Request a Quote
LiFePO4 Battery Charging Method--IMPROVE BATTERY
September 30, 2021

LiFePO4 Battery Charging Method

The charger of the LifePO4 battery pack is different from the ordinary lithium ion battery. The highest termination charging voltage of lithium batteries is 4.2 volts; while the lifePO4 battery is 3.65 volts. When charging LifePO4 battery pack, it is connected to the balance charging board. Generally, it is directly charged in series from both ends. The charger voltage is greater than the battery pack voltage. The cable detection of the voltage of each single cell is equivalent to connecting a zener tube in parallel. The charging voltage of the single cell will not exceed the voltage stabilization value, while the other single cells continue to be charged and charged through the zener tube bypass.

common lifepo4 battery power connectors
Common lifepo4 battery power connectors

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 charged to supplement the balance. 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 charging the entire LifePO4 pack because one cell is fully charged.

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 LifePO4 battery pack, the charging current is automatically adjusted. If the prescribed constant voltage value is appropriate, it can not only ensure the full charge of the power battery, but also minimize gassing and water loss. This charging method only considers the change of the battery voltage in a single state, and cannot effectively reflect the overall charging status of the battery. Its initial charging current is too large, often causing damage to the power battery. Consider of this disadvantage, constant voltage charging is rarely used.
  2. Constant current charging method: During the entire charging process, the charging current is kept constant by adjusting the output voltage. Keep the charging current constant, the charging rate is relatively low. The constant current charging control method is simple, but because the acceptable current capacity of the LifePO4 battery pack gradually decreases with the progress of 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 simple, convenient, and easy to implement, and the charging power is easy to calculate.
  3. Constant current and constant voltage charging method(CCCV): This charging method is a simple combination of the above two. first constant current and then constant voltage. The recommended constant current is 0.2C-0.3C. Constant voltage recommendation 3.65. That is, 0.2C-0.3C current charge in the constant current process, when the battery voltage reaches 3.65V, use 3.65V voltage constant voltage charge, when the charging current is lower than 0.1C (or 0.05C), stop charging, the battery is already full. When you charge with a constant voltage power supply, please keep observe charging current. It is recommended not to charge with  higher voltage. After adjusting the voltage, ensure that the charging current is below 0.5C, which is good for the battery.
  4. Chopping wave charging method: Use the chopping method to charge. In this method, the current of the constant current source is unchanged, and the switch tube is controlled to turn on for a period of time and then turn off for a period of time, cyclically. The advantage of this method is that when the battery is charged through an external circuit, The ion generation inside the battery requires a certain response time. If it is continuously charged, its capacity potential may be reduced. After charging for a period of time, adding a turn-off time can allow the ions produced at the two poles of the battery to have a diffusion process, giving the battery a time to "digest", which will greatly increase the utilization rate of the battery and improve Charging effect.

If you want to maximize the effectiveness of the LifePO4 battery, please use it frequently, let the electrons in the lithium battery always in a flowing state. If you don't use the lithium battery often, please remember to complete a charging cycle for the LifePO4 battery every month and do a battery calibration, that is, deep discharge and deep charge once.