Someone gave me an old car battery charger.

6 volts 10A and
12 volts 2A and 10A, determined by a slide switch.

A friend brings over a dead 12v battery.

On the charger, on 10A, it charges at 9amps.
On 2A, it charges at 7 amps.

Based on the meter on the charger.

What does it mean to be a 2 amp charger if it charges at 7 amps?


After an hour the charging rate dropped to 6 amps on the 10A setting,
and then it was 5 amps on the 2A setting.

On Friday, May 1, 2015 at 12:03:37 PM UTC-6, micky wrote:
Someone gave me an old car battery charger.

6 volts 10A and
12 volts 2A and 10A, determined by a slide switch.

A friend brings over a dead 12v battery.

On the charger, on 10A, it charges at 9amps.
On 2A, it charges at 7 amps.

Based on the meter on the charger.

What does it mean to be a 2 amp charger if it charges at 7 amps?


After an hour the charging rate dropped to 6 amps on the 10A setting,
and then it was 5 amps on the 2A setting.

Sounds like the battery has had it or if you leave on the 10 amp setting
for 24 hours and it comes down more it might be salvageable...(might).
It could be borderline. Is there water in all the cells? One dry cell
is not good. Top them up with distilled water and see what happens.
I've had successes and lots of failures. The longer they stay dead before
charging then the odds are against you.
====

On 5/1/15 2:03 PM, micky wrote:
Someone gave me an old car battery charger.

6 volts 10A and
12 volts 2A and 10A, determined by a slide switch.

A friend brings over a dead 12v battery.

On the charger, on 10A, it charges at 9amps.
On 2A, it charges at 7 amps.

Based on the meter on the charger.

What does it mean to be a 2 amp charger if it charges at 7 amps?


After an hour the charging rate dropped to 6 amps on the 10A setting,
and then it was 5 amps on the 2A setting.


I'd take the battery off the charger and use a multimeter to see if the
terminal voltage was over 11.5. I'd let the battery sit overnight and
see if it was still over 11.5. Why fool with a battery if a cell is shorted?

If the voltage was good, I'd use the multimeter to check the charging
current. If it really charges a good battery at 7 amps on the 2 amp
setting, that would explain why someone gave it away. I'd check the
charging voltage because the charger could damage batteries if it's too
high.

Roy wrote:
On Friday, May 1, 2015 at 12:03:37 PM UTC-6, micky wrote:
Someone gave me an old car battery charger.

6 volts 10A and
12 volts 2A and 10A, determined by a slide switch.

A friend brings over a dead 12v battery.

On the charger, on 10A, it charges at 9amps.
On 2A, it charges at 7 amps.

Based on the meter on the charger.

What does it mean to be a 2 amp charger if it charges at 7 amps?


After an hour the charging rate dropped to 6 amps on the 10A setting,
and then it was 5 amps on the 2A setting.

Sounds like the battery has had it or if you leave on the 10 amp setting
for 24 hours and it comes down more it might be salvageable...(might).
It could be borderline. Is there water in all the cells? One dry cell
is not good. Top them up with distilled water and see what happens.
I've had successes and lots of failures. The longer they stay dead before
charging then the odds are against you.
====

Meter should have two scales, one for 6V and one for 12V. No?

"Tony Hwang" wrote in message
...
..
====

Meter should have two scales, one for 6V and one for 12V. No?

It may have two scales, but I would not think for the 6/12 volt but more for
the 10 and 2 amps.

On 05/01/2015 04:35 PM, Ralph Mowery wrote:
"Tony Hwang" wrote in message
...
.
====

Meter should have two scales, one for 6V and one for 12V. No?

It may have two scales, but I would not think for the 6/12 volt but more for
the 10 and 2 amps.






Correct logic.


Also: For the sake of economy I doubt the mfg would have two scales.


More than likely it's a cheap, non-regulated charger. On an
over-discharged battery, I'd believe the initial output on the 2amp
setting might be high.

If it does not eventually taper down. the battery indeed could have a
shorted cell.


Easy enough to check:

After the charger has run a while...
turn it off and let any surface charge dissipate.

If the battery voltage is about 10.5 no need to go further...dead cell


One could investigate further by putting on safety glass, removing the
caps and seeing if perhaps the electrolyte in one of the cells is all black.

Roy wrote:
On Friday, May 1, 2015 at 12:03:37 PM UTC-6, micky wrote:
Someone gave me an old car battery charger.

6 volts 10A and
12 volts 2A and 10A, determined by a slide switch.

A friend brings over a dead 12v battery.

On the charger, on 10A, it charges at 9amps.
On 2A, it charges at 7 amps.

Based on the meter on the charger.

What does it mean to be a 2 amp charger if it charges at 7 amps?


After an hour the charging rate dropped to 6 amps on the 10A setting,
and then it was 5 amps on the 2A setting.

Sounds like the battery has had it or if you leave on the 10 amp setting
for 24 hours and it comes down more it might be salvageable...(might).
It could be borderline. Is there water in all the cells? One dry cell
is not good. Top them up with distilled water and see what happens.
I've had successes and lots of failures. The longer they stay dead before
charging then the odds are against you.
====

Could be one shorted cell throwing off current reading.
I always use hydrometer when checking battery.

