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POPULAR TYPES OF RECHARGEABLE BATTERIES Why are Li-ion batteries preferred in the EV segment?

Nov 28, 2022

With the constant push for green mobility by the Government of India and people’s inclination to contribute to environmental safety, the adoption of electric vehicles is picking up pace in the country. This column illustrates why lithium-ion batteries are one of the most popular types of rechargeable batteries, which offer efficient charging. - Akash Agarwal, Senior Marketing and System Manager, Analog Devices

As India has an ambitious target of achieving 100% EV adoption by 2030, the government is continuously coming up with appropriate incentives to push the sector’s growth. The 100% FDI provision has encouraged the players to manufacture world-class vehicles and accelerate EV penetration. According to the Minister of State for Heavy Industries, a total of 3.11 lakh EVs were sold in 2021. And, till the first half of 2022, 4.19 lakh EVs were sold. This is quite encouraging for all the stakeholders, especially electric vehicle and battery manufacturers. However, despite all efforts, manufacturers are attracting criticism from consumers for the unwanted events of vehicles supported by Li-ion batteries catching fire over the last few months. These are unfortunate events and not good for the health of the industry and the overall EV growth ambitions of India.

Safety norms for manufacturers

To deter such incidents, the government is working to formulate safety norms that manufacturers will have to adhere to. It will soon release a notification to mandate amended AIS 156 and AIS 038 for the respective categories. The additions to the standard provide an additional test to avoid fire incidents in the future. It will also introduce battery certification to ensure safety and deter fire incidents. Recently, the Bureau of Indian Standards (BIS) has come up with a new standard, ‘IS 17855: 2022’ which is about the testing procedure of the characteristics of performance, reliability, and electrical functionality of EV battery packs.

Considering the situation and the negative impact the recent fire incidents have generated on EV growth, EV and battery manufacturers are in constant pursuit of the best ways to deliver quality battery solutions and ensure the safety of their valued consumers.

Why do EV catch fire?

The rising temperature of cities and the poor thermal management of Li-ion batteries are considered the key reasons behind the fire, but that’s not true. The major causes are battery abuse, cell or pack manufacturing defects, and short circuits leading to abnormal changes in chemical reactions within the battery cells. Also, lithium-ion batteries sometimes undergo thermal runaway when the cell temperature rises rapidly and the amount of heat generated exceeds the amount of heat dissipated. This situation, when it goes undetected, results in Li-ion batteries catching fire.

Thermal runaway is the most hazardous battery safety problem, and it can eventually lead to dangerous results, such as fire or explosion of the battery. For preventing thermal runaway, diagnosis and prognosis of the potential causes are important. There are numerous causes of thermal runaways, like internal short circuits caused by physical damage, overcharging of the battery beyond its maximum voltage, and battery temperatures outside the safe region either on the low side or the high side. The government, in its new amended safety regulation, has mandated a warning system for a thermal runway event.

How can an efficient Battery Management System (BMS) help?

Once a battery reaches a thermal runaway state, it is very difficult to contain its impact. Hence, the cause of the thermal runaway needs to be prevented and avoided. Also, one of the key aspects of Li-ion batteries is that they need to be constantly monitored, whether in parking or during shipment, as the batteries are always on.

An efficient Battery Management System (BMS), which is responsible for maintaining the battery in a safe operating area and always monitoring the battery, prevent the rise of short circuit current to abnormal limits, performs its duties efficiently, it can prevent thermal runaway events and eventually prevent fire. An inefficient BMS that fails to perform its duties will not be able to detect any warning signs and eventually will not be able to prevent a thermal runaway.

Characteristics of Li-ion batteries

Lithium-ion batteries are one of the most popular types of rechargeable batteries. Due to the various advantages it offers, it is preferred in the EV segment. Advantages like the best energy-to-weight ratios, high energy density, high open circuit voltage, and low self-discharge rate make them fit for vehicles. Besides, their inherent safe chemistry, longer life cycle, efficient charging, and ability to operate at low temperatures make them the best batteries for EVs.

However, certain internal changes due to improper use of the battery or abuse of the battery can lead to a fire in Li-ion batteries. But it can be prevented by adopting some proactive approaches and technical robustness at the manufacturing stage.

