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