On Friday, May 1, 2015 at 2:03:37 PM UTC-4, micky wrote:
Someone gave me an old car battery charger.

6 volts 10A and
12 volts 2A and 10A, determined by a slide switch.

A friend brings over a dead 12v battery.

On the charger, on 10A, it charges at 9amps.
On 2A, it charges at 7 amps.

Based on the meter on the charger.

What does it mean to be a 2 amp charger if it charges at 7 amps?



It means the battery is very low on charge. IDK exactly how
they come up with those ratings, but I would suspect that it's
rated at putting out 2A at a particular charging voltage. If
the battery is very low, or bad, it will present a bigger load,
the charging voltage will be lower, and the current higher. I
see that on my old Sears charger all the time. If it's on 2 or
10A, on either, if the battery is very low, it will initially
charge at a much higher current. After 5 or 10 mins, it starts
dropping down as the battery charges.




After an hour the charging rate dropped to 6 amps on the 10A setting,
and then it was 5 amps on the 2A setting.

On Sat, 2 May 2015 04:50:54 -0700 (PDT), trader_4
wrote:

On Friday, May 1, 2015 at 2:03:37 PM UTC-4, micky wrote:
Someone gave me an old car battery charger.

6 volts 10A and
12 volts 2A and 10A, determined by a slide switch.

A friend brings over a dead 12v battery.

On the charger, on 10A, it charges at 9amps.
On 2A, it charges at 7 amps.

Based on the meter on the charger.

What does it mean to be a 2 amp charger if it charges at 7 amps?



It means the battery is very low on charge. IDK exactly how
they come up with those ratings, but I would suspect that it's
rated at putting out 2A at a particular charging voltage. If

If you're having the same thing, Trader, there's no point in my pursuing
the question anymore. And I'll figure the charger is good enough.

the battery is very low, or bad, it will present a bigger load,
the charging voltage will be lower, and the current higher. I
see that on my old Sears charger all the time. If it's on 2 or
10A, on either, if the battery is very low, it will initially
charge at a much higher current. After 5 or 10 mins, it starts
dropping down as the battery charges.

To everyone, yes the battery was very much discharged. I knew that.
The hydrometer shoed 4 cells in the red (semi-cheap hydrometer, no
number assigned to red) and the other 2 very close to the red.
However the battery's voltage was above 12.6 anyhow. (well maybe I
didn't wait until the "surface charge" dissipated, like Philo said to
do. But then the owner came and took the battery away. He has a
charger he thought wasn't working. This is for the truck he rarely
drivesl, but I guess he wanted to drive it the day he got the battery.)

Thanks, and thanks all.


After an hour the charging rate dropped to 6 amps on the 10A setting,
and then it was 5 amps on the 2A setting.

On 5/2/15 3:57 PM, micky wrote:
To everyone, yes the battery was very much discharged. I knew that.
The hydrometer shoed 4 cells in the red (semi-cheap hydrometer, no
number assigned to red) and the other 2 very close to the red.
However the battery's voltage was above 12.6 anyhow. (well maybe I
didn't wait until the "surface charge" dissipated, like Philo said to
do. But then the owner came and took the battery away. He has a
charger he thought wasn't working. This is for the truck he rarely
drivesl, but I guess he wanted to drive it the day he got the battery.)

I quit fooling with hydrometers decades ago. In some batteries, it's
hard to get to the electrolyte. Gas bubbles, as in a glass of ginger
ale, will cause false readings.

Before charging, voltage should tell you the state of charge and if all
cells are working. Headlights will show how the battery handles a load
of a few amps. It's also a way to check the state of charge if a
battery has recently been on a charger. Turn the lights on 15 seconds,
then off.

In my experience, a deeply discharged battery charges slowly at first
because the electrolyte is weak.

Most DMMs will measure 10A DC. That's a way to check the gauge on the
charger.

On Sat, 02 May 2015 17:53:34 -0400, J Burns wrote:

On 5/2/15 3:57 PM, micky wrote:
To everyone, yes the battery was very much discharged. I knew that.
The hydrometer shoed 4 cells in the red (semi-cheap hydrometer, no
number assigned to red) and the other 2 very close to the red.
However the battery's voltage was above 12.6 anyhow. (well maybe I
didn't wait until the "surface charge" dissipated, like Philo said to
do. But then the owner came and took the battery away. He has a
charger he thought wasn't working. This is for the truck he rarely
drivesl, but I guess he wanted to drive it the day he got the battery.)

I quit fooling with hydrometers decades ago. In some batteries, it's
hard to get to the electrolyte. Gas bubbles, as in a glass of ginger
ale, will cause false readings.

I didn't have those problems with this battery.

Before charging, voltage should tell you the state of charge and if all
cells are working.

??

Headlights will show how the battery handles a load
of a few amps.

It was already out of the car.

It's also a way to check the state of charge if a
battery has recently been on a charger. Turn the lights on 15 seconds,
then off.

Again, out of the car.

In my experience, a deeply discharged battery charges slowly at first
because the electrolyte is weak.

Most DMMs will measure 10A DC. That's a way to check the gauge on the
charger.

Thanks.

On Fri, 01 May 2015 14:03:34 -0400, micky
wrote:

Someone gave me an old car battery charger.

6 volts 10A and
12 volts 2A and 10A, determined by a slide switch.

