With the continuous upgrading of new energy vehicles and the adjustment of charging demands, high-power AC/DC fast charging technology has become the focus of the company's technological research and development. High-power AC/DC fast charging technology can not only improve the utilization efficiency of charging piles and save land and costs for charging station construction to the greatest extent, but also better meet users' travel needs.
What is high power?
While my country lacks a clear standard definition for "high-power," charging piles frequently mentioned and referred to as "high-power" generally have a power output of 350kW. On December 26, 2016, TSLA CEO Elon Musk announced an increase in charging power from 120kW to 350kW. Also at the end of 2016, several foreign automakers announced the construction of supercharging stations in Europe, typically with a power output of 350kW. Furthermore, some European and American countries have been conducting research on high-power charging piles, aiming for a power output of 350-500kW.
my country's regulations stipulate that charging current should be below 250A and voltage below 750V, which corresponds to approximately 187.5kW. Therefore, a 350kW charging station exceeds domestic standards. In fact, my country does have 350kW charging stations, but these are currently only used on buses and not on electric passenger vehicles.
Does high-power fast charging affect battery life?
There has long been a rumor among consumers that "fast charging damages batteries." To discuss the impact of fast DC charging on batteries, we must first understand electric vehicle batteries.
Most electric vehicles on the market currently use lithium batteries. Ideally, during the charging and discharging process of a lithium battery, lithium ions (Li+) move from the positive electrode to the negative electrode and back to the positive electrode. As long as the chemical structure of the positive and negative electrode materials remains essentially unchanged, the reversibility of the battery's charging and discharging is very good, and lithium-ion (Li+) batteries can guarantee long-term cycling.
The key to fast charging is ensuring that lithium ions (Li+) are quickly extracted from the positive electrode and rapidly inserted into the negative electrode, without causing lithium ion (Li+) deposition. However, high-power charging often leads to increased battery temperature, which can cause side reactions such as electrolyte decomposition and electrode deposits, reducing reversibility and gradually decreasing battery capacity.
In fact, when an electric vehicle is charging, the BMS on the vehicle will estimate the state of charge (SOC, i.e., the remaining battery capacity) of the power lithium battery pack and automatically adjust the charging current according to the condition of the battery pack to ensure that the SOC is maintained within a reasonable range and prevent damage to the battery due to overcharging or over-discharging. Therefore, there is no need to worry too much about the damage to the battery caused by fast charging.
Challenges of 350kW High-Power Charging
From a cost perspective, chargers and charging modules are the core equipment for charging, accounting for 45%-55% of the total cost of charging piles. The investment cost of a charging station is 2.5 million yuan, and the cost of power distribution facilities is around 1.6 million yuan. The average cost of a standard charging pile is between 5,000 and 20,000 yuan, while the market price of a 120KW DC charging pile is around 100,000 yuan, and the price of a 350KW charging pile is even more expensive. However, in reality, most operating companies have not yet achieved profitability, and only a very few well-operated charging stations have recovered their costs within a year. Although the government has provided certain subsidies for construction, very few companies have actually received these funds. For the construction and operation of fast charging piles, charging pile companies may need to invest even more in operation and maintenance. Furthermore, acquiring suitable sites and increasing power capacity are significant obstacles faced by charging operation companies.
From a charging safety perspective, the heat dissipation issues of charging stations themselves, including technological breakthroughs in modules, charging guns, and cables, are all crucial factors directly linked to safety. Furthermore, whether high voltage will lead to more severe radiation and negatively impact health remains a point of contention among consumers.
In terms of vehicle type, foreign electric vehicles are generally larger, such as the TSLA. However, most Chinese electric vehicles are A0 or A00 class models. The smaller space makes it difficult to install larger, high-voltage components, posing a significant challenge for using high-power charging stations. In fact, smaller models are lighter, carry fewer batteries, and have lower battery capacity. Currently, experts have analyzed user fast-charging needs and found that slow charging and regular fast charging are sufficient for passenger vehicle use in scenarios such as commuting, daily commuting, long-distance travel, short-distance travel, and emergency travel; the demand for super-high-power charging is not significant.
In summary, the promotion of electric vehicles is still in its early stages, and neither the usage rate of electric vehicles nor the corresponding charging infrastructure has kept pace with development. While increasing the power of charging piles is a trend, it needs to be developed gradually in accordance with market demand. The development of high-power charging piles requires advance planning and preparation in five aspects: user demand, operational needs, demand for power lithium batteries, national policies, and sound standards—all are indispensable. Just as roads must be built before wealth can be obtained, the development of charging infrastructure must be at the forefront for the development of electric vehicles.
