6F22 carbon battery.Full technical analysis: Why lithium battery explosion news continues

　　The application of lithium batteries in daily life has suddenly expanded, mainly due to the widespread use of smartphones, wearable devices, electric bicycles and new energy vehicles. Over the years, there have been constant news about how to use batteries, lithium battery explosions and other news, but among them Often contains a lot of misleading information. In this article, we start from simple applications to complex applications of lithium batteries.

　　To measure battery performance, there are several important indicators:

　　1. Charge and discharge rate: the higher, the better

　　"C is a special symbol that describes the charge and discharge current of a battery. 1C discharge represents the current that takes the battery from full to empty within 1 hour. The iPhone 6 battery capacity is 1810mAH, so the 1C discharge current of this battery is 1.81 amps; Each battery used in the BYD e6 electric car has a capacity of 200AH, so the 1C discharge current of this battery is 200 amps. If a battery is discharged at a high rate, it usually releases less energy than at a low rate.

　　The amount of electricity released at different discharge rates

　　From the test results in the picture above, we can see that the energy released by this power battery using 10C discharge is 85% of that under 1C discharge, and the energy released using 20C discharge is only 70% of that under 1C discharge.

　　2. Number of charge and discharge cycles: the more, the better

　　500 times is a common value for lithium batteries. The number of charge and discharge times of lithium batteries made of different materials ranges from 300-3000 times. The specific meaning of this value may be slightly different in each factory, but it can be roughly understood as: according to the charge and discharge rate specified by the manufacturer (for example, 1C discharge, 0.3C charge; charge from 0% to 100% each time, and follow this cycle) , after 500 cycles, the battery capacity remains 80% of the original. The relationship between the number of charge and discharge times and usage habits is huge. Let’s give a few examples.

　　1. The influence of charge and discharge intensity on the number of cycles

　　Factory label: Each time, charge from 0% to 100%, discharge at 1C, charge at 0.3C, the capacity will decay to 80% after 500 times. This is the most stringent test cycle. It does not need to be so strict. See below.

　　If each power cycle is between 25% and 75%, discharge at 1C and charge at 0.3C, the capacity will decay to 80% after 2000 times.

　　If each power cycle is between 50% and 100%, discharge at 1C and charge at 0.3C, the capacity will decay to 80% after 1800 times.

　　2. The impact of shallow charging and discharging on lifespan

　　Factory label: Each time, charge from 0% to 100%, discharge at 1C, charge at 0.3C, and the capacity will decay to 80% after 500 times. This is the most stringent test cycle. It does not need to be so strict. See below.

　　Each power cycle is between 25% and 75%. Discharge at 1C and charge at 0.3C. The capacity will decay to 80% after 2000 times.

　　Each power cycle is between 50% and 100%. Discharge at 1C and charge at 0.3C. The capacity will decay to 80% after 1800 times.

　　It can be seen from the above two examples that the smaller the charging and discharging rate is, the more beneficial it is to improve the lifespan; shallow charging and shallow discharging are also beneficial to improving the lifespan.

　　3. Internal resistance: the smaller, the better

　　This parameter changes at any time with the load, temperature and other factors. As the battery life decreases, the internal resistance gradually increases. The smaller the internal resistance of the battery, the better it can be charged and discharged at a high rate. The internal resistance of ordinary 18650 batteries is around 50mΩ, and the internal resistance of power-type 18650 batteries is around 15mΩ. If you want to know the internal resistance, you need to use special equipment to measure it, and ordinary multimeters will not work.

　　Tools for measuring battery internal resistance

　　4. Battery consistency

　　The higher the consistency in capacity, internal resistance, and charge and discharge curves of batteries produced using the same materials and processes, the better. Whether batteries can be assembled into battery packs on a large scale is very critical. The larger the battery pack, the higher the consistency requirements.

　　On the following pages we will rank the application in order of difficulty:

　　1. Lithium batteries in mobile phones, tablets, and wearable devices

　　2. Lithium batteries in laptops and mobile power supplies

　　3. Lithium batteries in electric bicycles

　　4. Lithium batteries in electric vehicles

　　Introduce some knowledge respectively, so that the paging is sorted from small to large according to the battery size.

　　I. Lithium batteries in mobile phones, tablets, and wearable devices

　　Why is this field the easiest? Because there is only one lithium battery in these devices, and they are basically ternary lithium batteries. Ternary means three elements: nickel, cobalt, manganese, and the cathode material Li (NiCoMn) O2 of this lithium battery. They are not exactly the same. The ratio of the three elements will be adjusted according to the usage requirements.

　　1. Charge and discharge rate

　　Batteries used in digital devices usually have very low requirements on this. It’s hard for you to use a fully charged mobile phone until it automatically shuts down within an hour, right? No one would design a digital device with a battery life of only 1 hour. They can last at least 3 hours, so the discharge rate of the battery is about 0.3C to meet the demand. The charging requirements are often very low. Usually, everyone can accept a digital device that is fully charged in 3-4 hours, so the charging requirements for the battery are It is also about 0.3C.

　　Regardless of whether it is domestically produced or imported lithium batteries such as Panasonic and Samsung, 1C discharge is the minimum specification. The battery discharge requirements of digital equipment are far lower than the general standards of the battery industry. The charging rate is roughly equivalent to the basic indicators that the battery industry can currently achieve. If there is no extremely special design, there is generally no need to worry.

　　OPPO’s battery flash charging feature puts forward higher requirements for charging

　　Recently, there have been special cases in the mobile phone industry. OPPO, as a representative, has proposed the feature of fast charging, which actually places special demands on battery manufacturers. Taking OPPO's latest N3 as an example, VOOC flash charging promises to charge 75% of the battery in 30 minutes. This works out to a charging current of 1.5C, which is 10 times the charging rate of ordinary mobile phone batteries. It makes sense that the N3 is priced at 3,999 yuan. At least this battery will be one or two times more expensive than ordinary batteries.

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