A friend brings over a dead 12v battery.

On the charger, on 10A, it charges at 9amps.
On 2A, it charges at 7 amps.

Based on the meter on the charger.

What does it mean to be a 2 amp charger if it charges at 7 amps?


After an hour the charging rate dropped to 6 amps on the 10A setting,
and then it was 5 amps on the 2A setting.


Every charger I've had has been like that. Unless you want to pay
bigger bucks for a charger with true constant current regulation I
think what you have is all you can expect.

On 5/2/15 7:19 PM, micky wrote:
On Sat, 02 May 2015 17:53:34 -0400, J Burns wrote:

On 5/2/15 3:57 PM, micky wrote:
To everyone, yes the battery was very much discharged. I knew that.
The hydrometer shoed 4 cells in the red (semi-cheap hydrometer, no
number assigned to red) and the other 2 very close to the red.
However the battery's voltage was above 12.6 anyhow. (well maybe I
didn't wait until the "surface charge" dissipated, like Philo said to
do. But then the owner came and took the battery away. He has a
charger he thought wasn't working. This is for the truck he rarely
drivesl, but I guess he wanted to drive it the day he got the battery.)

I quit fooling with hydrometers decades ago. In some batteries, it's
hard to get to the electrolyte. Gas bubbles, as in a glass of ginger
ale, will cause false readings.

I didn't have those problems with this battery.

How do you know the red readings were correct? You said it was a dead
battery. I would have expected a dead battery to draw more current after
an hour, not less.

I remember another thing that can throw a hydrometer off. Sulfuric acid
settles when a battery sits; that's why turning the lights on for a few
seconds can improve starting power. If a battery has been sitting a long
time, the hydrometer may sample the watery stuff at the top.

I know a situation where a hygrometer can be useful. After you charge a
battery and give any tiny bubbles time to clear out, a hydrometer can
tell you the condition of each cell.

Before charging, voltage should tell you the state of charge and if all
cells are working.

??

The exact voltage depends on the temperature and the kind of battery.
At 60 F, a normal car battery should show 12.63V at 100%, 12.43 at 75%,
12.22 at 50%, 12.04 at 25%, and 11.87 discharged. A lower reading would
show one or more shorted cells. (I use a lithium coin cell to calibrate
my meters. There are better voltage standards, but I don't have one now.)

Headlights will show how the battery handles a load
of a few amps.

It was already out of the car.

It's also a way to check the state of charge if a
battery has recently been on a charger. Turn the lights on 15 seconds,
then off.

Again, out of the car.

Another load could be clipped to the battery. In my case, I would have
disconnected the ground from the battery in my car and used jumpers to
connect the test battery to the car.

On 5/1/2015 11:03 AM, micky wrote:
Someone gave me an old car battery charger.

6 volts 10A and
12 volts 2A and 10A, determined by a slide switch.

A friend brings over a dead 12v battery.

On the charger, on 10A, it charges at 9amps.
On 2A, it charges at 7 amps.

Based on the meter on the charger.

What does it mean to be a 2 amp charger if it charges at 7 amps?


After an hour the charging rate dropped to 6 amps on the 10A setting,
and then it was 5 amps on the 2A setting.


I have similar 2A/10A charger and on mine the meter does not have two
different scales for 2A and 10A.

On mine, if it's set for 10A it charges more quickly but it also shuts
down the charging earlier. At the 10A rate the green LED indicating
fully charged turns on but if I then switch it to 2A it charges some more.

As to voltage, a fully charged lead acid battery, with no load, will be
2.3V per cell x 6 cells = 13.8V. Once it's under load, it's 2.1V/cell or
12.6V. If you have a shorted cell (or more than one shorted cell) it's
easy to check because under noload the voltage will be lowered by the
number of shorted cells x 2.3V.

An alternator/rectifier/voltage regulator, or battery charger, needs to
put out 14.4-14.8V to properly charge a car battery. While people call
car batteries "12 volts," they are not 12 volts except under load where
they are between 12V and 12.6V.

An article entitled is "Car Batteries Are Not 12 Volts" is available at
http://www.landiss.com/battery.htm.

On 5/3/15 3:45 AM, sms wrote:

As to voltage, a fully charged lead acid battery, with no load, will be
2.3V per cell x 6 cells = 13.8V. Once it's under load, it's 2.1V/cell or
12.6V. If you have a shorted cell (or more than one shorted cell) it's
easy to check because under noload the voltage will be lowered by the
number of shorted cells x 2.3V.

An alternator/rectifier/voltage regulator, or battery charger, needs to
put out 14.4-14.8V to properly charge a car battery. While people call
car batteries "12 volts," they are not 12 volts except under load where
they are between 12V and 12.6V.

An article entitled is "Car Batteries Are Not 12 Volts" is available at
http://www.landiss.com/battery.htm.


A battery that has just been on a charger or come in from driving may
well read 13.8 volts, but it will settle down over a period of hours. A
brief load helps it settle faster.

The article points out that it's hard to know the best voltage for an
automobile regulator. They all seem to be temperature compensated these
days, providing more voltage for a cooler battery. That helps.

A battery used for for a couple of 10-minute drives a day would probably
last longer with more charging voltage. A battery on the interstate 10
hours a day would probably last longer with less voltage. How can a car
manufacturer predict your driving habits?

