The Sam's HID has a cutoff relay switch. When the charge is complete, the relay switches the charger off. When the battery voltage drops below a certain point, the relay switches the charger back on again.
This is also why it is important to not unplug the light until it is fully charged. If you use the light till the battery is nearly dead and are charging it and unplug it before the light is fully charged and then plug it back in and the full charge LED light goes on you may have only gotten it above the low voltage turn on threshold for the relay. Needless to say this is short of a full charge and will have less then full the full amount of run time.
Take Care,
mtbkndad :wave: