Liquid Cooling vs. Air Cooling for High-Power DC Charging Cabinets: Which Technology Should You Choose?

As the driving range of new energy vehicles (NEVs) continues to increase-and with the growing demand for rapid energy replenishment at highway service areas, logistics parks, bus depots, and large-scale charging stations-high-power DC charging is emerging as a key development direction for NEV charging infrastructure.

 

Compared to standard low-power charging equipment, high-power DC charging systems must transfer more energy in less time; consequently, components such as charging modules, power devices, busbars, connectors, and charging cables are subjected to higher thermal loads.

Against this backdrop, thermal management technology has become a critical factor in the design of high-power DC charging cabinets.

Currently, high-power charging equipment primarily employs two thermal management methods:

 

· Air cooling
· Liquid cooling

 

So, what exactly are the differences between air cooling and liquid cooling? Why is liquid cooling gaining increasing importance in DC fast charging? And how should one make the right choice when purchasing these cabinets?

 

 

The core function of a high-power DC charging cabinet is to convert AC power from the grid into DC power suitable for the traction batteries of new energy vehicles.

 

The basic energy conversion process can be summarized as follows:

 

AC Grid → Power Module → DC Output → Charging Dispenser → EV Battery

 

During this process, components within the power module-such as semiconductor devices, inductors, capacitors, transformers, and other power electronics-generate heat.

 

Although modern charging modules boast high conversion efficiency, in charging systems operating at the hundreds-of-kilowatts level, even a small percentage of efficiency loss can result in a significant absolute thermal load.

 

For instance, when a high-power charging system continuously delivers hundreds of kilowatts of power, the heat generated by internal losses must be continuously dissipated; otherwise, the following issues may arise:

 

· Rising temperatures of power components
· Reduced charging efficiency
· Output power limitations
· Compromised component lifespan
· Activation of system protection mechanisms
· Reduced stability during prolonged operation

 

Therefore, for a high-power DC charging cabinet, the cooling system is not merely an auxiliary component but a critical element that determines the equipment's sustained output capability.

 

 

An air-cooled DC charging cabinet uses air as the cooling medium to dissipate heat generated inside the equipment into the surrounding environment via components such as fans, heat sinks, and air ducts.

 

A typical air-cooled system usually includes:

 

· Cooling Fan
· Heat Sink
· Air Duct
· Air Filter
· Temperature Sensor
· Ventilation Structure

 

Its basic operating principle is:

 

Heat Generation → Heat Sink → Forced Airflow → Heat Dissipation → Ambient Air

 

Fans drive air across power modules and heat sinks, carrying heat out of the equipment.

This approach features a relatively mature design and remains highly practical for medium-power DC charging equipment and applications with suitable environmental conditions.

 

 

A liquid-cooled DC charging cabinet employs a coolant as the heat transfer medium.

 

Compared to air, liquid circulating through a specially designed cooling loop can more effectively transfer heat generated inside the equipment to a heat exchanger for subsequent dissipation into the environment.

 

A typical liquid-cooled system may include:

 

· Coolant Pump
· Cooling Plate
· Heat Exchanger
· Radiator
· Coolant Reservoir
· Temperature Sensor
· Flow Sensor
· Pressure Monitoring System

 

The basic operating process can be summarized as:

 

Power Module → Cooling Plate → Coolant → Heat Exchanger → Radiator → Heat Dissipation

 

In higher-power charging systems, liquid cooling technology can be applied not only to the power modules inside the cabinet but also to high-current charging cables and connectors.

 

For instance, publicly available industry data shows distributed charging systems-featuring a 600 kW power cabinet paired with 500 A liquid-cooled charging cables-designed to support simultaneous charging for multiple vehicles while dynamically allocating power based on real-time vehicle demand.

 

 

1. Better suited for high power density designs

As DC charging power continues to rise, charging cabinets require the installation of more or higher-capacity power electronics modules.

If one were to simply add more fans and increase airflow, issues such as internal airflow path design, heat sink dimensions, noise levels, and cabinet space constraints would become significant challenges.

 

In contrast, liquid cooling systems utilize cooling plates and circulation loops to extract heat directly from the vicinity of heat-generating components, thereby offering greater design flexibility for high power density equipment.

 

2. Facilitates high-current charging

Charging power can be simply expressed as:

 

P = U × I

 

In other words, for a given voltage, increasing charging power requires higher current.

However, as current increases, heat generation in conductors, cables, and connectors becomes more pronounced.

 

 

Liquid cooling solutions should be prioritized for projects with the following characteristics:

 

1. Highway ultra-fast charging stations

Highway service areas typically require short vehicle dwell times, creating a high demand for rapid energy replenishment capabilities.

When multiple vehicles charge simultaneously, charging equipment may operate under high loads for extended periods, placing greater demands on thermal management systems.

 

2. Commercial vehicle and logistics fleets

Logistics vehicles usually operate on defined schedules with specific windows for recharging.

For fleets requiring quick turnaround times, high-power DC charging can help minimize the time vehicles spend at charging stations.

The U.S. Department of Energy has also noted that DC fast charging is suitable for certain fleet applications where vehicles need to recharge during short stops.

 

3. Buses and heavy-duty electric vehicles

Buses, trucks, port vehicles, and other commercial electric vehicles typically feature large battery capacities; consequently, charging infrastructure may require higher power output and the ability to operate continuously for longer durations.

With the development of high-power charging standards and systems-such as MCS-the importance of liquid cooling technology in high-current charging applications has become increasingly significant.

 

4. High-Utilization Charging Stations

If a charging station is required to serve a large number of vehicles continuously throughout the day, the equipment's actual operating load may be far higher than that found in typical office or residential settings.

 

 

As the demand for charging new energy vehicles continues to rise, high-power charging systems are evolving in several key directions.

 

1. Higher Power

Charging systems are shifting from traditional, lower power levels toward capacities of hundreds of kilowatts or even the megawatt (MW) range.

 

2. Higher Power Density

Configuring more power modules within the same cabinet footprint places greater demands on thermal management and structural design.

 

3. Modularity

Modular power cabinets allow for the configuration of varying numbers of power modules based on project requirements, while also facilitating maintenance and power scalability.

 

4. Intelligent Power Allocation

Future charging stations will not necessarily deliver fixed power to every vehicle; instead, power will be dynamically allocated based on factors such as vehicle State of Charge (SOC), real-time charging demands, and the load on other charging terminals.

 

Currently, 600 kW-class distributed charging systems are already employing dynamic power allocation, enabling multiple vehicles to share a centralized power cabinet.

 

5. Expanded Application of Liquid Cooling Technology

Driven by the need for higher power and current, liquid cooling technology will extend beyond power cabinets to be increasingly applied to components such as charging guns, cables, and connectors.