Battery charging connection keeps on even after disconnecting to power

Either there's a major internal problem (failed components, etc.) or there's dirt in the charging port.

Use a magnifying glass, a strong light and a pointed wooden toothpick. Look into the port and clean away any dirt, especially tiny little balls (they could be carbide particles that pollute the entire atmosphere of the planet). If the center bar of the port is leaning against one side of the port, VERY CARFULLY bend it to the center.