CategoriesLiFePO4 Battery knowledge

LiFePO4 Battery Charging Guide

LiFePO4 Battery Charging Guide

To ensure your RUIXU Lithium Iron Phosphate (LiFePO4) battery provide its maximum life, follow these Charging Instructions.

When charging LiFePO4 make sure that you are not using a charger meant for other lithium ion chemistries, which are typically set to a higher voltage than required by LiFePO4 batteries. A lead-acid battery charger can be used if the voltage settings are within the ranges of LiFePO4 batteries.

 

Charger Inspection

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.

Charging Guidelines

When to Charge your LiFePO4 Battery 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 <8V), remove the load and charge immediately. Please note that we recommend storing batteries at 50% state of charge (SOC) to minimize irreversible capacity loss.

Charging Temperature

LiFePO4 batteries can be safely charged between -20°C to 55°C (-4°F to 131°F). However, at temperatures below 0°C (32°F) the charge current must be reduced, until the temperature is >0ºC (32ºF), as follows:

1. 0°C to -10°C (32°F to 14°F) charge at 0.1C (10% of the battery capacity)

2. -10°C to -20°C (14°F to -4°F) charge at 0.05C (5% of the battery capacity)

LiFePO4 batteries do not require temperature compensation for voltage when charging at hot or cold temperatures. All RUIXU LiFePO4 come with a BMS that protects the battery from over-temperature. If the BMS disconnects due to high temperature, wait until the temperature reduces before using or charging the battery. Please refer to your specific battery’s Data Sheet for the BMS high temperature cut-off and reconnect values.

Charge Profiles

LiFePO4 batteries can be charged with either a 1-stage profile (constant current (CC) aka Bulk Stage) or a 2-stage profile (constant current, constant voltage (CC-CV) profile aka Bulk and Absorption Stages). The 1-stage profile will charge the battery ~97% and the 2-stage profile will charge the battery 100%. The 1-stage profile is sufficient, since LiFePO4 batteries do not need to be fully charged; this will not reduce life as it does with lead-acid.

 

1-Stage Charge Profile – CC

STEP CHARGE DESCRIPTION STEPS DESCRIPTION CHARGE PARAMETERS
Step 1 – Charge at a constant current until the battery reaches termination voltage. 1 *Recommended
Charge Current
≤0.5C (C = Capacity of battery system)
SYSTEM VOLTAGE 12V 24V 36V 48V
Stop Termination
Voltage
14V – 14.6V 28V – 29.2V 42V – 43.8V 56V – 58.4V

 

2-Stage Charge Profile – CC-CV

 

2-STEP CHARGE DESCRIPTION STEPS DESCRIPTION CHARGE PARAMETERS
Step 1 – Charge at a constant current until the battery reaches
absorption voltage.
Step 2 – Hold absorption voltage until charge reduces to termination current.
1 *Recommended     Charge Current ≤0.5C (C = Capacity of battery system)
SYSTEM VOLTAGE 12V 24V 36V 48V
2 Absorption  Voltage 14V – 14.6V 28V – 29.2V 42V – 43.8V 56V – 58.4V
Stop Termination
Current
≤0.05C (C = Capacity of battery system)

 

 

Charging Series Systems

When connecting batteries in series, please make sure each battery is within 50mV (0.05V) of each other before putting them in service. This will minimize the chance of imbalance between batteries. If your batteries get out of balance, the voltage of any battery is >50mV (0.05V) 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. Refer to tables on page 2 for charging parameters for series systems.

Charging Source

Inverter/Charger and/or Charge Controller Below are the key, typical charger inputs when using an inverter/charger or charge controller with LiFePO4 batteries. Many inverter/ chargers require additional parameters, please contact RELiON 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. Note: Charge current must be reduced at temperatures below 0°C (32*F). See details in Charge Temperature section.

Charging Source

Alternator and DC to DC Chargers Depending on the quality of the alternator it may work fine with LiFePO4 batteries. However, low quality alternators with poor voltage regulation can cause the BMS to disconnect LiFePO4 batteries. If the BMS disconnects the batteries the alternator may be damaged. To protect your LiFePO4 battery and alternator please be sure to use a compatible high-quality alternator or install a voltage regulator. You can also use a DC to DC charger to safely and effectively charge your batteries including house banks.

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