The red LED will start to light when the voltage across R2 is more than about 1.8 volts ( the value will depend on the type of LED fitted )
The voltage across R2 is set by the current flowing into the battery. A charging current that is more than 180 mA will cause the red LED to glow.
If the supply is exactly 16 volts then when the battery is fully charged the red LED would go out.
16 V-14.4 V = 1.6 V across R2 = 160 mA Voltage across the LED is 1.6 V and therefor too low for a 1.8 V LED to light.
A battery with a dead cell ( V battery less than 14 volts ) would keep the red LED light as long as the battery was in the charger.
The voltage across R2 is set by the current flowing into the battery. A charging current that is more than 180 mA will cause the red LED to glow.
If the supply is exactly 16 volts then when the battery is fully charged the red LED would go out.
16 V-14.4 V = 1.6 V across R2 = 160 mA Voltage across the LED is 1.6 V and therefor too low for a 1.8 V LED to light.
A battery with a dead cell ( V battery less than 14 volts ) would keep the red LED light as long as the battery was in the charger.