The report presents a review of current literature, testing and modelling in support of guidelines how to address current risks with batteries from e-bikes and e-scooters. It has been shown that a fire initiated in a battery module can have an exceedingly fast fire growth and may pose new risks that cannot be accommodated within the current design methodology. The data from measurements indicated that the fire growth in terms of heat release rates may be faster than the currently used models. The tests present typical heat release rates from open fire tests in combination with release of toxic and flammable gases from cells and modules. Using accelerating rate calorimetry, conditions when single cells enter a thermal runaway could be determined. Utilizing the information from the testing, simulations of a module were performed to investigate the effect of mass ejection from cells during the thermal runaway, complementing the knowledge how the thermal propagation was disrupted in the module.

The information gathered from literature, testing and modelling was used to propose a design fire. Although, the fully developed fire is no more severe than a usual fire the very fast fire growth rate may cause deflagration type events that compromises the fire resistance properties.

Note that while the proposals are general, they mainly influence possible future dwellings thus dissemination of current risks to the public is necessary. Some of the recommendations can be summarized as follows; Being mindful of batteries and where to charge battery modules; Keep a watch on the health of your batteries, which includes but are not limited to observing if they have been damaged in any way or become unusually hot during operation and perhaps most importantly do not charge batteries where escape routes can be compromised.   

This final report summarises the work carried out during the project SI2.825082 financed by the European Commission – DG GROW. Within this project a theoretical Round Robin with the aim to analyse how the initial assessment method is interpreted by different laboratories, and the first and second phase of the initial testing activities to investigate the fire source, the design of the combustion chamber and secondary opening have been carried out. The final step in the project was an experimental Round Robin where four façade systems were tested at three different laboratories using the assessment method document, resulting in 24 tests. Additional tests were added to the project with funding from industrial partners. The tests were used to determine a calibration scheme and suitable performance criteria for classification. Furthermore, a substantial work has been done to ensure that the project is communicated in a good way to all stakeholders and Member States representatives.The theoretical Round Robin was performed with 29 laboratories, all members of European Group of Organisations for Fire Testing, Inspection and Certification (EGOLF). Over 200 questions covering the whole assessment method were asked, and thereafter analysed. The results show clearly which parts of the assessment method needs to be improved and clarified, as well as some practical details regarding the test method that had to be addressed.The first phase of the initial testing program defined the requirements of the fuel source and the combustion chamber. A large quantity of wood, of two different wood species (spruce and pine), had been acquired and thereafter characterised by measurement of dimensions, weight and moisture content. Over 4000 sticks have thus been density graded. After the selection of sticks to the different wood cribs a series of tests have been performed, mainly in accordance with the original test plan. Some modifications to the test plan were made during the course of the experimental study e.g., tests with a crib platform with either a grated or a solid floor. Also, a theoretical study through numerical modelling has been made to study the impact of changes of the combustion chamber geometry on the heat exposure to the test specimen. The simulations showed only small deviations between the regular and the enlarged combustion chamber. The changes of the