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Pioneering the Future of Liquid-Cooled Charging Stations: Innovations in Efficient and Cool Charging Technology

Charging System Overview

Today, there are three main types of charging, with a fourth, faster option under exploration: Liquid-Cooled Charging Piles.

EV Charging Stations:  Level 1 and Level 2 chargers use onboard converters to manage the power flow to the battery pack. Level 3 and higher-level charging typically involve external converters and Electric Vehicle Supply Equipment (EVSE) control to safely and efficiently handle higher power loads. Even though EVSE communication protocols between the charger and vehicle set the appropriate charging current, Level 3 power converters still require effective thermal management, often utilizing liquid cooling technology.

Electrical System

Maintaining temperature stability for vehicle batteries and battery packs under various operating and charging conditions is crucial. Low temperatures can reduce battery power and capacity, affecting range, while high temperatures can accelerate battery degradation. Therefore, effective thermal management is essential for extending battery life and enhancing performance.

Liquid cooling is a key technology for cooling battery cells and packs. Methods such as cold plate cooling and immersion cooling in insulating liquid effectively remove heat generated by the battery by circulating coolant through the battery pack, ensuring it operates within an optimal temperature range. However, the risks associated with cooling cannot be overlooked. Liquid cooling systems require complex fluid flow channels and numerous connections, increasing the potential for failure. If a failure occurs, the liquid cooling system could cause adjacent cells in the battery pack to short-circuit, leading to thermal runaway and other serious consequences.

As for charging cables, the technical limitations of cables and electrical connectors become more apparent as the charging rate increases. DC fast chargers require larger conductors to carry higher currents, making the cables bulky and inconvenient for users. Liquid-cooled charging cables, on the other hand, use thinner wires and liquid cooling technology to effectively reduce the temperature at the DC contacts of the cable and vehicle electrical connectors, while also making the cables lighter and easier to handle and use.

Liquid-Cooled Charging System

A liquid-cooled charging system includes: a liquid-cooled charging gun (vehicle plug), coolant, liquid-cooled cable, an overall cooling system (thermal management system, including circulation pump, reservoir, radiator, etc.), charging gun core flow channel structure, tail cable locking structure, and temperature control.

Introduction to liquid cooled supercharged gun

Charging gun structure diagram

Standard DC charging guns typically handle currents below 250A, while super-fast charging guns can handle around 500A, generating significant heat at the contact points. To reduce the temperature around the terminals and address the cooling issue for charging guns under high current, liquid cooling tubes are often added around the terminals. These tubes circulate high specific heat capacity liquids like silicone oil, water, or glycol to lower the terminal temperature, ensuring the charging gun operates properly. The internal structure of a liquid-cooled charging gun is shown below:

Cooling Cable

The cable’s dimensions, flexibility, and the strength of the flow channel tubes are critical factors. Oversized or overly stiff cables can negatively impact user experience. If the flow channel strength is insufficient, it can lead to coolant blockages or tube ruptures and leaks when the cable is crushed or subjected to pressure.

Contact Components and Terminals

Choosing the cooling position for the contact components requires a comprehensive cable connection plan. Liquid leakage in hydraulic systems is a significant industry challenge. The charging gun’s complex and variable usage environment involves frequent dragging, movement, and occasional dropping or crushing, necessitating higher sealing standards for the connection points.

When the charging gun works, the voltage through the terminals is higher, the current is larger, the terminal position will produce a large amount of heat; in the selection of shell materials usually consider thermal conductive plastics, in order to facilitate the export of heat from the terminals. At the same time, in order to solve the problem of heat dissipation of charging gun terminals, pay attention to the following matters:

  1. The outer surface of the terminal is plated with a material of high thermal conductivity, often silver;
  2. The use of copper material slot or jack (contact parts) to create a terminal and wire connection;
  3. As the charging gun insertion process involves mechanical collision, in order to fix the terminals and connect the wires, and to ensure the dustproof and waterproof performance of the gun head, some of the gun head will also be filled with high thermal conductivity inside the potting gel.
  4. Contact resistance is an important quality indicator of cable and terminal termination, which determines the heat generation of the termination part, this indicator is particularly important in the high-power charging line, in order to reduce the heat generation of the termination part and enhance the current-carrying capacity, we recommend that the cable and the contact parts with ultrasonic welding.

liquid cooling plate

The liquid cooling module is the core of the liquid cooling charging system, and the heat dissipation principle: the coolant is driven by the water pump to circulate between the inside of the liquid cooling charging module and the external radiator, taking away the heat of the module.

The heat dissipation principle of the liquid-cooled charging gun is to set a liquid-cooled pipe in the charging cable, so that the coolant takes away the heat of the charging module, thereby reducing the temperature rise during the charging process. This heat dissipation method can effectively protect the charging cable and charging module, while improving the charging efficiency and charging speed.

Liquid cooling circulation system

In the whole system, current, temperature, coolant flow and noise need to be monitored in real time to achieve high charging efficiency, safety, low loss, low noise and low pollution.

Coolant

Coolant needs to meet the low freezing point, high flash point, low viscosity, high specific heat capacity, environmental protection, insulation and other characteristics, coolant selection to ensure high cooling efficiency.

For liquid cooling cooling system, the choice of cooling medium is also very important, ordinary charging pile coolant only ‘antifreeze’ and ‘cooling’ role, good coolant cooling system components also have a certain degree of corrosion prevention, rust removal and other protective effects. At present, the vast majority of charging pile coolant on the market does not have its own core technology, this coolant is easy to corrode, clogging liquid cooling plate, damage to the water pump leading to failure, with great harm.

Liquid-cooled charging system performance parameters

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