What is a battery thermal management system?

As one of the core three electrical systems of pure electric commercial vehicles, the power battery pack is mainly effective in providing energy for the drive of electric trucks.

For power batteries, temperature is one of the key factors affecting the normal charging and discharging performance and range of the battery.

Excessively cold temperatures in winter can lead to a significant reduction in vehicle range, while excessively hot temperatures in summer can affect battery heat dissipation or even spontaneous combustion.

In order to maintain a good performance of the battery pack in all ambient temperatures, many vehicle manufacturers equip it with a thermal management system. So what exactly does a thermal management system do? And what are the mainstream thermal management systems in trucks?

What is a battery thermal management system?

There is no doubt that the temperature at which the battery is used and the ambient temperature are extremely important for purely electric trucks. In partially harsh conditions such as extreme heat or cold, there is a risk of damage to the battery, which can reduce its performance and service life.

Although the external styling of most pure electric trucks has seen the traditional large open grille on fuel vehicles removed in favour of a more technical, closed design, the three electric systems still generate heat when the pure electric truck is in operation and also require some cooling.

For example, if the battery overheats during use, it will have a certain impact on the safety and service life of the battery itself. In addition, in winter, the battery performance and efficiency of pure electric trucks will become lower if the vehicle is used in cold areas, the most direct impact is that the range is greatly reduced, and in too low a temperature, electric trucks usually also appear to be too slow or even difficult to charge.

Of course, the motor also needs coolant to dissipate heat. At present, pure electric trucks are mostly equipped with permanent magnet synchronous motors, which still need coolant to dissipate heat under heavy load and hill climbing conditions. If the motor gets too hot for too long, the permanent magnets may be demagnetised and irreversible damage may occur.

The application of the battery thermal management system is one of the key technologies to ensure that the power battery is used properly in different temperatures and under different conditions to maximise the use of battery energy to assist in driving. Its main objective is to keep the battery temperature within the right range, thus allowing the battery pack to operate optimally.

For example, the thermal management system can adjust the temperature of the battery itself for different ambient temperatures to reduce the impact of external temperatures on battery performance. In addition, the thermal management system can inhibit the formation of localised hot zones and reduce temperature differences within the battery pack, thus avoiding the effects of localised overheating of the battery pack.

At present, the mainstream battery thermal management solutions in the commercial vehicle market are mainly divided into two categories: air-cooled and liquid-cooled.

Most of the pure electric small trucks, micro trucks and light trucks are mainly air-cooled, while liquid-cooled are more often used in pure electric heavy trucks and tractor trailers, where the charging and discharging power is greater.

By air cooling we actually mean natural cooling, the principle of which is to use natural wind to cool down the battery. 

It is reported that there is also an upgraded air-cooling solution, where a material that can conduct heat is added to the electrode ends of the battery cell, allowing heat to be transferred through the heat-conducting material to the metal casing to dissipate heat, and its overall cooling efficiency will be even better.

The main advantage of air-cooled cooling is that it is simple and low cost, and there is no possibility of liquid leakage, making it more reliable overall.

If the local temperature is suitable for all seasons and there is no extreme heat or cold weather, air-cooling is also sufficient and suitable for pure electric truck operation.

On the whole, air-cooled thermal management is clearly a more suitable option for purely electric micro trucks and electric light trucks, which are mainly price-friendly.

Although it has certain advantages in terms of price, this air-cooled technology with air as the medium has obvious disadvantages. After all, it can only rely on external blowing air for cooling, which is inefficient and ineffective and has limited cooling effect when discharging at high power.

Moreover, air cooling is also directly affected by the external temperature, especially in extremely hot or cold weather conditions, and the heat dissipation and heat transfer efficiency of the battery will be affected to a certain extent.

Compared to electric trucks with air-cooled battery thermal management, liquid cooling is much more relaxed in terms of heat dissipation and insulation. The principle is that the coolant in the coolant lines inside the battery pack removes the heat generated by the battery during operation, thus cooling the battery.

In simple terms, liquid cooling means that several pipes are arranged in the battery pack and when cooling is required, coolant is poured into the pipes to remove the heat generated by the battery through water circulation to achieve the cooling effect.

In addition to cooling the battery pack more efficiently, some of the liquid-cooled thermal management systems also heat the battery pack, allowing the battery to quickly enter optimal operating conditions even at low temperatures.

Clearly, liquid cooling has a higher and more efficient heat dissipation than air cooling, even in the face of heavy loads or high power output, when the battery power load is too high, the liquid cooling water circulation heat dissipation system can cool the battery pack in time, and the heat dissipation is also more uniform and the temperature difference between the battery cells is smaller, which can effectively improve the stability and service life of the battery pack.

Liquid-cooled thermal management solutions are more efficient in keeping the battery temperature within a reasonable range, allowing the battery pack to be further enhanced in terms of efficiency, stability and durability.

However, liquid-cooled electric trucks are significantly more expensive than air-cooled ones, and the overall design is more complex. If you are using your vehicle in a suitable temperature environment and have good driving habits, air cooling is perfectly adequate.

Of course, if the environment is relatively harsh, the temperature difference between the seasons is large, and there are often heavy loads, then liquid cooling is obviously more suitable.

Whether it is a pure electric micro-truck or a pure electric light truck, many manufacturers have equipped the battery pack with a heating function. The principle is to warm the battery by means of an electric heating wire to prevent the battery from working at too low a temperature, thereby improving the efficiency of the battery.

Especially in the north, where the ambient temperature is relatively low, the battery heating function allows the battery to work more efficiently, thus increasing the range and reducing excessive battery degradation.

For new energy trucks, an efficient battery thermal management system is extremely important and has a great impact on the driving experience.

Although air-cooled thermal management solutions currently account for a higher proportion of pure electric micro-trucks and pure electric light trucks, liquid-cooled electric trucks are clearly more advantageous from the point of view of usage effect and technology.

It is believed that as the technology continues to improve, update and reduce costs, more and more products will adopt liquid-cooled battery thermal management systems.