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(White paper 2025)

The global energy transition has launched a new and volatile category of cargo onto the world’s oceans. The maritime transport of lithium-ion (Li-ion) batteries—as standalone components, within Electric Vehicles (EVs), and in large-scale Battery Energy Storage Systems (BESS)—has grown exponentially, introducing a risk profile that challenges traditional maritime safety protocols. Ship fires remain a top safety concern and a leading cause of financial loss in the marine insurance sector, and the unique characteristics of Li-ion battery fires are exacerbating this problem.

The core hazard is thermal runaway, a violent, self-sustaining chemical reaction that generates extreme heat, releases toxic and explosive gases, and can propagate catastrophically through a cargo hold. This is not a conventional fire; it does not require oxygen to burn, rendering traditional CO₂ suppression systems largely ineffective and making extinguishment at sea nearly impossible. Incidents like the catastrophic losses of the Felicity Ace and Fremantle Highway have served as stark warnings of the potential consequences.

While the International Maritime Dangerous Goods (IMDG) Code provides a foundational regulatory framework, a dangerous gap exists between its minimum requirements and the best practices necessary to ensure safety. This white paper provides an in-depth analysis of this new risk landscape, synthesizing global regulations, industry guidelines, and incident reports. It details the essential, multi-layered loss prevention strategies required of shippers and carriers, from stringent pre-shipment validation of battery quality and State of Charge (SoC) to the critical onboard practices of on-deck stowage and specialized crew training.

Finally, it examines the future outlook for this burgeoning sector, highlighting the innovations in technology and procedure that are essential for navigating this perilous passage with greater safety and resilience.

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1. A Sector in Transformation: The Growth of Battery Cargo

The global push for decarbonization, crystallized in the IMO’s 2050 net-zero targets, has ignited an unprecedented demand for lithium-ion battery technology. This has fundamentally altered the cargo mix on the world’s oceans.

• Electric Vehicles (EVs): The sea trade of EVs has surged, now accounting for approximately 25% of all cars shipped by sea, a dramatic increase from less than 10% pre-pandemic.
• Battery Energy Storage Systems (BESS): These large, containerized power units are essential for grid stability and renewable energy projects. The market in producing nations like China, which dominates global production, has been projected to grow at a compound annual rate of 33%.

This rapid growth, however, has introduced a severe and complex risk profile that challenges traditional maritime safety assumptions and equipment, which were not designed for this type of fire hazard.

2. The Core Hazard: Understanding Thermal Runaway

The fundamental danger of all Li-ion battery transport stems from their high energy density and potential for thermal runaway. Unlike a conventional fire, thermal runaway is a chemical chain reaction within the battery cell itself, making it a fundamentally different and more dangerous event at sea.

2.1 Triggers and Characteristics

Thermal runaway is initiated when the heat generated within a battery cell exceeds its capacity for heat dissipation, leading to an uncontrollable temperature rise. The primary triggers fall into three categories:

• Mechanical Abuse: Physical damage from impact, crushing, or puncture that causes an internal short circuit.
• Electrical Abuse: Overcharging, over-discharging, or external short circuits that lead to excessive heat generation.
• Thermal Abuse: Exposure to high external temperatures or internal short circuits caused by manufacturing defects.

Once triggered, the event has several defining characteristics that make it uniquely hazardous in a maritime environment:

• Intense, Oxygen-Independent Fire: The chemical reaction produces its own heat, does not require an external oxygen source, and can reach temperatures exceeding 1,000°C. This renders traditional CO₂ firefighting systems largely ineffective at stopping the reaction.
• Toxic and Flammable Gas Release: A critical danger is the massive volume of vented gases, including highly toxic hydrogen fluoride (HF) and carbon monoxide (CO), alongside explosive gases like hydrogen (H₂) and methane. In a confined cargo hold, this can create a deadly atmosphere and a severe explosion risk.
• Cascading Propagation: The intense heat from one failing cell can trigger a domino effect in adjacent cells and containers. This propagation is what turns a localized incident into a ship-threatening conflagration that is nearly impossible for a crew to control.
• Difficulty of Extinguishment and Re-ignition: As seen in the fire curve comparison, Li-ion battery fires reach their peak intensity much faster than traditional fires and are notoriously difficult to extinguish. Due to the stored chemical energy, they have a high risk of re-igniting hours or even days after being suppressed.

3. The Regulatory Landscape: Navigating a Complex Framework

The maritime transport of Li-ion batteries is primarily governed by the International Maritime Dangerous Goods (IMDG) Code.

3.1 Classification and Key Provisions

• Class 9 Dangerous Goods: All Li-ion batteries are classified as Class 9 Miscellaneous Dangerous Goods. The table below summarizes the key UN Numbers.

