Electric Vehicle fire incidents

Recently, in India, there have been multiple incidents of two-wheeler electric vehicles (EVs) catching fire.

What is the response of the government?

·         The Union Government constituted an expert panel to probe the recent series of Li-ion battery explosions in electric vehicles (EVs).
·         Last month, the government asked the Centre for Fire Explosive and Environment Safety (CFEES) to probe the incident in Pune and give suggestions to prevent such incidents.

Who are the major electric vehicles (EVs) manufacturers?

Pure EV, Ola, Okinawa, and Jitendra EV scooters.

What factors contributed to the growth of electric vehicles?

·         The growing concern over climate change gave the push to the development of electric vehicles.
·         The cost of Li-ion (Lithium-ion) batteries has decreased significantly in the last decade.
·         The governments are providing incentives and private industry is ramping up plans for capturing the market.

The convergence of these factors is leading to the transition in the transportation sector.

What is an electric vehicle?

·         An electric vehicle (EV) operates on an electric motor, instead of an internal-combustion engine. Batteries are used to power electric motors.
·         As the electric vehicle runs on electricity, it emits no exhaust from a tailpipe and does not contain the liquid fuel components, such as a fuel pump, fuel line, or fuel tank.

Which type of battery is used in electric vehicles?

The most common type of battery used in modern electric vehicles is the lithium-ion battery.

Why lithium-ion batteries are most preferred batteries?

Because they charge faster, last longer, and have high energy density. They are also lightweight and require low maintenance.

What are the components of lithium-ion batteries?

Every Li-ion battery consists of three active components:

1.      The anode, typically graphite.
2.     The cathode, typically based on nickel, cobalt, and manganese-based oxide.
3.     An electrolyte, typically a salt of lithium in an inorganic solvent.

Manufacturing of lithium-ion battery is a complex task involving forming sheets of the anode and cathode and assembling them into a sandwich structure held apart by a thin separator.

What is the function of separators in lithium-ion batteries?

The main function of separators is to keep the anode and cathode apart to prevent electrical short circuits.

What causes battery fires?

Battery fires, like other fires, occur due to the convergence of three parts of the “fire triangle”:

·        Heat: If an adverse event such as a short circuit occurs in the battery, the internal temperature can rise.  This can lead to a series of reactions that release heat in an uncontrolled manner.
·        Oxygen: Such events rupture the sealed battery exposing the components to oxygen.
·        Fuel: The liquid electrolyte, which is flammable and serves as a fuel.

The combination leads to catastrophic failure of the battery resulting in smoke, heat, and fire, released instantaneously and explosively.

What causes such adverse events?

The trigger for such events can be a result of:

·         Internal short circuits (like a manufacturing defect that results in sharp objects penetrating the separator).
·         External events (like an accident leading to puncture of the cell and shorting of the electrodes).
·         Overcharging the battery which leads to the heat releasing reactions on the cathode (by a faulty battery management system that does not shut down charging).
·         Bad thermal design (by not allowing the battery’s internal heat to be released).

How to prevent battery fires?

The fire triangle should be broken. Tightly controlled manufacturing will prevent accidental short-circuiting. Robust thermal management is critical, especially in India where temperatures are high. Finally, battery packs need to be protected from external penetration.

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