AMSA: Ensuring safe carriage of battery powered vehicles on ships

While this information is targeted at ships operating on ocean going voyages, the risks apply equally to all vessels carrying BEVs. Vessel types mentioned in this notice are roll-on, roll-off passenger ferries (RORO PAX) and pure car and truck carriers (PCTC). BEVs have been in operation for some time. Current statistics indicate that BEVs are less likely to catch fire than conventional internal combustion engine vehicles. Electric vehicle battery fires are rare. The available data indicate the fire risk is between 60 times greater1 for internal combustion engine (ICE) vehicles. However, the consequences of a BEV fire can be higher. 

The issue of lithium-ion battery fires gained widespread recognition within 2023, prompting the industry to take action in order to address and mitigate this phenomenon. TT Club emphasized the critical dangers of lithium-ion batteries, highlighting that there appears to be a concerning lack of awareness regarding the harmful effects of highly toxic combustion products and their impact on the health and wellbeing of individuals exposed to these gases.

In light of an incident that took place during summer, there has been focus on the risks that Li-Ion batteries pose to ships onboard, considering that decarbonization and electrification are increasing the number of shipping goods that contain Li-Ion batteries, from  electric vehicles (EVs) to a wide range of consumer and electronic goods. In particular, the incident involved the Fremantle Highway car-carrying vessel that caught fire off the Dutch coast with thousands of vehicles on-board enroute from Germany to Egypt. 

Risks associated with battery-powered vehicles 

#1 Increase in weight of the vehicles in comparison with internal combustion engine vehicles of the same footprint.

There is an approximate 25% increase in weight compared to vehicles of the same footprint2. This may result in deck loading limitations being exceeded and could adversely affect the stability of the vessel, if not accounted for. 

#2 The risk of a fire should a battery cell go into thermal runaway. 

This is when the heat generated within a battery exceeds the amount of heat that is dissipated to its surroundings. Without intervention (cooling) the internal battery temperature will continue to rise and with this the potential for a fire to spread and an explosion to occur if the resultant gases are allowed to build-up in the space. Most modern BEV’s have an internal cooling system to maintain battery temperature. Modern batteries are designed to vent instead of exploding however the vented gases need to be extracted from any enclosed spaces to avoid pressure building-up and leading to an explosion. 

#3 While the likelihood of fires for BEVs is very low compared to fires from internal combustion engines (ICE vehicles are 60 time more likely to catch fire), the fires involving BEVs reach full potential in a shorter period in comparison.

Typically flames shoot upwards and outwards simultaneously. BEV fires can reach temperatures of more than 1600 degrees centigrade, hot enough to burn metals like aluminium, commonly used in BEV construction to reduce weight. See below diagram which compares the time taken by BEV fires. 

#4 The gases produced by BEV fires form a vapour cloud which is both toxic and potentially explosive (hydrogen).

For every 1-kilowatt hour (KWh) of battery power, 6000 litres of vapour are produced. A single 55 KWh battery could produce 330,000 litres of vapour. 

#5 Significantly increased likelihood of re-ignition of a BEV fire.  

These fires are a chemical chain reaction, cooling with water slows the reaction but doesn’t stop it completely.  Once the cooling is removed, heat from the chemical chain reaction will build up rapidly once again and re-ignition is highly probable.  

Detection and prevention of thermal runaway 

To assist in the prevention and early detection of thermal runaway ship operators should consider the following: 

• As with ICE vehicle, crews should inspect BEVs before and after loading to ensure they are safe to load. With BEV’s crews should ensure no damage has occurred to the battery or if the battery management system is displaying any faults. Some BEVs have a lower ground clearance and may be damaged during loading.  
• If damaged, a small amount of fluid may leak from under the vehicle. The battery and drive-unit are liquid-cooled, typically with glycol-based automotive coolant. The coolant is typically either clear or blue in colour and if found leaking, may indicate the high-voltage battery casing has been damaged. Any fluid leakage must be investigated immediately and should prompt further action following investigation. 
• Smoke detectors situated on the vehicle decks may take some time to activate as the smoke flow from the thermal runaway can be prevented from reaching detectors due to the physical design of the vehicle decks and the airflow created by ventilation systems.  
• Flame detectors are designed to detect the infrared radiation of fires. Such detectors are activated by the presence of flames; thus, it is possible to identify the location of vehicles on fire and respond quickly. 
• The installation of closed-circuit television (CCTV) systems with flame recognition capabilities/ thermal detection properties where vehicles, including BEVs, are located can allow early detection of fires. Typically, thermal runaway can be detected at 60-70 degrees centigrade. The position of CCTV systems should be considered. Typically, these are placed fore and aft on a vehicle deck. Operators should consider fitting increased numbers of CCTV cameras with thermal detection capabilities in the athwartship directions to enable rapid detection of thermal runaway. This also allows for the precise location of the fire to be identified. 
• Charging stations for BEVs while enroute should be installed in compliance with the SOLAS regulation II-1/45, and SOLAS regulation II-2/20.3. There is further guidance in the IMO Maritime Safety Committee Circular 1615 “Interim Guidelines for Minimizing the Incidence and Consequences of Fires in Ro-Ro Spaces and Special Category Spaces of New and Existing Ro-Ro Passenger Ships”. 
• BEVs should be clearly marked and should ideally be located in a designated area known to the crew. The location should, where possible, be on weather decks, away from dangerous goods, have sufficient drainage, adequate separation between vehicles for crew members wearing breathing apparatus to access from multiple access paths and be well clear of all emergency muster points. 
• Crew members who conduct safety patrols of the vehicle decks should be made familiar with the early signs of thermal runaway and if possible equipped with thermal handheld detectors. Early indications of thermal runaway are: 
  • Off-gassing. This is a release of various gases from the battery, including carbon dioxide, carbon monoxide, hydrogen, and volatile organic compounds. During the early phase of gas generation, the off-gases can be heavier than air and accumulate at deck-level or be lighter than air and dissipate or accumulate at deck-head level if the space is not appropriately ventilated. Owing to the various battery chemistries, it is not possible to predict which will dominate. 
  • A damaged battery can create rapid heating of the battery cells. If you notice hissing, whistling, or popping, a possible sweet chemical smell, black “smoke” (nanoparticles of heavy metals, not smoke) or white vapour coming from the high-voltage battery or the vehicle generally, assume that it is in thermal runaway and take appropriate firefighting measures.  Early intervention will minimise the spread of any fire to adjacent vehicles.  
  • Fire patrols should pay special attention to look for evidence of battery coolant leakage, smoke or heat from the areas of vehicles where a battery is normally located, for example the underside. They should also listen for “popping sounds” which may be indicative of a potential thermal-runaway event. 
• Crew should conduct frequent emergency drills and training in the identification and initial response to a BEV battery fire. Early detection and prompt action can minimise the spread of a fire.