Flooded roads, electric cars: Will submersion cause electrocution? [Informative Talk]

As the monsoon season begins, the familiar sight of cars stalled in suddenly flooded roads reappears, often due to drivers underestimating water depth. Experts warn that attempting to navigate flooded areas can endanger both vehicles and lives, emphasizing that even SUVs are not immune to the risks.

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If there is a car in front of me, I can refer to the water level rising on the front car's muffler. But if I am the first car, I should open the window and stick my head out. If the water goes over half of my wheels as the car slowly enters, I should not proceed.

Automotive specialists advise that passenger cars require extreme caution when water levels reach just 15-20 cm, approximately half the wheel height. At this depth, brake performance can degrade, steering becomes difficult, and the vehicle may be swept away by unexpected currents. Professor Kim Pil-soo of Daelim University's Department of Future Automotive Engineering suggests referencing the water level against the preceding car's muffler or, if driving alone, by opening a window and observing the water's rise relative to the tires. He also recommends turning off energy-consuming systems like air conditioning before entering water.

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If the water level is less than half of the wheel, it is okay to pass, but if the water level is higher than half of the wheel, it is not okay to pass.

The most critical threat to a submerged vehicle is not electricity, but the engine itself. Water entering the engine through the intake can lead to a 'water hammer' effect, where the incompressible water prevents proper compression in the cylinders. This can bend or break pistons and connecting rods, necessitating a complete engine replacement and incurring repair costs ranging from millions to tens of millions of won. This is a primary reason why flood-damaged cars are often declared a total loss.

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There is no 100% safety. Even with double waterproofing, electrical energy and water are incompatible, so electric cars should stay away from water.

For electric vehicles (EVs), concerns about electrocution arise during heavy rains. While current EVs feature high waterproofing standards for their high-voltage batteries and safety systems that automatically cut power in case of abnormal current, the risk of electrical leakage cannot be entirely eliminated. Professor Kim advises that EVs should avoid water exceeding one-third of the wheel height, as water and electricity are fundamentally incompatible. He also points out that submerged speed bumps could damage the battery pack, making EVs potentially more vulnerable than internal combustion engine vehicles in flooded conditions. The safest approach in flooded areas, for all vehicles, is to avoid them entirely, choose a detour, or never enter underground parking lots.

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Electric cars should not pass even if the water reaches one-third of the wheels, and it is better to find a detour.