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Pure Electric Vehicle Power Battery Thermal Management Technology Analysis

DATE: May 8th, 2024
Pure electric vehicle power battery will generate a lot of heat when charging and discharging, and the temperature will be very low after low-temperature static. At this time, the power battery needs a thermal management system to cool or heat it to ensure the mileage, service life, and safety. In this article, TKT will introduce the main functions, main classifications, and working principles of battery thermal management systems, which will serve as a reference for the design and selection of thermal management systems for electric vehicles.

Main Functions of Battery Thermal Management System

Battery thermal management system is one of the key technologies to cope with the heat-related problems of the battery and ensure the performance, safety, and life of the power battery. The main functions of the thermal management system include:

1. Effective heat dissipation when the battery temperature is high, to prevent thermal runaway accidents.
2. Preheating when the battery temperature is low, to raise the battery temperature, to ensure the charging and discharging performance and safety at low temperatures. 3. reducing the temperature in the battery pack;
3. Decrease the temperature difference within the battery pack, inhibit the formation of localized hot zones, and prevent the high-temperature location of the battery from decaying too quickly, reducing the overall life of the battery pack.

The Main Classification Of Battery Cooling System

The temperature environment within the battery pack (PACK) has a great impact on the reliability, life, and performance of the battery cells, so it is particularly important to maintain the temperature within a certain temperature range within the PACK. This is mainly realized by cooling and heating, and the cooling methods are mainly divided into three categories:

1. Air-cooled BTMS system: air cooling (air cooling) technology is the use of natural wind or vehicle refrigeration system generated by the cold air, through heat convection or heat conduction way to take away the heat, to achieve the purpose of battery cooling. Air-cooling technology is characterized by a simple system, low cost, and easy maintenance, and is widely used.

2. Liquid-cooled battery thermal management system: Liquid cooling technology uses liquid as the heat transfer medium, and the liquid will take away the heat when flowing through the internal pipeline of the power battery. The liquid used in liquid cooling is mostly coolant, which circulates in the vehicle cooling system. The heat carried away by the coolant is dissipated into the air through the radiator.
Some vehicles have a heat exchanger in the cooling system to couple the vehicle cooling system with the refrigeration system to increase the cooling effect of the system. Liquid cooling technology and air cooling technology, compared with the cooling capacity, good uniformity, fast rate, and other characteristics.

3. Direct cooling technology is to use the refrigerant in the refrigeration system to take away the heat of the power battery directly, and install a set of expansion valves and evaporators inside the power battery, and the refrigerant evaporates and absorbs heat in the evaporator.
Since direct cooling technology does not have a heat exchanger in liquid cooling technology, the efficiency of direct cooling is higher. However, when the power battery is cooled, the refrigerant in the refrigeration system needs to be partially separated, which will affect the cooling effect of the passenger compartment and lead to reduced comfort.

Battery heating system

Power battery heating technology mainly has two kinds of battery self-heating and the use of external heating elements. Battery self-heating, as the name suggests, is the use of the battery in charging and discharging due to their work to generate heat to increase the battery temperature, but this way of heating efficiency is slow and has been abandoned.

The use of external heating elements is mainly the use of heating film and PTC, heating film is tightly attached to the surface of the battery module, in the power-generated heat to increase the battery temperature. Battery heating methods are similar to cooling methods, and there are three types of heating: air heating, water heating, and refrigerant direct heating.

Thermal Management System

Batteries can be cooled and heated independently of each other, but as vehicles become more and more integrated, higher demands are placed on the vehicle thermal management system.
Therefore, a thermal management system that can realize both battery cooling and heating for the battery has appeared. Even some vehicles use heat pump air conditioning to develop a highly integrated thermal management system, which organically combines the vehicle cooling system, power battery cooling/heating, and passenger compartment cooling and heating in 3 major systems.

Principle of the thermal management system

1. Power battery cooling principle. When the power battery temperature is high and needs to be cooled, the air conditioning refrigeration solenoid valve, air heat exchanger solenoid valve, battery electronic expansion valve, and battery cooling solenoid valve in the system will open (the battery heating solenoid valve is closed).
When the refrigerant flows through the battery electronic expansion valve, it expands by throttling, evaporates and absorbs heat in the plate heat exchanger of the battery pack, and takes away the heat to realize the purpose of battery cooling.
If the passenger compartment also has a cooling demand, just open the refrigeration electronic expansion valve (air conditioning and heating solenoid valve are closed), part of the refrigerant in the car evaporator evaporation and heat absorption, to realize the passenger compartment refrigeration.

2. Power battery heating principle. When the battery temperature is low and needs to be heated, the battery heating solenoid valve, battery electronic expansion valve, water heat exchange solenoid valve, air conditioning heating solenoid valve opens (heating electronic expansion valve, air conditioning refrigeration solenoid valve, air heat exchange solenoid valve, refrigeration electronic expansion valve closes).
The high-temperature refrigerant compressed by the compressor flows through the plate heat exchanger of the battery pack to heat the low-temperature battery. After heating, the refrigerant temperature is lowered and flows through the plate heat exchanger, absorbing the heat from the electric drive circuit and realizing waste heat recovery.
If the passenger compartment also needs to be heated, the heating electronic expansion valve is opened, and some of the high-temperature refrigerant flows through the condenser in the car, releasing heat to the passenger compartment, and then joins with the battery-heating refrigerant before the plate heat exchanger to continue to participate in the cycle.
If the ambient temperature is very low, the system turns on the PTC to assist in heating the passenger compartment.

Advantages of TKT's EV Thermal Management System

1. Patented design and trusted expertise in battery thermal management for improved battery reliability.
2. Liquid cooling (coolant) combined with PTC heating ensures long-lasting performance.
3. Lighter weight compared to other products in the market, thus reducing the burden on the vehicle.
4. Utilizes an integrated layout scheme. We can provide ATS and BTMS system integration solutions.
5. CAN control is adopted to avoid damage to the battery pack by misoperation. The system adapts to changing conditions and realizes high-precision control.
6. Intelligent thermal control: prevent overheating or overcooling. Extends battery cycle life.
7. Quality and performance recognized by customers worldwide. A large number of cases for you to choose from, or choose exclusive OEM service.
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