Fast electric vehicle (EV) charging standards, such as the Combined Charging System (CCS) and Charge de Move (CHAdeMO), regulate the safe, efficient delivery of direct current (dc) to battery traction packs.
As shown in Figure 1, high-power dc fast chargers operate at up to 500 kW with peak currents reaching 600A, charging EV battery traction packs from 0 to 80% in 10 to 30 minutes.
Figure 1. Delta’s UFC 500-kW compact charging station, servicing both passenger and commercial EVs. (Image: Delta)
This article explores the critical role of advanced cooling systems in high-power dc fast chargers, explains how liquid cooling prevents thermal runaway in electric vehicle supply equipment (EVSE) connectors, and outlines the strategies EV manufacturers use to minimize thermal buildup in battery traction packs. It also reviews battery degradation risks associated with high-power dc fast charging and highlights real-world data on its impact on EV battery state of health (SOH).
Why high-power dc chargers require advanced cooling
High-power dc fast chargers generate substantial heat, requiring effective thermal management to prevent sustained high temperatures that could lead to thermal runaway and fires. As Ohm’s Law dictates, doubling the charging rate quadruples heat output. Without efficient thermal dissipation, certain high-power dc fast chargers can exceed 270° C during a 10-minute charge.
Most high-power dc fast chargers manage heat by circulating a water-glycol mixture through sealed loops. As shown in Figure 2, these liquid cooling systems absorb thermal energy from internal components, which external radiators dissipate using low-speed fans or air conditioning.
Figure 2. Air-cooled systems use fans and radiators to dissipate heat, while liquid-cooled systems circulate a water-glycol mixture to absorb and transfer thermal energy in high-power dc fast chargers. (Image: Penoda Power)
Compared to stand-alone air-cooled systems in Level 1 and Level 2 chargers, liquid cooling improves heat transfer at lower flow rates and sustains optimal operating temperatures.
Liquid cooling for EVSE connectors
Most high-power dc charging connectors integrate advanced liquid cooling channels around power contacts, where current density is highest. As shown in Figure 3, CHAdeMO-compliant connectors incorporate liquid-cooled heat-exchange surfaces near the positive terminals to optimize thermal dissipation.
Figure 3. An illustration of a liquid-cooling system used in CHAdeMO charging cables and connectors, showing coolant flow, integrated cooling tubes, and temperature sensors for efficient thermal dissipation. (Image: Fujikura)
These liquid-cooled connectors also feature integrated coolant tubes running alongside high-current conductors, allowing coolant to absorb and transfer heat away from critical interfaces. In some designs, coolant channels extend directly to the EV connection point, improving heat removal at the cable and connector interface.
Advanced EVSE thermal management systems incorporate multiple sensors that monitor heat levels in connectors and cables, feeding data to control systems that dynamically adjust cooling output. These AI-driven systems optimize heat dissipation, protecting key EVSE components and EV batteries, while ensuring safe, reliable, and fast charging performance.
How EVs manage heat during high-power charging
High-power dc fast chargers require advanced EV battery thermal management systems (BTMS) to maintain optimal conditions — typically 20° to 45° C. These systems regulate temperatures during charging and discharging, protecting batteries, motors, and inverters.
When needed, BTMS also redistributes waste heat from the electric motor to warm the battery pack in cold conditions, improving efficiency and extending range.
EVs use four primary battery cooling methods, each with distinct advantages and limitations:
- Passive air cooling relies on ambient airflow and convection to regulate battery temperature. While simple, cost-effective, and maintenance-free, it provides minimal heat dissipation and is inadequate for high-power or ultra-fast charging. Once common in early EVs, passive air cooling has been largely phased out in favor of more effective methods, though it remains in use for some low-speed vehicles (LSVs) with lower thermal demands.
- Active air cooling uses an EV’s air conditioning system and, in some cases, additional fans to circulate cooled air around battery traction packs. Although it improves thermal management over passive air cooling, its limited capacity (~1 kW) is insufficient for ultra-fast charging without supplemental cooling solutions.