geometry of the combustion chamber for the large exposure test can be done according to the results from the experimental program, it is beneficial for two reasons: it would make the preparatory work when mounting the test specimen simpler and it would ensure that falling parts will not damage the wood crib during a test.Based on the results a proposal has been made on the characteristics of the fuel source and the geometry and design of the combustion chamber, to be used in the second phase.During the second phase of the initial testing activities large and medium-scale exposure testing was performed on full façade geometries. The testing program including three repeatability tests in addition to gather information on variation in volume flow of the fan in medium-scale exposure as well as effects of the modified combustion chamber and wind in large-scale. From the repeatability tests it was decided to keep a constant height of the wood crib in large-scale due to otherwise large variations in exposure to the façade. Furthermore, the wind effects on the façade temperatures were significant even with a moderate wind of 1-2 m/s. At the end of the second phase three tests in medium and three tests in large-scale were done to investigate the effect of a secondary opening. It was indicated that asymmetrically placed opening would be the most appropriate placement.A short test series on alternative fuel source for the large exposure test was also performed where a propane diffusion burner was used instead of wood cribs. It was shown that if the combustion chamber would be reduced in height similar exposure to the façade could be achieved using the propane burner. There are several benefits with this alternative fuel source such as decreased height, less cleaning, higher safety and therefore less costs associated to10testing. For the medium exposure test the alternative gas burner described in DIN 4102-20 might be an appropriate alternative fuel source for the wood crib. However, no further investigations were made in this project in this regard.An update of the assessment method was made to take into account the latest information such as the repeatability tests and the second phase of the testing program. These changes such as the placement of the wood crib and the secondary opening was used in the experimental Round Robin.In tandem to this work, two surveys on falling parts were performed to find out the needs of Member States (MS) and setting criteria to be used during the Round Robin. Furthermore, an inquiry on the capacities for indoor and outdoor testing of different testing laboratories connected with EGOLF was made and is reported here.The work on the experimental Round Robin was completed in March 2024 and presentations of the tests and specimens are discussed in this report, more detailed information is available in the comparative documents. These include comparisons between tests on the same type of façade system at the different laboratories. This enables inter-laboratory comparisons for each monitored quantity and position. The inert tests are used to determine suitable calibration schemes for the medium and the large-scale exposure method, whereas the remaining tests are used to determine the performance criteria. Here it should be noted that average temperature is a more stable assessment criterion than a peak temperature or above a certain temperature during a certain time interval. The consortium would like to stress that arranging this type of Round Robin exercise is a severe logistic challenge which requires extensive planning.The project has been communicated through different channels. The project web page is the main communication channel where all reports and other documentation is published (https://www.ri.se/en/what-we-do/projects/european-approach-to-assess-the-fire-performance-of-façades). In addition to the webpage a YouTube channel is available showing a few of the tests and recent seminars, see webpage for a link.A Comments Handling Document has been kept and it includes almost 1000 comments that have been received during the project. These comments were handled continuously and communicated through the above-mentioned web page.

