The concept of "low carbon travel and green living" has penetrated into every aspect of people's lives, and new energy vehicles are becoming more and more popular. I went out to interview a few electric car owners, and apart from getting to the point of why they chose electric cars, I also found that they all had some doubts about charging, especially fast charging.
Why does the fast charging mode only work once a day? Why do they have to wait for an hour or two for fast charging? Will the battery life decrease faster with more fast charging? Will it explode?
What is fast charging?
The concept of fast charging is relative to slow charging. The speed of charging an electric vehicle is closely related to the power of the charger, the charging characteristics of the battery and the temperature. The average car owner charges their car at home on AC power, which is a form of slow charging and takes 6 to 8 hours to fully charge. Fast charging is generally high-power DC charging, by increasing the current, half an hour can be charged to 80% of the capacity of the battery, speeding up the charging time.
This is where the question arises as to why it takes an hour or two to fully charge a battery when it can be charged to 80% in half an hour?
In fact, this is a bottleneck in the current battery technology, most of the electric cars on the market are lithium-ion batteries, the principle of fast charging is to ensure that lithium ions are quickly embedded from the positive electrode, and then quickly embedded in the negative electrode. This process is divided into three stages, namely constant current pre-charging, high current constant current charging and constant voltage charging.
When the lithium battery has been pre-charged in the first stage, its state is already relatively stable, so in the second stage, the charging current can be increased appropriately. After the charge exceeds 80%, the charging current must be reduced in order to protect the safety of the battery, so the charging time to 100% will be longer. In addition, in winter, when the temperature is lower, the battery requires a lower charging current and the charging time becomes longer.
The effect of fast charging on the battery
After an introduction to the principle of fast charging, I believe you have a preliminary understanding of this, but will it affect the capacity of the battery or even explode?
In fact, when the current increases, a semi-permeable membrane (SEI membrane) on the surface of the negative electrode (graphite) will break to a certain extent, causing the electrode material and electrolyte to react with each other. The increase in temperature is accompanied by side reactions such as decomposition of the electrolyte and the formation of deposits on the electrode, which, to a certain extent, will slowly reduce the capacity of the battery. However, this is not the only factor that affects the capacity of the battery. Generally speaking, every time a power battery is charged and discharged from the time it is manufactured, whether it is a fast charge or a slow charge, it will cause the battery capacity to decay.
In addition, when it comes to whether fast charging will cause an explosion, this is actually a matter of overcharging the battery. 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 it's consumers or car companies pursuing high range, it's not just about increasing battery capacity, it's also about improving the management and upgrading of the battery management system BMS.
When charging an electric car, the BMS on the electric car will estimate the state of charge of the power battery pack and automatically adjust the size of the charging current according to the condition of the battery pack to prevent damage to the battery from overcharging and overdischarging. Some charging stations also restrict fast charging to once a day, so there is no need to worry too much about the impact of fast charging on the battery.
Fast charging instead of slow charging?
Since it is said that fast charging is not as bad as it seems, as long as it is done according to a safe standard, will fast charging replace slow charging completely?
In fact, this involves a cost issue, fast charging will use a higher current and power, so many cars, all fast charging, for the power company to achieve such a power supply is still a bit difficult. In addition, fast charging requires some ancillary equipment, such as converting AC to DC power, which also increases the cost.
Slow charging is relatively small in terms of charging current and power, which has less impact on battery life, and the cost of charging is low when electricity is low, which is very suitable for general car owners to use their cars for commuting to work and charging at home at night. Therefore, I believe that the slow-charging mode will not be replaced, but will develop in concert with the fast-charging and even power-changing modes.
In any case, the promotion of electric vehicles is still short, both the use of vehicles and the corresponding charging technology have not kept up with the development needs. I believe that with the development of technology, the problem of why fast charging still takes one or two hours, as mentioned by some car owners, will be solved slowly and the idea of charging for 500 km in 5 minutes will eventually become a reality.
The fast charging pile provided by Grasen has high quality, elegant design, good performance. It can charge to 80% within 30 minutes.If you are interested, welcome to visit our website www.grasen.com and send us inquiry sales@grasen.com for more information.
-- Marcus Groll，A Charging Station Owner in UKRAINE
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