- Liquid cooling circulates a water-glycol mixture through sealed loops, efficiently absorbing and dissipating heat. It provides superior thermal regulation and precise temperature control, minimizing the thermal impact of high-power dc fast charging. As the de facto standard in modern high-performance EVs, liquid cooling ensures safe, reliable, and sustained high-power charging.
- Refrigerant-based cooling directly cools battery cells through a thermal exchange system similar to air conditioning. It delivers exceptional cooling performance, reduces temperature variations, and prevents hotspots. Although refrigerant-based cooling has been explored in research and implemented in some thermal management systems, its adoption in commercial EVs remains limited and unconfirmed.
The battery degradation risks of high-power dc fast charging
The impact of high-power dc fast charging on EV battery SOH is complex, with multiple factors impacting degradation beyond charging speed alone. One major concern for EV manufacturers is lithium plating, a process in which lithium ions accumulate as metallic deposits instead of intercalating smoothly into the anode. This reduces battery capacity and can form dendrites, which may lead to short circuits.
Battery degradation intensifies as a high-power dc fast charge approaches full capacity. At higher states of charge, fewer intercalation sites remain, increasing the risk of lithium plating. Higher C-rates (the charging speed relative to battery capacity) further exacerbate this issue by generating excess heat and reducing ion diffusion time.
Fast charging also accelerates electrolyte decomposition and the growth of the solid-electrolyte interface (SEI) layer on the anode. A thickened SEI layer increases internal resistance, driving further chemical degradation, reducing capacity, and shortening battery lifespan.
The data on fast charging, battery health, and range
Real-world data on fast charging’s impact presents a more nuanced picture than laboratory studies and academic research initially suggested. A 2024 Recurrent Auto analysis of Tesla vehicles found no statistically significant difference in range degradation between vehicles fast-charged more than 70% of the time and those fast-charged less than 30% of the time.
While long-term effects remain unverified, the study suggests that Tesla EVs relying heavily on fast charging retain comparable driving range to those using slower charging methods. Notably, the study primarily analyzed Tesla data, and battery SOH and range results may vary for other EV models depending on specific thermal management strategies and battery chemistries.
To mitigate degradation risks, many EVs incorporate preconditioning systems that optimize battery temperature — typically 20° to 45° C — before high-power charging. Once charging begins, advanced battery management systems (BMS) dynamically adjust power output as the battery nears full capacity.
Conclusion
High-power dc fast chargers operate at up to 500 kW with peak currents reaching 600A. Charging EV battery traction packs from 0 to 80% in just 10 to 30 minutes, these chargers (along with their connectors and cables) require advanced thermal management systems to prevent overheating and mitigate the risk of thermal runaway.
High-power dc fast chargers also rely on EV BTMS to maintain optimal operating conditions, typically 20° to 45° C, regulating temperatures during charging and discharging to protect batteries, motors, and inverters. Liquid cooling plays a critical role across the charging ecosystem, dissipating heat in EVSE, connectors, and EVs.
References
- Update: Scientists Reveal how EV Fast Charging Impacts Battery Health, Recurrent Auto
- CHAdeMO 3.0 Released, CHAdeMO
- Research on Fast-Charging Battery Thermal Management System Based on Refrigerant Direct Cooling, Nature
- Battery Thermal Management in EV Using AI, IJCRT
- High Performance Heavy Duty EVs Require High Performance Battery Thermal Management Equipment, CEJN
- Does Fast Charging Affect EV Battery Life?, Pod Point
- Does Fast Charging Damage EV Batteries?, EuroNews
- Does dc Fast Charging Damage EVs?, EVESCO
Related EE World content
- Why High-Power dc EV Chargers Require Liquid Cooling Systems
- How Can Liquid Cooling be Applied to Charging Cables During dc Fast Charging?
- How Do Air and Liquid Cooling Compare in EV Chargers and Cyclers?
- Redefining EV Charging With High-Protection Isolated Air Cooling
- What Thermal Management Strategies Are Most Effective For EVs?
Filed Under: Batteries, Charging, FAQs, Thermal Management