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 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.

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.

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.

** Dead = what ?

10 years old with no voltage on the terminals.



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

Based on the meter on the charger.

** Not to be trusted, use another DC amp meter to check.

Car battery chargers often use "moving iron" meters cos they are rugged and cheap BUT they also over read the 100HZ/120Hz pulsed current by up to 100%.


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.

** Suspect a shorted cell in the battery.

Use your DMM to see that the voltages are on and off charge.


.... Phil

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.

"An alternator/rectifier/voltage regulator, or battery charger, needs to
put out 14.4-14.8V to properly charge a car battery."

I like to see 15.5 when cold.

Another thing to note is that some cars actually pull more current when running than when cranking. Surprised the hell out of me to find that out. It was a fairly decent engine but three coils and six fuel injectors would not run on this partly dead battery when the charging system failed. But it would crank. Damndest thing.

Huh, in the old days the radio was the biggest drain, with a vibrator and tubes and such.

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 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 15:15:00 -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.