery. When a
battery is badly discharged you will probably need to charge it at about
13.2
Volts; that's 2.2 Volts per cell. During the heavy charge it is a good
idea to
monitor it's temperature, voltage, and cell specific gravity periodically.

If your charger cannot reach 13.2 Volts you will need to charge it for
more
time. Or have a garage do a quick charge on it.

Don
Click to expand...
 
Hi

My recollection of the battery section that I once took and my work as a
industrial controls mechanic, is that as a battery discharges its internal
resistance increases. As the internal resistance increases the voltage will
drop across a constant load.

Further, allowing a battery to sit with the acid in it and not charged is
one of the worst things that can happen to a battery aside from freezing.

When a battery has been sitting for extended periods, the material on the
plates turns into more or less insoluble lead sulfate crystals. This
reduces the surface area in the active battery approximating a permanent
discharged condition.

There is a process that allows such batteries to sometimes be saved, but it
has some dangers and you are well advised to get in the net and take a look
at some of the interesting information that battery manufactures post.

Al.

"Mike" <no_spam@comcast.net> wrote in message
news:buSdnYoOltC7jV7cRVn-3w@comcast.com...
A while back, I had a brand new battery that sat for a long time,
eventually
loosing its charge. It was slow-charged for several hours until the
battery
voltage read ~ 12/12.5 volts. I was actually having problems with the
battery handling a load; cranking for 4-5 seconds revealed a slow-down on
the starter. I proceeded to do a gravity test, which the battery failed. I
brought the battery into Sears where they put the battery on some
cutting-edge technology machine that didn't use gravity testing. I was
actually arguing with the manager because he was telling me that gravity
tests are very inaccurate. How can this be? Battery acid has greater
gravity
than plain water, which makes up most of the fluid in a dead battery, thus
causing the "balls" to drop in the tube. This was a while ago, but the
thought just popped in my head...

Thanks
Click to expand...
 
On Fri, 17 Dec 2004 15:36:46 -0500, Mike wrote:

Hi Don,

"~" meant approximate, so I don't remember exactly what it read. Could have
been well over 13 volts, but the question in my post was whether that Sears
manager was BS'in me.

The manager was wrong about the "gravity test" being inaccurate. He might
Click to expand...
have been arguing with the term "gravity test" as opposed to "specific
gravity test". But he has to justify the use of his expensive machinery.
Other than that, you seem to be doing fine, except that there are people
who will complain about your top-posting. :)

Good Luck!
Rich


Thanks for your feedback.
Mike

"Dbowey" <dbowey@aol.com> wrote in message
news:20041217134032.08215.00002166@mb-m05.aol.com...
Mike posted:

A while back, I had a brand new battery that sat for a long time,
eventually
loosing its charge. It was slow-charged for several hours until the
battery
voltage read ~ 12/12.5 volts. I was actually having problems with the
battery handling a load; cranking for 4-5 seconds revealed a slow-down
on the starter. I proceeded to do a gravity test, which the battery
failed. I brought the battery into Sears where they put the battery on
some cutting-edge technology machine that didn't use gravity testing. I
was actually arguing with the manager because he was telling me that
gravity tests are very inaccurate. How can this be? Battery acid has
greater
gravity
than plain water, which makes up most of the fluid in a dead battery,
thus causing the "balls" to drop in the tube. This was a while ago, but
the thought just popped in my head...

I'm not certain what thought just popped into your head, but specific
gravityreadings are a good indication of lead/acid cell condition.

When you measured 12.5V you should have kept charging the battery. When
a battery is badly discharged you will probably need to charge it at
about
13.2
Volts; that's 2.2 Volts per cell. During the heavy charge it is a good
idea to
monitor it's temperature, voltage, and cell specific gravity
periodically.

If your charger cannot reach 13.2 Volts you will need to charge it for
more
time. Or have a garage do a quick charge on it.

Don
Click to expand...
 
Darn... have to remember about top posting, but then again you're the only
complainer, yet ;)

Thanks.
Mike

"Rich Grise" <rich@example.net> wrote in message
news:pan.2004.12.18.01.24.49.567809@example.net...
On Fri, 17 Dec 2004 15:36:46 -0500, Mike wrote:

Hi Don,

"~" meant approximate, so I don't remember exactly what it read. Could
have
been well over 13 volts, but the question in my post was whether that
Sears
manager was BS'in me.

