The market for electric vehicles (EVs) is moving faster toward mass adoption, but the overall cost of vehicles must come down so more people can afford to purchase them. EV original equipment manufacturers (OEMs) are developing new technologies every day with that goal in mind.  Central to this comes the battery. One of the ways they are looking to reduce costs is by adopting a thermal management system that is more efficient, durable and easy to integrate. To date, the most common cooling systems are indirect , which use refrigerants and water-glycol mix that doesn’t come into direct contact with the battery.

While both systems have their benefits, a third option is emerging. Direct immersion cooling, a process in which the battery is directly submerged in a dielectric coolant, is expected to be deployed in production vehicles between 2025 and 2027. In preparation, OEMs are deciding which systems provide the most cooling power for the least integrated cost—and immersion cooling is clearly leading the way, here’s why: 

Refrigerant Cooling

To use refrigerant cooling in an EV, an A-coil or evaporator must be built to run underneath the battery pack. This system has two significant flaws:

• The tube containing the refrigerant must be shorter than four feet long because otherwise it doesn’t have the necessary cooling effect.
• It requires OEMs to build a redundant system to heat the battery.

While the system does effectively cool the battery, it requires significantly more hardware and engineering time than other methods, which increases the costs of using this method. 

Water-Glycol Cooling

In contrast, water-glycol cooling can be cost-effective up to specific heat levels that depend on the size of the battery and how quickly it is charged. As batteries get larger and the need for faster charging becomes paramount, however, the amount of heat generated increases significantly.

The more heat that is generated (charging an EV battery quickly—a key consumer demand—generates intense heat, i.e. >12-15 KW of heat in the case of 350 KW supercharger), the more cooling jackets are necessary. The additional parts, combined with the engineering necessary to make a water-glycol system work effectively, can, in some cases, quadruple the price of the system. OEMs must then pass this cost on to the consumer.

Why Immersion Cooling Is the Answer

Unlike refrigerant cooling and water-glycol systems, an immersion cooling system is simple to construct. All that is needed is a container to hold the fluids and two tubes (one into the battery pack and one out) typically called an inlet and outlet.  By reducing the number of parts, the costs to build a battery pack become less expensive. By lowering the price of the components, the overall price of the vehicle can come down, making them more accessible to more people.

In today’s EVs, battery packs  tend to be larger than necessary, which drives up production costs and limits cargo capacity. Immersion cooling allows OEMs to downsize their battery packs  as they no longer need the excess capacity to account for potential overheating. Smaller batteries cost less to manufacture, and OEMs can pass the savings on to the consumer. Moreover, less weight helps to increase the overall efficiency of the e-Powertrain, therefore preserving the battery’s range while downsizing. 

Though OEMs are in the early stages of testing immersion cooling in production vehicles, the indications are that this emerging cooling technology will eventually become standard for most EV battery-cooling systems. Its cost-effectiveness, combined with its safety profile, make it the logical choice for EV OEMs in the future.

Learn about Lubrizol's EVOGEN™ thermal management fluids

Our View

The shift to mass production of EVs is becoming more likely as governments around the world pass legislation to deal with the effects of climate change. To make EVs attractive to the public, the costs of the vehicles will have to come down and finding the most effective battery cooling solution is key to that effort. As immersion cooling becomes more common, the fluids necessary to cool the batteries will have to evolve as well. 

For more information on immersion cooling, contact us or visit the Electrification section of Lubrizol360.