Does LiFePO4 batteries need absorption?

LiFePO4 batteries are a type of lithium battery with a nominal voltage of 3.2V per cell. Unlike lead-acid batteries, LiFePO4 batteries do not require absorption charging. In this article, we will discuss the charge voltage, compatibility with existing chargers, different charging scenarios, parallel and series connections, balancing batteries, battery meters, charging below 0℃, and storage recommendations for LiFePO4 batteries.

LiFePO4 Battery Charge Voltage:

Can Existing Chargers Charge LiFePO4 Batteries?

Before using an existing charger, it is important to check if it has a repair or desulfuration function, as this can cause damage to LiFePO4 batteries. Additionally, if the charger has a battery voltage detection function, it may not charge a LiFePO4 battery that has reached its discharge protection threshold. It is also important to ensure that the charger is in good condition, insulated, and that its output voltage and current are within the recommended range for LiFePO4 batteries.

Different Scenarios for Charging LiFePO4 Batteries:

LiFePO4 batteries can be charged using AC to DC chargers, such as those used for low-speed vehicles or machinery. For solar systems, a charge controller with a 3-step charge process can be used, with the charge voltage set to 14.40V. LiFePO4 batteries can also be charged using an alternator, but a DC to DC converter is needed to limit the charge current and prevent overheating.

Charging LiFePO4 Batteries in Parallel:

When charging LiFePO4 batteries in parallel, it is important to consider the maximum charge current for each individual battery. The recommended charge current should be lower than the charge limit for a single battery to ensure that all batteries can be fully charged. It is also important to use the correct connection method to ensure similar resistance values for each circuit.

Charging LiFePO4 Batteries in Series:

Before connecting LiFePO4 batteries in series, it is important to check that the voltage difference between each battery is within 50mV. This helps to ensure that the batteries are properly balanced and that one battery does not cut off the entire circuit prematurely. Regular balancing between batteries is also recommended to optimize performance and prolong battery life.

Importance of Balancing Batteries in Series:

Balancing batteries in series is crucial to ensure that each battery is charged and discharged equally. This helps to prevent one battery from reaching its charge or discharge protection threshold before the others, which can result in an imbalance in the series circuit. Regular balancing, typically done once every few months, helps to maintain optimal performance and prolong battery life.

Battery Meters for LiFePO4 Batteries:

Battery meters that display voltage, current, state of charge (SOC), and other status information are useful for monitoring LiFePO4 batteries. Current and time-based battery meters are more accurate for LiFePO4 batteries than voltage-based meters, as LiFePO4 batteries have a flat discharge curve. These meters can accurately calculate the amount of energy discharged and charged, providing accurate SOC readings.

Charging LiFePO4 Batteries Below 0℃:

LiFePO4 batteries should not be charged below 0℃ unless they have a self-heating mechanism that can bring the battery temperature above 5℃. The energy source for heating the battery can be from the charge current or from the battery itself in some cases. It is important to ensure that the battery is at a safe temperature before initiating the charging process.

Storage Recommendations for LiFePO4 Batteries:

When storing LiFePO4 batteries, it is best to store them at around 50% state of charge (SOC). If the battery has a charge/discharge switch, it is recommended to turn it off to avoid accidental short circuits. Proper storage helps to maintain battery health and prolong its lifespan.

Conclusion:

LiFePO4 batteries do not require absorption charging and only need two stages of charging – constant current and constant voltage. Existing chargers need to be checked for compatibility with LiFePO4 batteries. When charging LiFePO4 batteries in parallel or series, it is important to consider the maximum charge current, use the correct connection method, and balance the batteries regularly. Battery meters, charging below 0℃, and proper storage techniques are also important factors to consider when using LiFePO4 batteries.