Our customers are confused about charging LiFePO4 batteries. Therefore, we have compiled these issues and rewritten an article about them. When customers replace lead-acid batteries with LiFePO4 batteries, they want to know if they can use a lead-acid charger to charge the lithium batteries. As a professional brand producing LiFePO4 batteries, POWERWIN advises not to use lead-acid chargers for LiFePO4 batteries. Doing so will affect the performance and lifespan of the LiFePO4 battery. Let's delve into these issues about charging LiFePO4 batteries.

What are the basic physical principles of charging LiFePO4 batteries?


Due to their different materials, LiFePO4 batteries have distinct charging characteristics. The charging curve is different from that of lead-acid batteries. LiFePO4 batteries are known for their simpler charging process and methods. They have a relatively flat charging curve, which means they can be charged at a constant voltage without the need for complex charging algorithms.

LiFePO4 Battery Charging Pattern


This curve shows the charging pattern of a LiFePO4 battery, which covers two stages.

T1: CC (Constant Current) Phase

In the CC phase, the LiFePO4 battery is charged with a constant current. The voltage gradually increases until it reaches the set point for constant voltage, which may vary depending on the charging method.

T2: CV (Constant Voltage) Phase

In the CV phase, the battery is maintained at a constant voltage. Meanwhile, the charging current gradually decreases until it reaches the termination current of 2A (0.02C), also known as the trickle current. Once the termination current is reached, the charging process is interrupted, indicating that the battery is fully charged.

It is important to note that the CC and CV phases during the charging process are designed to control the charging current and voltage, ensuring the safety and effectiveness of the battery charging process. The specific parameters and duration of these phases may vary depending on the charger and battery type.

Lead-Acid Battery Charging Method

This curve shows the charging pattern of lead-acid batteries, which includes three phases.

T1: Bulk/Boot PhaseIn this phase, the battery charges at its maximum current capacity. The voltage will steadily rise until it reaches the absorption voltage set point. This phase is similar to the Constant Current (CC) phase in LiFePO4 battery charging.

T2: Absorption PhaseOnce the battery voltage reaches the absorption voltage set point, the voltage remains constant while the current gradually decreases until the battery is fully charged (within 10-20%). To prevent overcharging, the absorption phase generally does not exceed 3 hours. This phase is similar to the Constant Voltage (CV) phase in LiFePO4 battery charging.

T3: Float PhaseAfter the absorption phase, the battery voltage drops to the float voltage set point, and the current decreases to a low maintenance level. This phase prevents the battery from discharging and offsets any self-discharge. If the battery experiences significant discharge, the controller can switch the charging process back to the bulk/boost or absorption phase to replenish the energy lost during self-discharge.

The charging pattern of lead-acid batteries shares similarities with that of LiFePO4 batteries but also has some key differences. Compared to LiFePO4 batteries, lead-acid batteries typically have a lower absorption voltage set point and a slightly lower float voltage set point. Additionally, lead-acid batteries may produce sulfate crystals during charging, requiring periodic equalization charging to prevent capacity degradation.

How to Properly Charge LiFePO4 BatteriesProperly charging LiFePO4 batteries ensures their longevity and performance. However, with the emergence of numerous charging options, users face significant challenges in determining the best charging solution. We recommend three reliable methods for charging LiFePO4 batteries: LiFePO4 battery chargers, generators, and solar panels.

  1. LiFePO4 Battery Charger

    LiFePO4 battery chargers are the most common and reliable method for charging LiFePO4 batteries. These chargers typically feature advanced functions such as overcharge protection, temperature monitoring, and automatic shutoff, further enhancing battery life and safety.

    Use a dedicated LiFePO4 battery charger to charge your LiFePO4 battery and plug the charger directly into the battery. The charger will automatically complete the charging process. 

    POWERWIN P20 is the best choice to charge the lifepo4 batteries 

 

You can select the appropriate charging mode according to the table below:

  1. Generator

When you are engaged in outdoor activities or in remote areas with limited electricity, a generator is an ideal choice for charging LiFePO4 batteries. When using a generator to charge LiFePO4 batteries, please note the following points:

  • Ensure the generator's power output is sufficient to meet the battery's charging requirements. The generator's power should be greater than or equal to the charger's rated power.
  • Ensure compatibility between the generator's output voltage and the battery charger's input voltage. Most generators output 220V, while battery chargers typically have an input voltage of 12V or 24V. You will need to use an inverter to convert the generator's AC power to the DC power required by the LiFePO4 battery charger.
  • Set the correct charging voltage and current. The charging voltage for LiFePO4 batteries should be between 3.0V and 3.65V, and the charging current should not exceed 0.5C of the battery's capacity.

If the AC generator or generator supports DC output, you will need to add a DC-DC charger between the battery and the generator.

  1. Solar Panels
    Charging LiFePO4 batteries with solar panels is an eco-friendly and sustainable method. However, you need to use a solar charge controller to regulate the output voltage of the solar panels and ensure it does not exceed the battery's charging voltage limit.

When using solar panels for charging, follow these steps:

  • Connect the solar charge controller to the solar panels.
  • Set the output voltage of the solar charge controller to the nominal voltage of the battery.
  • Connect the solar charge controller to the battery.
  • Place the solar panels in a sunny location.
  • Monitor the battery voltage to ensure it does not exceed the charging voltage limit.

A typical 12V 100Ah LiFePO4 battery can be charged using a 300W solar panel and can be fully charged within a day (with effective sunlight exposure of 4.5 hours/day).

Moreover, charging with solar panels is very convenient for individuals who frequently engage in outdoor activities (such as camping, fishing, hiking, or outdoor work). You can easily carry portable solar panels and set them up for battery charging. You don't have to rely on power outlets or generators, which produce noise and emit harmful fumes.

The POWERWIN solar panel is the best partner with charging the lifepo4 battery !

  • Monocrystalline with 24% efficiency and 95% light transmittance.
  • Grade-A Monocrystalline Silicon Solar Cells.
  • Yields 110W in foldable solar power.
  • Built with IP65 waterproof ETFE material.
  • Offers various outputs: DC5525, USB-C, USB-A, PV, etc.
  • Supports MC/4 PV Cable for series and parallel wiring.
  • Warranty: 12 Months (24 months for subscribers)