The manager was wrong about the "gravity test" being inaccurate. He might
have been arguing with the term "gravity test" as opposed to "specific
gravity test". But he has to justify the use of his expensive machinery.
Other than that, you seem to be doing fine, except that there are people
who will complain about your top-posting. :)

Good Luck!
Rich


Thanks for your feedback.
Mike

"Dbowey" <dbowey@aol.com> wrote in message
news:20041217134032.08215.00002166@mb-m05.aol.com...
Mike posted:

A while back, I had a brand new battery that sat for a long time,
eventually
loosing its charge. It was slow-charged for several hours until the
battery
voltage read ~ 12/12.5 volts. I was actually having problems with the
battery handling a load; cranking for 4-5 seconds revealed a slow-down
on the starter. I proceeded to do a gravity test, which the battery
failed. I brought the battery into Sears where they put the battery on
some cutting-edge technology machine that didn't use gravity testing. I
was actually arguing with the manager because he was telling me that
gravity tests are very inaccurate. How can this be? Battery acid has
greater
gravity
than plain water, which makes up most of the fluid in a dead battery,
thus causing the "balls" to drop in the tube. This was a while ago, but
the thought just popped in my head...

I'm not certain what thought just popped into your head, but specific
gravityreadings are a good indication of lead/acid cell condition.

When you measured 12.5V you should have kept charging the battery. When
a battery is badly discharged you will probably need to charge it at
about
13.2
Volts; that's 2.2 Volts per cell. During the heavy charge it is a good
idea to
monitor it's temperature, voltage, and cell specific gravity
periodically.

If your charger cannot reach 13.2 Volts you will need to charge it for
more
time. Or have a garage do a quick charge on it.

Don
Click to expand...
 
Yeh, I've actually heard of that procedure. It's more or less "blasting" the
battery with a load to dislodge the crystals....

Thanks!
Mike

"ALBERT C. GOOD JR." <retirement@pa.net> wrote in message
news:WmLwd.277$uN2.119693@monger.newsread.com...
Hi

My recollection of the battery section that I once took and my work as a
industrial controls mechanic, is that as a battery discharges its internal
resistance increases. As the internal resistance increases the voltage
will
drop across a constant load.

Further, allowing a battery to sit with the acid in it and not charged is
one of the worst things that can happen to a battery aside from freezing.

When a battery has been sitting for extended periods, the material on the
plates turns into more or less insoluble lead sulfate crystals. This
reduces the surface area in the active battery approximating a permanent
discharged condition.

There is a process that allows such batteries to sometimes be saved, but
it
has some dangers and you are well advised to get in the net and take a
look
at some of the interesting information that battery manufactures post.

Al.

"Mike" <no_spam@comcast.net> wrote in message
news:buSdnYoOltC7jV7cRVn-3w@comcast.com...
A while back, I had a brand new battery that sat for a long time,
eventually
loosing its charge. It was slow-charged for several hours until the
battery
voltage read ~ 12/12.5 volts. I was actually having problems with the
battery handling a load; cranking for 4-5 seconds revealed a slow-down
on
the starter. I proceeded to do a gravity test, which the battery failed.
I
brought the battery into Sears where they put the battery on some
cutting-edge technology machine that didn't use gravity testing. I was
actually arguing with the manager because he was telling me that gravity
tests are very inaccurate. How can this be? Battery acid has greater
gravity
than plain water, which makes up most of the fluid in a dead battery,
thus
causing the "balls" to drop in the tube. This was a while ago, but the
thought just popped in my head...

Thanks
Click to expand...
 
The manager was not entirely wrong. Specific gravity tells you if the
battery is charged and what percent of charge it is at. But the
battery can have a high internal resistance as another poster said.
What the guy at the store probably was talking about was a "load
test". It is commonly done in the battery service shops. They put a
load of so many amps and measure how much the voltage drops and how
quickly. That is the real test to see if the battery is any good.

By the way, when charging it needs to be charged at around 14 volts to
14.6 volts. 13 volts will never charge it up fully. 13.6 volts is a
good "float" voltage to maintain a battery at for long periods.

Desulphating a battery to recover it requires a charge voltage of
around 16 volts or so. The temperature must be monitored closely.
Sometimes it helps but if the battery has been sitting for a long
period with no charge it is probably history.

If a battery is discharged to "flat" you must get it charged up as
soon as possible. Letting it sit for more than a day in the discharged
condition will pretty much ruin it.

Regards
Gary

On Fri, 17 Dec 2004 15:36:46 -0500, "Mike" <no_spam@comcast.net>
wrote:

Hi Don,

"~" meant approximate, so I don't remember exactly what it read. Could have
been well over 13 volts, but the question in my post was whether that Sears
manager was BS'in me.

