Wet batteries cause serious fire on ship

A small hybrid passenger catamaran vessel was operating in coastal waters when the fire alarm sounded. There were no passengers on board. The fire alarm panel indicated fire in both the battery room and the engine room of the starboard pontoon. An engineer opened the door to the starboard engine room and saw smoke. He immediately closed the door to reduce air intake. The port engine and the batteries in the port pontoon were still operational.

The crew assumed that the starboard engine room was the source of the fire and released Novec fire extinguishing agent into the starboard engine room. Approximately seven minutes later, the crew released Novec into the battery room. These actions resulted in the smoke development being temporarily reduced. A search and rescue (SAR) vessel soon arrived on the scene and evacuated the four crew members. The catamaran was towed to port and firefighting operations lasted several days before the vessel was deemed safe to board.

Technical investigations revealed that the fire had started in a battery stack module. It is very likely that seawater that had entered through the ventilation outlet had reached the batteries through the fan. This caused a short circuit and arcing, which were considered to be the cause of the fire.

The loadboard plan lacked important information on flooding points from the ventilation system to the battery room. As a result, the supervisory staff responsible for approving the loadboard plan were unaware of the location of the ventilation outlet and the associated risk. Following the accident, the ship’s owners made several changes to the ventilation system.

The investigation also found that the battery system had a low protection rating (IP), so that the ingress of seawater into the battery modules and high-voltage components would have had serious consequences. A higher IP rating (and therefore a higher degree of protection) would have reduced the consequences of seawater entering the battery compartment. It seems that the regulations do not sufficiently address the need to protect battery systems against ingress.

• Lessons learned
• Because the fire was wrongly suspected to be in the engine room, it took about seven minutes for the extinguishing agent to reach the battery room. For a fire extinguishing agent to be effective, it must be released quickly and, if possible, automatically.
• Overall battery safety was not sufficiently addressed in the regulations. The risk assessment of the battery system did not take into account all the risks associated with the system. For example, the risk of seawater ingress through the ventilation devices was not taken into account.
• The protection class (IP) of marine battery systems should be carefully checked.
• Classification societies may have different requirements for battery safety, which may result in different battery safety standards being applied to different vessels. Based on the current rules and regulations, the same failure may occur again.
• There is currently no fire extinguishing system that can safely extinguish a lithium-ion fire.
• Novec is unsuitable as a fire extinguishing agent in battery rooms because it is difficult to use correctly, has a poor cooling effect and decomposes into toxic gases at high temperatures.

Editor’s note: Given the ongoing electrification of all means of transport, including seagoing vessels, this accident represents an important milestone. The above findings are an edited summary of the multitude of serious and previously unaccounted for risks uncovered during the investigation. Interested readers are advised to consult the original report for more detailed information.