This study presents a coupled model incorporating a thermal propagation model and a fire model to investigate the fire safety of a large lithium-ion battery (Li-ion) module. The thermal propagation model employs a three-dimensional (3D) finite element method (FEM), while the fire model utilizes computational fluid dynamics (CFD). Literature data on material properties and thermal runaway characteristics of 18650 cells with Nickel-Manganese-Cobalt (NMC) chemistry, including the onset temperature of rapid thermal runaway (TR), maximum cell temperature, vent gas composition, and volume, are used as input data. Simulation results highlight that thermal convection serves as the dominant heat transfer mechanism, contributing over 50 % of the total heat flux driving TR propagation. TR propagation initiates gradually but accelerates rapidly in a string-wise pattern. The gas temperature inside the module significantly influences TR process through convective heat transfer. The computed heat release exhibits linear correlation with experimental values, but underpredicts total heat release by approximately a factor of three. This discrepancy is likely due to the omission of combustion of solid particles as well as heat release from ancillary components (e.g., cables, insulation in the module). The calculated total heat release correlates linearly with the cumulative number of cells entering TR, confirming that accurate TR propagation modelling is critical for reliable prediction of overall energy release

Thermal runaway in lithium-ion battery cells poses significant safety risks due to rapid heat generation and potential thermal propagation within a battery system. This study investigates the total heat released and the fraction of energy contained in gas and particles ejected during thermal runaway using a purpose-built calorimeter setup. The results show that the fraction of ejected heat is significantly influenced by the state of charge (SOC) and cell mass loss. Notably, the non-ejected heat was higher at 75% SOC compared to 100% SOC due to higher fraction of ejected heat at high SOC. This will have implications in thermal propagation scenarios. Additionally, the study compares the results with accelerating rate calorimetry tests, highlighting the limitations of the latter in measuring the total heat released during thermal runaway. The findings show the need for comprehensive testing methods that can improve thermal management and safety in battery systems.

Lithium-ion batteries are increasingly used in various applications, from household devices to electric vehicles, as part of the green transition. However, their application poses unique risks, including thermal runaway, which can lead to the release of flammable and toxic gases, fires, and explosions. Notable accidents, such as the explosion on the hybrid ferry MF Ytterøyningen and the battery storage facility in McMicken, highlight the need for a thorough understanding of these risks.

This literature study investigates the explosion hazards associated with lithium-ion batteries in compartments where flammable gases can accumulate. It examines how battery parameters, ventilation, and suppression systems influence explosion risks and compares computational methods for safety modeling. The focus is on lithium-nickel-manganese-cobalt-oxide (NMC) and lithium-iron-phosphate (LFP) batteries, which dominate today’s market.

Key parameters for evaluating explosion risks include the lower flammability limit (LFL), laminar burning velocity, explosion pressure, and the rate of pressure increase. These are influenced by battery design, state of charge (SoC), cell format, chemistry, and aging. The study reveals that LFP cells, despite their higher thermal stability, produce battery vent gases with higher hydrogen and hydrocarbon concentrations, resulting in a lower LFL and potentially higher explosion risks.

Mitigation strategies such as mechanical ventilation and deflagration panels are discussed, highlighting their effectiveness in different scenarios. Various fire suppression systems are evaluated for their cooling abilities and effectiveness in preventing thermal propagation and re-ignition.

The study identifies a significant gap in validated models that capture the dynamics from gas dispersion to explosions, emphasizing the need for high-resolution models developed alongside experimental validation. Future research should focus on explosion risks in large, confined spaces like maritime vehicle decks and enclosed parking garages, assessing the number of vehicles required to pose a hazard in case of explosions.

