Mobile phones are used everyday. Lithium batteries are very common in our life. Many electronic devices use lithium batteries, such as mobile phones and UAVs. In fact, the power adapter is responsible for converting the AC power of the power grid into the low voltage DC power that can be afforded by electronic products such as mobile phones, such as AC220V to DC5V. Some power adapters supporting fast charging protocol can also be converted to higher DC voltage, such as 9V, 12V, 20V of Qualcomm QC2.0/3.0 protocol.
There are special power management chips inside mobile phones and other electronic products, which can control the charging process of lithium batteries.
At present, the common charging mode of lithium battery is constant current and constant voltage charging. The charging process of lithium batteries can be divided into four stages: 1-pre-charging; 2-constant current charging; 3-constant voltage charging; and 4-stop charging.
1) Precharging: When the battery voltage is relatively low (e.g. below 3.0V), because of the poor lithium ion activity inside the battery, it can only be charged with a smaller current (e.g. 200mA), otherwise it will cause some damage to the battery.
2) Constant current charging: that is, constant charging current, is what we often call CC mode. Constant current charging requires constant current. Generally, the charging current is between 0.2C and 1C. Be careful not to exceed 1.5C. Otherwise, the battery will be damaged greatly. In this process, the battery voltage will continue to rise until the battery voltage reaches 4.2V and enters the constant voltage charging stage. When the battery voltage rises to a certain level (e.g. 3.0V), constant current charging begins with a larger current. At this stage, the charging current is larger (usually the maximum current set, such as 2A), and the battery voltage rises rapidly.
3) Constant Voltage Charging: When the battery voltage rises to the upper limit (e.g. 4.2V), it is changed to constant voltage charging. At this stage, the charging voltage keeps at a stable value and the charging current decreases gradually.
4) Stop charging: When the charging current decreases to a certain threshold (e.g. 200mA), the battery is considered to be full and the charging is over.
The charging process mentioned above is a charging process under the condition of full discharge (over discharge) of lithium battery. In practical use, because overdischarge will affect the performance of lithium batteries to some extent, power management chips in mobile phones and other electronic products have overdischarge protection, and under non-extreme circumstances, there is less overdischarge. Therefore, there are fewer pre-charged states in daily charging.
Wendy
2019-8-6
Disclaimer: This article comes from individual, KRECO has the right of final interpretation.
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