Direct Cooling System

Core Working Principle and Technical Characteristics

An automotive battery direct cooling system (Direct Refrigerant Cooling System) is an advanced thermal management technology that utilises refrigerant from the air-conditioning system (such as R1234yf or R134a) to cool the traction battery directly. Moving away from the conventional "refrigerant–coolant (aqueous ethylene glycol solution)–battery" indirect heat exchange approach, it integrates the evaporator directly within the battery pack or between battery cells, allowing the refrigerant undergoing a gas-liquid phase change to absorb heat directly from the cells during operation.

In terms of technical characteristics and heat exchange efficiency, direct cooling systems offer distinct advantages:

High-efficiency phase-change heat transfer and high thermal conductivity: The refrigerant undergoes a phase change (liquid evaporation to absorb heat) within the evaporator channels, delivering heat exchange efficiency far superior to conventional liquid convective cooling. This direct heat transfer method dissipates intense thermal loads during high-power charging/discharging or extreme operating conditions with minimal temperature differentials and rapid response times, effectively preventing localised cell overheating.

Simplified architecture and lightweight design: Compared to indirect liquid-cooling systems, the direct cooling layout eliminates intermediate coolant circulation hoses, high-power water pumps, electronic valves, and bulky coolant-to-refrigerant intermediate heat exchangers (chillers), substantially reducing the overall weight, component count, and packaging footprint of the thermal management system.

Global Market Application and Evolution

Direct cooling systems are widely adopted in new energy vehicles (NEVs) engineered for high C-rates and optimised space packaging. They have gained rapid traction particularly in pure electric vehicle (BEV) models built on 800V and higher ultra-fast charging platforms, effectively managing instantaneous high heat flux during high-power fast charging.

As vehicle thermal management architectures evolve towards integrated, multi-in-one heat pump systems, direct cooling technology is progressing towards intelligent dual-mode switching between direct cooling and direct heating, dynamic coupling with cabin air-conditioning circuits, and microchannel structural optimisation. Modern direct cooling not only secures safe battery thermal limits under extreme rapid charging conditions, but also enhances overall vehicle energy efficiency and cold-weather driving range.

Operating Specifications and Safety Limitations 

It is strictly prohibited to run the air-conditioning cooling system or perform high-power DC fast charging if the vehicle has sustained severe undercarriage impact/bottoming out, or if a refrigerant leak occurs at the base of the battery pack or along the air-conditioning pipe joints. Refrigerant loss leads to abnormal system pressure and cooling failure, which can quickly trigger instantaneous localised cell over-temperature and present severe safety hazards.

It is strictly prohibited to recharge the system with non-certified, impure, or mismatched replacement refrigerants. Using substandard refrigerants or those with excessive impurities will corrode the internal pipe walls, cause electric compressor seizure or electrical short circuits, and severely compromise the sealing integrity of the battery’s internal microchannel passages.