Lithium-ion battery safety is a topic of large importance, and testing is associated with large costs. Safety evaluation is therefore needed also at an early stage in cell design and development, in order to evaluate potential short-comings or to screen large platforms of materials and cells. Previous thermal runaway tests on lab-scale cells have, however, indicated differences in heat release and temperature increase as compared to commercial cells. On the other hand, these could also vary between different commercial cells due to differences in cell materials, size, format, and design. In this work, thermal runaway characteristics of industrial-scale cells are compared against each other as well as with lab-scale cells. Tests were performed on lab-scale coin cells and five different industrial-scale cells ranging from 5 to 157 Ah, covering different cell formats and materials. The coin cells were built using electrodes and separator extracted from one of the industrial-scale cells. The results show that the thermal runaway will be less violent and reach lower maximum temperatures using lab-scale cells, depending on the lower proportion of active materials as compared to inactive components. It is also shown that the ratio between cell capacity and heat capacity is a useful indicator for the comparability of thermal runaway scenarios. This ratio varies considerably for small cells, but not so much for different commercial cells. The data available suggests that a cell capacity of at least 1 Ah is needed to achieve a good comparison of the thermal runaway scenario with larger commercial cells.

Fires involving electric vehicles have attracted considerable attention in the media. In particular, the toxic gases released upon combustion of electric vehicles and lithium-ion batteries has been a major concern. In this study, the results of six large-scale vehicle fire tests are presented including three electric vehicles, two internal combustion engine vehicles, and one electric vehicle with the battery pack removed. Additionally, separate battery component tests were performed. In two of the vehicle fire tests a sprinkler system was used to assess the effect of water application on the combustion gases. Furthermore, calculations of the heat release rate, peak heat release rate and total heat release were performed, as well as chemical analysis of gas and soot. Peak heat release rate and total heat release were affected by the fire scenario and vehicle model, but not significantly by the type of powertrain. Regarding the combustion gases, hydrogen fluoride represented the largest difference between electric vehicles and internal combustion engine vehicles. Additionally, battery specific metals such as manganese, nickel, cobalt and lithium were found in higher concentrations in the electric vehicle tests than in the internal combustion vehicle tests, in which larger quantities of lead were found.

Lately, concerns regarding fires in electric vehicles in enclosed spaces such as in road tunnels and parking garages have been raised and there are indications that parking of electric vehicles may be prohibited in some spaces. For the success of electromobility and the transition from fossil to renewable fuels, it is important to understand the risks and consequences of fires in electric vehicles and to provide technical solutions if necessary, so as not to hinder the widespread adoption of electric vehicles.

In this work, a literature review on fires in vehicles has been conducted. The focus was on fires in enclosed spaces involving electric vehicles. A comprehensive risk assessment of electric vehicle fires was performed using systematic hazard identification. In addition, a workshop with representatives from three Swedish fire and rescue services was carried out to evaluate the emergency rescue sheets/response guides.

The main conclusions are; That statistics regarding vehicle fires need to be improved, as of today the root causes of fires are missing in the data, which could potentially result in non-fact based regulations; The data studied in this work does not imply that fires in electric vehicles are more common than fires in internal combustion engine vehicles; Fires in electric vehicles and internal combustion engine vehicles are similar in regards to the fire intensity and peak heat release rates. 

The most effective risk reductions measures on vehicle level, to decrease the number of fires in EVs, could not be defined based on that relevant data on the root causes of fires in EVs are currently not publicly accessible. The most effective risk reduction measures, to limit fire spread, on infrastructure level were the use of fire sprinkler systems, fire detection systems (early detection) and increased distance between parked vehicles.

Battery Energy Storage Systems (BESS) is a vital part of electrification of the shipping industry. However, there are potential risks that must be considered for BESS installation. The article presents HAZID as an earlystage hazard identification method for installation of harbour BESS. The HAZID identified critical factors such as proximity to the marine environment and safe distances between BESS containers

The increasing use of lithium-ion batteries requires further efforts in safety testing and evaluation. It is of utmost importance that the effects of different test conditions are understood, particularly for validation of computer models. While plenty of data from thermal runaway tests are available in literature, few are from large test series. The missing systematic approach to evaluate the impact of different test conditions implies uncertainty when comparing test results. In addition, the fast pace in cell development, including an increasing utilization of larger cells, necessitate the validation of previously published results. This work presents thermal runaway data from 37 tests on one type of large format prismatic lithium-ion cell (157 Ah). The tests are conducted in a closed pressure vessel with inert atmosphere as well as in an open setup below an exhaust collector hood. Further, six different thermal runaway trigger methods are employed as well as four different states of charge. Emphasis is put on the gases produced, a key aspect for safety evaluation. The results are compared with literature data and a new modified method is proposed for calculating the characteristic venting rate in a closed pressure vessel. It is concluded that the trigger method affects the gas production rate, mass loss, and maximum temperature of the cell as much as its state of charge. The large cell format potentially impacts the specific total gas production and enhances the effects of different trigger methods, but has a small impact on other evaluation parameters. No significant differences were observed in the test results due to the different test setups, apart from differences due to potential combustion of the released gases in ambient atmosphere. 

