Explained: Why e-scooters have been catching fire in India

At least four incidences of two-wheeler vehicles bursting into flames after being fueled by lithium-ion batteries have been reported. What exactly are Li-ion batteries, and how do they function? What sparked the fires in these vehicles?

At least four documented incidents of two-wheeler electric cars — built by companies including Ola, Okinawa, and Pure EV — bursting into flames in the previous five days have brought to light safety concerns about such vehicles, particularly the batteries that power them.

EVs are powered by lithium-ion batteries, which are similar to those found in cellphones and smartwatches and are thought to be more efficient and lightweight than their counterparts. They may, however, offer a fire hazard, as proven by recent events.

What exactly are lithium-ion batteries and how do they function?

Lithium-ion (Li-ion) batteries are the most common battery type today, powering millions of consumer goods around the world, from electric automobiles to smartphones to laptops. An anode, cathode, separator, electrolyte, and two current collectors make up a Li-ion battery. The lithium is stored in the anode and cathode, while the electrolyte transports positively charged lithium ions from the anode to the cathode and back through the separator. The mobility of the lithium ions in the anode produces free electrons, which generate a charge at the positive current collector.

The lightweight, high energy density, and ability to recharge make Li-ion batteries superior to other types and more suited for items like electric cars and smartphones.

A Li-ion battery can store 150 watts-hour per kilogram, whereas a lead-acid battery can only store roughly 25 watts-hour per kilogram. Simply put, Li-ion batteries are more efficient than other battery types while maintaining a product's compact form factor. This means that an electric car equipped with Li-ion batteries will have a longer driving range, and smartphones will last longer throughout the day.

However, one of the Li-ion batteries' most significant advantages — their great energy density — could also be the battery's undoing. According to a blog post by Ather Energy, a two-wheel EV manufacturer, Li-ion batteries' high energy density causes them to become unstable in certain settings, causing them to malfunction.

What is a battery management system, and how does it work?

A BMS is an electronic system that is connected to all of the cells in a Li-ion battery pack and continuously measures their voltage and current flow. A BMS is also equipped with a number of temperature sensors that provide it with data on the temperatures in various parts of the battery pack. All of this information aids the BMS in calculating various battery pack metrics such as charging and discharging rates, battery life cycle, and efficiency.

So, why did the batteries on the Ola, Okinawa, and other EVs catch fire?

The exact cause of the Ola and Okinawa EVs catching fire is unknown at this time since the firms have said that they are researching the situation. According to Okinawa's preliminary findings, which were based on "reliable sources, the media, and local authorities," the fire in its scooter was caused by short-circuiting caused by "negligence in charging the vehicle."

These cases, however, serve as a cautionary reminder of the dangers of Li-ion battery pack problems. According to industry experts, a variety of factors such as manufacturing flaws, external damage, or BMS deployment flaws could cause these batteries to catch fire.

Temperature, on the other hand, plays a critical function in a Li-ion battery pack, according to specialists. "While Li-ion batteries operate better in warmer temperatures, excessively high temperatures might cause the battery pack's ambient temperature to rise to 90-100 degrees, which is when they become extremely prone to catching fire," an EV manufacturer representative stated on condition of anonymity.

Aside from that, EVs and electronic devices have battery packs that contain hundreds of batteries. Given that a battery pack is tightly packed with a number of Li-ion cells, this implies that even if a few batteries malfunction and cause a short circuit, it can start a chain reaction that results in a fire.

Temperature, on the other hand, according to experts, plays a significant role in a Li-ion battery pack. "While Li-ion batteries perform better in warmer temperatures, excessively high temperatures may cause the battery pack's ambient temperature to rise to 90-100 degrees, which is when they become extremely prone to catching fire," a representative from an EV manufacturer said on condition of anonymity.

EVs and electronic devices, on the other hand, have battery packs that contain hundreds of batteries. Because a battery pack contains a large number of Li-ion cells, even if a few of them malfunction and generate a short circuit, it can cause a chain reaction that culminates in a fire.

What has been the public's response to the fires?

While the firms conduct their own investigations into the events, the Ministry of Road Transport and Highways has requested an inquiry into the vehicles that caught fire unexpectedly, and is said to have contacted the Centre for Fire Explosive and Environment Safety (CFEES) for assistance.

What are some examples of fires caused by malfunctioning Li-ion batteries in the past?
There have been several incidents where Li-ion battery-powered equipment or vehicles have burst into flames. Samsung's Note 7 and a Tesla Model S that caught fire while parked in a Shanghai parking garage are two examples that stick out.

In the case of the Tesla fire, the firm stated that the fire was caused by a single battery module located in the vehicle's front, and that no other system flaws were discovered during its investigation.

In Samsung's case, which affects thousands of Note 7 smartphones, the company blamed the fire on manufacturing flaws. In some cases, the insulation tape around the batteries was missing, causing short circuiting, and some batteries had sharp protrusions inside the cell, causing damage to the separator between the anode and cathode.