The battery pack enclosure not only protects the batteries from external damage and ingress of dirt or debris, but it can temporarily contain a fire in the enclosure, providing time for fire extinguishing and preventing propagation to other cars. However, for such Li-ion battery fires, the encasing also makes firefighting more difficult by preventing direct access to the battery pack itself.
The BMS monitors voltage, current, resistance and temperature of the battery, which are all vital to allowing the battery to function at its optimum potential. It is also critical for balancing the cells, which means ensuring that every single cell within each module of the battery pack charges and discharges at the same level. Cell balancing is critical to prevent over-charging or over- discharging of any single cell within the pack. Over-charging or over- discharging batteries can lead to battery failure.
The BMS also monitors the State of Charge and State of Health.
FIRE RISK AND THERMAL RUNAWAY
Li-ion batteries can fail due to:
• Manufacturing defects. • Battery management software faults.
• Internal/external short circuits.
• End of life. • Battery abuse:
• Mechanical damage – This is external damage, such as dropping from a height, indentation, or punctures, etc., which can result in damage to the internal components, rendering the battery unstable.
• Electrical abuse – Over- charging or over-discharging the battery. This can occur due to manufacturing faults in battery cells and ineffective monitoring of the voltage by the BMS.
• Thermal abuse – Subjecting the batteries to extreme temperatures (both high and low), or its local temperature is too high which could be due to poor battery design or manufacture, or the BMS not regulating the temperature properly.
66 | ISSUE 113 | SEP 2025 | THE REPORT
CHALLENGES FOR FIREFIGHTING ON DIFFERENT TYPES OF VESSELS
Firefighting on different vessel types can present different problems. Below are some of the difficulties that can be encountered when fighting a fire on these ship types.
RO-RO AND PCTC VESSELS
A 1kWh battery can emit up to 6,000 litres of toxic and flammable vapour. This flammable gas mixture can contain gases including hydrogen, carbon monoxide, and hydrogen fluoride.
Ro-Ro and PCTC ships lack transverse bulkheads which means large open spaces on each deck that allow a fire to spread quickly longitudinally as there are no subdivisions to contain the fire. The lack of subdivision also makes fire suppression more difficult. This is illustrated in the GA Plan for this vessel type, an example of which is shown below.
Each type of battery abuse described can lead to battery failure. Mechanical abuse can cause the separator to break, causing a short circuit by contact between the two electrodes, whilst electrical abuse can lead to formation of dendrites (branches of lithium) which can pierce the separator, again resulting in short circuit. Thermal abuse at high temperatures can lead to electrolyte breakdown.
The battery failure can lead to a phenomenon known as ‘thermal runaway’. Thermal runaway is the term used to describe when a reaction becomes self-accelerating; this occurrence is not exclusive to batteries. In the context of batteries, battery failure can result in exothermic (heat generating) reactions taking place, the heat generated from these reactions allow for more reactions to take place, creating a positive feedback loop. Eventually, the reaction reaches an uncontrollable, self- sustaining and self-accelerating state, i.e., thermal runaway.
The time taken to reach thermal runaway can be very fast, giving little time to react, and with devastating consequences.
MARITIME INCIDENTS INVOLVING LI-ION BATTERIES
Whilst root causes are often difficult to determine due to extensive damage, several high-profile ship fires have been linked to Li-ion batteries, including:
• S-TRUST (USA, 2022) – Charging of Li-ion batteries on the bridge.
• FELICITY ACE (Atlantic, 2022) – Carrying new EVs and ICE on board.
• FREMANTLE HIGHWAY (Netherlands, 2023) – Carrying new EVs and ICE on board.
• MORNING MIDAS (North Pacific, 2025) – Carrying new EVs and ICE on board.
Additionally, the number of Superyacht fires are on the rise. Superyachts generally carry an array of ‘toys’ onboard, typically battery powered. These can include e-scooters, e-bikes, sea bobs, drones and now electric jet skis are being introduced into the market.
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