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Recommendations and Guidelines for Battery Crash Safety and Post-Crash Safe Handling
BASt.
BASt.
Swedish National Road and Transport Research Institute.
EMI.
Show others and affiliations
2014 (English)Report (Other academic)
Abstract [en]

Electric vehicles (EV) present a research challenge for safety engineers. These vehicles are designed using conventional vehicle design strategies but do not contain conventional materials or structures. Accident analyses cannot be conducted until sufficient EVs are involved in a crash and are reported in crash databases. Until such data exists, researchers must use other research methods to understand and predict potential problems.

The passive safety activities in the EVERSAFE project used conventional accident analysis, computer simulation, physical testing, and literature reviews to get a better understanding of the issues for EV and their battery systems. Based on current practice, Lithium-ion (Li-ion) batteries are the main chemistry that should be explored and pouch type cells are the most vulnerable for damage.

Conventional vehicles were used in EVERSAFE as a surrogate for EVs to identify expected deformation and acceleration loads from real crashes. Based on available information and previous compatibility research, the main issue that arose was that for small vehicles. These vehicles experience the highest accelerations in car-car crashes and even some fixed barrier crashes. Except for a handful of cases, there was not enough data to confirm that EVs have a higher injury or fire risk than similar conventional vehicles.

Chemical analyses of the battery components identified the potential processes that can lead to emissions of flammable or toxic gases. These chemicals develop when the battery temperatures are too high and can develop if mechanical loading causes an internal short circuit or an external heat source affects the battery. There are several harmful chemicals contained in battery electrolytes and hydrofluoric acid (HF) appears to be the most relevant gas to monitor.

Simulation activities in EVERSAFE have developed new battery models and an effective methodology to assess worst case loading in a battery was also developed. The models were used to explore both local cell-level deformations as well as whole vehicle crash performance. The simulations confirmed the ability of ductile structures to protect the battery and at the same time identify the risks created when the battery pack structures start to deform and result in crushing of the cell structures.

Component tests of the battery cells demonstrated that the pouch cell can be quite resilient to shear and penetration loads. They are more sensitivity to crushing loads and the ductile plastic structures in the battery can be a useful safety element. This information underlines the need to maintain the battery in an undeformed part of the vehicle.

Full scale crash tests demonstrated safe battery performance even for more severe tests than those the vehicle are required to meet. Both a side impact and a rear/front multiple impact could not provoke thermal activity or hazardous emissions from the battery in a Mitsubishi iMiEV or a BMW i3. These results can be used to promote consumer trust in the technologies.

A complementary part of the study was to determine what procedures and equipment are needed for rescue services if they attend a crash with an EV. There appears to be no fundamental changes in the rescue approach at a crash scene. There is a need for better support for rescue services to identify the type of energy source (internal combustion, electric, or both) of a given vehicle. There are some actions needed for an EV that must be considered when attending a crash and these can only be done when the vehicle is known to be an EV. eCall is one tool that can facilitate the identification of EVs as well as update the status of the battery to the rescue services. Rescue sheets are being developed in ISO committees and these need to be made available in standard and secure locations in a vehicle. There is the potential for fire and toxic gas and a firefighter must be able to identify the appropriate type of safety equipment to wear. Knowledge of the chemical processes that

can occur in a battery is important. It is more important that firefighters have access to methods that

identify risk of fire or chemical hazards. Thermal imaging cameras and portable gas detectors,

already available on rescue vehicles, may be sufficient for monitoring EVs at a crash site.

Place, publisher, year, edition, pages
2014. , p. 99
Series
EverSafe ; D3.1
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:vti:diva-14297OAI: oai:DiVA.org:vti-14297DiVA, id: diva2:1367933
Projects
EverSafeAvailable from: 2019-11-05 Created: 2019-11-05 Last updated: 2019-11-05Bibliographically approved

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23456785 of 8
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