How to charge lithium iron phosphate batteries?

How to charge lithium iron phosphate batteries?

To charge LiFePO4 batteries, you must use a compatible charger that can apply constant current/constant voltage (CC/CV) charging technology with the correct voltage and current settings. The CC/CV charging technology consists of two stages:

1. Constant current stage
At this stage of LiFePO4 battery charging, the charger provides a constant current to the battery until the voltage reaches its maximum limit (usually around 3.6 to 3.8 volts per battery). This stage provides most of the battery's power and restores its capacity.

2. Constant pressure stage
At this stage, the charger maintains a constant voltage at the maximum limit while gradually reducing the current until it reaches the lowest level (usually around 5% of the rated capacity). This stage completes charging and balances the battery.

When the current drops below the minimum level or the timer expires, the charging process terminates. Some chargers may also have a third stage, called float charging or maintenance stage, where the charger maintains a low voltage (usually about 3.3 to 3.5 volts per battery) to prevent self discharge and keep the battery fully charged (SOC).

Steps for correctly charging lithium iron phosphate batteries

Check if your charger is compatible with the battery specifications in terms of voltage and current. You can find this information on the battery label or data sheet. For example, if you have a 12 volt 100 Ah LiFePO4 battery, you need a charger that can provide at least 14.6 volts (3.65 volts per battery) and preferably 10% to 30% of the rated capacity (in amperes). You may ask, can a regular charger be used to charge lithium iron phosphate batteries? Before using a regular charger, it is best to check compatibility to ensure its use.

Connect the charger to a power source (AC or DC), depending on the specifications of the charger. Make sure to connect the positive (+) terminal of the charger to the positive (+) terminal of the battery, and connect its negative (-) terminal to the negative (-) terminal of the battery. If your charger has these features, you may also need to connect a temperature sensor or communication cable.

Turn on the power and start charging. Use a multimeter or battery monitor to monitor the charging process. You should see that the voltage and current vary according to CC/CV charging technology. A fully charged LiFePO4 battery typically has a voltage of approximately 3.6 to 3.8 volts per cell, depending on the manufacturer's specifications.

After the charging process is completed, disconnect the charger from the power supply and battery. You can store the battery in a fully SOC state or use it immediately. If the battery is not used for a long time, please store it in a cool and dry place and regularly check its voltage. You may need to charge every few months to prevent capacity loss.