It's not an automatic power cut. It's an automatic charge cut. The battery of an electric car has a memory function under normal circumstances. When the battery is fully charged, the battery will start self-protection and automatically stop charging. But it doesn't power off. It stays on. It is best to unplug the charger immediately after the charge is full. Otherwise, the battery aging will be overcharged for a long time, and the battery will be damaged.
Mainly by detecting the charging current, at the beginning, when the charging current is large, the red light; When fully charged, the charging current becomes very small, then cut off the charging circuit, through the switch, then green light.