Correct charging method of lithium iron phosphate battery

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 charging skills of lithium iron phosphate batteries.

1. Before solving the problem, first we need to understand the structure and working principle of lithium iron phosphate battery. LiFePO4 is used as the positive electrode of the battery. It is connected to the positive electrode of the battery by aluminum foil. The ions can pass but the electrons cannot. On the right is the negative electrode of the battery composed of carbon (graphite), which is connected to the negative electrode of the battery by a copper foil. Between the upper and lower ends of the battery is the electrolyte of the battery, and the battery is hermetically sealed by a metal casing. When a lithium iron phosphate battery is charged, the lithium ions in the positive electrode migrate to the negative electrode through the polymer separator; during the discharge process, the lithium ions in the negative electrode migrate to the positive electrode through the separator. Lithium-ion batteries are named after lithium ions migrate back and forth during charging and discharging.

2. When the battery is charged, lithium ions migrate from the surface of the lithium iron phosphate crystal to the crystal surface, enter the electrolyte under the action of the electric field force, pass through the diaphragm, and then migrate to the surface of the graphite crystal through the electrolyte, and then embed the graphite crystal. in the grid. At the same time, the electrons flow to the aluminum foil collector of the positive electrode through the conductor, flow to the copper foil collector of the negative electrode through the tab, battery pole, external circuit, negative pole, and negative ear, and then flow to the graphite negative electrode through the conductor, so that the The charge of the negative electrode is balanced. After the lithium ions are deintercalated from the lithium iron phosphate, the lithium iron phosphate is converted into iron phosphate.

3. When the battery is discharged, the lithium ions are deintercalated from the graphite crystal, enter the electrolyte, pass through the separator, and then migrate to the surface of the lithium iron phosphate crystal through the electrolyte, and then re-embedded into the lattice of lithium iron phosphate through the surface. . At the same time, the battery flows to the copper foil collector of the negative electrode through the conductor, flows to the aluminum foil collector of the positive electrode of the battery through the tab, battery negative pole, external circuit, positive pole and positive pole, and then flows to the iron phosphate through the conductor. The lithium positive electrode balances the charge of the positive electrode.

Matters needing attention: Remind the lithium iron phosphate battery to pay attention to waterproof and dustproof when using it, so there should be no water in the storage place, which will affect the performance and service life of the battery.

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 advantages of this method are 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.