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[email protected] clare@snyder.on.ca is offline
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Default 10/2 amp battery charger

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.