Thermal runaway is a major concern for lithium-ion batteries in electric vehicles. A manufacturing fault or unusual operating conditions may lead to this event. Starting from a single battery cell, more cells may be triggered into thermal runaway, and the battery pack may be destroyed. To prevent this from happening, safety solutions need to be evaluated. Physical testing is an effective, yet costly, method to assessing battery safety performance. As such, the potential of a numerical tool, which can cut costs and reduce product development times, is investigated in terms of capturing a battery module’s tolerance to a single cell failure. A 3D-FE model of a battery module was built, using a commercial software, to study thermal runaway propagation. The model assumes that when the cell jelly roll reaches a critical value, thermal runaway occurs. This approach was considered to study the module’s tolerance to a single cell failure, which was in reasonable agreement with what had been observed in full-scale experiments. In addition, quantitative sensitivity study on the i) model input parameters, ii) model space, and iii) time resolutions on the computed start time instant and time duration of thermal runaway were performed. The critical temperature was found to have the greatest influence on thermal runaway propagation. The specific heat capacity of jelly roll was found to significantly impact the thermal runaway time duration. The multi-physics model for battery thermal propagation is promising and worth to be applied with care for designing safer batteries in combination with physical testing.

Post-flashover fires inherently lead to external fire plumes, constituting a hazard for rapid fire spread over façades. As multi-storey mass timber buildings with internal visible timber surfaces become more common, there are concerns that such buildings would produce larger external plumes and hazards (assuming all other parameters equal). The literature reveals only indications of this, and how the actual exposure relates to different test methods for assessment is unknown. Here we utilise a series of full-scale mass timber compartment tests to quantify the exposure to the external façade. An incombustible external façade is instrumented with gauges at positions corresponding to reference data from several different assessment methods. The results show that there is an increase in plume duration, height, and temperatures when increasing the areas of exposed timber, but that this increase is less for normal- to large-opening compartments, than was previously seen in small-opening compartments. Also, normal variations in external wind speed have a larger influence on plume heights than the effect of doubling exposed timber surfaces. Test methods used for regulatory compliance differ significantly not only in exposure but also in pass/fail criteria. The proposed European large exposure method and the BS8414 method exhibit exposures on par with the severe end of what could be expected from mass timber compartments, whereas methods like SP Fire 105 and Lepir II produce significantly less severe plumes. However, the safety level is always a combination of exposure and assessment criteria. This data can help justify assessment criteria from a performance perspective. © 2023 The Authors. 

The temperature heterogeneity due to fire in large open-plan office compartments is closely associated with fire spread behaviour and has been historically limited to experimental investigations using timber cribs. This study explores the ability of Computational Fluid Dynamics (CFD) models, specifically the Fire Dynamics Simulator (FDS), to reproduce the results of full-scale tests involving fire spread over timber cribs for continuous fuel-beds. Mesh schemes are studied, with a fine mesh over the crib and 2 × 2 cells in the wood stick cross-section by default, this being relaxed in the surrounding regions to enhance computational efficiency. The simple pyrolysis model considers the charring phase and moisture. In application to the TRAFIR-Liège LB7 test, this calibrated “stick-by-stick” representation shows a good agreement for interrelated parameters of heat release rate, fire spread, gas phase temperature, and burn-away, a set of agreements which has not been demonstrated in previous studies. Fire spread shows relatively high sensitivities to: heat of combustion, ignition temperature, thermal inertia, radiation fraction, heat release rate per unit area, and the fuel load density. An approximately linear regression was found between the different fire modes and the thermal exposures, with “travelling” (and decaying) fires characterised by heat fluxes associated with the fire plume, while the growing fires were associated with proportionally higher heat fluxes on the horizontal surfaces of the sticks, in conditions where these receive more pre-heating. The trends in the overall HRR are more dependent on the fire spread rates than variations in the stick burning rates. © 2022 The Author(s)

Electric vehicles (EVs) and other vehicles with alternative energy carriers (such as hydrogen) are becoming increasingly common, and with them new fire risks. This report provides the technical details of computational fluid dynamics simulations carried out as part of the BREND 2.0 project to assess the tenability conditions within a ro-ro space from EV fires, via assessment of temperatures, radiation and spread of toxic species. The simulations primarily considered variation in compartment ventilation and fuel source. In all scenarios a selection of gaseous species, gas temperatures and radiative intensity are recorded at point locations and as 2D slices across the ro-ro space. From the gaseous species fractional effective concentrations, for irritant gases, and fraction effective doses, for asphyxiants, can be calculated to provide an assessment for tenability conditions in each scenario. This report contains the results of the simulations and some general observations but no detailed analysis of the implications of the results in terms of safety of EV fires on a ro-ro space.

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. 

Façade fire testing has been high on the agenda worldwide due to the increased hazard of many occurrences of severe fire spread on façades. There is also international work going on to create a European standard for façade fire testing. In this context it is interesting to clarify what different national test methodologies are based on. This report is a review of the development that led to the Swedish standard for assessing fire performance of façades, SP Fire 105. The review starts from the development in the 1950s with assessing fire exposure from compartment fires and follows further development until 1990s. The fire exposure in the first edition of SP Fire 105 published 1985 was based on two test campaigns including external flames from room fires performed at Lund University during the late 70-ties and early 80-ties. In the early 90-ties the geometry of the air intake in the combustion chamber and the opening under the test specimen was slightly reduced leading to a lower effective thermal exposure of the façade than in the first edition of SP Fire 105. An important observation done already in the 1950s at the Swedish fire laboratory in Stockholm and in the late 1970s at Lund University was that the wind is influencing the test results when doing experiments outside.