These proceedings include papers and extended abstracts from the 7th International Conference on Fires in Vehicles – FIVE 2023, held in Stavanger, Norway, April 24-25, 2023. The proceedings include an overview of research and regulatory actions coupled to state-of-the-art knowledge on fire related issues in vehicles, such as passenger cars, buses, trucks and trains, or related infrastructure, such as car parks or vehicle transport at sea. Fires in transport systems are a challenge for fire experts. New fuels that are efficient and environmentally friendly are rapidly being introduced, with emphasis on high energy density batteries. This rapid development, however, introduces new fire risks not considered previously and we risk getting a situation where we do not have enough knowledge to tackle them. In this context FIVE represents an important forum for discussion of the fire problem and for exchange of ideas. Fire protection in road, rail, air, and sea transport is based on international regulations since vehicles cross borders and the safety requirements must be the same between countries. Therefore, understanding of safety and regulations must be developed internationally and the FIVE-conference has a significant role to play as a place to exchange knowledge. FIVE attracts researchers, operators, manufacturers, regulators, rescue services and other key stakeholders. Of particular value is the mix of expertise and the international participation in the conference. The conference is unique as it includes fires in different types of vehicles. In recognition of the fact that many of the fire problems faced by these vehicles are the same, the solutions to them can also be similar. In the proceedings you will find papers on vehicle fire development, bus fires, alternative fuel and electric vehicles, and car park fires. We are grateful to the renowned researchers and engineers presenting their work and to the keynote speakers setting the scene. We sincerely thank the scientific committee for their expert work in selecting papers for the conference.

Thermal propagation is one of the major challenges when batteries will be used in dwellings in large scale. It means the exothermic reactions in the cell are out of control and can lead to a fast release of flammable and toxic gases. In a system involving a large number of cells, thermal runaway can rapidly propagate from one battery cell to the whole system, which means substantial fire and explosion risks, an event that is important to mitigate and prevent. Multi-physics simulations together with full-scale testing is a cost-effective method for designing safer batteries. This project aims at simulating thermal runaway initiation and propagation using a multi-physics commercial software GT-Suite. 

A battery thermal runaway model containing 12 prismatic cells based on 3-D Finite Element approach was built using GT-Suite. The computed thermal runaway time instants versus thermal runaway cell number were compared with full-scale experimental data with reasonable agreement. Quantitative sensitivity study on the model input parameters and model space and time resolutions on the computed start time instant and time duration of thermal runaway were performed. The thermal runaway model was then extended with an electric equivalent sub-model to simulate the short circuit. With the electrical model acting as the input to the thermal model, the most interesting output of the simulation is the change in temperature of the cells, dependent on the current in the cells, with respect to time. The current is determined by the value of the external resistance through which the short takes place and the voltage level of the battery pack. The obtained results from the above short circuit simulations can only be used as a starting point and not as absolute values for neither triggering the thermal model nor for accurately simulating a battery under an electrical load. Furthermore, GT-Suite was applied to simulate the gas dispersion inside a room. A comparative study of the dispersion of toxic gases during thermal runaway, utilising an arbitrary release of HCN to represent the battery gases, in a small compartment with natural ventilation was investigated and the results compared the same situation simulated in FDS. The pipe based modelling supported by GT-Suite has limited applicability and overestimated the concentrations close to the ceiling whereas the lateral concentrations where underestimated. 

The multi-physics model for battery thermal runaway process is promising and worth to be applied with care for designing safer batteries in combination with full-scale testing.