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Best Ways to Charge A LiFePO4 Lithium Battery

John Marius
John Marius
—
03/12/2022

Battery scientists talk about energies flowing in and out of the lithium battery as part of ion movement between anode and cathode, which makes the charging and discharging of lithium batteries an exception from the chemical reaction of traditional lead acid batteries. While lead acid offers some flexibility in terms of voltage cut-off, the LiTime lithium battery cells are very strict on the correct setting to prevent overcharging along with the LiTime LiFePO4 lithium charger to prolong the battery life.

Part 1: Precautius to Notice Before Charging the Lithium Battery

Since the different logic from lead-acid battery, you probably can't charge the lithium battery fully when using the normal charger, therefore, utilizing the charger designed for LiFePO4 lithium battery is crutial.

lifepo4 and lead acid battery charging curve

1.1 How Does LiFePO4 Lithium Battery Charge?

LiFePO4 (Lithium Iron Phosphate) batteries, like those commonly used in golf carts, RV, marine trolling motors charge using a two-stage process called CC/CV—Constant Current (CC) followed by Constant Voltage (CV). This process helps charge the battery safely and efficiently.

1. Constant Current (CC) Phase

  • Initial Charging: During this phase, the charger applies a constant current to the battery. This current is typically set according to the battery's specifications, often at a rate of 0.5C to 1C (where C is the capacity of the battery in amp-hours).
  • Voltage Increase: As the battery charges, its voltage gradually increases. In the case of a LiFePO4 battery, the nominal voltage is around 3.2 to 3.3 volts per cell, with a maximum charging voltage of about 3.6 to 3.65 volts.

2. Transition to Constant Voltage (CV) Phase

  • Reaching Full Charge Voltage: Once the battery voltage reaches the maximum charge voltage (around 3.6 to 3.65 volts), the charger switches from constant current to constant voltage.
  • Constant Voltage Control: In this phase, the charger maintains the voltage at the set level (e.g., 3.6 volts) while the current gradually decreases as the battery continues to charge. This allows the battery to absorb the remaining energy without exceeding the voltage limit.

3. Termination of Charging

  • Current Tapering: As the battery becomes fully charged, the current decreases significantly. Charging is typically terminated when the current drops to a specific threshold (often around 0.05C or lower), indicating that the battery is fully charged.
  • Balanced Charging: This method helps ensure that all cells within a battery pack are charged evenly, which is crucial for maintaining battery health and performance.

When charging your lithium LiFePO4 batteries, always remember to match your charger to deliver the correct current and voltage for the lithium battery you are charging. Below is the charging voltage references.

lithium battery charging voltage

1.2 What Would Happen if Charging LiFePO4 Lithium Batteries With A Lead-Acid Battery Charger

Firstly, your lithium battery may not be fully charged. If a lead-acid charger operates at lower voltages (like those used in some flooded lead-acid charging profiles), it may not provide enough voltage to fully charge a LiFePO4 battery. This can lead to incomplete charging and reduced capacity over time.

Lead-acid chargers use different charging profiles (bulk, absorption, float), which do not suit the CC/CV method required for LiFePO4 batteries, risking damage to the LiFePO4 cells.

What's more, from LiFePO4 lithium batteries BMS safety prospective, most LiFePO4 batteries have a built-in Battery Management System that protects against overvoltage and overcurrent. However, if the charger does not match the battery’s requirements, the BMS may activate, cutting off charging or causing erratic behavior.

lifepo4 battery management system for off-grid

If the BMS does not function correctly due to inappropriate charging, it can lead to cell imbalances, which can degrade battery performance and lifespan.

As a result, for safety using the LiFePO4 lithium batteries, charge them with proper battery chargers.

Part 2: 3 Best Ways to Charge LiFePO4 Lithium Batteries

If you’re looking to get the most out of your LiFePO4 lithium battery while still maintaining its performance, then knowing the best ways to charge a LiFePO4 battery will make it a worthwhile investment.

You may also like: How to Jump Start a Dead Lithium Battery

1. Using A Lithium Battery (LiFePO4) Charger

The ideal way to charge a LiFePO4 lithium battery is using a dedicated lithium iron phosphate battery charger, as it will be well programmed to protect the battery. LiTime LiFePO4 battery charger can provide multilevel protections to prevent Over Temperature, Over Voltage, Short Circuit, and Reverse Polarity.

lifepo4 lithium battery charger

2. Using Solar Panels + MPPT

Whether in a home, a boat, or an RV, using a solar energy system to charge LiFePO4 batteries is highly recommended.

Follow the steps to charge

Solar Panels: Ensure that the solar panels have the appropriate specifications and capacity to generate enough electricity to meet the charging needs of the LiFePO4 batteries. Consider factors such as size, efficiency, and the solar panel's ability to capture sunlight even in low-light conditions.

charge rv battery with solar panel

Charge Controller: Use a charge controller specifically designed for LiFePO4 batteries. Look for a controller that supports Lithium Iron Phosphate (LiFePO4) battery chemistry and is capable of regulating the power output of the solar panels according to the battery's charging requirements. It should offer features like overcharge protection, temperature compensation, and various charging modes (bulk, absorption, and float) to optimize the battery's lifespan.