I once owned a charger with a switch for conventional or
maintenance-free batteries. The maintenance-free does better with more
charging voltage.

On Sun, 03 May 2015 00:45:45 -0700, sms
wrote:

On 5/1/2015 11:03 AM, micky wrote:
Someone gave me an old car battery charger.

6 volts 10A and
12 volts 2A and 10A, determined by a slide switch.

A friend brings over a dead 12v battery.

On the charger, on 10A, it charges at 9amps.
On 2A, it charges at 7 amps.

Based on the meter on the charger.

What does it mean to be a 2 amp charger if it charges at 7 amps?


After an hour the charging rate dropped to 6 amps on the 10A setting,
and then it was 5 amps on the 2A setting.


I have similar 2A/10A charger and on mine the meter does not have two
different scales for 2A and 10A.

On mine, if it's set for 10A it charges more quickly but it also shuts
down the charging earlier. At the 10A rate the green LED indicating
fully charged turns on but if I then switch it to 2A it charges some more.

As to voltage, a fully charged lead acid battery, with no load, will be
2.3V per cell x 6 cells = 13.8V. Once it's under load, it's 2.1V/cell or
12.6V. If you have a shorted cell (or more than one shorted cell) it's
easy to check because under noload the voltage will be lowered by the
number of shorted cells x 2.3V.

An alternator/rectifier/voltage regulator, or battery charger, needs to
put out 14.4-14.8V to properly charge a car battery. While people call
car batteries "12 volts," they are not 12 volts except under load where
they are between 12V and 12.6V.

An article entitled is "Car Batteries Are Not 12 Volts" is available at
http://www.landiss.com/battery.htm.



In the aircraft world they are referred to as a 14 volt system, with
12 cell battery systems referred to as 28 volt.

As for the chargers - a "decent"charger limits the charge current as
well as the voltage, so a 2 amp charger will not put out over 2 amps
into the battery for trickle charging and will limit the voltage to
14.4 so it will never boil a battery dry.. Most chargers out there
fall short of "decent" but there are more and more "microprocessor
controlled" 3 stage chargers on the market for approaching an
affordable price.

Some will test the battery for shorted cells, indicate the failure,
and refuse to charge a defective battery.

On Saturday, May 2, 2015 at 8:51:52 PM UTC-4, J Burns wrote:
On 5/2/15 7:19 PM, micky wrote:
On Sat, 02 May 2015 17:53:34 -0400, J Burns wrote:

On 5/2/15 3:57 PM, micky wrote:
To everyone, yes the battery was very much discharged. I knew that.
The hydrometer shoed 4 cells in the red (semi-cheap hydrometer, no
number assigned to red) and the other 2 very close to the red.
However the battery's voltage was above 12.6 anyhow. (well maybe I
didn't wait until the "surface charge" dissipated, like Philo said to
do. But then the owner came and took the battery away. He has a
charger he thought wasn't working. This is for the truck he rarely
drivesl, but I guess he wanted to drive it the day he got the battery.)

I quit fooling with hydrometers decades ago. In some batteries, it's
hard to get to the electrolyte. Gas bubbles, as in a glass of ginger
ale, will cause false readings.

I didn't have those problems with this battery.

How do you know the red readings were correct? You said it was a dead
battery. I would have expected a dead battery to draw more current after
an hour, not less.


I've heard that totally dead batteries may draw less current.
But every auto battery I've even tried to charge, the current
is initially higher, then starts coming down in 5 or 10 mins.
The more drained it was, the higher the current it pulled from
the charger. But then I haven't had one that was like connected
to a load to totally drain it down to absolute zero.

On Sunday, May 3, 2015 at 4:44:08 AM UTC-4, J Burns wrote:
On 5/3/15 3:45 AM, sms wrote:

As to voltage, a fully charged lead acid battery, with no load, will be
2.3V per cell x 6 cells = 13.8V. Once it's under load, it's 2.1V/cell or
12.6V. If you have a shorted cell (or more than one shorted cell) it's
easy to check because under noload the voltage will be lowered by the
number of shorted cells x 2.3V.

An alternator/rectifier/voltage regulator, or battery charger, needs to
put out 14.4-14.8V to properly charge a car battery. While people call
car batteries "12 volts," they are not 12 volts except under load where
they are between 12V and 12.6V.

An article entitled is "Car Batteries Are Not 12 Volts" is available at
http://www.landiss.com/battery.htm.


A battery that has just been on a charger or come in from driving may
well read 13.8 volts, but it will settle down over a period of hours. A
brief load helps it settle faster.


Exactly. A fully charged batter is around the 12.6V that you state.
When it's being charged or right after it's been charged, then it will
be temporarily higher, but that higher level is temporary and not
necessary for it to be fully charged. To bleed off that excess, you can
just put on the headlights for a minute, then measure the voltage.


The article points out that it's hard to know the best voltage for an
automobile regulator. They all seem to be temperature compensated these
days, providing more voltage for a cooler battery. That helps.

A battery used for for a couple of 10-minute drives a day would probably
last longer with more charging voltage. A battery on the interstate 10
hours a day would probably last longer with less voltage. How can a car
manufacturer predict your driving habits?

