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Lithium Iron Phosphate Battery Charging Method

Views: 504     Author: Hakey     Publish Time: 2021-06-10      Origin: Site

Lithium Iron Phosphate Battery Charging Method


The full name of lithium iron phosphate battery is lithium iron phosphate lithium ion battery. Because its performance is particularly suitable for power applications, the word “power” is added to the name, that is, lithium iron phosphate power battery. Some people also call it “lithium iron power battery”, and do you know the charging skills of lithium iron phosphate? The following will introduce you to the correct charging method of lithium iron phosphate battery pack.



Correct charging method of lithium iron phosphate battery pack


It is recommended to use the CCCV charging method for charging the lithium iron phosphate battery pack, that is, constant current first and then constant voltage. The constant current is recommended to be 0.3C. Constant voltage recommendation 3.65. That is, in the process of constant current charging with 0.3C current, when the battery voltage reaches 3.65V, use 3.65V voltage constant voltage charging, and stop charging when the charging current is lower than 0.1C (or 0.05C), that is, the battery has been charged. full. When you use a constant voltage power supply to charge, it also depends on the charging current. It is recommended not to charge with a too high voltage. After adjusting the voltage, ensure that the charging current is below 0.5C, which is good for the battery.


Generally, the upper limit voltage of lithium iron phosphate battery charging is 3.7~4V, and the lower limit voltage of discharging is 2~2.5V. Considering the five aspects of discharge capacity, discharge median voltage, charging time, constant current capacity percentage, and safety, constant current and constant voltage are adopted. For the lithium iron phosphate battery pack, it is reasonable to set the charging limit voltage at 3.55~3.70V, the recommended value is 3.60~3.65V, and the discharge lower limit voltage is 2.2V~2.5V.


The charger of lithium iron phosphate battery pack is different from ordinary lithium battery. The maximum termination charge voltage for lithium batteries is 4.2 volts; lithium iron phosphate battery packs are 3.65 volts. When the lithium iron phosphate battery pack is charged, it is the cable connected to the balance charging board. Generally, it is charged in series directly from both ends, and the charger voltage is greater than the battery pack voltage. The cable detects the voltage of each single cell, which is equivalent to connecting a voltage regulator tube in parallel. The single cell charging voltage will not exceed the voltage regulation value, while other cells continue to be charged through the voltage regulator tube bypass charging.


Because the power of each cell is nearly full at this time, it is just balancing each cell, so the charging current is small, and each cell is fully balanced. The charger can only protect the terminal voltage of the entire battery pack. The balanced charging board ensures that each cell is overcharged and each cell is fully charged. It cannot stop the charging of the entire lithium battery pack because one cell is fully charged.


Lithium iron phosphate battery charging method


(1) Constant voltage charging method: During the charging process, the output voltage of the charging power supply remains constant. With the change of the state of charge of the lithium iron phosphate battery pack, the charging current is automatically adjusted. If the specified constant voltage value is appropriate, it can not only ensure the full charging of the power battery, but also minimize gas evolution and water loss. This charging method only considers the change of a single state of the battery voltage, and cannot effectively reflect the overall charging status of the battery. Its initial charging current is too large, which often causes damage to the power battery. In view of this disadvantage, constant voltage charging is rarely used.


(2) Constant current charging method: During the whole charging process, the charging current is kept constant by adjusting the output voltage. Keeping the charging current unchanged, the charging rate is relatively low. The constant current charging control method is simple, but because the acceptable current capacity of the lithium battery pack gradually decreases with the charging process, in the later stage of charging, the power battery receiving capacity decreases, and the charging current utilization rate is greatly reduced. The advantage of this method is that the operation is simple, convenient, easy to implement, and the charging power is easy to calculate.


(3) Constant current and constant voltage charging method: This charging method is a simple combination of the above two. In the first stage, the constant current charging method is adopted to avoid excessive charging current at the beginning of constant voltage charging. The second stage adopts the constant voltage charging method, which avoids the phenomenon of overcharging caused by constant current charging. Like any other sealed rechargeable battery, the lithium iron phosphate battery pack should be controlled in charge and cannot be overcharged, otherwise it will easily damage the battery. Lithium iron phosphate batteries generally use a charging method of constant current first and then voltage limiting.


(4) Chopping charging method: The charging is carried out by the method of chopping. In this method, the current of the constant current source remains unchanged, and the switch tube is controlled so that it is turned on for a period of time and then turned off for a period of time, and the cycle repeats. The advantage of this method is that when the battery is charged through an external circuit, The ion production inside the battery requires a certain response time, and if it is continuously charged, it may reduce its capacity potential. After charging for a period of time, adding an off time can make the ions generated at the two poles of the battery have a diffusion process, so that the battery has a “digestion” time, which will greatly increase the utilization rate of the battery and improve the charging effect.