Normal.
Since the wattmeter is usually converted by measuring voltage, if the battery has a nominal voltage of 60V and the actual measured voltage is 60V, it should only be charged than less than 50%, because a 60V battery can reach 72V.
Under normal circumstances, the battery power is low and the internal resistance of the battery is large. When no electricity is used, it is the electromotive force of the battery. When electricity is used, a voltage drop occurs. occur on the internal resistance, thereby reducing the output voltage.