I once owned a charger with a switch for conventional or
maintenance-free batteries. The maintenance-free does better with more
charging voltage.

BMW has a solution. Their new cars now have some sophisticated
charging/monitoring system that closely controls the battery. A
real nice feature of this for the consumer is that if you replace
the battery, you have to go to the dealer to have the new battery
registered into the car computer. I'm sure this is really about
making those batteries work better and not making money for the
stealerships, by leading you to them to buy their batteries, right?

On 5/3/15 9:39 AM, trader_4 wrote:
On Saturday, May 2, 2015 at 8:51:52 PM UTC-4, J Burns wrote:
On 5/2/15 7:19 PM, micky wrote:
On Sat, 02 May 2015 17:53:34 -0400, J Burns wrote:

On 5/2/15 3:57 PM, micky wrote:
To everyone, yes the battery was very much discharged. I knew that.
The hydrometer shoed 4 cells in the red (semi-cheap hydrometer, no
number assigned to red) and the other 2 very close to the red.
However the battery's voltage was above 12.6 anyhow. (well maybe I
didn't wait until the "surface charge" dissipated, like Philo said to
do. But then the owner came and took the battery away. He has a
charger he thought wasn't working. This is for the truck he rarely
drivesl, but I guess he wanted to drive it the day he got the battery.)

I quit fooling with hydrometers decades ago. In some batteries, it's
hard to get to the electrolyte. Gas bubbles, as in a glass of ginger
ale, will cause false readings.

I didn't have those problems with this battery.

How do you know the red readings were correct? You said it was a dead
battery. I would have expected a dead battery to draw more current after
an hour, not less.


I've heard that totally dead batteries may draw less current.
But every auto battery I've even tried to charge, the current
is initially higher, then starts coming down in 5 or 10 mins.
The more drained it was, the higher the current it pulled from
the charger. But then I haven't had one that was like connected
to a load to totally drain it down to absolute zero.


If the lights will glow but the engine won't turn over, I'd expect the
charge to start slow. If a motorcycle or riding mower had been left in a
shed for months, I'd expect the charge to start slow. In that case,
stratification of the electrolyte might be part of the problem.

I like the AGM battery I put in my mower. It stays perky over the
winter because the electrolyte doesn't stratify and self-discharge is
very low.

On 5/3/15 9:51 AM, trader_4 wrote:
BMW has a solution. Their new cars now have some sophisticated
charging/monitoring system that closely controls the battery. A
real nice feature of this for the consumer is that if you replace
the battery, you have to go to the dealer to have the new battery
registered into the car computer. I'm sure this is really about
making those batteries work better and not making money for the
stealerships, by leading you to them to buy their batteries, right?

I like that! I haven't even been able to find out if my Walmart battery
is low-maintenance or maintenance-free. The cell caps can be removed,
but that doesn't prove it's not maintenance-free.

I'm very curious about the specifics because after charging, it may take
48 hours to come down to a "proper" voltage.

On 5/3/15 9:06 AM, wrote:
In the aircraft world they are referred to as a 14 volt system, with
12 cell battery systems referred to as 28 volt.

I imagine that's because automobile systems were developed to power a
starter from a battery, and, in the days of generators, you could be
down to 12 volts on the road.

Aircraft electrical systems were designed primarily to power equipment
aloft, without much variation in engine speed.

On Sat, 02 May 2015 20:51:48 -0400, J Burns wrote:

On 5/2/15 7:19 PM, micky wrote:
On Sat, 02 May 2015 17:53:34 -0400, J Burns wrote:

On 5/2/15 3:57 PM, micky wrote:
To everyone, yes the battery was very much discharged. I knew that.
The hydrometer shoed 4 cells in the red (semi-cheap hydrometer, no
number assigned to red) and the other 2 very close to the red.
However the battery's voltage was above 12.6 anyhow. (well maybe I
didn't wait until the "surface charge" dissipated, like Philo said to
do. But then the owner came and took the battery away. He has a
charger he thought wasn't working. This is for the truck he rarely
drivesl, but I guess he wanted to drive it the day he got the battery.)

I quit fooling with hydrometers decades ago. In some batteries, it's
hard to get to the electrolyte. Gas bubbles, as in a glass of ginger
ale, will cause false readings.

I didn't have those problems with this battery.

Actually, with any battery I've tested. I've never had a problem sucking
up enough electrolyte or having bubbles get in the way. The floating
part of the hydrometer has a semi-spherical bottom, and if there were
bubbles, they would go right past the floating part and up to the
surface of the electrolyte.

How do you know the red readings were correct?

How could they not be? There was nothing adhering to the floating
part. What else could cause a bad reading?

You said it was a dead
battery. I would have expected a dead battery to draw more current after
an hour, not less.

I remember another thing that can throw a hydrometer off. Sulfuric acid
settles when a battery sits; that's why turning the lights on for a few
seconds can improve starting power. If a battery has been sitting a long
time, the hydrometer may sample the watery stuff at the top.

I know a situation where a hygrometer can be useful. After you charge a
battery and give any tiny bubbles time to clear out, a hydrometer can
tell you the condition of each cell.

How?. What hygrometer changes its reading so quickly it can
distinguish one cell from another? And why would the condition of
the cell aftect the humidity above the cell?

