Why is it unsafe to use power banks on the subway?
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Guangzhou Metro recently proposed that "passengers should not use mobile power banks on the subway". Is this the rhythm of banning power banks on the subway? Why is it unsafe to use power banks on the subway? Power banks have exploded in the subway. To be precise, Guangzhou Metro's suggestion this time is not a ban. According to Ye Zichuan, director of the publicity department of Guangzhou Metro Company, passengers can carry power banks if they want, but first of all, they must ensure that the mobile power banks are regular products with quality assurance and take basic protection and protection. Try not to use power banks for charging during the operation of the subway. Relevant departments have no regulations on the use of power banks on the subway. Guangzhou Metro's suggestions are currently only non-mandatory suggestions. The suggestions are more based on protecting the safety of the majority of subway passengers and preventing dangerous accidents. In May this year, smoke was found at the tail of a subway train on Shenzhen Line 4, and passengers were evacuated urgently. Later, the fire department found that it was caused by the explosion of a mobile power bank carried by a passenger. Although the accident did not cause casualties, it was enough to arouse people's attention to the safety of using mobile power banks on the subway. There is a risk of explosion when using mobile power banks. Once an accident occurs on the subway, the impact range is wide and the number of people affected is large. This is also the main reason why Guangzhou Metro wants to dissuade passengers from using power banks. As early as last year, airplanes said no to power banks with energy values that do not meet the standards. It is also the only public transportation that has regulations on carrying power banks. When passengers board an airplane, power banks must be handled in accordance with the regulations on carrying lithium batteries in civil aviation passenger luggage issued by the Civil Aviation Administration in 2011. The standard for implementation is the rated energy value (watt-hours) of the power bank. Power banks with less than 100 watt-hours can be boarded; power banks with a rated energy value of 100 to 160 watt-hours must be boarded with the consent of the airline; power banks with a rated energy value of more than 160 watt-hours are not allowed to board. Unsafe factors in mobile power supplies The structure of a power bank mainly consists of three parts: the shell, the battery cell and the circuit board. Consumers are more familiar with the shell of the power bank. In addition to being beautiful, the shell also needs "strength". Strength is reflected in strength and heat resistance. Only with high strength can the internal circuit board and battery cell be firmly protected in accidental collisions and falls. Heat resistance is reflected in the fact that it can play a certain flame retardant role when accidents such as spontaneous combustion occur inside the power bank, reducing the damage caused by accidents. Roughly speaking, the shells of power banks on the market are mainly made of plastic and metal. In comparison, metal shells have advantages in strength and heat resistance. The battery cell is a very critical part of the power bank. Its material has a direct impact on the safety of the mobile power supply. A good battery cell can be used for a long time and is relatively safe. At present, in the mainstream mobile power products, our common battery cells are mainly 18650 and polymer. From the appearance, the 18650 is cylindrical, like an enlarged version of the No. 5 battery, while the polymer battery cell is generally flat. In terms of material form, the 18650 uses a liquid electrolyte, while the polymer uses a solid polymer electrolyte (which can be dry or gelatinous). The "18650" of the 18650 battery cell represents the surface scale. 18 refers to the battery diameter of 18.0 mm, and 650 refers to the battery height of 65.0 mm. There are usually three types of battery cells: imported, domestic and second-hand. The imported ones are mainly high-quality battery cells produced by large foreign manufacturers such as Sanyo and Samsung. Domestic 18650 batteries are mainly produced by domestic brand manufacturers, and the overall level is still a certain distance away from foreign ones. Second-hand telecommunications are also called disassembled batteries, which refer to batteries that are disassembled and reassembled from old products. This type of battery is the culprit of many mobile power explosions and combustion incidents in recent years. Due to the low cost of 18650 batteries, many mobile power manufacturers use 18650 batteries. Some even use inferior 18650 batteries in order to reduce costs. The 18650 battery contains liquid electrolytes. Mobile power supplies using this type of battery will cause the internal voltage to rise sharply when charged. Once overcharged or overheated, it may cause short circuits, combustion, etc.; if it encounters vibration or collision, it is easy to cause electrolyte leakage, corrode circuit boards, and cause accidents. Polymer batteries are generally made of a mixture of lithium cobalt oxide, lithium manganese oxide, and ternary lithium. They are also afraid of leakage and short circuits. But compared with 18650, its safety is relatively better. A mobile power bank with a large capacity, such as 8000mAh or more, if it is composed of multiple 18650 batteries connected in parallel, will have serious consequences if it explodes, while polymer batteries will basically not explode, and serious ones will produce flames. The main function of the circuit board is to control the voltage and current during the input and output process, and it can also realize other functions such as lighting and power display. A good circuit board can improve the conversion rate, reduce the impact of resistance on charging, and allow the power bank to perform at its maximum performance. Excellent circuit design can protect the battery, reduce loss and heat, and maximize the conversion of battery energy into output energy, while also having the function of stabilizing voltage and current. A good circuit board can automatically adjust when the power supply is overcharged or discharged, and automatically turn off the charging function when the power is fully charged, which can protect the charging safety of mobile phones and other devices. Choose a good mobile power bank to ensure safety Whether you are on the subway or in your own room, using a low-quality mobile power bank will bring unimaginable consequences. In order to protect the lives of yourself and others, it is important to choose a good mobile power bank. From the perspective of safety, Tencent Technology's advice to consumers when choosing mobile power supplies is: 1. Buy mobile power supplies produced by manufacturers with product quality and corporate reputation, and do not buy low-priced counterfeit products for cheap. Battery cells and circuit boards have certain fixed costs. The higher the quality of the battery cells, the higher the manufacturer's purchase cost, and the price will naturally be more expensive than poor quality ones. The more well-known mobile power supply brands may have better product quality and better after-sales service. 2. It is best to choose a mobile power supply with polymer batteries. The output efficiency of polymer batteries is relatively stable, and it also has the characteristics of light weight, safety and efficiency. 3. While considering the beauty of the shell, pay attention to the strength and heat resistance of the shell. 4. Don't blindly pursue a high conversion rate. The conversion rate of the mobile power supply is very important. If the conversion rate is too low, it means that the line loss of the mobile power supply will be large, it may heat up, and even explode. However, if the advertisement claims that the conversion rate is as high as 90%, then you should be vigilant, because the current conversion rate of about 85% is already very good. As a winner of Toutiao's Qingyun Plan and Baijiahao's Bai+ Plan, the 2019 Baidu Digital Author of the Year, the Baijiahao's Most Popular Author in the Technology Field, the 2019 Sogou Technology and Culture Author, and the 2021 Baijiahao Quarterly Influential Creator, he has won many awards, including the 2013 Sohu Best Industry Media Person, the 2015 China New Media Entrepreneurship Competition Beijing Third Place, the 2015 Guangmang Experience Award, the 2015 China New Media Entrepreneurship Competition Finals Third Place, and the 2018 Baidu Dynamic Annual Powerful Celebrity. |
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