Fire and explosion hazards&#;due to the chemical composition and energy density of Li-ion batteries, there is a risk of fire and explosion, which can be caused by different types of abuse (e.g., thermal abuse, electrical abuse, and mechanical abuse) and internal short circuit;
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In automotive engineering, the design of battery packs involves a large number of cells, their complex interconnections, and monitoring systems. This approach not only offers benefits but also entails risks, which include the following [ 6 11 ]:
Electric vehicles use lithium ion batteries in the form of battery packs, which consist of connected cells, as shown in Figure 1 4 ]. These cells are often first assembled into modules and then combined into battery packs. A battery pack also includes a battery management system (BMS), battery enclosures, thermal management system (TMS), connectors and cables, a voltage regulator, and safety features [ 5 ].
Over the years, lithium ion batteries (LIBs), introduced by Sony [ 1 ] in , have established themselves as the dominant choice for powering a wide array of consumer electronics due to their high energy and power density compared to other types of batteries, as well as falling costs. Lithium ion batteries have also been widely adopted in the automotive industry, significantly propelling vehicle electrification. This is demonstrated by the increasing global production of various EVs, exceeding 10 million units in , with forecasts for projecting sales of about 14 million units [ 2 3 ], including battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and fuel cell electric vehicles (FCVs).
These tests help to identify weak points in battery systems and evaluate their behavior in harsh situations. The result of revealing weaknesses in the batteries under investigation may be mechanical or electrical damage to the batteries and, as a result, initiation of a thermal runaway (TR) of the battery, ending in a battery fire. TR is a chain reaction causing overheating, combustion, or even explosion of batteries. TR can stem from both external factors, like abuse, and internal factors, like manufacturing impurities. The severity of the consequences depends on multiple variables, such as the state of charge, charging/discharging rate, cell type, history, and materials. International, national, and regional standards set pass/fail criteria for battery tests. For instance, some standards, like UN/ECE-R100.02 [ 13 ], UL [ 14 ], and ISO -4 [ 16 ], require no fire, explosion, rupture, or leakage under foreseeable misuse.
The widespread adoption of lithium ion battery technology with the concomitant risks of their use in vehicles has necessitated the development of global standards and regulations to ensure their safe introduction into automotive industry [ 6 11 ]. The United Nations Economic Commission for Europe (UNECE) issues type approval regulations, creating consistent technical guidelines for vehicles and components. In the US, the National Highway Traffic Safety Administration (NHTSA) sets safety requirements through the Federal Motor Vehicle Safety Standards (FMVSS) [ 6 7 ].
The TR process results in fires accompanied by the release of vast amounts of heat [ 9 17 ]. In the case of using a battery pack in an electric vehicle, extinguishing fires in individual cells is extremely challenging due to their integration into modules and the entire battery pack being covered by the battery pack enclosure. This often leads to fire and the destruction of the entire vehicle [ 18 19 ].
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Safety verification of battery packs during tests at research facilities carries a higher likelihood of such fires. With similar difficulties in extinguishing fires in integrated cells and the substantial heat generated, there is an increased risk of serious damage to expensive research infrastructure and threats to the health and life of the research personnel. The risk is further amplified by the production of large quantities of highly toxic gases.
The simplest way to ensure the safety of battery pack vibrational tests is to conduct them in isolated rooms, accepting the risk of ignition of the testing device without additional protections. There are also trends in increasing the safety levels by attempting to control fires at vibration test stations, such as the setup by Data Physics [ 20 ], which implemented sample shielding and a water mist fire suppression system. Despite these shields, this solution still exposes the environment to the effects of ignition, such as the emission of harmful gases and hot fragments detaching from the batteries. Leaving a burning battery on the vibration exciter head causes the transfer of a large amount of heat to the inside of the exciter and risks damaging it.
The presented risks associated with battery testing, related to the significant health hazards for the personnel and economic risks for research laboratories, necessitate the search for effective methods of protecting personnel and battery testing equipment during tests in testing laboratories. Particularly important are vibration testing laboratories using expensive testing equipment&#;electrodynamics exciters (shakers), slip tables and sensors, and acquisition systems.
Given the difficulties in extinguishing fires in lithium ion cells enclosed in battery pack casings, and the harmful effect of high temperature on the vibration exciter in the testing laboratory, it is advisable not to isolate the battery pack in which thermal runaway has begun at the station but to quickly evacuate it from the vibration table (a headexpander or slip table) to, for example, a fire-extinguishing chamber filled with water, which according to the literature is the most efficient method of extinguishing a fire [ 21 ]. Such a system was prototyped by the ENVIBRA Research & Development Group as part of the project &#;High fire safety stand for vibration testing of electric vehicle battery modules and full battery packs&#;; a schematic of the system is shown in Figure 2 . In addition, the chamber can also absorb toxic gases and store them in a sealed tank for later disposal. In the absence of a fire, the stand can be used to observe and monitor the behavior of the sample after the vibration tests.
The implementation of this system for protecting the infrastructure and extinguishing the battery is hindered by the currently used method of attaching the battery to the vibration table on the vibration test stand&#;with dozens to hundreds of bolts&#;requiring tens of minutes for disconnecting the battery from the stand. The large number of fasteners is necessary due to the need for a rigid grip on the battery, ensuring the transmission of vibrations from the exciter to the specimen or the device under test (DUT)&#;in this case Li-ion battery packs&#;without changes in amplitude beyond normative tolerances.
A solution to the problem would be to use a fastening (clamping) system that has the ability to quickly disconnect, which would in turn allow rapid evacuation of the battery pack from the test stand. But it is also essential to ensure that the mounting system effectively transfers vibration between the vibration exciter and the battery pack.
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