Why Does Electric Vehicles Catch Fire? How to Prevent?
You might have recently come across a video posted on social media wherein an Ola S1 Pro was spotted catching fire while parked on a roadside. The incident took place in Pune last week. Electric vehicles (EV) catching fire has become one of the most significant issues for the Indian electric vehicle industry. More than four videos of electric scooters catching fire have gone viral, and in one case, two individuals were killed in the incident. Industry experts warn that these incidents can not only bring down the growth of the EV production industry but also slow down the country’s initiation step towards the neutralization of carbon. Electric two-wheeler sales in India are expected to be 330-350K units in FY22. While the industry is sure of hitting one million units in FY23, it is certain that in the first six months of FY23, sales and production will be lower than in the second half as most OEMs have decided to go for corrective measures.
Is the Hot Summer Causing the Fire?
It seems that EVs are catching fire when parked in the sunlight. Some netizens attribute those fires to rising temperatures in the cities and the poor thermal management system of the EV battery. Besides the reality of climate change and summers getting hotter, manufacturers argue that an EV comprising lithium-ion (Li-ion) cells requires a few hundred degrees Celsius before suffering a ‘thermal runaway incident’ and the fires that emerge as a result.
While hot weather conditions and inadequate thermal management systems of the battery can negatively impact performance and shorten life, they do not cause fires. Manufacturers of most modern Li-ion batteries ensure that they automatically switch off around 45-55 degrees Celsius. Even if these safety features aren’t built-in, it’s impossible for the ambient heat and the heat generated by batteries together to result in a spike of a few hundred degrees Celsius.
Arun Vinayak, CEO, and Founder, Exponent Energy explains, “99 percent of battery fires are due to short circuits leading to uncontrolled current. This is the only scenario in which cells heat themselves up beyond 100°C.Temperature affects life and performance of the battery, but it doesn’t result in a fire. For a lithium-ion battery to catch fire, you need to get to a few hundred degrees Celsius. That’s not possible through ambient heat or the heat generated by an operational battery. Fundamentally, there has to be a short circuit for the battery cell to hit that sort of temperature which results in it catching fire. In other words, the temperature outside is irrelevant to whether the battery will catch fire or not.”
Role of Lithium-ion in Catching Fire
Lithium-ion cells have two terminals, an anode (-ve) and a cathode (+ve). Each of these terminals is separated. The space between them is taken up by a separator, an appropriately named component. During the electrical discharge, the motor connects the anode and cathode in a controlled fashion, followed by a controlled flow of current drawn from the cells. One of the reasons for internal short-circuiting in the battery is poor cell quality. Shortcomings in battery manufacturing cause the accidental connection of the anode and cathode, which short circuits the regular path of the current, eventually resulting in fire. When these cells short-circuit, they also release flammable gasses through a process that lessens the probability of a thermal runaway called cell venting.
Dr. Akshay Singhal, Co-Founder, and CEO of Log9 Materials says, “One of the challenges of the two, three and entry-level four-wheeler EV segments is that we borrowed technology from the West and without applying our minds copy-pasted it into our vehicles without taking into consideration Indian conditions. Many OEMs didn’t look at how we can make these vehicles safer and resilient here.”
However, more than poor cell quality, it’s the battery packaging design that has the strongest bearing on safety. Battery packaging refers to the way manufacturers assemble the cells, join them electrically and hold them together. Even though the EV contains quality cells that are packaged well, fires can still occur from overcharging. What is the maximum voltage of an NMC (nickel, manganese, and cobalt) and LFP (lithium Ferro phosphate) battery, which are both lithium-ion battery chemistries? It’s approximately 4.2V for NMC and 3.6V for LFP. If the user overcharges an NMC battery by barely 0.05V, it will create dendrites similar to ice crystals in caves. Overcharging happens as a result of an inadequate BMS that does not have the requisite intelligence or sensing to manage cells. EVs powered by lithium-ion batteries are considered safer, efficient, and lighter when compared to their counterparts.
What to do When the Battery Catches Fire?
If the lithium-ion battery overheats, users should try moving the device away from flammable materials and cutting off the current supply. If it is an electric vehicle, immediately users must evacuate and should not attempt to extinguish lithium battery fires themself. A standard ABC or BC dry chemical fire extinguisher must be used in case of fire since these are considered Class B fires.
How to Prevent EVs from Catching Fire?
Coming to failsafe measures, multiple types can be built into the system. For example, with a proper built-in temperature sensor, if the battery cell is going above a specific temperature, the system either cuts off power, immobilizes the vehicle, or pushes a notification to the customer that they need to take this vehicle to a secluded place where if at all something happens, it doesn’t result in the loss of life and property.
Guaranteed measures are also required on the charger side. There are smart chargers used to charge EVs. These chargers can communicate with the battery pack and get data on the temperature or the battery’s health. If failsafe measures are built-in, the charger can share that the battery temperature is too hot and can’t be charged right now because it requires some cooling first. After all, one cell catching fire and exploding will not lead to loss of life or property. But if the entire battery pack explodes, it’s a different story altogether.