Air and liquid cooling are the two most common methods to dissipate excess heat generated in electric vehicle (EV) charging stations and EV battery cyclers. This article discusses the importance of effective thermal management, highlighting each approach’s key benefits and disadvantages. It also explores evolving cooling technologies helping to shape the design of new EV chargers and battery cyclers.
Understanding thermal risks in EV chargers
Widely used in homes and workplaces, alternating current (ac) chargers, which correspond to Level 1 (120 Vac) and Level 2 (208/240 Vac) charging, typically produce minimal heat compared to direct current (dc) rapid charging stations. These ac chargers, suitable for residential and public settings, deliver a gradual, steady charge, relying on onboard EV systems to efficiently convert and distribute energy.

Figure 1. An AC EV charger featuring side vents to optimize airflow, installed in a home garage. (Image: J.D. Power)
However, ac chargers, particularly Level 2 units, can face significant heat dissipation challenges in hotter climates. Conversely, public dc charging stations, categorized as Level 3 (400 to 900 Vdc), consistently generate considerable heat due to higher currents, increased electrical resistance, and power conversion inefficiencies. Located in shopping areas and along highways, these stations are often directly exposed to sunlight, further elevating temperatures.
Notably, dc charger thermal levels vary based on power rating, operational conditions, and the efficiency of their cooling systems.
Continuous, excessive heat, if not effectively managed, can damage essential components in ac and dc chargers, such as capacitors, inductors, and control circuits. Overheated chargers also heighten the risk of thermal runaway in EV batteries, potentially causing structural degradation, reduced charge capacity, and increased fire risk. Additionally, overheating can negatively affect battery management systems (BMS), onboard chargers (OBC), and vehicle control units (VCU).
Heat dissipation in EV battery cyclers
Thermal risks are significant in EV battery cyclers, which test and analyze lithium-ion battery traction packs. These systems simulate real-world conditions through repetitive charging and discharging cycles, helping engineers optimize EV battery performance, endurance, and lifespan.
EV battery cyclers support ac and dc modes. Ac mode is used for basic battery conditioning and life-cycle testing, while dc mode replicates rapid charging and high-power discharging scenarios.
During rapid dc charges and discharges, EV battery cyclers generate substantial heat. Ineffective heat dissipation can heighten stress on battery cells, potentially affecting structural integrity and increasing the risk of thermal runaway. Additionally, excessive heat can compromise the accuracy of cycler testing data, leading to unreliable battery health and performance assessments.
Comparing air and liquid cooling
Air-cooling systems in EV ac chargers are favored for their simplicity, cost-effectiveness, and minimal maintenance. Implementation varies depending on the charger’s power level. Lower-powered ac chargers, such as those typically used in homes, often employ passive cooling methods such as natural convection and heat sinks. Higher-powered ac chargers may combine heat sinks with fans for more effective heat management. In hotter climates, these active air-cooling systems struggle to dissipate heat as efficiently as their liquid-cooling counterparts.

Figure 2. An EV recharging at a public, rapid charging station that features advanced liquid cooling technology. (Image: CEJN Industrial)
Widely deployed in industrial settings, liquid cooling systems are now popular for high-power, ultra-fast EV charging stations and battery cyclers. Without proper cooling, power converters in 150-kW fast dc chargers can experience temperature rises exceeding 200° C during a 10-minute charge.
Liquid cooling employs a water-glycol mixture to efficiently lower high temperatures around heat-generating components. In some advanced designs, coolant is routed from the charger through cables and connectors directly to the EV’s connection point. Liquid cooling systems are also typically costlier than their air-cooling counterparts and require regular maintenance for sediment removal, coolant replacement, and seal inspections to prevent degradation and leaks.
Advancements in EV and battery cycler cooling technologies
Advanced heat dissipation technologies are poised to significantly improve EV charger cooling systems. For example, graphene-based composites and phase-change materials (PCMs) are set to boost cooling efficiency, while smart thermal management systems will increasingly incorporate sensors with sophisticated AI/ML capabilities.
Engineers are developing cooling system prototypes using two-phase subcooled flow boiling, which dissipates heat up to 10 times more efficiently than single-phase liquid cooling. This innovation is key to achieving rapid, five-minute charging solutions capable of handling 2,500 amperes.
EV cycler manufacturers are also exploring advanced cooling methods for testing batteries beyond Li-ion, such as solid-state and lithium-sulfur. Nanofluid liquid cooling systems, essential for fast-charging simulations and high-load conditions, will significantly bolster thermal conductivity and heat transfer. Adopting real-time thermal imaging and predictive analytics will further refine battery modeling and improve the precision of testing processes.
Summary
Air and liquid cooling are the primary methods for dissipating excess heat in EV charging stations and battery cyclers. Air cooling, favored for its simplicity and cost-effectiveness, is commonly used in ac chargers. Liquid cooling systems, valued for their efficiency, are becoming the go-to choice for high-power, ultra-fast EV charging stations and battery cyclers. These systems use a water-glycol mixture to rapidly cool heat-generating components. In some advanced models, the coolant is channeled directly from the charger through cables and connectors to the EV’s connection point.
References
- Where Are Liquid-Cooled Connectors and Connectors for Liquid Cooling Used in EVs?, ConnectorTips
- Liquid Cooling Rapid Chargers – How Does It Work?, Heliox
- Optimal Design of Liquid Cooling Structures for Superfast Charging Cable Cores Under a High Current Load, Science Direct
- Electronics Cooling with Nanofluids: A Critical Review, Science Direct
- Successful Thermal Management with Liquid Cooling, e-Motec
- Battery Cycler, Unicous
- What Does an EV Home Charger Cost?, D. Power
- Liquid Cooling Solutions for EV Charging Stations, CoolingStyle
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