An EV battery soaked in sea water can overheat, catch fire, and even explode. Yet the same thing does not happen in fresh water. The reason is ocean water can be 1,000 times more electrically conductive. We investigate how water from the salty ocean gets into a battery after a hurricane, and what happens next. The good news is this is very unlikely to happen.
How Does An EV Battery Soaked in Sea Water Overheat?
Salt in water forms a natural electrolyte, containing ions which are microscopic electrical charges. These ions facilitate the flow of an electric current through the salty liquid. This phenomenon can make an EV battery soaked in sea water after a hurricane overheat, catch fire, and even explode.
An electric vehicle battery contains a large number of individual cells inside a robust, waterproof case. Electric wires pass in and out of the case, admitting electronic signals and sending electricity in and out. There are also ports to equalize pressure.
How Ocean Water Enters Through These Ports
These openings are well sealed by the factory, and should prevent seawater entering an electric vehicle battery. However, if the battery is damaged, then these seals may fail. They may also fail due to an inherent manufacturing defect. In both cases, seawater may enter immediately, or sometimes weeks later.
How Salt Water Intrusion Causes Battery Failure
Electric car batteries have terminal connecting points, that deliver their energy to the electric motors. As they do so, electrons flow from their negative to their positive terminal. The battery voltage matches the electric motor specification, ensuring a smooth, regulated flow.
However, if salt water comes in contact with those terminals via a failed open port, then the battery can short-circuit through the liquid. This induces rapid corrosion and electric arcing, and generates excessive current and heat. This outcome can cause rapid corrosion of the positive battery terminal.
This corrosion can also deposit on the negative battery terminal forming a bridge, which eventually becomes a permanent short circuit. This is why an EV battery soaked in sea water can explode days after a provider removes the vehicle from salt water, and dries it out.
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