202538 Li-ion battery hazards

As edited from USCG Safety Alert 14-25

Battery fire

An integrated Li-ion battery bank recently caught fire on board a passenger vessel. It was found that loosely crimped lugs overheated and initiated the fire. No one was injured and the vessel sustained minimal damage, but this casualty highlights the safety hazards posed by Li-ion batteries.

The resulting investigation found, among other things, that all Li-ion installations used for propulsion, control and electrical power must undergo an engineering plan review and be fitted with supporting safety systems. Additionally, these systems should be tested and inspected at installation and periodically afterward, and be properly maintained by competent mariners, regardless of the battery bank size or end consumer.

Some notes on Li-ion batteries

Energy density: Li-ion batteries are used on vessels because their high energy densities allow for longer voyages and full electrification. However, high energy density increases risk because if a fire occurs, it will burn hotter and longer.

Thermal runaway: Upon internal failure or short circuit, Li-ion batteries may release hightemperature flammable gases that can catch fire or explode. The heat output of a fire can increase the rate of off-gassing, and those off-gasses in turn increase the size of the fire in an uncontrolled chain reaction.

Fire suppression resistance: A thermal runaway fire is very difficult to suppress once it has begun to propagate to other battery modules. Instead, fire management strategies focus on early detection, fire containment, and heat absorption with a waterbased suppression system.

Toxic off-gasses: In thermal runaway, Li-ion batteries release varied toxic gases, many above their ‘Immediately Dangerous to Life or Health’ thresholds, placing passengers and crew in potential danger. Further, the composition of off-gasses varies dramatically across different Li-ion battery chemistries and manufacturer makes and models.

Battery Management: Li-ion batteries will often have a battery management system to prevent degradation from overcharging, undercharging, or over-cycling. Propulsion, electrical loads, topping loads, and recharging cycles are managed by complex integration systems, which are key in mitigating the increased risks of Li-ion battery systems.

Lessons learned

• Batteries should be visually inspected for signs of deterioration, such as bulging cells or corroded electrical connections. Documentation on the completion of required maintenance should be maintained.
• Crew members responsible for battery operation and maintenance should be trained in the manufacturer’s guidelines and operational procedures and familiar with the functioning of the battery management system.
• Crew should know how to respond to abnormal battery conditions or fires. Safety drills for Li-ion battery fires should be performed, and Li-ion battery system arrangements and risks should be considered when conducting other drills.