Electric vehicle supply equipment (EVSE) typically incorporates air or liquid cooling systems to prevent overheating and maintain charging efficiency. This article explores the thermal challenges of electric vehicle (EV) chargers and the strategies EVSE manufacturers use to manage them. It also reviews the advantages and limitations of air and liquid cooling systems, explaining why manufacturers of high-power fast and ultra-fast commercial dc EV chargers are increasingly choosing the latter option.
Managing thermal challenges
Many commercial EVSE operators install high-power fast and ultra-fast EV chargers (Figure 1) in public outdoor parking lots or along highway rest areas. These chargers can quickly overheat without protection from direct sunlight and efficient thermal cooling. Even indoor ultra-fast dc chargers in climate-controlled parking garages are at risk of temperature spikes without effective thermal management.
Figure 1. The ADS-TEC Energy ChargePost: a compact, battery-integrated system delivering up to 300 kW of ultra-fast charging power with dual charging points. (Image: ADS-TEC)
The optimal operating temperature for high-power fast and ultra-fast dc EV chargers ranges between 68° and 113° F (20° to 45° C). Most EVSE operators implement safety protocols beyond 113° F (45° C), limiting power output, throttling charging speeds, and extending charging times.
Continuous exposure to excessive heat accelerates the degradation of EVSE charging cables, connectors, and crucial electronic components. Overheating EVSE infrastructure increases the risk of thermal runaway in EV batteries and can negatively impact battery management systems (BMS), onboard chargers (OBCs), and vehicle control units (VCUs).
To mitigate thermal challenges, manufacturers design EVSE infrastructure with reliable materials that withstand high temperatures, such as thermoplastics with UL94 V0 flame retardant properties, aluminum for casings, and UV-stabilized, fire-resistant materials like PC (polycarbonate) Siloxane for charging plugs and cables. Additionally, installing solar panel canopies (Figure 2) over EV chargers provides shade and generates renewable energy.
Figure 2. Fastned EV chargers under a solar-panel canopy, providing renewable energy generation and protection from the elements. (Image: ChargeMap)
Most importantly, manufacturers of high-power fast and ultra-fast dc EV chargers integrate advanced thermal management systems that ensure optimal performance and rapid charging times by efficiently regulating temperatures and dissipating excess heat.
The advantages and limitations of air cooling
EVSE air-cooling (Figure 3) systems typically rely on forced convection, using IP20 or IP65 forced air-cooled modules to reduce thermal buildup and maintain optimal operating temperatures.
Strategically placed fans circulate ambient air over and around heat sinks attached to crucial EVSE components, while air vents help remove hot air and draw in cooler air. Temperature sensors monitor heat levels and dynamically adjust fan speed to ensure efficient cooling at varying voltages and environmental conditions.
Figure 3. A comparison of air-cooling techniques: natural, IP20 forced, and IP65 independent forced air cooling with enhanced heat dissipation.(Image: UUGreenPowerCo)
The primary advantages of air-cooling systems for EVSE manufacturers are operational simplicity, minimal component requirements, and easy integration into existing designs. Air-cooling systems are generally more cost-effective to manufacture compared to their liquid-cooling counterparts, and the absence of liquid-based components reduces the risk of leak-related failures.
Despite their key advantages, EVSE air-cooling systems require thicker copper wires in charging cables to effectively dissipate heat generated by fast charging at higher voltages, raising manufacturing costs and increasing overall cable weight. Additionally, air-cooling systems fail to effectively cool cable cores directly.
These systems also generate significant noise when operating at higher temperatures, and direct exposure to circulating outside air can lead to dust buildup, component corrosion, higher maintenance costs, and reduced lifespan. Lastly, air-cooled systems require frequent dust removal, fan replacement, and heat sink cleaning.
Although still used in residential ac chargers and some dc fast chargers below 150 kW, air cooling is insufficient for ultra-fast EV chargers at higher power levels. During high-power sessions (150 kW+), temperatures can exceed 392° F (200° C) within a 10-minute fast charge. As dc charging gun capacity increases from 250 to 500A, air-cooled systems face significant thermal management challenges.
