Power battery preheating and cooling have both benefited from the battery thermal management system, which is a crucial skill. It can make sure that its power battery performs safely and consistently at the appropriate temperature.
For this article, we’ll summarize the present research state on the power battery’s thermal management systems, compare and analyze four types of cooling system, including liquid cooling, air cooling, heat pipe, phase-change materials, and two heating system types, including external heating and internal heating.
What is Battery Thermal Management System?
By controlling the temperature of the batteries, a battery thermal management system will keep them functioning safely and effectively.
High battery temperature can hasten battery aging as well as pose some safety risks; low temperatures, on the other hand, can cause a reduction in battery capacity as well as a weakened charging or discharging performance.
The battery thermal management system regulates the battery’s operational temperature by either supplying heat during periods of extreme cold or dispersing heat during periods of extreme heat. Engineers adjust battery temperature within those systems using passive, active, or the hybrid heat exchange techniques.
In active solutions, the temperature of the battery is often changed by a pump or fan pumping a working fluid, like water, air, or another liquid. The passive approach involves transferring heat from the battery using either heat sink or pipelines made of materials that are thermally conductive. Key design elements of both passive and active systems are combined in the hybrid solution.
The battery Thermal Management System controls and dissipates heat produced by the electrochemical reactions that take place in the cells, enabling safe and effective operation of the battery.
Types of Battery Thermal Management System
The systems with and without moving fluids are categorized according to BTMS’s first main categorization in this way. The former are referred to as the active BTMS, while the latter are referred to as the passive BTMS.
Active BTMS
The most often utilized active BTMS in electric cars nowadays are those based on the coolant or forced air. For instance, Lexus and Toyota both employ fans to blow cool air via its battery cells.
The cooling fluid, which is often a solution of ethylene glycol and water, travels via tubes in close interaction with cells in Audi or Tesla vehicles.
Whenever liquid coolants were utilized, they can circulate inside the pipes as well as act indirectly or be in contact with cells (which are immersed inside the fluid). All the liquid cooling examples shown above use indirect systems.
The heat transfer efficiency loss between indirect and direct systems is one of their key drawbacks. This is mostly because of the resistance of heat transfer at the junction. This is between both the pipe carrying the refrigerant as well as the cell.
Nevertheless, indirect systems permit the utilization of common coolants currently used within combustion cars. This is because there isn’t any direct contact seen between this fluid as well as the battery’s electrical parts. This is why manufacturers who employ liquid cooling favor it over other alternatives today, not to mention how inexpensive it is.
More on Active BTMS
We’ve seen great increase in interest between the industrial and scientific levels about the submersion of cells into cooling fluids. The primary benefit of this setup is a more efficient heat transfer due to direct contact found between this cooling fluids and its cells. According to studies, compared to the indirect systems, the transfer might rise by as much as four times.
However there are substantial obstacles that prevent the execution of this unique solution today in the electric vehicles.
The primary one involves the requirement for more research in dielectric fluids which ensure proper cell operation, really aren’t incompatible with the various battery-pack components (current collectors, cells, electronics, etc.), are reasonably priced, and ensure the vehicle’s safety whenever there’s an impact.
Utilizing fluids having a boiling point within the necessary range of temperature for these cells, to take advantage of a liquid-vapor phase shift, is a more severe example of this possibility.
Passive BTMS
Active BTMS have drawbacks, and passive systems work around such drawbacks. While it is not currently used in electric vehicles, such kinds of systems has lately grown in significance due to the practical benefits.
Phase change material and the heat pipes are two significant families that stand out from the various passive alternatives. For use in BTMS, PCMs—particularly those exhibiting the solid-liquid phase transition have been thoroughly investigated. These two features make them desirable for preserving a consistent temperature across the battery pack. This is near to the applied PCM’s temperature at the phase change.
The heat transmission from these cells into the PCM and from its PCM into the battery pack at the exterior, is however, constrained by the aforementioned PCM families’ generally low thermal conductivity.
Several publications inside this literature suggest doping this PCM with the nanoparticles, expanded graphite, fibers, among other solutions, to overcome this constraint. Another option is to embed the PCM inside porous structures (often metallic ones).
Despite its success in establishing high thermal uniformity inside this battery pack, the PCMs have several drawbacks that prevent them from being the favored choice at the moment. They consist of the following:
- Poor thermal conductivity
- Loss of energy density whenever PCM becomes doped
- Restricted capacity for thermal storage
- Added weight to the battery pack
Hybrid BTMS
Lastly, hybrid systems are able to combine at least two aforementioned options to benefit from both passive and active systems.
The usage of PCMs using forced air, the PCMs using liquid cooling, and PCMs using heat pipes is among the most researched combinations. For the initial instance, using forced air as well as liquid cooling, for evacuating the generated heat outside is the goal to establish a proper distribution of temperature inside its battery pack.
Improved heat transmission from this PCM into the exterior of its cells is indeed the goal when using PCMs that include heat pipes such that the natural convection may cool these cells.
Although modern BTMS systems perform far better than the pure active or passive systems in managing the battery pack’s temperature, their complexity as well as expense prevent their widespread use in the electric vehicles.
