FCC Exam Question: 1-18C4

What would be an indication of a malfunction on a GMDSS station with a 24 VDC battery system?

A. A constant 30 volt reading on the GMDSS console voltmeter.
B. After testing the station on battery power, the ammeter reading indicates a high rate of charge that then declines.
C. After testing the station on battery power, a voltmeter reading of 30 volts for brief period followed by a steady 26 volt reading.
D. None of the above.
Correct Answer: A

Explanation: A constant 30-volt reading on a GMDSS console voltmeter for a 24 VDC battery system indicates a malfunction. A healthy 24 VDC lead-acid battery system, whether charging or fully charged, should operate in the range of approximately 25.2 to 27.6 VDC (12.6V to 13.8V per 12V battery). A constant 30 volts suggests a severe overcharging condition, likely due to a failed voltage regulator in the charging system, which can damage batteries and other equipment. Option B describes normal battery charging behavior; after discharge, a healthy charger will deliver a high current that gradually declines as the battery recharges. Option C describes a transient high voltage followed by a stable 26-volt reading, which is a normal float or maintenance charge voltage for a 24V system.

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Includes Elements 1, 3, 6, 7R, 8, and 9.