Lithium batteries challenge regulations and onboard safety on car carriers and container ships

Increasing numbers of lithium batteries are crossing the oceans inside cars, electronic equipment and energy storage systems. Their expansion is changing the risk profile of a maritime industry that must transport larger volumes of cargo whose characteristics can complicate the response to a fire.

The main challenge arises when a damaged, defective or overheated battery enters a process known as thermal runaway. In this process, temperatures rise uncontrollably in a self-sustaining reaction that can spread between cells and release flammable and toxic gases, as well as trigger new fires after the initial flames have been brought under control.

This scenario is particularly relevant to car carriers, where thousands of vehicles may be transported on enclosed decks with limited space between them. During a fire, gaining direct access to its source can be difficult, while the response must also prevent the flames from spreading to other vehicles.

The European Maritime Safety Agency (EMSA) has identified thermal runaway, gas generation and the potential for reignition among the factors that must be considered when designing detection and response procedures for these vessels.

Regulation seeks to keep pace with change

The growth of these cargoes is also driving updates to international regulations.

Amendment 42-24 to the International Maritime Dangerous Goods (IMDG) Code became mandatory on January 1, 2026, introducing new classification entries specifically for battery-powered vehicles. These include UN 3556 for vehicles powered by lithium-ion batteries, UN 3557 for those equipped with lithium metal batteries and UN 3558 for vehicles powered by sodium-ion batteries.

The next revision is already on its way. Amendment 43-26, adopted by the International Maritime Organization’s (IMO) Maritime Safety Committee in May 2026, introduces new criteria for batteries and electric vehicles, including special provision SP 980, intended to assess a vehicle’s safety condition before it is offered for transport.

The amendment may be applied voluntarily from January 2027 and will become mandatory in January 2028.

Meanwhile, the IMO continues to work on vessel design and onboard response systems. In March 2026, its Sub-Committee on Ship Systems and Equipment identified priority measures to reduce fire risks on ships carrying new energy vehicles, including electric vehicles, with a view to establishing new mandatory provisions by 2032.

The discussion extends beyond car carriers. In the container ship segment, the organization finalized draft amendments to SOLAS during 2026 that include portable infrared thermal imaging cameras and water mist lances as additional tools for fire detection and firefighting.

Fires reveal the severity of the risks

Regulatory concerns have also been fueled by a series of casualties that exposed the difficulties of tackling fires on ships carrying electric vehicles.

In February 2022, the “Felicity Ace” caught fire in the Atlantic while carrying 3,965 vehicles and subsequently sank. According to information reviewed by EMSA, the crew reported that the fire had started in an electric vehicle, although the cause of the casualty could not be conclusively established.

A year later, the fire aboard the “Fremantle Highway” once again brought this type of cargo into focus. The vessel was carrying 3,784 vehicles, including 498 electric vehicles. In this case, the Panama Maritime Authority’s investigation concluded that the evidence indicated the ignition source was an electric vehicle located within a block of 24 such vehicles on deck 8.

In 2025, the “Morning Midas” added another case. The car carrier was transporting 3,048 vehicles, including 70 electric vehicles and 681 hybrids, when it caught fire in the North Pacific. After drifting at sea, it eventually sank on June 23. However, the exact cause of the fire remained undetermined in the information reviewed by EMSA.

The three incidents illustrate an important distinction: the presence of electric vehicles aboard a ship is not, by itself, sufficient to establish the origin of a fire. While the investigation into the “Fremantle Highway” identified an electric vehicle as the ignition source, the causal link remains unresolved in other cases.

When the risk travels inside a container

Beyond car carriers, batteries are also transported as dangerous goods in containers, where the problem begins even before the cargo reaches the ship.

Proper declaration, documentation, packaging and stowage are essential to ensure that the shipping line and crew know what they are carrying and where it is located aboard the vessel. An incorrect declaration can result in a container being placed in an unsuitable stowage position and hinder the response during an emergency.

According to reports cited by Allianz Commercial, “around a quarter of cargo-related incidents are associated with misdeclared cargo,” including batteries and chemicals.

The problem was also illustrated by the “Genius Star XI.” In December 2023, the vessel was carrying lithium-ion battery energy storage systems when it encountered adverse weather in the North Pacific.

The National Transportation Safety Board (NTSB) investigation determined that 41 of these systems broke free from their lashings and shifted inside the cargo holds. The deformation sustained by some of them caused batteries in three units to enter thermal runaway, triggering two fires. Damage was estimated at US$3.8 million.

Unlike other casualties, this case allowed investigators to establish directly the sequence that led from cargo movement and damage to the outbreak of fire.

More batteries, but not necessarily more fires

The growth of these technologies coincides with a period in which onboard fires and explosions have remained at elevated levels.

A total of 250 incidents were recorded in 2024, the highest figure in the past decade. In 2025, the total fell to 218, although it remained the second-highest figure over that period. Meanwhile, global lithium-ion battery deployment in 2025 was six times higher than five years earlier.

Both trends are occurring simultaneously, but the available data do not establish that one is a direct consequence of the other. The increase in batteries transported expands the industry’s exposure to this type of cargo, but does not, by itself, demonstrate that they are responsible for the overall rise in maritime fires.

What the investigated incidents do show is that, when a battery enters thermal runaway or is damaged during transport, the characteristics of the fire may require procedures and systems that differ from those traditionally used.

By MundoMaritimo