04.8 Electrocution risk
When an EV is in a collision, what happens electrically?
Overall, there is a very small risk of electrocution when managing an electric vehicle incident, however responders should remain alert & follow their SOPs.
Following a collision where airbags have deployed, electric vehicle high voltage systems should isolate automatically.
But! Responders have no way of knowing, detecting or measuring whether that has happened, so best practice is always to assume the EV is live while managing an incident & wear appropriate personal protective clothing (PPC) & personal protective equipment (PPE).
Remember that EV high voltage systems typically run at 400V DC (direct current) & above, not AC (alternating current), so the risk of electrocution is low, but still poses a serious threat to responder safety.
Can responders be electrocuted by an electric vehicle?
To understand this, let's take a quick look at DC vs AC power.
EVs use DC power:
With DC electrical circuits, an emergency responder must touch both the positive & negative sides of the circuit to run the risk of electrocution.
The electricity grid uses AC power:
With AC electrical circuits, contact with only one side is required to suffer electrocution; the power is trying to find 'earth', so if you touch AC power it will travel through your body to ground.
(For firefighters, think of dealing with downed grid power lines; if a fire occurs we 'pulse' the water as there is a risk of electrocution through an unbroken stream of water, from the AC grid power line to the person holding the hose.)
We have found no incidents of responder electrocution in relation to EVs
Through our research, we have not found any verified incidents where emergency responders have been electrocuted, or nearly electrocuted, from a direct stream of water onto a burning EV, submersion in a body of water, cutting into an EV during road rescue or from stranded energy (live battery cells in the HV battery pack).
However, the risk remains & you should always follow your agency SOPs.