Thanks for your feedback.
Mike

"Dbowey" <dbowey@aol.com> wrote in message
news:20041217134032.08215.00002166@mb-m05.aol.com...
Mike posted:

A while back, I had a brand new battery that sat for a long time,
eventually
loosing its charge. It was slow-charged for several hours until the
battery
voltage read ~ 12/12.5 volts. I was actually having problems with the
battery handling a load; cranking for 4-5 seconds revealed a slow-down on
the starter. I proceeded to do a gravity test, which the battery failed. I
brought the battery into Sears where they put the battery on some
cutting-edge technology machine that didn't use gravity testing. I was
actually arguing with the manager because he was telling me that gravity
tests are very inaccurate. How can this be? Battery acid has greater
gravity
than plain water, which makes up most of the fluid in a dead battery, thus
causing the "balls" to drop in the tube. This was a while ago, but the
thought just popped in my head...

I'm not certain what thought just popped into your head, but specific
gravityreadings are a good indication of lead/acid cell condition.

When you measured 12.5V you should have kept charging the battery. When a
battery is badly discharged you will probably need to charge it at about
13.2
Volts; that's 2.2 Volts per cell. During the heavy charge it is a good
idea to
monitor it's temperature, voltage, and cell specific gravity periodically.

If your charger cannot reach 13.2 Volts you will need to charge it for
more
time. Or have a garage do a quick charge on it.

Don
Click to expand...
 
I performed a load test on the battery myself with a load tester, but I
can't remember the exact results.

Thanks for your words of wisdom.
Mike

"Gary Schafer" <gaschafer@comcast.net> wrote in message
news:9s77s0p2ip25u1o1uj66vbp8l8jtpmaa8m@4ax.com...
The manager was not entirely wrong. Specific gravity tells you if the
battery is charged and what percent of charge it is at. But the
battery can have a high internal resistance as another poster said.
What the guy at the store probably was talking about was a "load
test". It is commonly done in the battery service shops. They put a
load of so many amps and measure how much the voltage drops and how
quickly. That is the real test to see if the battery is any good.

By the way, when charging it needs to be charged at around 14 volts to
14.6 volts. 13 volts will never charge it up fully. 13.6 volts is a
good "float" voltage to maintain a battery at for long periods.

Desulphating a battery to recover it requires a charge voltage of
around 16 volts or so. The temperature must be monitored closely.
Sometimes it helps but if the battery has been sitting for a long
period with no charge it is probably history.

If a battery is discharged to "flat" you must get it charged up as
soon as possible. Letting it sit for more than a day in the discharged
condition will pretty much ruin it.

Regards
Gary

On Fri, 17 Dec 2004 15:36:46 -0500, "Mike" <no_spam@comcast.net
wrote:

Hi Don,

"~" meant approximate, so I don't remember exactly what it read. Could
have
been well over 13 volts, but the question in my post was whether that
Sears
manager was BS'in me.

Thanks for your feedback.
Mike

"Dbowey" <dbowey@aol.com> wrote in message
news:20041217134032.08215.00002166@mb-m05.aol.com...
Mike posted:

A while back, I had a brand new battery that sat for a long time,
eventually
loosing its charge. It was slow-charged for several hours until the
battery
voltage read ~ 12/12.5 volts. I was actually having problems with the
battery handling a load; cranking for 4-5 seconds revealed a slow-down
on
the starter. I proceeded to do a gravity test, which the battery
failed. I
brought the battery into Sears where they put the battery on some
cutting-edge technology machine that didn't use gravity testing. I was
actually arguing with the manager because he was telling me that
gravity
tests are very inaccurate. How can this be? Battery acid has greater
gravity
than plain water, which makes up most of the fluid in a dead battery,
thus
causing the "balls" to drop in the tube. This was a while ago, but the
thought just popped in my head...

I'm not certain what thought just popped into your head, but specific
gravityreadings are a good indication of lead/acid cell condition.

When you measured 12.5V you should have kept charging the battery.
When a
battery is badly discharged you will probably need to charge it at
about
13.2
Volts; that's 2.2 Volts per cell. During the heavy charge it is a good
idea to
monitor it's temperature, voltage, and cell specific gravity
periodically.

If your charger cannot reach 13.2 Volts you will need to charge it for
more
time. Or have a garage do a quick charge on it.

Don
Click to expand...
 
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