Before charging, voltage should tell you the state of charge and if all
cells are working.

??

The exact voltage depends on the temperature and the kind of battery.
At 60 F, a normal car battery should show 12.63V at 100%, 12.43 at 75%,
12.22 at 50%, 12.04 at 25%, and 11.87 discharged. A lower reading would
show one or more shorted cells.

I'm dubious, but it doesn't matter this time. He had hoped to take the
battery with him so I started charging right away.

(I use a lithium coin cell to calibrate
my meters. There are better voltage standards, but I don't have one now.)

Headlights will show how the battery handles a load
of a few amps.

It was already out of the car.

It's also a way to check the state of charge if a
battery has recently been on a charger. Turn the lights on 15 seconds,
then off.

Again, out of the car.

Another load could be clipped to the battery.

Do i have another load, other than his car or my car, which I don't want
to bother? A lot of things could have done. My question was "What does
it mean to be a 2 amp charger if it charges at 7 amps? " I don't see
how any of this would have helped to answer that question.

In my case, I would have
disconnected the ground from the battery in my car and used jumpers to
connect the test battery to the car.

But you were not here. Thanks anyhow.

On Sun, 03 May 2015 00:45:45 -0700, sms
wrote:

On 5/1/2015 11:03 AM, micky wrote:
Someone gave me an old car battery charger.

6 volts 10A and
12 volts 2A and 10A, determined by a slide switch.

A friend brings over a dead 12v battery.

On the charger, on 10A, it charges at 9amps.
On 2A, it charges at 7 amps.

Based on the meter on the charger.

What does it mean to be a 2 amp charger if it charges at 7 amps?


After an hour the charging rate dropped to 6 amps on the 10A setting,
and then it was 5 amps on the 2A setting.


I have similar 2A/10A charger and on mine the meter does not have two
different scales for 2A and 10A.

Neither does mine. Two of you seem to have gotten the impression that
my ammeter had two scales, but I don't know where you got that
impression.

On mine, if it's set for 10A it charges more quickly but it also shuts
down the charging earlier. At the 10A rate the green LED indicating
fully charged turns on but if I then switch it to 2A it charges some more.

As to voltage, a fully charged lead acid battery, with no load, will be
2.3V per cell x 6 cells = 13.8V. Once it's under load, it's 2.1V/cell or
12.6V. If you have a shorted cell (or more than one shorted cell) it's
easy to check because under noload the voltage will be lowered by the
number of shorted cells x 2.3V.

An alternator/rectifier/voltage regulator, or battery charger, needs to
put out 14.4-14.8V to properly charge a car battery. While people call
car batteries "12 volts," they are not 12 volts except under load where
they are between 12V and 12.6V.

An article entitled is "Car Batteries Are Not 12 Volts" is available at
http://www.landiss.com/battery.htm.

Thanks for the info.

On Sun, 03 May 2015 15:03:13 -0400, J Burns
wrote:

On 5/3/15 9:51 AM, trader_4 wrote:
BMW has a solution. Their new cars now have some sophisticated
charging/monitoring system that closely controls the battery. A
real nice feature of this for the consumer is that if you replace
the battery, you have to go to the dealer to have the new battery
registered into the car computer. I'm sure this is really about
making those batteries work better and not making money for the
stealerships, by leading you to them to buy their batteries, right?

I like that! I haven't even been able to find out if my Walmart battery
is low-maintenance or maintenance-free. The cell caps can be removed,
but that doesn't prove it's not maintenance-free.

The only "maintenance free" battery is one you cannot maintain. If you
can remove the caps it is possible to maintain the battery - so it
will be a "low maintenance" battery by definition.

I'm very curious about the specifics because after charging, it may take
48 hours to come down to a "proper" voltage.
It's called a "surface charge". After charging a battery to a full
charge, the voltage will often be higher than the "chemically
dependent" charge - the voltage predicted by the chemical reaction -
but with a light load the "surface charge " will dissappear and the
true battery voltage will be evident.

The true voltage will vary depending on the acid strength used in the
battery - batteried for cold climates generally start with a higher SG
than batteries for a warm climate because to reduce self discharge in
hot climates they start out with a lower SG. This means the battery
sold for use in the Kalahari desert will have a lower voltage than a
battery sold for use in Ottawa, Ankorage, or Nunavit

On Sun, 03 May 2015 15:15:00 -0400, J Burns
wrote:

On 5/3/15 9:06 AM, wrote:
In the aircraft world they are referred to as a 14 volt system, with
12 cell battery systems referred to as 28 volt.

I imagine that's because automobile systems were developed to power a
starter from a battery, and, in the days of generators, you could be
down to 12 volts on the road.

Aircraft electrical systems were designed primarily to power equipment
aloft, without much variation in engine speed.
And the avionics need to be designed to function optimally at the
prevailing operating voltage. Something designed with a 12 volt
maximum voltage wouldn't last long at 14 - and in the aircraft world
they are nothing if not precise when it comes to specs.

Automobile owners, if told their system was a 14 volt system, would be
all bent out of shape to find the resting state voltage to be only
12.6.

On 5/3/15 3:42 PM, micky wrote:
On Sat, 02 May 2015 20:51:48 -0400, J Burns wrote:



You said it was a dead
battery. I would have expected a dead battery to draw more current after
an hour, not less.

