Do Electric Vehicles Overheat Differently Than Internal Combustion Engine Vehicles?

When it comes to the question of whether electric vehicles (EVs) overheat in the same way as their internal combustion engine (ICE) counterparts, the answer is both yes and no. This article delves into the nuances of heat management in EVs, highlighting the differences and similarities with ICE vehicles.

Why EVs Typically Don't Overheat

Under normal driving conditions, the amount of heat generated by the batteries, motors, and electronics of an EV is minimal. The components stay barely warm to the touch, which is why EVs are generally cheaper to run. Unlike ICE vehicles, which waste about 75% of their energy in heat, EVs convert a much higher percentage of their energy into useful work. A tiny amount of heat generated in EVs, such as that which keeps you warm in the winter, is appreciated but the rest is considered wasted energy.

The Challenge of Overheating in EVs

While EVs typically don't overheat under normal conditions, they can struggle to keep their batteries and motors cool when driven very hard, similar to the conditions of a race car. EVs often lack the advanced cooling systems found in traditional ICE vehicles, making them more susceptible to overheating under extreme conditions. For example, a Tesla car may go into a "limp mode" with reduced power output after just a few laps on a race course due to overheating.

Why Overheating in ICEs and EVs Is Different

The mechanics of overheating between ICE and EV vehicles are quite different. In an ICE, the engine overheats when it is run hard and the cooling system fails to manage the heat. This can lead to various issues, including warped aluminum heads or damage to the head gasket, which can be expensive to repair. However, in EVs, overheating is primarily a concern for the battery pack.

Battery Temperature Management in EVs

Any electrical system, including EVs, is not 100% efficient. Any losses in the system are generally converted into heat. In an EV, the battery pack and motor generate heat during high-performance driving. Many EVs have active thermal management systems designed to keep the battery pack and motor temperatures within safe limits. These systems typically include a cooling fluid that circulates through the battery pack, a refrigerant compressor, and a radiator.

For instance, the Nissan LEAF has a passive air-cooled battery pack. Under hot ambient temperatures and continued fast charging, the battery management system may limit fast charging speeds and acceleration to prevent the battery from overheating. The effectiveness of these systems can decline over time, similar to the cooling systems in ICE vehicles.

Consequences of Excessive Heat in EVs

If not properly managed, the excessive heat in an EV can lead to permanent damage to the battery pack, especially the drive motors which use permanent magnets. Once the temperature exceeds the Curie temperature, typically around 250°C, the performance of the magnets will degrade, leading to the "brickification" of the motor. This can cause significant issues with driving performance.

Modern EVs are equipped with monitoring systems that shut down the drive before the motor or battery pack overheats. However, the system can fail, leading to potential overheating issues. Tesla cars, for example, often enter a "limp mode" when the battery pack gets too hot, limiting the power output to around 120 HP.

Conclusion

While EVs are designed to minimize heat generation and overuse, they still face the challenge of managing heat under extreme conditions. The primary concern with EVs is the battery pack, which can be permanently damaged if overheating occurs. Unlike ICE vehicles, which have a more straightforward cooling system, EVs rely on more complex thermal management systems. Proper maintenance and understanding of these systems are crucial to ensuring the safe and efficient operation of electric vehicles.