GMDSS Battery Fails Load Test Before Departure
MV Ganga Voyager is preparing to sail from Kandla. The GMDSS battery is a dedicated 24 V lead-acid bank rated 200 Ah at the 10-hour rate; it supplies the VHF/DSC, MF/HF/DSC and Inmarsat C. The vessel has an emergency generator. The battery is four years old. On float the charger holds 27.2 V. A hydrometer check shows all cells at 1.250 except cells 3 and 7 at 1.160 and 1.170; electrolyte level was below the plates in two cells and has just been topped up with distilled water. A load test at the calculated GMDSS load of 20 A starts at 25.2 V and falls to 21.0 V after 40 minutes. The manufacturer's end voltage is 21.0 V. Sailing is scheduled in six hours. The master wants to know if the battery can be accepted and whether the topping-up has solved the problem.
1. Assess the battery against the GMDSS autonomy requirement for this vessel and decide whether it can be accepted for the planned voyage. Show your reasoning.
Read the worked answer
The vessel has an emergency generator, so the GMDSS battery must be able to supply the GMDSS load for at least one hour (SOLAS minimum; the manufacturer or flag may require more). At 20 A, one hour needs 20 Ah. The bank is rated 200 Ah at the 10-hour rate, so a healthy bank should easily meet this. But the load test reaches the end voltage of 21.0 V after only 40 minutes, not one hour, and two cells have specific gravity 1.160/1.170 against 1.250. That indicates lost capacity and failing cells. Topping up after the plates were exposed does not restore capacity and may have diluted electrolyte. Therefore the battery should not be accepted for the voyage. The 40-minute result is below the one-hour requirement, and the cell imbalance makes the failure likely to worsen. The correct decision is to replace or have the bank professionally reconditioned and retested, not to sail on the strength of float voltage.
2. What technical actions would you take before accepting or rejecting the battery, and what records should be kept?
Read the worked answer
Actions: isolate and remove the battery from service; check charger output and ripple; inspect terminals and cells; do not just add acid; carry out a controlled refresh/equalise charge only if the manufacturer permits, then repeat specific gravity readings and a full load test with a calibrated load and timer. Check each cell voltage under load; a weak cell will reverse. Verify the battery is dedicated to GMDSS and that the 20 A load calculation includes VHF/DSC, MF/HF/DSC, Inmarsat C, emergency lighting if applicable, and alarm panels. Replace with a battery of at least the same rating and type. Records: date/time, battery age, electrolyte levels, SG per cell, float and load voltages, load current, duration to end voltage, charger readings, actions, replacement serial number, and the signature of the GOC/engineer. Enter the defect and repair in the radio log and maintenance record; inform the master and, where required, class/flag.
3. If no replacement battery can be obtained within six hours, what operational restrictions and notifications would you recommend?
Read the worked answer
If no compliant battery can be obtained within six hours, the vessel should not sail on an ocean passage. The GMDSS installation would not meet the required autonomy, so the deficiency is not curable by an operational workaround. Options are: delay sailing until a replacement or approved shore service is available; remain in port; or, only with flag/class acceptance, move to a nearby repair facility under restricted conditions with the master's written assessment and additional communications cover. Notify the flag administration/MMD, class surveyor and company DPA; record the deficiency. Do not rely on the emergency generator alone as a substitute for the GMDSS battery, and do not disable alarms to hide low voltage. If the vessel must remain at anchor, maintain a listening watch on VHF and inform the port authority. The master's decision should be based on the actual autonomy test, not on the charger's float voltage.