(1) Constant voltage charging method: During the charging process, the output voltage of the charging power supply remains constant. The charging current is automatically adjusted according to the change in the state of charge of the lithium-ion battery pack. If the specified constant voltage value is appropriate, it can ensure the complete charging of the power lithium battery while minimizing gas evolution and water loss. This charging method only considers the change in the single state of battery voltage and cannot effectively reflect the overall charging status of the battery. Its initial charging current is often too large, which can damage the power lithium battery. Due to these shortcomings, constant voltage charging is rarely used.
(2) Constant Current Charging Method: Throughout the charging process, the charging current is kept constant by adjusting the output voltage. Maintaining a constant charging current results in a relatively low charging rate. While the constant current charging control method is simple, the acceptable current capacity of the lithium-ion battery pack gradually decreases as the charging process progresses. Towards the end of charging, the battery's ability to receive current decreases, significantly reducing the utilization rate of the charging current. The advantages of this method are its simplicity, convenience, ease of implementation, and ease of calculating the charging capacity.
(3) Constant Current Constant Voltage Charging Method: This charging method is a simple combination of the two methods mentioned above. The first stage uses constant current charging to prevent excessive charging current at the beginning of constant voltage charging. The second stage uses constant voltage charging to prevent overcharging during constant current charging. Like any other sealed rechargeable battery, lithium iron phosphate battery packs require controlled charging to prevent overcharging, which can easily damage the battery. Lithium iron phosphate batteries generally use a constant current followed by a voltage limiting charging method.
(4) Chopper Charging Method: Charging is performed using a chopper method. In this method, the current of the constant current source remains constant, while the switching transistor is controlled to turn on for a period of time and then off for a period of time, repeating this cycle. The advantage of this method is that when the battery is charged through an external circuit, there is a certain response time for the appearance of ions inside the battery. If it is continuously charged, it may reduce its capacity potential. However, by adding a period of off after charging for a period of time, the ions appearing at the two electrodes of the battery can have a diffusion process, giving the battery time to digest the ions. This greatly increases the utilization rate of the battery and improves the charging effect.
