Like combustion engines, electric car batteries require a cooling system. Lithium-ion batteries are known for their efficiency and high-energy density, making them the battery of choice for electric car manufacturers. Sudden changes in temperature, such as high temperatures, cause loss of battery efficiency and degradation.
Liquid cooling systems are by far the most effective cooling system for batteries and you don’t have to buy a top-of-the-line electric car to get the most efficient thermal management system.
Before you buy an electric car, check out these 5 EVs that are innovating with their liquid-cooling systems.
- Tesla
- BMW i-3 and i-8
- Chevy Volt
- Ford Focus Electric
- Jaguar I-PACE
Why Use a Liquid Cooling Battery System?
Every electric car battery needs a cooling system. Batteries operate optimally at certain temperatures. Therefore, they were designed to only take certain temperature fluctuations.
Discharging the battery causes the discharge of heat. This could offset the working temperature significantly. Batteries operate better when they operate between 20-40ºC range, as well as keep the temperature difference within the battery pack to a minimum (less than 5ºC). Operating outside of this range can cause different charging and discharge rates and deteriorate the battery pack.
There are four cooling systems for batteries:
- Phase change material
- Fan cooling
- Air cooling
- Liquid cooling
However, phase change material, fan cooling, and air cooling are not as energy-efficient, nor as compact as a liquid cooling system. Compared to liquid-cooling, these systems are not ideal at cooling the battery for optimal life. The Nissan Leaf, for example, uses an air cooling system. It works but it isn’t the best for long-term battery performance.
Elon Musk has called Nissan’s air cooling system “primitive” compared to Tesla’s liquid cooling system. Everyone has an opinion.
Many EV companies prefer a liquid cooling system. With a better cooling system, many companies have further innovated these systems to extend what an electric vehicle can use.
Tesla’s Liquid Cooling System Is State of The Art
Tesla patented a liquid cooling system they call a battery management system (BMS). Tesla’s system also helps keep the battery warm during cooler temperatures. The BMS Tesla patent has every battery cell against the coolant pipe. This provides better thermal management because the pipes snake around the cells to provide more area for the heat to transfer.
This allows Tesla to push the limits of its cars including using the Ludicrous mode, a mode that allows a Tesla to expand on power and acceleration. However, there are still limits including the fact that even Tesla batteries can only be conditioned at 50ºC, just above the upper limits recommended for batteries, but still above the upper limits. Some even report using Ludicrous mode too often will damage the battery.
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BMW’s Liquid-Cooled Batteries Apply Simplicity
BMWs do not use coolant tubes that wrap around each cell. Instead, they use coolant tubes that go directly over the battery. It is a surprisingly simple design. But can it do the same job that a Tesla BMS can?
BMWs are one of the strongest competitors to Tesla when it comes to electric cars. Furthermore, BMW’s electric fleet is trying to push limits that even Tesla is yet to push including range and charging rates of batteries.
One of the greatest advantages of BMW’s liquid cooling system is its ability to disassemble. This allows the cooling system to easily be replaced and even repaired. Tesla’s cooling system is essentially a snake that wraps around thousands of cells. It cannot be easily disassembled. Therefore, you are less likely going to need a full battery replacement with a BMW than with a Tesla.
Chevy Volt Is Among the First to Provide Long-Lasting Batteries
The Chevy Volt (or Bolt) was the first commercially available plug-in hybrid. Although its reign is officially over, it will still have its mark on history in more than one way:
- Without the Chevy Volt, electric cars may not have been brought to the masses.
- It provided the first long-lasting battery to the masses.
Chevy Volts were among the first commercially available EVs that provided liquid-cooled batteries. Many of the other vehicles, including the Nissan Leaf, were air-cooled and their batteries just did not last long. Therefore, the Chevy Volt provided the first 100,000-mile battery under warranty to the masses.
Even though the Chevy Volt was more of an electric car for everyone, its liquid-cooled batteries were still a feat of engineering that promised quality. Coolant circulates through 144 metal plates (or fins) between the Volt’s 288 cells. These plates are incredibly thin, they are just 1 mm thick. When the battery is too cool, a heating coil heats the entire system.
GM claimed that the battery is reliable from -13 to 122ºF (-25 to 50ºC). Their batteries could stand some extremes. While the Chevy Volt may no longer be in production, it still helped make electric cars what they are today.
Ford Focus Electric Innovated Preconditioning and Charging
While the Chevy Volt was the first commercially available electric vehicle, it had many competitors that planned to bring affordable electric vehicles to the masses including Ford. Ford developed many electric vehicles including the limited production Ford Focus Electric to areas including California, New York, and New Jersey.
Unlike the Chevy Volt, this was an all-electric vehicle and Ford claimed they wanted to optimize the battery since there was no engine for the Ford Focus Electric to fall back on. They utilized a liquid cooling system that cooled and heated the battery for optimal performance.
That was not innovative by itself though. What the liquid cooling system helped do that was innovative was precondition the battery. By preconditioning the battery, the Ford Focus Electric could optimize the charging of the battery. This helps speed up charging the battery because the battery can only be charged at optimal temperatures. The Ford Focus Electric is among the first electric cars to utilize this, and now it is something many vehicles try to make standard.
The Jaguar I-PACE Optimizes Energy Efficiency in A Way You Probably Did Not Think Of
The previous cars mentioned talked about how liquid cooling systems bring down battery temperature to more optimal temperatures. This is passive as the liquid coolant can absorb energy and transfer the energy away from the battery. But, heating the battery from cool temperatures to optimal temperatures is different. Many vehicles use heating coils which heat the battery to an optimal temperature. That is good, but where is that heat energy coming from?
The energy is usually coming from the battery itself. In other words, you are using energy from the battery to heat the battery to optimal temperatures to get a more energy-efficient battery. It is a logic loop that consumes energy and will cut the range of a battery.
The Jaguar I-PACE innovated a thermal management system that helps solve this. In fact, they boast their cars have 30 extra miles per charge compared to their competitors.
An electric vehicle tries to control the temperature of three parts:
- The battery
- The motor
- The driver cabin
Each is individually temperature controlled during the drive. So what Jaguar thought is instead of wasting energy from the battery to heat each part individually, why not harness the energy from parts that have reached the upper limits of their optimal temperature to heat the other parts?
For instance, let us say the motor is getting a little too hot but the battery is a little too cool for optimal performance. The Jaguar I-PACE is designed to take the heat from the motor and transfer it to the battery to bring the battery to an optimal temperature. This not only makes the vehicle more energy efficient by utilizing what would be wasted energy but adds additional layers to control the temperature of these parts to produce the optimum drive with a Jaguar I-PACE.
This system is brilliant and now many vehicles are trying to harness wasted energy produced during the operation of these vehicles to make them more efficient.
Concluding Thoughts on Liquid-Cooled Batteries
Electric cars are going to become more common on the road. Many companies are innovating their batteries to have their cars compete with everything else on the road. The ones that hold the most promise use liquid-cooled batteries. Now some electric vehicles have extended range and optimal charging rates that could even compete with the range of gasoline-powered vehicles and even how quickly they can refuel.
More importantly, these systems are allowing companies to innovate their systems to even harness energy waste like the Jaguar I-PACE, a difficult but very rewarding goal in engineering.
With these innovations, it is far more likely that electric vehicles will one day dominate the road.
Photo by Macau Photo Agency on Unsplash