EV Batteries and Safety Challenges: From Maintenance to Thermal Runaway

Know the factors that affect battery health, protection technology, and fire risk mitigation measures in electric vehicles.

Batteries are among the most important components in electric vehicles (EVs). They affect mileage, performance, ownership costs, and safety. Users need to understand how they work, what affects their lifespan, and the safety risks they may pose.

One risk to understand is thermal runaway, a condition in which reactions inside the battery cell produce uncontrolled heat and can trigger a chain reaction in other cells. Not all battery failures lead to fire, but the impact can be very serious if the protection system fails to control these conditions.

How can users maintain battery health while reducing safety risks?

Understanding Thermal Runaway and Its Causes

Lithium-ion batteries consist of many cells working together in a single system. Under normal conditions, charging and discharging stay within predetermined voltage, current, and temperature limits. However, when certain faults occur, heat can rise beyond safe limits, causing internal breakdowns and chain reactions known as thermal runaway.

In general, three groups of factors can trigger thermal runaway.

First, electrical failure, such as short circuits or short circuits in cells caused by internal damage, production defects, or degradation.

Second, mechanical failure, such as collisions, hard impacts, or punctures of battery parts. Internal damage is not always visible from the vehicle's exterior, so a professional inspection is still necessary after an accident.

Third, thermal failure occurs when the battery experiences excessive heat due to cooling system failure, improper operating conditions, or other disturbances. If it leads to thermal runaway.

Signs to prevent proper heat management to watch for include smoke, unusual odors, hissing sounds, excessive heat, or warnings from the vehicle system. Changes in the battery's shape are also a red flag. However, some thermal runaway events may not show easily recognizable signs, so users should not rely on visible signs alone.

Lithium-ion battery fires can reignite after the initial fire appears extinguished because heat and internal reactions continue. The released gases can also be dangerous if inhaled. Therefore, handling them requires special procedures and equipment to manage the risk safely.

Six Steps to Keeping EV Battery Health

1. Manage the battery charge rate

The State of Charge (SoC) indicates the percentage of energy available inside the battery. For everyday use, a charge range of around 20–80% can be a practical guide for many electric vehicles. However, the recommended limit still depends on the type of battery chemistry and the manufacturer's instructions.

Users don't always need to charge to 100% if their travel needs don't require it. You can still fully charge when needed, especially if the manufacturer recommends it. For vehicles stored for a long time, follow the manufacturer's battery storage instructions and avoid leaving them at a low charge.

2. Pay attention to the temperature of the battery

Overheating can accelerate battery degradation, while temperatures that are too low can limit performance and charging capability. Therefore, park in the shade whenever possible and use the vehicle's temperature management features.

Don't assume one temperature limit applies to all battery types. Cell design, the cooling system, and the manufacturer's recommendations determine safe limits and temperature-control strategies.

3. Use charging as needed

AC (slow charging) can be a practical option for daily needs. High-power DC charging, or fast charging, is useful when traveling requires faster charging, but follow the manufacturer's recommendations for frequency and conditions of use.

If the vehicle offers battery preconditioning, use it as directed, especially before fast charging. This system helps prepare the battery temperature so charging occurs under appropriate conditions.

4. Do not leave the battery empty for too long

Vehicles left in very low SoC conditions for days or weeks risk further discharge due to the vehicle's system power consumption. If the vehicle will be out of use for a long time, check the storage instructions and battery power check schedule.

5. Pay attention to software updates

The Battery Management System (BMS) monitors cell conditions, voltage, current, and temperature, and helps control the charging and discharging process. Official software updates may include improved control or safety functions. Therefore, follow the manufacturer's update notifications.

6. Do regular check-ups

During service, ask whether they can check the state of health (SoH), cooling system, connectors, and related electrical systems. These checks become even more important after the vehicle has been impacted, flooded, or has shown unusual warnings.

Technology That Protects Batteries from Thermal Runaway

Prevention doesn't depend only on the user. Vehicle and battery manufacturers also have a major responsibility to apply safety technology that helps reduce the risk of thermal runaway.

BMS helps keep the battery operating within predetermined limits. Meanwhile, the Thermal Management System (TMS), with air or liquid cooling, helps control temperature. Liquid cooling systems can provide more even temperature control in certain designs; however, their effectiveness still depends on the overall design.

At the cell and module level, battery design can include a thermal barrier, gas discharge path, fuse, and isolation mechanism to reduce the chance of one cell's failure spreading to another.

The choice of battery chemistry also affects safety characteristics. Lithium Iron Phosphate (LFP) batteries, for example, generally have better thermal stability than nickel-based chemicals such as NMC (Nickel Manganese Cobalt). However, LFP batteries generally have lower energy density. These differences should be treated as design considerations, not guarantees that a battery type is completely free of fire risk.

What Should Users Do in an Emergency Situation?

If you see smoke, smell strong odors, notice abnormal heat, or see serious battery warnings, safety is the priority. When possible, stop the vehicle in a safe place, turn it off, evacuate passengers, and stay away. Do not attempt to open or repair the high-voltage battery yourself, because thermal runaway can escalate quickly.

Call emergency services or the fire department and tell them the vehicle has a high-voltage battery. Do not approach the vehicle again or assume the situation is safe just because the smoke or fire has disappeared. Follow the directions of a trained officer.

After an accident, an inspection at an authorized workshop or competent facility is still necessary, even if the exterior damage appears to be minor. Battery damage can occur without being visible from the outside.

Users also need to ensure that the home charging installation meets electrical requirements, uses appropriate, quality charging devices, and includes proper protection and grounding. Avoid vehicle modifications that could interfere with the cooling system, battery protection, or electrical installations.

The Role of Industry and Regulation

The safety of electric vehicle batteries is a shared responsibility between manufacturers, charging facility providers, regulators, workshops, firefighters, and users. Manufacturers must implement appropriate safety design and testing, provide clear usage information, and tackle possible product defects through vehicle repair or recall mechanisms if necessary.

To support the development of a safe and reliable battery ecosystem, the National Battery Research Institute (NBRI) also provides industry consulting on battery technology, technical evaluation, and the development and application of battery technology. Through a research-based approach and expertise in batteries, this consultancy can help the industry understand battery characteristics, evaluate technical problems, and consider safety and reliability in the development and use of battery technology.

Safety standards also need to be understood in the context of their scope. UN Regulation No. 100 contains safety requirements for electric vehicles and rechargeable electric energy storage systems. Meanwhile, UN 38.3 regulates battery testing for transportation, not comprehensive certification of vehicle safety during use.

Meanwhile, increasing the capacity of workshops and firefighters to handle electric vehicles must keep pace with the growth of the EV population. Batteries that no longer meet vehicle needs can also be evaluated for second use, as long as their technical condition, inspection results, and safety requirements allow.

Conclusion: Durable Batteries Must Run With Safety

Thermal runaway is a risk worth taking seriously, but it is not a reason to consider all electric vehicles dangerous. Safety depends on design quality, protection systems, battery condition, maintenance, and user behavior. Ultimately, safe battery use requires both technical protection and disciplined user habits to reduce the risk of thermal runaway.

Keep three principles in mind. First, choose a vehicle with a well-designed battery management and protection system. Second, follow charging recommendations, avoid extreme operating conditions, and check periodically. Third, recognize red flags and don't risk handling high-voltage battery faults yourself.

EV batteries aren't just components to be recharged; they're high-tech energy systems that require proper management. With a solid understanding and disciplined maintenance, users can help maintain battery performance and support safer electric vehicle use. In the end, safety and durability go hand in hand: manage the battery well, follow recommended practices, and respond quickly to warning signs.