By: Anand Kabra
We take a closer look at why battery safety is important in electric vehicles and what are new developments taking place in this field.
The Current Scenario
There are different types of lithium-ion batteries available in the market and many are still under development. Today, the most widely available chemistry combinations are NMC (Nickel, Manganese, Cobalt), NCA (Nickel, Cobalt, Aluminium), and LFP (Lithium, Ferrous Phosphate). A lot of research is being carried out worldwide for more varieties of chemistry.
The Indian Scenario
Indian weather is quite harsh and extreme, especially in the summers where temperatures go up to 40-45 degrees Celsius and when you hit the road, it may even cross 55-60 degrees Celsius. When the electric vehicle is running, the battery, not only, provides the required power but also starts to heat up.
Based on the design of the battery, the driving conditions and what time in the day is the EV driven, the battery’s temperature could fluctuate from as low as 5 degrees Celsius to 20 degrees Celsius above the ambient temperature. So, imagine if the ambient temperature is 40 degrees Celsius, the battery temperature could go up to as high as 60 degrees Celsius if the vehicle is running continuously.
The Safety Concern
Chemistries like NMC are basically unstable beyond a certain high temperature and, if the battery is fully charged, there is a risk of what is known as thermal runaway. Thermal runaway happens when there is a huge current flow and the temperature of the cell and battery start rising rapidly. One of the cells might, typically, turn rogue and go into a thermal runaway scenario, resulting in the battery catching fire. This is a critical point in battery or cell designing, especially under Indian conditions.
What Causes Thermal Runaway?
Thermal runaway happens when there is a huge current flow in a cell and the temperature of the cell and battery start rising rapidly. One of the cells might, typically, turn rogue and go into a thermal runaway scenario, resulting in the whole battery catching fire. This is a critical point in battery or cell designing, especially under Indian conditions.
Poor cell design (electrochemical or mechanical), manufacturing flaws, external abuse of cells (thermal, mechanical, or electrical), battery pack design or manufacture, protection electronics design or manufacture, and charger or system design or manufacture are all possible causes of failure. This can also happen during a crash. If the battery is not well-designed, and if anything penetrates the cell in case of a crash, that can also cause a thermal runaway.
Addressing the Issues
Safety is paramount and the battery design plays a major part in this. There are many safety solutions available. An ideal situation would be to keep the battery at low temperatures all the time, but this would mean investing heavily in active cooling solutions, which makes it a costly affair and not practical for the low-cost two/three-wheeler segments in India.
The other cost-effective options are different types of battery designs that can be built through multiple fuses. A lot of safety redundancies can be built into a battery design where one makes sure that, even if thermal runaway happens in one cell, it does not cascade onto the rest of the battery.
Future of EV Batteries
In future, chemistries will be cobalt-free, because cobalt is another unstable material that causes fire. We might move to sodium and other technologies in future, where the risk of fire or thermal runaway gets eliminated or, at least, reduced to a large extent, controlling safety right at the source.
Therefore, the solid-state electrolyte is the future and some developments may be taking place as we speak. The industry is focused on the rider’s safety, especially if one is going to travel long distances.
About the author: Anand Kabra is the Vice-Chairman and Managing Director of Kabra Extrusion Technik Ltd. Battrixx is a division of Kabra Extrusion Technik Ltd.
Disclaimer: The views and opinions expressed in this article are solely those of the original author. These views and opinions do not represent those of The Indian Express Group or its employees.