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The idea of "low carbon travel and green life" has penetrated into every aspect of people's lives, and new energy vehicles are becoming more and more popular. Xiao Bian went out to interview several electric car owners, in addition to get to why they chose electric cars, and found that they were all doubtful about charging, especially fast charging.
Why is the charging mode of fast charging mode only available once a day? How fast does it take one or two hours? Will the battery life drop faster if it is filled more quickly? Will it explode?
Here, Xiaobian is going to answer questions and answer questions for you.
What is fast charge?
Sooner or later, there is bound to be slow. The concept of fast charging is relative to slow charging. Electric vehicle charging speed is closely related to charger power, battery charging characteristics and temperature. In general, the owners of their own household electric charging are in the form of slow charging. It takes 6 to 8 hours to fill the electricity. Fast charge is usually charged by high power DC. By increasing the current, the battery can be charged to 80% capacity in half an hour, so as to accelerate charging time.
Speaking of this, we have another problem. Since half an hour will be able to charge 80% of the electricity, why is it full of electricity for one or two hours or even longer?
In fact, this is a bottleneck in current battery technology. At present, most of the electric vehicles on the market are lithium ion batteries. The principle of fast charging is to ensure that lithium ions are embedded quickly from the positive pole, and then the negative electrode is quickly embedded. The process is divided into three stages, namely constant current precharge, high current constant current charging and constant voltage charging.
When the lithium battery is in the first stage of pre charge, its state is relatively stable, so in the second stage, the charging current can be appropriately raised. After more than 80%, the charging current must be smaller to protect the battery, so it will take longer to charge to 100%. In addition, when the temperature is low in winter, the battery requires smaller charging current and longer charging time.
Effect of fast charging pile on battery
After introducing the principle of fast charging pile, I believe you have a preliminary understanding of it. Will it affect battery capacity or even explode?
In fact, when the current is increasing, a layer of semi permeable film (SEI film) on the surface of electrode negative electrode will be cracked to some extent, so that the electrode material and electrolyte will react with each other. In addition, temperature rise will be accompanied by some side effects, such as decomposition of electrolyte, deposition of electrodes, and to a certain extent, the capacity of batteries will gradually decrease. But this is not the only factor that affects the capacity of the battery, and the battery capacity will be reduced by every charge, either fast or slow, when the battery is finished.
In addition, when it comes to fast charging, it will cause an explosion, which is actually related to the overcharge problem of batteries. Whether the battery pack of an electric vehicle will be overcharged or overdischarged depends to a large extent on the management level of the BMS system. So whether consumers or car companies pursue high endurance, they should not only increase the battery capacity, but also improve the management and upgrading of the battery management system BMS.
When the electric vehicle is charged, the battery management system BMS on the electric vehicle will estimate the power state of the power cell group, and automatically adjust the charge current according to the condition of the battery pack, so as to prevent the damage of the battery. Moreover, some charging stations will stipulate that cars can only be charged once a day, so there is no need to worry too much about the impact of fast charging on batteries.
Fast filling instead of slow charge?
Since speaking, as long as a safety standard is charged, charging is actually not as horrible as it may be. Would it replace the slow charging completely?
In fact, this involves a cost problem, fast charging will use a larger current and power, so many cars will be quickly filled, and it is still difficult for the power supply company to achieve such a power supply. In addition, fast charging also needs some matching equipment, such as converting AC DC, so the cost will rise.
The charging current and power of the slow charge charging pile are relatively small, and the influence of the battery life is less, and the charge cost is low when the electric low peak is used. It is very satisfied with the application scene of the general owner's commuter car at night and home charging at night. So Xiaobian thinks that the slow charging mode will not be replaced, but will be coordinated with the fast charging or even switching mode.
In any case, the promotion time of electric vehicles is still short, no matter the use of vehicles or the corresponding charging technology has not kept pace with the development needs. It is believed that with the development of technology, it will take one or two hours, like some car owners, to solve the problem, and it will be solved slowly. The idea of driving 500 kilometers for 5 minutes will eventually become a reality.