Indore tragedy: why do EV batteries catch fire? | Explained Premium

Understand the causes of EV battery fires, safety risks, and precautions after the deadly Indore fire tragedy.

The story so far: A fire tore through a house in Indore on March 18, killing eight people including two children. An electric vehicle (EV) charging point outside the house appeared to have sparked the blaze. An investigation is underway.

Nearly every EV on the road today runs on lithium-ion batteries, which use the same chemistry powering millions of smartphones and laptops. They pack more energy than lead-acid batteries and are generally safe when managed well.

A common cause of EV battery fires is an event called a thermal runaway. A lithium-ion battery packs thousands of cells tightly together, each generating heat as it charges and discharges.

Normally, an onboard computer called the battery management system keeps the temperature within a safe range. But if something goes wrong, one cell can overheat, causing neighbouring cells to overheat in a chain reaction that can outpace the cooling system.

This process also releases a toxic cocktail of gases, including hydrogen fluoride, in a flammable vapour that eases the ‘path’ to a fire.

Manufacturers protect battery packs by packing them inside shells of reinforced steel or aluminium. However, a hard impact — like from a strong impact to the undercarriage — can deform the casing and puncture or deform the cells inside, leading to a short circuit.