How to Charge Lithium Iron Phosphate (LiFePO4) Batteries？

How do I charge a lithium iron phosphate battery? This is one of the most frequently asked questions by our customers. The answer is simple: Of course using a LiFePO4 charger, standard charger, solar or wind charge controller to charge our LiFePO4 deep cycle batteries. When charging LiFePO4 batteries, make sure you are not using a charger designed for other lithium-ion chemistries that are typically designed for higher voltages than what is required for LiFePO4. We are often asked if lead-acid battery chargers can be used to charge lithium iron phosphate. The short answer is yes, as long as the voltage is set within the acceptable LiFePO4 battery parameters. Our recommended charging voltage for Aolithium 12V LiFePO4 batteries is 10.0V - 14.6V. And recommended charging voltage for Aolithium 51.2V LiFePO4 batteries is 42.0V - 58.4V.

Charger Inspection

Before using a LiFePO4 charger, check that your charger's cables are insulated and unbroken. The charger's terminal connectors should be clean and properly mated to the battery terminals to ensure a good connection and optimal conductivity.

Charging Guidelines

LiFePO4 batteries do not need to be recharged after each use if they are not fully discharged, and LiFePO4 batteries are not damaged when they are partially charged (PSOC). You can recharge the LiFePO4 battery after each use or after it has been discharged to 80% DOD (20% SOC). If the Battery Management System (BMS) disconnects the battery due to low voltage (voltage will be less than 10.6 V), remove the load and recharge it immediately using the LiFePO4 battery charger.

Charging Temperature 

LiFePO4 batteries can be safely charged between 0°C and 55°C. LiFePO4 batteries do not require temperature compensation for voltage when charging at high or low temperatures. All Aolithium LiFePO4 batteries are equipped with an internal BMS that protects the battery from low and high temperatures. If the BMS is disconnected due to low temperatures, the battery must be warmed up so that the BMS can reconnect and receive charging current. If the BMS is disconnected due to high temperatures, the battery needs to cool down before the BMS will accept to charge the battery.

How to charge LiFePO4 batteries with lead-acid chargers

Most lead-acid battery chargers can be used with LiFePO4 batteries, as long as they meet the correct voltage guidelines. Our recommended charging voltage for LiFePO4 is 10.0V-14.6V, and the AGM and Gel algorithms usually meet the LiFePO4 voltage requirements. Water-rich battery charging algorithms typically have voltages higher than the LiFePO4 charging requirement, which will cause the BMS to disconnect. If this happens, it is usually recommended that you replace the charger with one that has a LiFePO4 charging profile. Since the BMS protects the battery, using a lead-acid charger will not normally damage the battery.

LiFePO4 charging using alternators and DC to DC chargers

Depending on the quality of the alternator, LiFePO4 batteries can be charged without modification. However, poor quality alternators with poor voltage regulation can cause the BMS to disconnect the LiFePO4 battery. If the BMS disconnects the battery, the alternator may be damaged. To protect your LiFePO4 battery and alternator, be sure to use a high-quality compatible alternator or install a voltage regulator. You can also use DC to DC chargers to safely and efficiently charge your batteries, including home banks. When using an alternator to charge LiFePO4 batteries, it is recommended that a DC to DC charger be installed.

LiFePO4 Battery Meters

If you are using a voltage-based meter designed for lead-acid batteries, it will not accurately measure the state of charge (SOC) of LiFePO4 batteries. Please replace your meter with one that measures current rather than voltage to accurately measure the state of charge of LiFePO4 batteries.

If you have any technical questions, please contact us at support@aolithium.com.