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The main purpose is to keep the batteries in their sweet spot.
The main purpose is to keep the batteries in their sweet spot.
( Source: gemeinfrei / Pixabay)

Electromobility Why electric vehicles require cooling systems

| Author / Editor: Jason Unrau / Nicole Kareta

Internal combustion engines have been liquid-cooled for more than 100 years, and it’s well-known that heat is the number one enemy of an engine, threatening to destroy it by overheating. But electric motors operate under a different set of rules and heat isn’t as critical for the motor. So why do electric cars have cooling systems?

An internal combustion engine operates normally at 190 to 220 °F. Exceed that temperature and your engine will soon overheat and it could be permanently damaged. Operating temperature on an electric car’s motors is about the same, but it barely matters. Under normal use, EV motors don’t overheat. While EV motors often have a coolant jacket to whisk away excess heat, it rarely gets warmer than a cup of tea. It’s critical to keep EV’s batteries in the right operating temperature, and that’s why a cooling system exists for electric cars.

Normal operating temperature range of an EV

An EV’s motor can commonly reach 200 degrees F, but that’s not a concern at all. It can operate continuously at that temperature without problems. But batteries are a different story.

Under normal use, an electric vehicle’s batteries like to be in the 60 to 80 °F range. Anything below 40 °F or above 115 °F can result in decreased range in the short term and, long-term, it can damage capacity and shorten the battery pack’s life.

How a cooling system helps

EVs are cooled in more than one way, both air and liquid cooled. Just like a petroleum-powered vehicle’s liquid-filled cooling system. The main purpose is to keep the batteries in their sweet spot. When the battery pack continuously operates when it’s too hot, it can cut the service life in half.

And when an EV is charging, the kinetic energy heats up the battery packs. An electric car’s cooling system will maintain the battery’s comfortable temperature so it can recharge at the most efficient rate.

Typical EV Cooling System Designs

On all electric vehicles, air cooling is a method relied upon to keep both the electric motor and the battery cool. Since the motor is so much smaller than a comparably-powered ICE engine, a higher volume of air can pass around it. Earlier EV systems like that of the first-generation LEAF used air cooling for the battery pack, but it’s difficult to maintain the right temperature especially in hot climates.

Liquid cooling systems are by far the most reliable and efficient for EVs, like those used in Tesla, Jaguar, and BMW models.

Two liquid cooling systems exist as well, each with a unique design:

  • Indirect cooling systems are much like those of a typical ICE car. A series of pipes in the battery pack circulates coolant. The coolant absorbs excess heat and carries it away to a heat exchanger similar to a radiator where the heat is dispersed into the atmosphere. A water pump circulates the liquid. Because an indirect system can be designed to a specific battery pack for a particular model, it allows for fantastic adaptability, but it’s not as efficient as a direct cooling system.
  • Direct cooling systems have the battery cells submerged in a coolant liquid. Obviously, the thermal exchange is much more efficient since the batteries are in direct contact with the cooling liquid. However, the liquid must not have the ability to conduct electricity or the complete system would short. This system is in the R&D stage and is not currently employed by any manufacturers.

Batteries for electric vehicles continue to be developed at a rapid pace to allow for higher capacity, faster recharging, and better cooling. As more efficient EV cooling methods are found, it could greatly increase EV ranges and extend the life span of battery packs.

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