The four processes of lithium battery charging

The four processes of lithium battery charging Lithium batteries have become very common in daily life. The basic use of electronic devices is lithium batteries, such as smart phones and drones. How to charge the lithium battery after the lithium battery is exhausted? Although there are many lithium battery charging ICs on the market that can help us complete the entire charging process, we still need to know this process. As long as we know the entire lithium battery charging process, we can clearly know the current battery charging stage and further control or command. As long as we fully know the charging process, we can directly use the microcontroller to control the charging of the lithium battery. In summary, the charging process of a lithium battery can be roughly divided into four stages, namely, single-drop charging; 2-constant current charging; 3-constant voltage charging; 4-stop charging. Trickle charging is the so-called trickle charging. We can use one word to think of it: trickle, which merges into the sea, that is to say, trickle charging is a kind of small current charging. What is the appropriate value for this small current? Generally, we can take 0.1c, and C represents the battery capacity. For example, Huawei’s latest mobile phone P30Pro is equipped with a 4200mAh battery capacity, so 0.1c is 420mA. However, we don't seem to have this process in the process of charging the phone. Every time we plug in the charger, we immediately start charging. The previous OPPO mobile phone's slogan was to charge for 5 minutes and talk for 2 hours to illustrate that there is no such process in mobile phone charging. So what is the meaning of trickle charge? This is because the lithium battery has the possibility of overdischarge (the overdischarge point is generally 3V), and the overdischarged battery has the possibility of damage, so we need to use a small current to test whether the battery is normal . After a period of time, if the battery voltage exceeds 3V, we think that the battery is in normal state and can proceed to the next stage of charging, otherwise we think that the battery is abnormal and give up charging. Constant current charging, that is, the charging current is stable, is the form of CC that we often say. The current for constant current charging must be stable. The charging current is generally between 0.2c-1c. Be careful not to exceed 1.5 degrees Celsius. During this process, the battery voltage continues to rise until the battery voltage reaches 4.2v, and it enters the constant voltage charging stage. Constant voltage charging, that is, the charging voltage is stable, is the CV type we often say. During the constant voltage charging process, the charging current continuously decreases until the current is less than 0.1°C, and the charging is stopped. Some people don’t understand why the current continues to drop. Let’s use a formula to describe it. Assuming that the input voltage is Vin, the battery voltage is Vbat, and the battery resistance is R, then the charging current can be expressed as: According to the formula analysis, Vin does not change, Vbat During the charging process, it continues to rise, while R remains unchanged, so Ibat will continue to fall as Vbat rises. Stop charging. After the constant voltage charging is over, the charging can be stopped. The above are the four charging stages of lithium batteries. Figure (1) describes the entire charging process. The ordinate is the battery charging current, and the abscissa is the battery voltage. Should the battery voltage be added? Lithium battery charging process In fact, there is no problem with this picture. 4.2v constant voltage stage u003d battery's own voltage + battery internal voltage drop. Although the battery voltage is increasing during the constant voltage charging process, the charging current is decreasing, so the voltage drop of the battery is also decreasing. One of these two variables is added, the other is reduced, and then stabilized at 4.2v. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Analyze the development prospects of hydrogen fuel power batteries