LiFePO4 Batteries: Choose high-quality LiFePO4 batteries that are suitable for your specific application (home, boat, or RV). Consider factors such as the battery's capacity, voltage, cycle life, and compatibility with the charge controller. Ensure that the battery bank's capacity is sufficient to store the energy provided by the solar panels and meet your power requirements during periods without sunlight.

System Sizing and Integration: Calculate the required capacity of the solar panels, charge controller, LiFePO4 batteries, and inverter based on your energy consumption and expected charging time. Consider factors like daily energy usage, peak load, location, and weather conditions. Ensure that all components are properly sized and integrated to maximize the overall system performance and efficiency.

Monitoring and Maintenance: Implement a monitoring system to keep track of the solar energy system's performance, battery status, and charging efficiency. Regularly inspect and maintain the system, including cleaning the solar panels, checking wiring connections, and monitoring battery health. Address any potential issues promptly to ensure optimal operation and long-term reliability.

3. Using Generator/Alternator

Charging LiFePO4 batteries using an alternator with a DC-DC charger is a reliable and efficient method, especially for RVers and other users who need to charge their LiFePO4 batteries while driving.

The DC-DC charger acts as an intermediary between the vehicle's alternator and the LiFePO4 batteries, ensuring the batteries receive the appropriate voltage and current for optimal charging. LiFePO4 batteries require specific charging profiles, and a DC-DC charger is designed to provide the necessary voltage and current regulation.

When the vehicle's alternator is running and providing DC power, the DC-DC charger converts the voltage output from the alternator to a level suitable for charging the LiFePO4 batteries. It also regulates the charging process, ensuring that the batteries are charged efficiently and safely.

One of the advantages of using a DC-DC charger is that it can handle different voltage requirements between the alternator and the LiFePO4 batteries. The charger adjusts the voltage accordingly and provides a controlled charging current to protect the batteries.

This charging method is particularly useful for RVers who frequently travel or rely on their LiFePO4 batteries for auxiliary or house power. It allows them to charge their batteries while driving, ensuring a constant and reliable power source.

However, it's important to note that not all DC-DC chargers are created equal. It's essential to choose a charger specifically designed for LiFePO4 batteries and compatible with their unique charging requirements. Make sure to select a reputable DC-DC charger that incorporates multi-stage charging and provides proper voltage regulation.

charge lifepo4 battery wiht alternator

Part 3: How To Charge LiFePO4 Lithium Batteries in Cold Weather

As with all batteries, cold temperatures can lead to reduced performance. However, LiFePO4 batteries maintain significantly better capacity and voltage retention in cold conditions compared to lead-acid batteries. Here are some important tips to remember:

  • Charging at Low Temperatures: When charging lithium iron phosphate batteries below 0°C (32°F), you should reduce the charge current to 0.1C. If the temperature drops below -10°C (14°F), the current should be decreased further to 0.05C.
  • Risk of Damage: Not reducing the charging current in freezing temperatures can cause irreversible damage to the battery. Therefore, utilizing the battery with low-temperature charging-off protection is really important.

lifepo4 battery for cold winter day

Read on the Best Practice to Store Batteries in Winter  to ensure the longevity and performance of your LiFePO4 batteries in cold weather.

Part 4: How to Charge LiFePO4 Lithium Batteries: 12V, 24V, 36V, 48V

Charging your LiFePO4 lithium batteries correctly is crucial for their longevity and performance. In this section, we will cover the steps and guidelines for charging different voltages of LiFePO4 batteries, including 12V, 24V, 36V, and 48V models.

1. Charging 12V (12.8V) LiFePO4 Lithium Battery

The most common lithium battery voltage used in various applications such as RVs, boats, and off-grid systems is the 12V LiFePO4 battery. Here’s how to ensure safe and efficient charging for your 12V (12.8V) battery:

  • Use a Compatible Charger: Ensure you're using a charger designed specifically for LiFePO4 batteries, as regular lead-acid chargers won’t provide the correct charging profile. A charger with a constant current (CC) phase followed by a constant voltage (CV) phase is essential for LiFePO4 batteries.
  • Charging Voltage: The ideal charging voltage for a 12V LiFePO4 battery is 14.6V. This is the voltage at which the battery should be charged until it reaches full capacity.
  • Charging Current: For most 12V LiFePO4 batteries, the recommended charging current is around 0.2C. For example, a 12V 100Ah battery can be charged at a rate of 20 amps. Recommend charger: LiTime 12V(14.6V) 20A LiFePO4 Lithium Battery Charger
  • Charge Time: Depending on the charger’s current output, a full charge could take anywhere from 4-8 hours. A higher charging rate will reduce this time but be mindful of the manufacturer’s specifications to avoid overcharging.

