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Emergency Response Approaches For Electric & Hybrid Vehicles in Türkiye

The IT grounding system in the architecture of electric vehicles reduces the risk
of electric shock caused by high voltage. However, it should be kept in mind that
short-circuiting the battery poles or direct contact with the battery cells will cause
electric shock and arc formation. If the fuse is not included in the system design
of the vehicles, it may cause the high voltage drive battery to discharge directly
by short-circuiting. It should be taken into account that such cases will lead to
unintended consequences. Emergency response teams, in particular, should
keep the safe distance from conductive parts of high voltage propulsion battery
and relevant components as well as orange cables in electric & hybrid vehicles
in addition to the aspects mentioned above. In general, there is no clear sign or
system interface for emergency response teams indicating that there is no voltage
in the components on the vehicle. In case of the interventions to be performed
in accordance with the specific directives of relevant vehicle manufacturers, it is
necessary to disable manually the high voltage system in the first place. For this
purpose, many electric & hybrid vehicles have MSD (VDA, 2020).
The most significant problem in the accidents involving electric & hybrid vehicles
is that emergency response teams, generally, do not know how to disable high
voltage systems and the locations of routes of high voltage power cables in that
vehicle. Dismounting of terminals of 12 V / 24 V low voltage battery (accumulator)
in conventional motor vehicles allows the disabling of electrical systems while
it is occasionally hard to access the related safety switches (MSD connector)
in high voltage propulsion battery systems in electric & hybrid vehicles, and
sometimes it is a quite challenging process to fail to find the locations of these
switches. Another significant risk in electric & hybrid vehicles for emergency
response teams and/or casualties is the possible exposure to electric current.
Another risk factor that may occur in electric & hybrid vehicles is thermal
risks. Thermal risks may occur as a result of high-value short-circuits in the
vehicles, energy stored chemically in cells, an external fire or the contact of
the propulsion batteries with other hot components. The ideal operating
temperature which allows lithium-based batteries operating in the most
efficient way is between 20 °C and 40 °C. The cells of many lithium-based
batteries are not suitable for operation or storage at temperatures above
60 °C. In this scope, special heating and cooling systems are used for high
voltage propulsion batteries, and these systems are of critical importance
in this sense. Battery cooling system failures used for lithium-based battery
concepts such as NMC and LTO, can similarly lead to thermal risks. Leaks
of the liquid used (glycol/water mixture) that may occur in the installations
of cooling systems, malfunctions related to cooling system equipment such
as compressors etc. may cause insufficient and ineffective cooling, therefore,
systems may also cause thermal errors.

Year 2 / Issue 3 / January 2023 203