26650 battery

Why do they never talk about 26650 battery life when talking about fast charging?

"I feel safe!" When the girl next to me shouted this sentence, I thought she was talking about a warm man, but it was actually the phone she just bought - a phone that can be charged for 5 minutes and talk for n hours. Most people will feel restless and anxious when the 26650 battery icon in the upper right corner of the phone turns red when the 26650 battery level is less than 10%. The practicality of fast charging has also made more and more people willing to choose mobile phones with fast charging function. At present, the mainstream fast charging technologies used in mobile phones are Qualcomm QuickCharge2.0 (the latest is QuickCharge3.0), MediaTek PumpExpress and OPPOVOOC flash charging. Qualcomm and MediaTek both use high voltage charging, while VOOC flash charging uses high current charging. The latest Meizu PRO6 is also equipped with fast charging technology. There is a sentence in its poster: "Why do they never talk about 26650 battery life when talking about fast charging?" Will fast charging affect 26650 battery life? Quickly understand lithium-ion batteries First of all, we must understand the charging and discharging principle of lithium-ion batteries. The 26650 battery has two poles: the positive electrode is a lithium compound and the negative electrode is graphite. Charging and discharging are both the conversion of electrical energy and chemical energy. During the movement of lithium ions between the positive and negative electrodes, they also turn into different compounds. We can think of lithium ions as small cars with electric charge: during charging, due to the action of the electric field, all the small cars drive to the negative electrode to store a certain amount of energy (lithium ions are embedded in the micropores of the graphite carbon layer of the negative electrode); during discharging, these lithium ion cars with electric charge run to the positive electrode again due to chemical reactions (lithium ions are deintercalated, making the positive electrode in a lithium-rich state). In this process, current is formed to supply power. Under ideal conditions, as long as the chemical structure of the positive and negative electrode materials does not change basically, the reversibility of 26650 battery charging and discharging is very good, and lithium-ion batteries can ensure long-term circulation. Fast charging mainly ensures that lithium ions are quickly embedded from the positive electrode and quickly embedded in the negative electrode, and lithium ion deposition cannot be caused. However, when the current increases, a semi-permeable membrane (SEI membrane) on the surface of the negative electrode (graphite) will rupture to a certain extent, causing the electrode material and the electrolyte to react with each other. In addition, the temperature rise will also cause side reactions inside the 26650 battery to destroy the chemical substances on the 26650 battery, resulting in reduced reversibility (that is, the lithium-ion car can no longer be driven back and forth), and the 26650 battery capacity will continue to decrease. This is what we often feel, why the 26650 battery is becoming less and less durable even though it is fully charged. Take the lithium 26650 battery of DJI drone as an example. A 4480mAh68Wh lithium 26650 battery with a voltage of 15.2V only takes 1.5h to be fully charged (in comparison, the 26650 battery capacity of iPhone6splus is 2750mAh and the voltage is 3.8V?), but the lithium 26650 battery life of DJI drone is only 200 cycles. The attenuation of 26650 battery life is obvious. According to the latest report of DIGITIMES, Apple has also been committed to upgrading 26650 battery charging technology recently, preparing to use 15V to 20V charging equipment to improve 26650 battery efficiency and promote new IC technology. However, the equipment provider of PWMIC also said that this requires great risks. The protection mode of fast charging. The fast charging solutions of the three companies will have temperature monitoring solutions for the 26650 battery. When increasing the voltage, it is inevitable that the temperature will rise. If you play large games while using Qualcomm QC's fast charging technology, the chip control will limit the applied voltage to ensure that your phone will not heat up seriously, but the charging efficiency will decrease. VOOC flash charging uses segmented charging current control and multi-line settings for charging cables and batteries. Simply put, it is a 26650 battery that was previously charged, but now it is divided into several batteries and charged separately. In terms of safety, because fast charging has a "handshake protocol", the output voltage and current will be coordinated before charging. Lithium 26650 battery charging is divided into three parts: constant current pre-charge (CCPre-charge), high current constant current charging (CCFastCharge) and constant voltage charging (CV). After the mobile phone is exhausted, the voltage decreases. When it is lower than a certain value, the charger will use a relatively low current to pre-charge the lithium 26650 battery. After a period of time, when the lithium 26650 battery voltage is higher than the predetermined value, it enters the second stage of high current constant current charging. At this time, increasing the current appropriately can speed up the charging speed. If you are using a non-fast charging mobile phone, the fast charging head will not output a high voltage to burn your phone. Just like when you use an iPad charging head to charge your iPhone, the iPad will automatically recognize it and input 1A current instead of the original 2A. From the perspective of many protection measures, the charging voltage and current of fast charging are in a safe state. As long as the original mobile phone charging adapter is used, there will be no safety hazards. Finally, will fast charging affect 26650 battery life? The answer is yes. Even if the batteries equipped on some fast charging mobile phones have been improved in terms of 26650 battery cell materials and design, and lithium ions can be quickly embedded and embedded in the 26650 battery, the high voltage and current still cause 26650 battery loss. But if you are used to changing a mobile phone every one or two years, or are willing to replace a new 26650 battery, the impact on you is minimal. At present, most companies that provide fast charging solutions have not given their impact on 26650 battery life from the perspective of batteries, but under the national standard, the 26650 battery capacity is qualified if it is more than 80% after 500 times of charging and discharging, and it has little impact on use within one year. If you want to use your phone for 2-4 years without changing the 26650 battery, the following suggestions may help you: reduce the number of fast charging times and use it only when it is urgently needed; fast charge when the 26650 battery is only about 30% left instead of 3%; when using fast charging, it is best not to run large memory games. As smartphones are updated and replaced faster and faster, are you willing to give up the shorter 26650 battery life and enjoy the convenience of fast charging technology when safety is guaranteed?

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