UN Number	Proper Shipping Name / Description	Common Cargo Type
UN 3480	LITHIUM ION BATTERIES	Standalone batteries shipped in bulk.
UN 3481	LITHIUM ION BATTERIES PACKED WITH/CONTAINED IN EQUIPMENT	Batteries in the same box as, or installed in, electronics.
UN 3171	BATTERY-POWERED VEHICLE or EQUIPMENT	Electric vehicles, e-scooters, etc.
UN 3536	LITHIUM BATTERIES INSTALLED IN CARGO TRANSPORT UNIT	Large, containerized Battery Energy Storage Systems (BESS).
UN 3556	VEHICLE, LITHIUM ION BATTERY POWERED	New, more specific entry for EVs, mandatory from Jan 1, 2026.

• Mandatory Pre-Shipment Testing: With very few exceptions, all battery designs must pass the rigorous tests outlined in the UN Manual of Tests and Criteria, Section 38.3. The Test Summary Report (TSR) is a mandatory document that provides proof of this compliance and must be made available by the shipper.
• Special Provisions (SPs): Key provisions modify the general rules. SP 188 provides an alternative path for small batteries (e.g., cells ≤20 Wh, batteries ≤100 Wh) but still requires robust packaging that can pass a 1.2m drop test. SP 376 imposes highly restrictive rules for the transport of Damaged, Defective, or Recalled (DDR) batteries.

4. A Multi-Layered Safety Strategy: From Shipper to Carrier

Given the severe risks and regulatory gaps, a proactive, defense-in-depth strategy is imperative.

4.1 Shipper’s Due Diligence

• State of Charge (SoC) Management: Adhering to an industry best-practice SoC limit of 30-50% is one of the most critical risk mitigation measures a shipper can take.
• Prohibiting Damaged Cargo: Shippers must have robust processes to identify and segregate any Damaged, Defective, or Recalled (DDR) batteries, which are forbidden from normal transport.
• Safe Packaging and Hazard Communication: Shippers are legally responsible for using the correct UN-specification packaging and ensuring all packages and containers are correctly marked, labeled, and documented with a Dangerous Goods Declaration (DGD).

4.2 Carrier’s Best Practices

• Stowage—On Deck Only: There is a universal industry consensus that all significant Li-ion battery shipments should be stowed on deck only. This is the single most important safety measure a carrier can take, as it allows for direct crew access for firefighting and safe venting of explosive gases.
• Enhanced Detection & Response: Best practice calls for vessels carrying these cargoes to be equipped with enhanced detection systems like thermal imaging cameras and gas detectors. Crew training must be urgently updated to focus on the realities of a battery fire, emphasizing boundary cooling with copious water as the primary strategy.

5. Lessons from Catastrophe: Notable Incidents

• Car Carrier Fires (Felicity Ace, Fremantle Highway): These catastrophic incidents, resulting in total loss of vessel and cargo and at least one fatality, have become stark warnings for the industry. While the exact causes were not officially determined, the presence of hundreds of EVs is widely believed to have contributed to the fires’ intensity and the inability of crews to extinguish them.
• Genius Star XI (2023): This incident demonstrated the critical limitations of CO₂ systems on a cargo ship when a second battery fire broke out after the system had been depleted on the first fire.
• Land-Based BESS Fires (Fengtai, Beijing, 2021): A catastrophic fire and explosion at a large BESS facility resulted in firefighter fatalities and highlighted the severe risks of system failures and poor-quality cells, serving as a warning for the transport of similar large-scale units.

6. Future Outlook: Challenges and Innovations

The future of the maritime industry is inextricably linked with the energy transition. The growth in battery transport will continue, driven by global decarbonization goals. The path forward requires a focus on innovation and collaboration.

• Innovation in Safety: The industry is innovating rapidly with advanced detection systems (thermal cameras, gas sensors), new firefighting technologies (piercing nozzles, water additives), and safer battery designs that are more resistant to thermal runaway propagation.
• Regulatory Evolution: The IMDG Code is continually evolving, with new UN numbers and stowage requirements being introduced to better manage the risks as they are understood.
• The Human Factor: There is a critical and urgent need to address the skills gap by providing seafarers with specialized training to manage these new technologies and respond effectively to the unique emergencies they can create.

In conclusion, the safe transport of lithium-ion batteries is a shared responsibility that demands a proactive safety culture. It requires diligent shippers, well-equipped and trained carriers, and a regulatory and insurance framework that supports and enforces best practices beyond the minimum requirements.

How Electrios Consultants Can Help:Specialized consulting firms like Electrios Consultants play a vital role in bridging knowledge and regulatory gaps. They offer services like:

• Pre-Shipment Protection: Testing and certification (including UN 38.3), detailed risk assessments, optimal packaging and stowage guidance, compliance verification, and support for product recalls.
• Post-Incident Support: Forensic analysis and litigation support, and developing corrective actions based on incident investigations.
• Training and Capacity Building: Delivering tailored training programs for crew and shore personnel on thermal runaway, toxic gas mitigation, and specialized firefighting techniques.

By adopting a multi-layered defense strategy and collaborating across the industry, the maritime sector can confidently navigate the challenges of transporting energy storage cargoes, ensuring greater safety and environmental protection.