Charger and LiFePO4 Battery: how to choose a charger matching with LiFePO4 battery?

LiFePO4 Batteries:

The main reason why we should talk about LiFePO4 battery in the first place is that we see all kinds of batteries in our life, from lead-acid batteries to lithium batteries, but why should we call this battery LiFePO4 battery instead of lithium battery? Well, it's because it's unique compared to other lithium-ion batteries in that it offers, LiFePO4 batteries boast a longer cycle life. Of course,it is usually known for its stability and safety, has a nominal voltage of 3.2 volts per cell. It exhibits a flat discharge curve, maintaining a relatively constant voltage until reaching near full depletion. Additionally, LiFePO4 batterie endures thousands of charge-discharge cycles with minimal capacity degradation.

Selection of Charger

Choosing the right charger is essential for battery safety and charging,there are several important factors to consider before you make your choice to avoid a safety incident or damage to your battery due to an inappropriate charger.

Voltage

LiFePO4 batteries typically have a nominal voltage of 3.2 per cell. Ensure the charger's output voltage matches the battery's requirements to prevent overcharging or undercharging. Overcharging can lead to permanent damage to the battery, and although the battery is equipped with a BMS protection system, it is recommended to choose the appropriate charger in order to ensure the optimal use of the battery; undercharging may result in the power not reaching the normal use of the battery, which also reduces the battery's use experience.

Charging Voltage > Battery Voltage >= Open Circuit Voltage > Discharge Voltage

The charging voltage has to exceed the battery voltage in order to be able to charge the battery, which is why the charging voltage of a 12.8V battery is 14.6V. Since the voltage of each cell is 3.2V, the charging voltage of this cell is 3.65V, then when purchasing a charger, we should strictly refer to the parameters of the battery, and we can calculate the required voltage of the charger according to the number of cells in the battery.

Open-circuit voltage is also known as resting voltage, i.e., the voltage state of the battery when it is not connected to any load and power input, which can reflect the battery's current charge.

Current

The charging current of lithium battery is determined by the battery capacity. The larger the current, the harder it is for the battery to be fully charged. This is also to protect the battery, allow the battery to be used normally, and avoid overcharging and over-discharging, which may lead to battery leakage, functional failure, or even explosion.

It is recommended to use CC and CV charging method for charging Li-FePO4 battery packs, i.e. constant current followed by constant voltage. The first stage adopts the constant current charging method to avoid excessive charging current at the beginning of constant voltage charging. The second stage adopts constant voltage charging method to avoid the phenomenon of overcharging caused by constant current charging. Lithium iron phosphate battery packs, like any other sealed rechargeable batteries, should be controlled for charging, and should not be indiscriminately charged, otherwise the battery will be easily damaged.

C-Rate

C-Rate is used to measure the charging speed, usually expressed as 0.2C,0.5C,1C, where C refers to the battery capacity in ampere-hours.According to the charging rate we can calculate the charging time and charging current, and vice versa, we can also calculate the charging time according to the charging current. For example, when we want to charge a 12V 100Ah LiFePO4 battery, especially if the recommended charging rate is 0.2C, then the charger should be 14.6V 20Ah, and the battery full charge time is 5 hours.
It is worth noting that if you want to fast charging, it is also important to know the impact of fast charging on the battery, fast charging is not only an increase in the charging rate, but also increase the charging current, which will reduce the battery's ability to reduce the number of battery charging and discharging cycles, long-term fast charging will affect the life of the battery. And fast charging will produce heat, a short period of time to produce high temperatures, over time, accelerated the battery aging speed.

Some customers feedback after charging but can not reach the product should have the use of time, this is why? When this problem occurs, after excluding the battery itself, first check whether the charger is adapted to the battery, if not adapted to the voltage does not reach the charging voltage indicated in the battery specification, which will lead to the battery is not full, can not achieve the desired length of use, fast power off. This also reminds us how important it is to choose the right charger.
In addition, after purchasing LiFePO4 batteries to replace Lead-Acid batteries, is it possible to charge Lithium Batteries using a Lead-Acid Battery Charger?
If it is a special charger for Lead-acid Batteries, then the answer is no. The two types of batteries have different requirements for charging voltage, charging market, and charging stages, and mixing them may cause safety problems.
If it is a smart charger, check if there is a charging mode for lithium battery, if not, please re-purchase a special charger for LiFePO4 battery to ensure the safe use of the battery.
If you have any questions about the charging process, charging voltage, and power level, you can check the SOC diagram (below) in the manual and battery guide, if you have any other questions, please consult the customer service for professional guidance when purchasing the charger.


Conclusion:

Choosing the right charger and charging rate is paramount for maximizing the performance and longevity of LiFePO4 batteries. By understanding the unique characteristics of this chemistry and following industry best practices, users can ensure safe, efficient, and sustainable charging practices, unlocking the full potential of LiFePO4 technology for various applications.