An EV battery is more than just a storage device because it forms the center of any electric car. Its temperature affects its efficiency in charging, its range, the amount of power that the electric motor gets, and the safety of the system as well.
This is where EV battery thermal management comes into play. Contemporary electric cars feature advanced cooling and heating mechanisms to ensure that the battery cells are maintained at their optimal working temperature range. This prevents the battery from overheating while the car is being charged quickly and driven aggressively, and from being too cold during the winter months.
As more electric cars appear on the market and the charging becomes faster, the battery packs increase in size, and the electric motors improve in performance, thermal management becomes one of the key technologies that define the performance of an electric vehicle.
The EV battery thermal management system is the one which is used to control the temperature of the battery pack inside the car.
The lithium-ion batteries are prone to heat during their charge/discharge cycles. The acceleration, fast driving, high charging rate and high temperatures can result in overheating of the battery. In such situations, the battery starts degrading quickly and its efficiency drops significantly.
On the other hand, in very cold temperatures, the battery will not be able to discharge properly and it will have poor charging performance.
The thermal management system is aimed at keeping the battery at certain operating temperatures. It may include liquid cooling, refrigerant cooling, heating, heat pump and others.
It is important to note that battery chemistry is very temperature-sensitive. When the battery is operating outside its comfortable temperature zone, its efficiency and charge/discharge capabilities will be affected.
In cases where the battery gets overheated, it can be possible that the car will limit the amount of energy going into and out of it, to protect it from any potential damage. This explains why EVs that have performed well at the start of a long drive may later show low efficiency during driving or charging.
On the other hand, cold batteries can be hard to charge effectively, especially when they require high charging currents. That is why some EVs use the battery pre-conditioning function prior to the fast charging process.
With recent advancements in EV technology, the need to use a liquid cooling method in many EVs has grown because of the need for an adequate cooling system when using high energy density batteries and fast charging systems.
In this case, there is the flow of the liquid cooling agent in and out of the battery. This liquid draws in the heat from the battery and flows out of it to the cooling element in order for the heat to be dissipated.
It occurs continuously and is controlled by sensors. The benefit of such a cooling system is that it allows for more precise temperature regulation of a large battery pack.
Before reaching a fast-charging station, the EV can take advantage of its navigation capabilities and software to prepare the battery for the process of charging. The EV system will warm up the battery if it is cold. In addition, the system will cool down the battery if required.
The result is that the battery will reach the proper temperature before charging.