What Is The Appropriate Charging Current For Lithium Batteries?

What is the appropriate charging current for lithium batteries? There is no unified standard for this, but it depends on what type of lithium battery and whether it supports fast charging technology, so that you can know how much lithium battery charging current is more appropriate. After knowing the type and properties of the lithium battery, how to calculate the charging current of the lithium battery? This is determined by the chemical substance of the lithium battery. Therefore, it is necessary to configure the performance of the charging IC according to the charging characteristics of the lithium battery itself to achieve the correct, safe and efficient use of the lithium battery. 

The charging current of the lithium battery depends on the capacity. The greater the current, the more difficult it is to fully charge the battery. This is done to protect the lithium battery can be used normally, because overcharge and overdischarge will cause the lithium battery to leak or fail to function, or even explode.

As far as the charging current of the rapid charging stage of the lithium battery is concerned, as a dynamic process, the optimal charging current of the lithium battery is actually divided into three stages.

1. Optimal current during precharging: that is, when the initial/no-load voltage of the lithium battery is lower than the precharging threshold, it must first go through a precharging stage. For a single lithium ion battery, this threshold is generally 3.0V. At this stage, the pre-charge current is about 10% of the current in the next stage-the constant current charging stage.

2. The best current during constant current charging: The so-called constant current means that the current is constant and the voltage gradually rises, and then it enters the fast charging stage. Most of the constant current charging current is set to be between 0.4 and 0.6C, which can be understood as 0.5C, that is, it can be fully charged in about two hours without considering other factors. The reason why 0.5C is chosen is that this current is a good balance between charging time and charging safety.

3. Charging current during constant voltage charging: For single-cell lithium-ion batteries, when the battery reaches a certain voltage value, it enters constant voltage charging. This voltage value is generally 4.2V. At this stage, the voltage remains unchanged and the current Decrease; this kind of current reduction is a successively decreasing process, most lithium battery protection choose 0.01C as the termination current, which means that the charging process enters the end state. Once charging is over, the charging current drops to zero.

The core of the best charging current for lithium batteries is the current design during constant current charging. It should be emphasized that most portable lithium batteries are better designed to be charged at 0.5C. For example, the conventional capacity of 18650 lithium batteries is 1800-2600mAh. Choose 1A charging, and the rate type is 1200-1500mAh, and the charging current of 0.5C is 0.7A. The maximum charging current of lithium batteries is strictly determined by the battery structure. Therefore, various lithium battery manufacturers do not agree with this regulation, some are set at 0.6C, and the highest requirement for portable lithium batteries is 1C.

How to calculate the charging current of lithium battery?

The maximum charge current that a lithium battery can accept is usually 1C or less. The charge current of a lithium battery is generally marked on the charger. You can see that the lithium battery usually uses a constant current and then a constant voltage charging mode. When the charger limits the voltage, it will perform trickle charging, so the charging time needs to add about 1 hour. If you want to calculate the charging time, divide the battery capacity by the charging current, add the conversion loss, and add one at the end Hours are almost there.

Lithium iron phosphate batteries generally can use 1C or higher (15C) charge and discharge current, so they are more suitable as power batteries. The charging time of the 18650 battery is the same as that of all secondary batteries. That is, the charging time of the battery is equal to the ratio of the nominal capacity to the charging current. However, due to the internal impedance generated when the lithium battery is charged, the 18650 battery is charged Time has to consider the factors that overcome this impedance.