CHARGING LITHIUM IRON PHOSPHATE BATTERIES (LIFEPO4)
How to charge a LiFePO4 batteries? That is one of the most common questions we get from our customers. The answer is simple: use a LiFePO4 battery charger, of course. When charging LiFePO4 batteries, make sure that you are not using a charger it's working volt range is out of the battery working range. We are often asked if a lead-acid battery charger can be used to charge lithium iron phosphate. The short answer is No.
CHARGER INSPECTION
Before using a LiFePO4 charger, check that your charger’s cables are insulated and free of breakage. Charger terminal connectors should be clean and properly mate with the battery terminals to ensure a good connection and optimum conductivity.
before using a lifepo4 charger, check that the communication cables are mate with the battery or not.
CHARGING GUIDELINES
If LiFePO4 batteries are not fully discharged, they do not need to be charged after each use. LiFePO4 batteries do not get damaged when left in a partial state of charge (PSOC). You can charge your LiFePO4 batteries after each use or when they have been discharged up to 80% DOD (20% SOC). If the Battery Management System (BMS) disconnects the battery due to low voltage ( cell voltage will be <2.8V), remove the load and charge immediately using a LiFePO4 battery charger.
CHARGING TEMPERATURE
LiFePO4 batteries can be safely charged between 0°C to 45°C (-32°F to 113°F). LiFePO4 batteries do not require temperature compensation for voltage when charging at hot or cold temperatures. All torphan LiFePO4 batteries come with an internal BMS that protects the battery from low and high temperatures. If the BMS disconnects due to low temperature, the battery must warm-up for the BMS to reconnect and accept the charging current. If the BMS disconnects because of high temperature, the battery will need to cool down before the BMS will accept charging the battery. Please refer to your specific battery’s datasheet for the BMS low temperature and high-temperature cut-off and reconnect values.
CHARGING LIFEPO4 IN PARALLEL
When connecting LiFePO4 batteries in parallel, please make sure each battery is within 0.1V of each other before putting them in service, This will minimize the chance of imbalance between batteries. If you’re charging 12V LiFePO4 batteries, the charging voltage should be between 14V – 14.2V. When charging 24V batteries in parallel, the charging voltage should be 28V – 28.4V. Charging 36V lithium batteries in parallel requires a voltage of 42V – 42.6V. Finally, charging 48V LiFePO4 batteries require voltage parameters of 56V – 56.8V. Below is a table with a summary showing the voltage requirements for each system voltage.
System Voltage Charging parameters
12V 14V – 14.2V
24V 28V – 28.4V
36V 42V – 42.6V
48V 56V – 56.8V
The voltage parameters apply to both charging profiles CC and CC-CV. If your charger’s voltage is lower than those listed in the table, it will not damage your battery, but it will be undercharged, and it will not provide the full rated capacity of the battery. If your charger’s voltages are higher than those listed in the tables above, the BMS may disconnect the battery and you may have to remove the load to reconnect.
CHARGING LIFEPO4 BATTERIES IN SERIES
When connecting batteries in series, please make sure each battery is within 20mV (0.02V) of each other before putting them in service. This will minimize the chance of an imbalance between batteries. If your batteries get out of balance, the voltage of any battery is >20mV (0.02V) from another battery in the set, you should charge each battery individually to rebalance. You can charge each battery individually periodically to avoid imbalance. When charging LiFePO4 batteries in series, it is best to use a multi-bank charger that charges each battery individually to ensure the cells remain balanced. You can also use a 24V battery LiFePO4 charger or a 48V battery LiFePO4 charger if you’d like to charge your system as a whole.
CHARGING LIFEPO4 WITH AN INVERTER/CHARGER AND/OR CHARGE CONTROLLER
Below are the key, typical charger inputs when using an inverter/charger or charge controller for charging LiFePO4 batteries. Many inverter/ chargers require additional parameters, please contact Torphan technical support for assistance. LiFePO4 batteries do not require equalizing charging. LiFePO4 batteries do not require temperature compensation for voltage when charging at hot or cold temperatures.
