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Plugged into Safety: A primer on the hazards of working with battery electric vehicles | March 2024
Battery Basics
According to Battery University, "The building blocks of a battery are the cathode
and anode, and these two electrodes are isolated by a separator. The separator is
moistened with electrolyte and forms a catalyst that promotes the movement of
ions from cathode to anode on charge and in reverse on discharge."
The anode releases electrons during discharge, and the cathode absorbs them.
Anodes are always negative and cathodes are positive.
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Each EV has a battery management system that is responsible for balancing
the voltage, currents and temperatures among cells and can shut down the
battery if needed.
BATTERY HAZARDS
Thermal Runaway Events
A thermal runaway event can be triggered by damage to a battery cell —
mechanically, through a collision or damage due to an internal or external short,
or as a result of electrochemical damage caused by overcharging or discharging,
or external temperature.
When one of these faults elevates the cell temperature, or a portion of the cell,
the materials inside begin to break down and can trigger an exothermic reaction.
As the temperature increases, so does the decomposition rate, which causes rapid
heating of the cell and can lead to fire or explosion.
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This reaction may spread to
nearby cells and modules, intensifying the event.
" In North America, there
are approximately
180,000 car fires each
year. If you look at
BEVs, even adjusting
for the population,
the rate of fire and
thermal events is
lower than in gasoline
vehicles. The hazards
are different, the
treatment is different,
but statistically there
is evidence that there
are fewer incidents if
they are designed and
treated properly and
training is provided."
— Rick Szymczyk
Senior Manager,
Automotive Centre
of Excellence, Ontario
Tech University
