The burning issue of EV fires.

Published in

Grinntech

5 min readJul 17, 2022

Recent case of Tata Nexon EV catching fire.

Since 2021, countless reports of electric vehicles catching fire have emerged raising concerns regarding their safety and roadworthiness in the present era. In India, at least one death has been reported to be directly caused by an EV catching fire that happened in the summer of this year. One Ather 450X, one Ola S1 pro, one Tata Nexon EV and two entire dealerships of Pure EV have caught fires reportedly caused by the battery packs entering into a state called “Thermal runaway”, a state where the temperature rise of the battery pack cannot be controlled at all. This is an extremely dangerous state that must be avoided at ALL costs as it can and sometimes WILL lead to loss of human life.

To understand how EV fires work, one must first make an attempt to understand how fires work in general. Any fire requires three key components to sustain itself viz., heat, fuel and oxygen. The supply of only one of them needs to be cutoff to kill a fire. Most fire extinguishers cutoff the supply of oxygen or heat or both in most cases. The supply of fuel on the other hand, can only be cutoff in certain situations such as fires that involve fuel pipes. Some fires are special in their own way. They generate their own oxygen and do NOT require an external source of oxygen such as air, these fires can get extremely hot in no time and are nearly impossible to control. Some common examples of substances that burn in such a manner are gunpowder, thermite and the elephant in the room, Lithium-ion batteries.

This is the reason why EV fires are so deadly, they generate their own oxygen to sustain themselves and generate extremely large quantities of heat. Adding insult to injury, battery packs are solids (rather solid blocks containing liquids) and its almost impossible to isolate them from the fire. This is a deadly combination and people’s concerns regarding their safety are quite genuine.

Chemical reactions involved in combustion of lithium-ion batteries. From the above equations, it is obvious that a lithium-ion battery produces sufficient oxygen to sustain its combustion. Any external supply of oxygen will only make the fire hotter.

The above information might just fan the flames of hysteria that exists against EVs but one must be assured that an EV is much less likely to catch fire than a conventional IC engine vehicle. Let’s look at the numbers here, out of 20,000 Nexon EVs sold by Tata between 2020 and 2022, just one has caught fire and zero people have reported injuries or death. Out of over 50,000 Ola S1 pros sold between 2021–22, just one caught fire and again, no injuries reported. The biggest reason for this is the fact that not a single component of an EV is likely to operate at a temperature beyond 100 degree Celsius whilst on the other hand, any IC engine can easily hit temperatures above 400 degree Celsius (conservative figures, diesel engines hit above 1000 at idle). This coupled with the fact that highly combustible liquids such as petrol are involved, the likelihood of a vehicle fire increases by several fold. In fact for every 100,000 EVs, 52 fires are reported annually in the US for petrol cars, the number is at 1529. This shows that an EV is nearly 30 times less likely to catch fire than a petrol-driven vehicle.

The danger in EV fires isn’t about the likelihood of fire, it’s about controlling and fighting EV fires which is the hard part. Only in the recent past have companies been able to develop fire extinguishing technology to deal with EV fires. (See Aqueous Vermiculite Dispersion (AVD) technology).

One of the common myths surrounding EV fire prevention and control is that this can be accomplished by the BMS. The BMS of a battery pack is incapable of either preventing or controlling a fire because of the fact that once a battery pack hits thermal runaway, there is no turning back for the battery. It WILL catch fire. A BMS can anticipate thermal runaway to a certain extent and can take some preventive action but even this is not guaranteed to completely prevent a fire from happening. Loss of life on the other hand, can be prevented as there is a time delay between a battery pack hitting thermal runaway and actually catching fire and passengers can be given enough warning to evacuate the vehicle. (One of the key reasons why, very few casualties have been reported).

EVs are by several orders of magnitude safer than IC engine or hybrid vehicles. The advent and further advancement of technologies such as AVD will only make EVs safer to use and will make fighting EV fires much easier. With the advent of sodium-sulphur batteries, EV fires may be eliminated all together thereby giving even more peace of mind to EV owners.

As of now, effective thermal management of battery packs, speedy evacuation procedures have already made EVs safer to drive. The automotive industry has also set standards on the quality and type of electronics and power electronics that can be used in an EV to reduce the chances of overheating, short-circuiting and any other factors that may lead to fire.

References

The burning issue of EV fires.

Written by Shreyas Maitreya