Liquid cooling technology is gradually replacing traditional air cooling
and becoming the mainstream choice for electric vehicle matching by major car
companies.
Recently, JAC New Energy's iEV6E sports version was officially launched,
and its self-developed liquid-cooled battery management and control technology
was also used in micro electric vehicles for the first time.
According to reports, the liquid cooling technology equipped with this
model can stably control the battery temperature within a suitable range of
15-35°C, and the vehicle can be used normally at ambient temperatures of -30°C
to 55°C. At the same time, this technology also ensures that battery single
failure will not cause fire or explosion in the battery pack, ensuring battery
life, fast charging performance, low temperature performance and safety
performance.
Coincidentally, Buick's VELITE6 PHEV, which will be launched within the
year, also uses a cell-level independent liquid cooling system. It is understood
that each single cell in the VELITE6 battery pack can pass through the cooling
fin for heat dissipation circulation, ensuring that the temperature difference
of each cell is within 2 degrees Celsius.
What is liquid cooling technology? It uses the coolant's large heat
capacity and its ability to take away excess heat from the battery system
through circulation to achieve the optimal operating temperature conditions of
the battery pack.
Gaogong Lithium Battery learned that in addition to the above two car
companies, domestic and foreign car companies currently include BMW, Tesla,
General Motors, Chevrolet, Geely, BMW Brilliance, BAIC, GAC, Yundu, Xpeng
Motors, Singularity Motors, etc. Liquid cooling technology is being introduced
in battery thermal management systems.
A senior executive of a large pack company said: “There were relatively few
people using liquid cooling technology in the early days, mainly because the
market was dominated by A00-class models, which did not have high performance
requirements. At the same time, liquid cooling technology was not used due to
cost issues; and this year’s subsidies Policies focus on batteries with long
cruising range and high energy density. Battery heating is becoming more and
more serious. While ensuring the performance of the vehicle, it is also
necessary to ensure a certain acceleration performance, so liquid cooling
technology has become a mainstream choice."
Data shows that active liquid cooling technology is expected to account for
55% of the power battery cooling system assembly in 2022; by model, liquid
cooling technology will account for 85% of the power battery cooling system of
plug-in hybrid models, and that of pure electric vehicles Liquid cooling
technology for the model’s power battery cooling system will account for
44%.
▌The inevitable choice for high-energy, high-rate batteries
According to the medium of heat transfer, battery cooling systems can be
divided into: air cooling, direct cooling and liquid cooling.
Air cooling is mainly divided into natural cooling and forced cooling
(using fans, etc.), using low-temperature air as the medium. This technology was
widely used in early electric passenger cars, such as Nissan Leaf, Kia SoulEV,
etc. Its obvious problems are slow cooling speed, low efficiency and poor
internal temperature uniformity.
Direct cooling uses refrigerant direct cooling, using the principle of
latent heat of evaporation of refrigerants (R134a, etc.) to establish an air
conditioning system in the vehicle or battery system. The evaporator of the air
conditioning system is installed in the battery system, and the refrigerant
evaporates. evaporates in the device and quickly and efficiently removes the
heat from the battery system. At present, the cooling method through direct
cooling is basically used in electric passenger cars, the most typical one is
the BMW i3 (i3 has two cooling solutions: liquid cooling and direct cooling).
Although its cooling speed is fast, its temperature uniformity is poor.
Liquid cooling uses liquid convection heat transfer to take away the heat
generated by the battery and reduce the battery temperature. The medium is
mainly conductive liquids such as water. Liquid cooling is currently the
preferred solution for many electric passenger cars. Typical products at home
and abroad include BMW i3, Tesla, GM Volt, BMW Brilliance Zino, and Geely
Emgrand EV. However, it should be noted that liquid cooling technology has high
requirements for sealing, requires closed liquid pipelines, and has a complex
structure.
Compared with other cooling technologies, liquid cooling technology has a
high heat transfer coefficient and fast cooling speed, which has a significant
effect on reducing the maximum temperature and improving the consistency of the
temperature field of the battery pack. At the same time, the size of the thermal
management system is also relatively small.
Industry analysts believe that the current cooling method for electric
vehicle power batteries is still air cooling, but as the electric vehicle market
puts forward higher demands for performance such as cruising range, energy
density, battery capacity, and charging rate, liquid cooling technology It will
gradually become a priority solution for major car companies.
Market data also directly confirms this judgment.
The main reason for this situation is that the current new energy market is
dominated by A00 and A0-level models. Models at this level are generally pure
electric vehicles. Since they are mainly used for transportation, their speed is
not high, and their demand for fast charging is also limited. , so the demand
for liquid cooling systems is limited and it is difficult to become the target
market for liquid cooling technology.
This year, the market structure of new energy passenger vehicles is
changing.
According to manufacturer data from the Passenger Car Association,
wholesale sales of pure electric passenger vehicles from January to July 2018
were 304,800 units, a year-on-year increase of 90%. Among them, A00-class cars
sold 173,700 units, a year-on-year increase of 63%; A0-class cars sold 42,600
units, a year-on-year increase of 295%; A-class cars sold 86,300 units, a
year-on-year increase of 106%. The structure of pure electric models is
accelerating upgrading.
At the same time, as subsidy thresholds increase and end users’ demands for
long cruising range become stronger and stronger, car companies have begun to
regard high-energy power batteries with fast charging functions as their first
choice. In order to meet the needs of car companies, battery companies will
choose ternary lithium batteries with higher energy density. In order to control
the temperature of the power battery and control the temperature difference
within a more stable range under high-rate discharge conditions, liquid cooling
technology is gradually gaining favor. .
Dr. She Peiliang, chief engineer of Shuangdeng Fulante, said: "The ternary
material is prone to oxygen evolution when overcharged, and is prone to
autocatalytic reactions when thermally out of control. The speed is too fast to
avoid risks such as explosion and fire. Therefore, it must be controlled well.
Its operating temperature range".
"Battery companies, pack companies and car companies that make ternary
material battery systems for passenger cars (there are also individual lithium
iron phosphate batteries) will definitely use liquid cooling systems; some
logistics vehicles use cylindrical ternary material battery systems, and they
will also Using liquid cooling technology.” he added.
Ma Junfeng, senior R&D director of Huating Power, said: "Under the
influence of subsidy policies, energy density is getting higher and cruising
range is increasing, and liquid cooling will be the standard configuration. At
present, the company uses liquid-cooled battery packs, with sales of 500 million
last year. This year it is expected to be 1.5-2 billion, and sales of 700
million have been achieved so far.”
A senior executive of a large pack company said: “As battery performance
gradually improves, liquid cooling will become an inevitable choice for new
energy passenger car companies. This year, the market share of liquid cooling
technology for battery cooling systems in pure electric passenger cars is
expected to reach 60%. "
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