Charging control method and charging system capable of tracking maximum efficiency

A charging control method includes: converting an input power to a DC power; receiving the DC power by a detachable cable to generate a bus power; converting the bus power to a charging power for charging a battery in a charging period; and adjusting the DC power and/or the charging power to track a maximum of a power conversion efficiency; wherein the power conversion efficiency includes one of the following: an input power conversion efficiency, which is a conversion efficiency of converting the input power to the charging power; a DC power conversion efficiency, which is a conversion efficiency of converting the DC power to the charging power; or a bus power conversion efficiency, which is a conversion efficiency of converting the bus power to the charging power.