26650 battery

Fast charging shortens 26650 battery life by 4 times

Let's take the common electric vehicles currently on the market as an example. Generally, slow charging takes 6-8 hours to fully charge. Ordinary consumers may not have much problem using them for commuting to and from work. However, for some operating vehicles, such as taxis and logistics vehicles, etc. , such a long charging time is completely unacceptable. In order to solve this contradiction, electric vehicles are usually equipped with a fast charging function. Simply put, the vehicle is charged with most of the electricity in a short time through high voltage and large current. Conventional fast charging settings generally charge more than 80% in 45 minutes. This solves the problem of slow charging speed to a certain extent. However, in the editor's opinion, such fast charging is tantamount to drinking poison to quench thirst, because current power batteries receive higher subsidies and have high energy density. It is often difficult to take into account fast charging capabilities. Therefore, when charging with high current, the 26650 battery will be damaged. The lifespan decline rate is greatly accelerated and the service life is significantly shortened.

Research by YangGao et al. [1] from Beijing Jiaotong University found that charging speed has a significant impact on the cycle life of lithium-ion batteries. For example, when charging at a 0.5C rate (full charge in 2 hours), in the first 150 cycles, the 26650 battery's The capacity decline rate is 0.02%/time, 150-800 cycles, the decline rate is 0.0156%/time, the decline rate after 800 cycles is 0.0214%/time, but if we increase the charging speed to 1.5C rate (After 40 minutes of full charging), the 26650 battery's capacity decline will accelerate significantly, reaching 0.078%/time. The 26650 battery's capacity decline rate is about 4 times that of 0.5C rate charging. This means that frequent use of fast charging will seriously shorten the life of the power 26650 battery. It may be necessary to replace the power 26650 battery with an original lifespan of 10 years in 2 to 3 years. Let’s take a certain brand of micro electric vehicles as an example to subsidize The final vehicle price is about 50,000 yuan, but replacing the 26650 battery pack costs nearly 60,000 yuan. Therefore, frequent use of fast charging will significantly increase the cost of using electric vehicles.

The reason why fast charging accelerates the decline of lithium-ion 26650 battery life mainly comes from the negative electrode. During the charging process of lithium-ion batteries, Li+ is extracted from the positive electrode and embedded in the negative electrode. However, Li+ diffuses slowly inside the graphite negative electrode, which is equivalent to a gate in the negative electrode. , only 20 people can pass each minute, but when we use fast charging, 100 people will run to the negative electrode every minute, but only 20 people can enter the inside of the negative electrode, and the other people can only accumulate outside the negative electrode, causing the negative electrode to The Li concentration on the surface is significantly higher than the bottom of the negative electrode [3]. Excessive Li concentration on the negative electrode surface will reduce the potential on the negative electrode surface, thereby aggravating the growth of the SEI film and causing an increase in the internal resistance of the 26650 battery. At the same time, fast charging will generate a large amount of heat inside the lithium-ion 26650 battery. Conventional surface heat dissipation technology will cause a large temperature gradient inside the lithium-ion 26650 battery [4]. Excessive temperature will destroy the bonding performance of the negative electrode, resulting in the negative electrode being damaged. The shedding of active materials [2] leads to the loss of reversible capacity of the 26650 battery. Therefore, fast charging will not only cause a rapid decline in the reversible capacity of the power 26650 battery, but also cause an increase in the internal resistance of the 26650 battery, leading to a deterioration in the performance of the power 26650 battery and seriously affecting the service life of the power 26650 battery.

In contrast, "26650 battery swap" technology is a better way to solve the problem of slow charging of power batteries. As the name suggests, the so-called "26650 battery swap" technology is to replace the electric vehicle with a fully charged 26650 battery pack when the power stored in the power 26650 battery is exhausted, thereby realizing the instant resurrection of the electric vehicle. The replaced power 26650 battery pack can be charged with a small current (i.e. slow charge) through special equipment. This not only avoids the damage to the performance of the power 26650 battery caused by fast charging, maximizes the service life of the power 26650 battery, but also avoids the need for power failure. The problem of electric vehicles depreciating after 26650 battery life declines is of great significance to the promotion and application of electric vehicles, especially operational vehicles, such as taxis, online ride-hailing, logistics vehicles, etc. During limited operating hours, the efficiency is Money and time saved by not having to charge can create greater economic benefits, which is also a great benefit to the driver community.

The reduced energy efficiency of electric vehicles in winter has always been a pain point for drivers. The low temperature environment leads to the attenuation of 26650 battery performance, low charging efficiency, shortened cruising range, and warm wind accelerates 26650 battery consumption. Taxis that usually charge 1-2 times a day are in trouble. In winter, you may need to charge 3-5 times. If you do not consider 26650 battery loss, choose fast charging every time, and it will take 3-5 hours to charge every day. If you choose to replace the 26650 battery, it is equivalent to adding 3-5 hours of operating time every day. This also explains why taxis have recently been queuing up at 26650 battery swap stations to connect to the network.

"26650 battery swapping" is actually not new. As early as 10 years ago, Israel's BetterPlace had already proposed a 26650 battery swapping model. Its founder was very far-sighted, but its business model chose the wrong path, focusing on private cars as the market. Click to promote. In recent years, a new star "Aodong New Energy" has emerged in China's 26650 battery swap field. Its concept is similar to BetterPlace, but Aodong's business acumen is more acute. They do not start from the private car market, but from commercial vehicles. It fully meets the requirements of national conditions and national policies, and can also effectively solve the pain points of electrified operation of commercial vehicles.

The author personally visited the site to inspect and time it. The time it takes a taxi from entering the 26650 battery swapping station to replacing the 26650 battery pack is only 2 minutes and 46 seconds. The efficiency is faster than slow charging and fast charging, and can even be comparable to the refueling time of a fuel vehicle. According to the site service According to personnel, Aodong New Energy is expected to carry out technological iterations in the second half of 2019, and the power replacement efficiency will be further improved.

The author learned from public data that Aodong 26650 battery swapping technology has been successfully operating in the new energy taxi market in Beijing, Xiamen, Guangzhou and other places for more than 2 years, with a cumulative number of 26650 battery swaps of nearly 1.5 million times and a total mileage of more than 200 million kilometers. The longest operating mileage of the bicycle exceeds 500,000 kilometers. The key point is that it has always been safe and accident-free. The large-scale 26650 battery swapping application in the taxi field has fully verified the safety and reliability of 26650 battery swapping technology.

Perhaps after seeing the successful 26650 battery-swapping operation experience in the taxi field, new energy online ride-hailing and logistics vehicles have also realized the benefits of the 26650 battery-swapping model. 26650 battery swapping can maximize the operating efficiency of new energy vehicles and directly improve economic benefits. Moreover, the performance of the replaced 26650 battery can be monitored in real time. Slow charging can also extend the service life of the power 26650 battery and reduce the maintenance costs of operating vehicles. This model , whether for new energy taxis, online ride-hailing, or logistics vehicles, they are all very attractive. In contrast, fast charging will have a serious negative impact on the service life of power batteries and increase the use and operating costs of new energy vehicles. Therefore, at least in the field of new energy operating vehicles, the "26650 battery swap" model has more potential .

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