Thermal Control of Batteries in the Electric Vehicles
The performance, dependability, as well as robustness of the electric cars that are battery – powered are all impacted by the thermal management of these vehicles. To operate well, electric cars require ideal temperatures. This battery pack, the power system, as well as other components must operate at the ideal temperature.
The charge, capable, and health of the battery are all maintained when kept at the ideal temperature. In ideal temperatures, power electronic system and the motors exhibit their optimum working profiles.
Electric cars and battery pack performance, lifespan, and cost are directly related. At ideal temperatures, the battery’s health, charge acceptance through regenerative braking, as well as the supply of the discharge power during beginning and acceleration are all at their peak. That battery life, maneuverability, and fuel efficiency of electric vehicles all suffer when the temperature rises. Battery thermal management is essential when taking into account the entire thermal impact of a battery on the electric cars.
System Thermal Control in Power Electronics
Electric motor control is handled by power electronic systems. This electric motor is driven in accordance with control instructions by power electronic system that work in tandem with electric vehicle management system. This power electronic system’s DC-DC converters, control circuits, and inverters are susceptible to temperature impacts.
The heat generated by these electronic circuits while they are operating must be released, and good thermal management is crucial. Control hiccups, component failures, including vehicle malfunctions can all be caused by poor heat management. In order to maintain ideal temperatures, the electronic system is typically coupled to the cooling system of the electric car.
Thermal management of the electric motors
The operating temperatures of an electric motor is crucial to the functioning of these vehicles since electric cars are motor-driven. When the load increases, the motor uses more battery power and gets hotter. In order for the motor to operate at peak efficiency in electric cars, cooling is required.
Electric vehicle cooling loops Maintenance of optimal temperature is crucial for electric cars to operate at a high level of efficiency. This electric vehicle’s cooling system controls the ideal temperature. The temperature of battery pack, and the motor temperature are all typically regulated by this cooling system. The electronics, batteries, motor, as well as related components are cooled inside this cooling loop by a coolant that is pumped by the electric pump. Radiators are utilized in cooling loops of electric cars to discharge heat into the surrounding air.
Evaporators are utilized in electric cars to dissipate heat from its cooling loop and its air conditioner is used to cool the systems inside its cooling loop.
Major Influences on Battery Thermal Management System
The usage of electric vehicles is expanding quickly. Global demand for the electric vehicles is fueled by a number of factors, including government subsidies and incentives, rising public awareness of climate change, stringent emission standards imposed by regulatory bodies, agreements to control pollution from our transportation sector, and improvements in the electric vehicle technology.
Therefore demand for the battery thermal management systems is thus increased as a result. The challenges associated with the thermal components include designing the cooling systems, enhancing designs to minimize power consumption, cost, and weight, and assessing the thermal designs of these thermal components.
The designing of the best flow channels, its choice of coolant, as well as the complexity regarding the flow and model are other factors that might cause issues while producing thermal components. Reducing the consumption of power without sacrificing system functionality and dependability is a major problem when creating thermal components.
The market of the battery thermal management systems is constrained by the complexity in component design in these systems. The use of the gasoline-powered vehicles is expected to decline in the coming years thanks to plans made by a number of governments, which include China, Germany, the United Kingdom, India, as well as France. This presents an appealing opportunity for global market for the automotives or car battery thermal management systems.
Why Is Battery Thermal Management System Important?
Encouraging the best battery performance
The battery heat management enables batteries to deliver electricity efficiently and safely. Chemical reactions take place during charging and discharging of the battery. These chemical reactions are temperature-dependent, much as many others. Thermal management focuses on preserving batteries at levels that are both safe and encourage their best performance.
Enables batteries function properly
The battery can operate as designed for long feasible with a decent TMS. The use of effective heat management strategies by engineers and designers guarantees that battery packs will have the following characteristics:
- Maintain their resistance to unintended self-discharge responses.
- Release energy at a desired voltage
Among all, temperature regulation is only one of the different factors which affect the efficiency and longevity of batteries. Batteries packs are made to work in particular situations.
Use your batteries properly so you can get the longest life possible out of them. Pay attention to elements like rate of discharge or charge and depth of the discharge.
Safeguards both people and batteries
The safety of batteries depends heavily on thermal control. The significance of proper temperature and design management is highlighted by fires connected to these lithium-ion batteries inside Samsung’s Galaxy phones. Samsung claims that battery flaws led to overheating and short-circuiting, not a deficiency in thermal management, yet thermal management clearly lowers the likelihood of these occurrences.
Batteries are designed to operate under specific conditions, according to battery designers. Nonetheless, they prepare for abuse scenarios. The actual world is complex and unexpected. Battery abuse can occur purposely or accidentally. Battery damage or operation outside the intended parameters are both considered abuse circumstances.
Conclusion
Battery temperature management enables batteries to function at their highest efficiency and for the greatest amount of time. Temperature affects all aspects of battery performance, including cycle life, voltage efficiency, self-discharge, as well as shelf life. To ensure optimal performance, the TMS maintains an optimal temperature.
