Explanation: A 24 VDC battery system is designed to operate within a specific voltage range, typically between 24 and approximately 28.8 volts when fully charged or undergoing various stages of charging (e.g., float, bulk, absorption). A constant reading of 30 volts on the GMDSS console voltmeter indicates that the battery charger is supplying excessive voltage. This condition, known as overcharging, can severely damage the batteries, reduce their lifespan, and potentially harm other connected equipment. It is a clear and immediate indication of a battery charger malfunction, specifically a faulty voltage regulator. Options C and D are less accurate or describe normal behavior. A high rate of charge (D) after testing on battery power is normal, as the charger works to replenish the drained battery (bulk charge phase). The sentence for C is incomplete, but if it implied a brief 30V, a *constant* 30V (B) is a more definitive malfunction.