Maintaining high-power EVSE performance with liquid cooling
EVSE liquid cooling systems (Figure 4) maintain optimal operating temperatures using a water-glycol mixture that efficiently reduces thermal buildup around crucial heat-generating components. Liquid cooling transfers heat at low flow rates, keeping internal temperatures roughly 18° F (10° C) lower than air-cooled modules. The heat capacity of water is up to 3,500 times greater than air, making it ten times more effective at dissipating heat.
Figure 4. A comparison of air and liquid-cooling systems in EVSE modules, highlighting heat dissipation methods using fans and radiators versus liquid cooling plates and circulation. (Image: Penoda Power)
Some high-power liquid cooling systems use dual-loop architecture to optimize heat dissipation. In this configuration, internal liquid-cooled modules rapidly absorb heat, while external radiators dissipate it with low-speed, high-volume fans or air-conditioning units.
Many systems use coolants like ethylene glycol or oil in modules and cables to prevent thermal buildup. These designs enable the use of smaller, lighter charging connectors and cables. In some advanced configurations, coolant flows through cables and connectors and may even extend directly to the EV’s connection point.
Although liquid cooling systems in high-power fast and ultra-fast dc EV chargers are more expensive to design and manufacture, they often result in a lower total cost of ownership (TCO) over time due to improved cooling efficiency, reduced component wear, and longer system lifespan.
Nevertheless, liquid cooling systems require precise temperature control and continuous monitoring to prevent coolant degradation and maintain optimal performance. Additionally, pumps and secondary fans used to dissipate heat from radiators draw extra power and may generate noise at higher temperatures. Notably, some liquid-cooled modules can achieve near-zero noise, with only minimal noise from external cooling systems.
Liquid cooling systems require minimal maintenance, such as coolant checks and radiator cleaning. Though sealed loops help prevent contamination, regular inspections are needed to prevent leaks that could degrade efficiency, damage infrastructure, or pose safety risks.
Accelerating the shift from air to liquid cooling
Many manufacturers initially integrated air-cooling systems into residential and commercial EV chargers. Managing increased voltage and thermal loads, however, requires larger heat sinks, thicker copper cables, and more high-speed fans.
Air-cooling systems draw two to three times more energy to maintain temperatures, reducing efficiency and reliability, especially in hotter climates. Frequent maintenance — six to 12 times per year — is also required for dust removal and fan replacement.
Although still used in lower-powered ac chargers and some dc fast chargers below 150 kW, air-cooling systems cannot cost-effectively maintain optimal performance in ultra-fast EV chargers at higher power levels. As a result, many manufacturers now prefer liquid cooling for high-power and ultra-fast dc chargers. While liquid cooling systems have higher upfront costs, they efficiently dissipate heat, draw less power, require minimal maintenance, and can support dc chargers up to 350 kW or more.
Conclusion
High-power dc EV chargers in outdoor parking lots or highway rest areas can quickly overheat without protection from direct sunlight and effective thermal cooling. To ensure optimal performance and rapid charging, EVSE manufacturers use advanced liquid-cooling systems to dissipate thermal buildup in indoor and outdoor units.
Air-cooling systems can’t cost-effectively maintain optimal performance in ultra-fast dc EV chargers at higher power levels. Nevertheless, they are still used in many lower-powered ac chargers and some dc fast chargers below 150 kW.
Related content
- How Do Air and Liquid Cooling Compare in EV Chargers and Cyclers?
- How Does Hot Weather Affect Electric Vehicles?
- Understanding Battery Overheating in EVs
- Redefining EV Charging with High-Protection Isolated Air Cooling
- What Are the Challenges With High-Voltage EV Charging?
References
- Liquid-Cooled vs Traditional Charging Stations: Which is Better?, Penoda Power
- Thermal Management for Safe and Efficient Fast-Charging of Battery Electric Vehicles on the Road, CEJN
- Value of EV Chargers that Can Withstand Extreme Temperatures, GreenCEV
- Successful Thermal Management with Liquid Cooling, E-Motec
- Electric Vehicle in Hot Weather – the Impact on Charging, ChargeMap
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Filed Under: Thermal Management