What manufacturers can do during the manufacturing process?

Manufacturers very well understand that batteries are not only the powerhouse for vehicles but also an important component in determining the features that matter to customers. Recognising this fact, they are continuously working to invent new technology and try new chemistries and configurations to improve battery pack performance and enhance safety features. However, they should increase their focus on some key elements during manufacturing.

They must work to make the BMS smarter, which will help in avoiding mishaps, and develop a battery monitoring system as per the requirements of the local environment. They can make this electronic system more robust to limit battery functions within its safe operating range. Through this concept, rechargeable battery cells can be managed better while ensuring proper monitoring of every cell. It can further help in monitoring the battery’s state, controlling its environment, calculating data, and reporting the same. During the charging and discharging of cells, maximum efficiency can be ensured with the help of the system.

With an efficient BMS, manufacturers can ensure effective thermal management during cell balancing, better monitoring of cell temperatures, managing charging current, and managing charge and discharge voltage to increase battery life, performance, and safety. While developing batteries, manufacturers must check the BMS and its efficacy in performing these tasks. Another good method that manufacturers can adopt to enhance battery safety is passive thermal management. In this method, a cooling method is used that absorbs extra heat through different thermodynamic processes such as radiation, conduction, and convection. This is an easier cooling process for smaller and mid-size batteries as compared to active cooling.

Apart from that, manufacturers can also think about using Latent Heat Systems (LHS) materials to increase battery safety. These materials absorb and store energy and reduce the hazardous thermal effects. They can prevent thermal runaway, keeping the temperature in equilibrium across the cells, and reducing the incidences of battery overheating. At the same time, the battery needs protection from short circuit conditions which occur due to certain system failures. BMS should be able to detect the short circuit condition as early as possible & take appropriate remedial measures to break the current path in the system. An efficient BMS will be able to restrict the rise of the short-circuit current flowing in the system. Controlling short circuits is important, as they can lead to a high-current situation beyond the control of the system. Many internal and external faults can cause a shortcircuit current. External faults such as mechanical damage, motor damage, or internal battery damage are some reasons for short circuit conditions. One of the reasons can be short circuits within the cell components (cathode and anode). This happens due to a faulty battery, poor battery design, cheaper quality, improper handling of the event, & more. To avoid such cases, manufacturers must use the best quality battery components and conduct extensive tests before launching the products in the market.

Measures required from consumers

Manufacturers’ actions alone are not enough to ensure battery safety. EVs demand equal care and attention from consumers. They must follow all the operating instructions provided by the manufacturer during the purchase. For instance, if they are going for any repair work, they should ensure the use of only components recommended by the manufacturer and not look to save a few bucks, especially on the battery and the associated components. Their precautionary steps will save them from any unfortunate events. It is also important to use the manufactured, provided, or recommended genuine chargers only to recharge the batteries. A faulty charger or unmonitored charging can impact both battery life and safety.

Electric vehicles are the future and the best way to combat rising fossil fuel prices and environmental deterioration. Quick adoption of EVs must be emphasised which is possible only when complete safety and unflinching trust is developed among the customers. This is will make everyone future-ready with appropriate solutions for upcoming challenges. In this endeavour, global leaders in the design and manufacturing of analog, mixedsignal, integrated circuits and semiconductors can help battery manufacturers immensely in developing a safe and secure battery management system for current and future battery technology.

Driving to the future

Li-ion batteries are the costliest and a critical component in an electrical vehicle. Li-ion batteries offer a path towards a green and pollution-free transportation option. But they need to be handled with care. The safety and protection of the Li-ion batteries is a shared responsibility between the cell manufacturers, equipment manufacturers and also consumers. All the stakeholders should work together to ensure that the entire journey of the batteries, from the manufacturing to the pack assembly to the usage in the vehicle, is safe and protected.

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  • Li-ion batteries are the costliest and a critical component in an electrical vehicle

    Li-ion batteries are the costliest and a critical component in an electrical vehicle

  • Akash Agarwal
Senior Marketing & System Manager
Analog Devices

    Akash Agarwal

    Senior Marketing & System Manager

    Analog Devices

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