Wet batteries cause a serious fire on the ship

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

The crew believed the fire had started in the starboard engine room, and Novec extinguishing agent was released into the starboard engine room. Approximately seven minutes later, the crew released Novec into the battery room. This agent temporarily slowed the development of the smoke. A search and rescue (SAR) vessel soon arrived on the scene and evacuated four crew members. The catamaran was towed to port, and extinguishing continued for several days before the vessel was deemed safe to board.

Technical investigations showed that the fire started in the battery stack module. It is highly likely that seawater seeping through the vent entered the vent fan and landed on the batteries. This caused a short circuit and an electric arc, which was considered the source of the fire.

The freeboard plan lacked important information about flooding of the ventilation system to the battery room. This meant that regulatory staff responsible for approving the freeboard plan were unaware of the location of the vent and its risks. After the accident, the shipowners made several changes to the ventilation system.

The investigation also found that the battery system had a low IP rating, so the ingress of seawater into high-voltage battery modules and components had serious consequences. A higher IP rating (and therefore a higher degree of protection) would reduce the consequences of seawater entering the battery room. The regulations do not appear to take sufficient account of the need to protect battery systems from ingress.

• Knowledge acquired
• Because the fire was incorrectly believed to have occurred in the engine room, approximately seven minutes passed before extinguishing agent was released into the battery room. For an extinguishing agent to be effective, it must be released quickly and, if possible, automatically.
• The safety of batteries as a whole was not adequately addressed in the regulations. The risk assessment for the battery system did not reflect all the risks associated with the system. For example, the risk of seawater ingress through ventilation systems was omitted.
• The Ingress Protection (IP) rating of marine battery systems should be carefully considered.
• Classification societies may have different requirements for battery safety, which may result in different ships having different battery safety standards. Based on the applicable rules and regulations, the same error may occur again.
• There is currently no fire extinguishing system that can safely extinguish a lithium-ion fire.
• Novec may be considered unsuitable as a fire extinguishing agent in battery rooms due to the complexity of proper use, its poor cooling effect and the fact that it converts to toxic gases at high temperatures.

Editor’s note: Given the ongoing electrification of all modes of transport, including maritime vessels, this accident is an important milestone. The conclusions mentioned above constitute a redacted summary of a multitude of serious and yet unresolved threats identified during the investigation. Interested readers are advised to consult the original report for more detailed information.