I remember another thing that can throw a hydrometer off. Sulfuric acid
settles when a battery sits; that's why turning the lights on for a few
seconds can improve starting power. If a battery has been sitting a long
time, the hydrometer may sample the watery stuff at the top.

I know a situation where a hygrometer can be useful. After you charge a
battery and give any tiny bubbles time to clear out, a hydrometer can
tell you the condition of each cell.

How?. What hygrometer changes its reading so quickly it can
distinguish one cell from another? And why would the condition of
the cell aftect the humidity above the cell?


I must have used the wrong word. What's the one that measures humility?
Until 1959, the best batteries were at Humble service stations. A
battery that's all puffed up could explode.


Do i have another load, other than his car or my car, which I don't want
to bother? A lot of things could have done. My question was "What does
it mean to be a 2 amp charger if it charges at 7 amps? " I don't see
how any of this would have helped to answer that question.

You said the battery was dead. If a 2-amp charger was charging at 7
amps, one possibility was that the battery was dead because of shorted
cells. A DMM would have told you. it would also have told you if it was
really charging at 7 amps.

On Sun, 03 May 2015 16:51:48 -0400, J Burns wrote:

On 5/3/15 3:42 PM, micky wrote:
On Sat, 02 May 2015 20:51:48 -0400, J Burns wrote:



You said it was a dead
battery. I would have expected a dead battery to draw more current after
an hour, not less.

I remember another thing that can throw a hydrometer off. Sulfuric acid
settles when a battery sits; that's why turning the lights on for a few
seconds can improve starting power. If a battery has been sitting a long
time, the hydrometer may sample the watery stuff at the top.

I know a situation where a hygrometer can be useful. After you charge a
battery and give any tiny bubbles time to clear out, a hydrometer can
tell you the condition of each cell.

How?. What hygrometer changes its reading so quickly it can
distinguish one cell from another? And why would the condition of
the cell aftect the humidity above the cell?


I must have used the wrong word. What's the one that measures humility?

That's what we need, a humility meter. Really. I can think of lots
of uses.

Until 1959, the best batteries were at Humble service stations. A
battery that's all puffed up could explode.


Do i have another load, other than his car or my car, which I don't want
to bother? A lot of things could have done. My question was "What does
it mean to be a 2 amp charger if it charges at 7 amps? " I don't see
how any of this would have helped to answer that question.

You said the battery was dead. If a 2-amp charger was charging at 7
amps, one possibility was that the battery was dead because of shorted
cells. A DMM would have told you. it would also have told you if it was
really charging at 7 amps.

But I never had any doubt that 7 amps, or between 6 and 8 amps, were
going into it. A lot more than 2 amps. I could that tell just by the
high number of hydrogen bubbles surfacing in each cell.

When I use the thing again, I'll check the voltages at the 2 and 10 amp
settings.

On 5/3/15 4:45 PM, wrote:
On Sun, 03 May 2015 15:03:13 -0400, J Burns
wrote:

On 5/3/15 9:51 AM, trader_4 wrote:
BMW has a solution. Their new cars now have some sophisticated
charging/monitoring system that closely controls the battery. A
real nice feature of this for the consumer is that if you replace
the battery, you have to go to the dealer to have the new battery
registered into the car computer. I'm sure this is really about
making those batteries work better and not making money for the
stealerships, by leading you to them to buy their batteries, right?

I like that! I haven't even been able to find out if my Walmart battery
is low-maintenance or maintenance-free. The cell caps can be removed,
but that doesn't prove it's not maintenance-free.

The only "maintenance free" battery is one you cannot maintain. If you
can remove the caps it is possible to maintain the battery - so it
will be a "low maintenance" battery by definition.

Lately I've read that maintenance-free means a calcium alloy on both
plates, and the cells may be accessible, maybe to check specific gravity.

I'm very curious about the specifics because after charging, it may take
48 hours to come down to a "proper" voltage.
It's called a "surface charge". After charging a battery to a full
charge, the voltage will often be higher than the "chemically
dependent" charge - the voltage predicted by the chemical reaction -
but with a light load the "surface charge " will dissappear and the
true battery voltage will be evident.

I've read 4 hours or maybe 8. My battery will hold its "surface charge"
a lot longer. An AGM will do that, but mine's not AGM.

The true voltage will vary depending on the acid strength used in the
battery - batteried for cold climates generally start with a higher SG
than batteries for a warm climate because to reduce self discharge in
hot climates they start out with a lower SG. This means the battery
sold for use in the Kalahari desert will have a lower voltage than a
battery sold for use in Ottawa, Ankorage, or Nunavit

I read about that in an Exide manual given to me in the 1970s. It didn't
say how much the voltage or SG might vary.

On 5/3/15 5:13 PM, micky wrote:
On Sun, 03 May 2015 16:51:48 -0400, J Burns wrote:


But I never had any doubt that 7 amps, or between 6 and 8 amps, were
going into it. A lot more than 2 amps. I could that tell just by the
high number of hydrogen bubbles surfacing in each cell.

When I use the thing again, I'll check the voltages at the 2 and 10 amp
settings.

I'm interested, and dadburnit, you've talked me into buying a hydrometer
to hang beside my hygrometer.

