EV Battery Cooling - How Does It Work?

The battery is the heart of an EV, providing the energy needed to drive. As the battery generates heat while charging and discharging, having an efficient battery cooling system is crucial. This increase in battery temperature can cause it to wear out faster and even become unsafe.

Temperature management between different parts of the vehicle like the battery, HVAC system (heating, ventilation, and air conditioning), electric motor, and inverter is managed through the Battery Thermal Management System (BTMS). For instance, when the motor gets hot, some of that heat can be sent to either warm up the cabin or charge the battery, making the most out of the energy.

Employing EV battery charging best practices aligns seamlessly with this comprehensive temperature management approach. By understanding the interplay between battery temperature, charging cycles, and heat dissipation, EV owners can maximize the battery's lifespan and maintain optimal performance throughout the vehicle's life.

EV Battery Cooling Methods

EV battery cooling primarily relies on two major techniques: air cooling and liquid cooling.

Air Cooling

Air cooling is a way to control the battery's temperature using the air around it. There are two types: passive and active.

Passive air cooling uses natural air from outside or inside the car to cool or warm the battery. It's simple, but has its limitations and it can only handle a small amount of heat.

Active air cooling takes air from the air conditioner, which has a cooler and a heater to adjust the air's temperature. This is more complex and can manage more cooling power, around 1 kW. Active air cooling not only cools the battery but it can also warm up the cabin.

Active cooling is better at removing heat from the battery, which improves how the car drives and charges. But it costs more and needs more energy to work. The difference between active and passive cooling is that the former needs extra parts like fans, heat sinks, and cooling fluids, while the latter just uses the regular air around it.

Understanding these cooling methods is crucial for optimizing the performance and longevity of electric vehicle batteries, ensuring they are charged optimally and efficiently, without subjecting them to excessive heat. This can also impact the choice of car battery charger amps that are compatible with specific cooling systems, aligning the charging process with the cooling mechanisms in place.

Liquid Cooling

Liquid cooling is a widely used method to keep electric vehicle batteries cool. It uses a liquid coolant, like water or ethylene glycol, to lower the temperature. This liquid flows through tubes or plates around the battery cells, carrying the heat to a different place, like a radiator. The liquid makes sure the cells don't touch the coolant directly.

Active liquid cooling uses pumps, fans, and other devices to actively extract and redirect the heat. Sometimes, direct-contact mediums like oil are used, which touch the battery cells directly. But this is more common in non-consumer EVs, as it's not as safe and doesn't protect the cells as well.

Cooling Methods Over Time

Today, the majority of batteries are cooled with liquids using active cooling, which improves temperature management. Since liquids are hundreds of times more efficient in carrying heat than air, managing temperature is much simpler.

When electric vehicles first became popular, making batteries was more expensive. Manufacturers adopted passive air cooling to reduce costs. However, battery prices have significantly decreased in recent years, and quick charging—which requires superior cooling—has gained popularity. This has decreased the popularity of passive air cooling.

For instance, about ten years ago, you could choose between a Chevy Volt with liquid cooling, a bit less range, but a stronger battery, or a Nissan Leaf with air cooling and a battery with greater range. It was too expensive back then to produce a powerful battery with a long range and active cooling.

Active cooling is more expensive since it requires additional components such a heat pump, heat exchanger, pump, valves, and temperature sensors. However, it is a lot more reliable at keeping the battery cool.

Why EV Batteries Need to Be Cooled

EV batteries need to be cooled primarily to maintain their optimal operating temperature range and ensure safe and efficient performance. These batteries are designed to work best within a certain temperature range, typically between 68°F and 77°F. When batteries are in use, they naturally generate heat due to the chemical reactions occurring within the cells. If this heat is not managed properly, several issues can arise.

While in operation, these batteries can handle temperatures ranging from -22°F to 140°F. During recharging, the acceptable temperature range is between 32°F and 122°F. It's important to manage battery heat during use and ensure it stays within these ranges. When temperatures climb to high levels, typically between 158°F and 212°F, there's a risk of thermal runaway—a dangerous chain reaction that can lead to battery pack destruction.

At times, batteries also require heating, especially when temperatures drop too low or when optimal performance is needed. For instance, cells can't be charged if the temperature is below 32°F. Certain car manufacturers, such as Tesla, even offer battery preheating in some models to boost performance. This feature can enable rapid acceleration, propelling the vehicle from 0 to 60 mph in less than 2 seconds.

Exploring the concept of recycling EV car batteries is imperative in the pursuit of sustainable mobility solutions. Recycling processes aimed at repurposing used EV batteries can help reduce environmental impact, conserve valuable resources, and contribute to a more eco-friendly approach to transportation.

Thermal Management Challenges

While both liquid and air cooling systems play a vital role in maintaining battery temperature, each method comes with its distinct challenges. Let's delve into some of these thermal management challenges and how they differ between liquid and air cooling systems.

Liquid Cooling Challenges

• Leaks: Liquid cooling systems introduce the risk of leaks over time, particularly as the battery ages. Pipe connections and seals can degrade, potentially compromising the system's integrity. Leaks not only diminish battery performance and lifespan but can also pose safety hazards if humidity infiltrates the battery's electrical components.

• Corrosion: Liquid cooling systems utilize coolants like glycol, which can lead to corrosion of cold plates as the coolant ages. Preventing corrosion requires regular coolant replacement as part of the vehicle's maintenance routine, adding to ownership costs and maintenance complexity.

• Clogging: The numerous small channels through which liquid travels within the battery create a risk of clogging over time. Blockages can impede proper coolant circulation, leading to uneven cooling and potentially causing hotspots within the battery.

Air Cooling Challenges

• Climate Variability: Different climates worldwide present diverse challenges for air-cooled batteries. Extreme temperatures, whether scorching heat or frigid cold, can impact battery efficiency and performance. To address this, air-cooled systems need to manage temperature fluctuations effectively to ensure reliable operation.

• Consistent Cooling: Unlike liquid cooling systems, which can actively regulate temperature even when the vehicle is parked, air cooling relies on external airflow. Ensuring consistent cooling in various driving and parking scenarios, especially during extended periods of inactivity, can be challenging.

Common Challenges

• Aging: As batteries age, thermal management becomes more complex. Older batteries may experience increased heat generation and energy loss due to degradation. The thermal management system needs to account for these changing conditions to maintain safe and efficient battery operation over time.

Examples of Battery Thermal Management Systems

Several automakers have pioneered innovative battery thermal management systems to address these challenges.

Tesla

Tesla's vehicles incorporate a liquid cooling system that uses a network of coolant-filled tubes to maintain consistent battery temperature. This approach enables efficient cooling and heating of the battery pack, ensuring optimal performance and longevity.

Chevrolet Volt

The Chevrolet Volt also employs a liquid cooling system, similar to Tesla's approach, to manage battery temperature. This helps maintain stable operating conditions and ensures the battery's efficiency and durability.

Nissan

Nissan's LEAF utilizes an air-cooling system, which has evolved over time to enhance its effectiveness. The latest iteration of the LEAF employs a more advanced air cooling system to mitigate potential thermal issues.

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