A rural fire service crew has doused a burning electric car with more than 20,000 litres of water as firefighters battled an invisible, self-sustaining chemical reaction.

The fire started after a Tesla was damaged in an accident on a NSW Mid North Coast road, near Diamond Beach, on October 18.

Firefighters found the blaze was almost impossible to tame, as a chemical reaction known as "thermal runaway" started in the battery pack.

Firefighters who were trained in managing electric vehicle (EV) fires were dispatched to the scene, and the car was deemed safe to remove after the battery pack cooled down.

The Diamond Beach brigade said their crew started training for such an event five years earlier, learning the nature of these fires and their potential to erupt unexpectedly.

But a leadin

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