Always monitor the charging process, especially during the first few charges, to ensure everything is working smoothly and there are no issues with the charger or battery.

2. Charging 24V (25.6V) LiFePO4 Lithium Battery

Charging a 24V (25.6V) LiFePO4 battery is similar to the 12V model but with slight differences in charging voltage and current. Here's how to charge a 24V battery effectively:

  • Use a 24V Lithium Battery Charger: Just like the 12V, ensure the charger is designed for 24V LiFePO4 batteries. These chargers typically have an output voltage of around 29.2V to 29.6V, which is the optimal charging voltage for 24V LiFePO4 batteries.
  • Charging Voltage: The ideal charging voltage for a 24V LiFePO4 battery is 29.2V to 29.6V, depending on the manufacturer's recommendation.
  • Charging Current: Just like 12V batteries, a safe charging current is 0.2C. So you can utilizing a 24V(29.2V) 20Ah battery charger to charge a 24 Volt 100Ah battery.
  • Charge Time: A 24V LiFePO4 battery usually takes around 5-10 hours to charge, depending on the charger’s current output.

3. Charging 36V (38.4V) LiFePO4 Lithium Battery

Charging a 36V (38.4V) LiFePO4 battery requires attention to voltage settings as well as the charging current. Here are the essential charging guidelines:

  • Use a 36V Lithium Battery Charger: This type of charger provides the necessary voltage output, typically between 43.2V and 44.4V, for charging 36V LiFePO4 batteries.
  • Charging Voltage: The ideal charging voltage for a 36V LiFePO4 battery is 43.2V to 44.4V. Be sure to verify this range with the manufacturer for accuracy.
  • Charging Current: 0.2C current. 
  • Charge Time: Expect the charging process to take anywhere from 6-12 hours, depending on the power of your charger.

4. Charging 48V (51.2V) LiFePO4 Lithium Battery

The 48V (51.2V) LiFePO4 battery is often used in higher-capacity systems, such as those in off-grid solar or large RV applications. To charge these efficiently:

  • Use a 48V Lithium Battery Charger: Make sure the charger is rated for 48V LiFePO4 batteries. The charger should provide an output voltage between 57.6V and 58.4V for optimal charging.
  • Charging Voltage: The ideal charging voltage for a 48V LiFePO4 battery is 57.6V to 58.4V.
  • Charging Current: The recommended charging current is typically 0.2C.
  • Charge Time: Charging a 48V LiFePO4 battery usually takes between 8-16 hours, depending on the charger’s capacity.

Common Charging Tips and Best Practices

To ensure optimal performance and longevity of your LiFePO4 batteries, here are some general charging tips:

  • Temperature Management: Charge your batteries in a temperature range of 0°C to 50°C (32°F to 122°F) to avoid damage. Extremely high or low temperatures can negatively affect the charging process.
  • Avoid Overcharging: Although LiFePO4 batteries are more forgiving than other chemistries, overcharging still reduces their lifespan. Always use a charger with an automatic cutoff or built-in BMS protection.
  • Charge in Well-Ventilated Areas: Ensure your battery and charger are in a well-ventilated space to avoid any overheating or buildup of gases.
  • Monitor Battery Health: Regularly check your battery’s performance through a battery monitor. 

By following these charging guidelines, your LiFePO4 battery will serve you for years with optimal performance.

FAQs About Charging LiFePO4 Lithium Batteries

1. Can I Leave the Lithium Battery on Charging All the Time?

Although it is generally safe to leave a LiFePO4 battery on the charger, as both the charger and the battery itself have a BMS (battery management system) to prevent overcharging, it’s still best to monitor the charging process.

Once the battery is fully charged, disconnecting it promptly is recommended to avoid unnecessary damage.
For convenience, LiTime offers chargers with Anderson connectors, allowing you to stop charging simply by unplugging the Anderson connector without needing to separate the battery terminals from the screws after charging.

However, for optimal safety, it’s advised to first unplug the AC plug before disconnecting the Anderson connector.

Lithium Battery Not Charging? Read on to find out why and how to solve.

How Fast Can I Charge My Battery?

Calculate the charge time by dividing the capacity of the battery (Ah for Amp Hours) by the charger output (A for Amps). For example, a 12V 100Ah LiTime LiFePO4 Lithium Battery can be charged from empty to full in 10 hours with a LiTime 12V 10A LiFePO4 charger (100 Ah divided by 10 A = 10 hours).

Can I Charge Lithium Battery with Trickle Charger?

Charging a lithium battery with a trickle charger is generally not recommended. Instead of a trickle charger, it's best to use a charger specifically designed for lithium batteries, which will ensure safe and efficient charging.

John Marius
John Marius
John Thompson, an automotive engineer with 15+ years of EV and lithium battery experience, holds a Master’s in Electrical Engineering from Stanford. He’s passionate about advancing battery tech and promoting green energy.

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