Seatrade Maritime: Wrong belt hooks led to $3.8m lithium battery fire

Improperly secured lashing belts were the likely cause of a fire onboard general cargo vessel Genius Star XI in the North Pacific, according to a National Transport Safety Board (NTSB) report.

The root cause of the fire, which caused $3.8m in damages, appears to be the use of the wrong size hooks at the end of the lashing belts securing the cargo of battery energy storage system (BESS) units to the deck. The hooks were too small to properly attach to the thicker D-rings welded to the floor of the cargo holds, leaving the hooks holding the D-ring by just their tips, rather than fully within the throat of the hook as designed.

The fire was spotted after the ship encountered heavy weather in the North Pacific, close to the Bering Sea.

Investigators found multiple lashing belt hooks had fractured; each fractured hook would have increased the load on the remaining belt hooks, as well as the stress on the D-rings, the NTSB report said. Multiple BESS units — each weighing in at 9.5 tonnes and containing 840 battery cells — broke free and shifted around the cargo holds.

Thermal runaway of lithium ion batteries started the fire, a phenomenon that can be caused by mechanical and electrical damage to a battery. Deformation was seen within the BESS units, with shelves bending and loosening from the bolts attaching them to the unit’s chassis. The loose shelves cause arcing and short circuits within the BESS units, and allow batteries to move around freely inside the unit. 

The alarm was raised and the crew immediately mustered. As the ship only had sufficient CO2 charge onboard to purge one hold, the master sent crew to check if there was fire in hold two. Confirming no signs of fire in hold two, hold one was cleared of personnel and CO2 released to douse the fire. The fire was successfully extinguished by the system, and checks carried out to ensure no reflashes had occurred.

The crew were then ordered to hold two to re-lash the shifted cargo.

The vessel again encountered heavy seas, wind, and swells on 28 December. While the ship was rolling heavily, the fire panel indicated a fire in hold two and smoke was seen coming from ventilation ducts. With no more CO2 for the fire suppression system, the vessel changed course to calmer waters to enable the crew to cool the hold from the outside with seawater using fire pumps. After four hours of spraying the hold, temperatures were seen to be decreasing and the fire appeared to have been put out.

On arrival at Dutch Harbor on 29 December, the ship anchored two miles from shore. Marine firefighters from T&T Salvage and Resolve Marine boarded the ship and confirmed the fires were extinguished. 

On 27 January 2024, a specialist company with expertise in lithium battery safety was employed by Wisdom Marine to carry out a damage assessment on the cargo and arrange disposal of damaged battery packs. Battery packs from severely burned BESS units were placed in specialised containers and stowed to ship with the vessel for eventual disposal at a proper facility. 

With its CO2 fire extinguishing system recharged, the cargo was all further secured with chain stays and the vessel left the port on 12 February after being declared safe to continue by the US Coast Guard (USCG). Genius Star XI arrived at San Diego, California on 24 February.

In total, 43 of the 160 BESS units were damaged, 41 of those had broken free from their lashing, and several had deformed shelving. Fire had broken out in three of the units, two on the tween deck of hold one and one on the tween deck of hold two.

There were no injuries to the 19 crew onboard nor environmental damage from the incident, and investigators found that the crew reacted appropriately to the fires and likely prevented the fire from expanding.