CHARGING LITHIUM IRON PHOSPHATE BATTERIES (LIFEPO4)

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 (voltage will be <10V), 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 Canbat 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.

HOW TO CHARGE LIFEPO4 BATTERIES WITH A LEAD-ACID CHARGER

Most lead-acid battery chargers can be used with LiFePO4 batteries as long as they are within the appropriate voltage guidelines. AGM and Gel algorithms typically fall within the LiFePO4 voltage requirements. The voltage for flooded battery charging algorithms is often higher than LiFePO4 charging requirements, which will result in the BMS disconnecting. If this happens, it is generally good practice to replace your charger for one with a LiFePO4 charge profile. Since the BMS protects the battery, using lead-acid chargers will typically not damage the battery.

Note that if the BMS disconnects due to low voltage, a lead-acid battery charger may not be able to reconnect the BMS, even if the charger has the acceptable charging parameters to charge LiFePO4. This is because when the BMS disconnects, the lithium battery will not have a voltage as it will read 0V on a voltmeter, while lead-acid chargers require the battery to read out a voltage to start charging. If the battery is reading 0V, the lead-acid battery charger will not be able to understand that a battery is connected and that it should start charging. This is also true for some low-quality lithium chargers. It is always recommended that you invest in a high-quality LiFePO4 charger to ensure high performance and longevity. Feel free to contact us should you have any questions.

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.

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. We recommend you replace the charger to avoid this inconvenience and to invest in a high-quality LiFePO4 battery charger.

CHARGING LIFEPO4 BATTERIES IN SERIES

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 Canbat technical support for assistance. LiFePO4 batteries do not require equalizing. LiFePO4 batteries do not require temperature compensation for voltage when charging at hot or cold temperatures.

CHARGING LIFEPO4 WITH ALTERNATOR AND DC TO DC CHARGERS