Wikipedia says stratification happens in normal use if you don't fully
charge a battery. The bottoms of plates sulfate and the tops corrode. I
want to check that with a hydrometer. Watch me drip acid on my pants!

There's a curb in front of my house. Maybe I should make a habit of
driving over it to keep my battery stirred up. I won't know until I buy
a hydrometer... unless of course I could borrow one...

In J Burns writes:

Wikipedia says stratification happens in normal use if you don't fully
charge a battery. The bottoms of plates sulfate and the tops corrode. I
want to check that with a hydrometer. Watch me drip acid on my pants!

There used to be a poster in one of the energy Usenet groups
who had worked aboard submarines, which have _big_ batteries.

He'd describe how they actually had small pumps in the batteries
to keep the solutions in motion to minimize stratification.

(I have absolutely no idea if subs still use lead acid
batteries these days)

--
__________________________________________________ ___
Knowledge may be power, but communications is the key

[to foil spammers, my address has been double rot-13 encoded]

On Sun, 03 May 2015 17:15:26 -0400, J Burns
wrote:

On 5/3/15 4:45 PM, wrote:
On Sun, 03 May 2015 15:03:13 -0400, J Burns
wrote:

On 5/3/15 9:51 AM, trader_4 wrote:
BMW has a solution. Their new cars now have some sophisticated
charging/monitoring system that closely controls the battery. A
real nice feature of this for the consumer is that if you replace
the battery, you have to go to the dealer to have the new battery
registered into the car computer. I'm sure this is really about
making those batteries work better and not making money for the
stealerships, by leading you to them to buy their batteries, right?

I like that! I haven't even been able to find out if my Walmart battery
is low-maintenance or maintenance-free. The cell caps can be removed,
but that doesn't prove it's not maintenance-free.

The only "maintenance free" battery is one you cannot maintain. If you
can remove the caps it is possible to maintain the battery - so it
will be a "low maintenance" battery by definition.

Lately I've read that maintenance-free means a calcium alloy on both
plates, and the cells may be accessible, maybe to check specific gravity.

I'm very curious about the specifics because after charging, it may take
48 hours to come down to a "proper" voltage.
It's called a "surface charge". After charging a battery to a full
charge, the voltage will often be higher than the "chemically
dependent" charge - the voltage predicted by the chemical reaction -
but with a light load the "surface charge " will dissappear and the
true battery voltage will be evident.

I've read 4 hours or maybe 8. My battery will hold its "surface charge"
a lot longer. An AGM will do that, but mine's not AGM.

The true voltage will vary depending on the acid strength used in the
battery - batteried for cold climates generally start with a higher SG
than batteries for a warm climate because to reduce self discharge in
hot climates they start out with a lower SG. This means the battery
sold for use in the Kalahari desert will have a lower voltage than a
battery sold for use in Ottawa, Ankorage, or Nunavit

I read about that in an Exide manual given to me in the 1970s. It didn't
say how much the voltage or SG might vary.
Normal battery SG for up to 25C is 1280.
1240 is common for tropical use.
1290 to 1300 works best for arctic use.

trader_4 posted for all of us...


BMW has a solution. Their new cars now have some sophisticated
charging/monitoring system that closely controls the battery. A
real nice feature of this for the consumer is that if you replace
the battery, you have to go to the dealer to have the new battery
registered into the car computer. I'm sure this is really about
making those batteries work better and not making money for the
stealerships, by leading you to them to buy their batteries, right?



Many car makers have this now. There is an article in "QST" magazine about
them and electrically installing ham radios properly. It's not just
connecting a wire to the positive... Both positive and negative sides must
be fused. I wonder how many alarm / radio shops know this?


--
Tekkie *Please post a follow-up*

On 5/3/15 5:58 PM, wrote:
On Sun, 03 May 2015 17:15:26 -0400, J Burns
wrote:


I've read 4 hours or maybe 8. My battery will hold its "surface charge"
a lot longer. An AGM will do that, but mine's not AGM.

The true voltage will vary depending on the acid strength used in the
battery - batteried for cold climates generally start with a higher SG
than batteries for a warm climate because to reduce self discharge in
hot climates they start out with a lower SG. This means the battery
sold for use in the Kalahari desert will have a lower voltage than a
battery sold for use in Ottawa, Ankorage, or Nunavit

I read about that in an Exide manual given to me in the 1970s. It didn't
say how much the voltage or SG might vary.
Normal battery SG for up to 25C is 1280.
1240 is common for tropical use.
1290 to 1300 works best for arctic use.

Thanks. I have a spreadsheet from batteryfaq.org. It's in fahrenheit.

80F is close to 25C. It says the SG at 80F for sb/sb or sb/ca (low
maintenance) is 1.265. I wonder how widely their figure applies.

One article about stratification says the watery mix at the top causes
corrosion and the concentrated mix at the bottom causes sulphation.
Another article says it's the other way around. It sounds as if a
certain SG is a happy medium between corrosion and sulphation. I wonder
if it varies with temperature. I wonder if it varies with plate composition.

If batteries were really, really simple, maybe some day I could understand!

I've read that the way to tell if a battery is really charged is to see
when the SG stops rising. As it's sampled at the top, that means it's
fully mixed.

Darn, I'm going to end up dripping acid on my pants!