Battery and Power Supply Failure on a GMDSS Equipped Vessel
You are the chief officer on a 150 m container ship in sea area A3. The vessel's GMDSS installation includes a VHF DSC, MF/HF DSC and radiotelephony, Inmarsat-C, NAVTEX, EPIRB and two SARTs. The emergency batteries are rated for 6 hours of operation for the VHF and MF/HF, and 1 hour for the emergency lighting. During a routine check, the battery voltage on the emergency bank reads 22.5 V on a 24 V nominal system, and the specific gravity of one cell is low. The battery charger shows a 'float' indication but the charge current is near zero. The vessel is due to sail in 12 hours. The master asks whether the vessel can sail and what maintenance should be done.
1. Assess the battery condition and explain the implications for GMDSS operation.
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A 24 V nominal lead-acid battery bank reading 22.5 V is significantly discharged or has a faulty cell; a fully charged bank should read about 25.5–26.5 V at rest. A low specific gravity in one cell indicates that cell is failing or sulphated, which will reduce capacity and may cause the bank to fail under load. The near-zero charge current on float suggests the charger is not delivering charge, or the battery is not accepting charge. The GMDSS emergency battery must be capable of supplying the required equipment for the specified period; if the bank is degraded, the vessel may not meet the carriage requirement. The vessel should not sail until the battery is replaced or proven capable of supplying the load for the required duration.
2. Describe the tests you would carry out to verify the battery's capacity and the actions to take before sailing.
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Carry out a capacity test by discharging the battery at the manufacturer's specified rate and measuring the time to the end voltage, or use a load test with a suitable load bank. Check the specific gravity of all cells and the electrolyte level. Check the charger output voltage and current, and confirm the charger is in the correct mode. Inspect terminals and connections for corrosion. If the battery fails the test, replace it with a battery of the correct type and capacity, and record the replacement. Confirm the emergency battery is connected to the GMDSS equipment and that the changeover works. Record all checks in the radio log and inform the master and the flag state or recognized organization if the deficiency cannot be rectified before sailing.
3. What records should be kept and what regulatory requirements apply?
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The radio log should record the battery checks, the results, any defects and the remedial action. The vessel's safety management system should include maintenance procedures for GMDSS batteries. The flag state and recognized organization may require notification of deficiencies affecting GMDSS. The battery should be maintained in accordance with the manufacturer's instructions and the vessel's planned maintenance system. The emergency battery should be tested at intervals not exceeding those specified by the administration, and the results recorded.