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Can I Charge A LiFePO4 Battery with a Normal Charger

David Lee
David Lee
—
25/06/2023

If you're considering using a LiFePO4 battery, you might wonder: Can I charge a LiFePO4 battery with a standard charger, or do I need a specialized charger? Understanding the charging requirements for these batteries is crucial for maximizing their performance and lifespan.

In this article, we'll explore the differences between standard chargers and those designed specifically for LiFePO4 batteries, helping you make an informed decision for your energy storage needs.

Summary First

Not recommended!

Using a standard charger may prevent the batteries from reaching a full charge, which can significantly impact their performance and lifespan over time. To ensure optimal functionality and longevity, it's essential to use a charger specifically designed for LiFePO4 batteries.

Why Do LiFePO4 Lithium Batteries Need a Different Charger?

1. Voltage Differences

A fully charged 12V LiFePO4 battery has a voltage of 14.6V, while a lead-acid battery reaches 12.6-12.7V. Even at 20% capacity, a LiFePO4 battery still holds around 13V, whereas a lead-acid battery drops to 11.8V. While the voltage differences seem minor, they significantly impact charging behavior.

12v lifepo4 battery voltage chart

2. Charging Algorithm Differences

LiFePO4 chargers use a constant voltage/constant current (CV/CC) charging algorithm, ensuring fast, efficient charging while preventing overcharging. Unlike lead-acid chargers, they do not allow trickle or float charging, as overcharging can damage lithium batteries.

lifepo4 and lead acid battery charging curve

A. LiFePO4 Battery Charging Stages

LiFePO4 batteries follow a two-stage charging process:

(1) Constant Current (CC) Phase (T1)

  • The charger provides a steady current, and the voltage gradually increases until it reaches the maximum charge voltage (typically around 14.6V for a 12V LiFePO4 battery).
  • This phase ensures rapid charging while maintaining battery safety.

(2) Constant Voltage (CV) Phase (T2)

  • Once the target voltage is reached, the charger maintains a constant voltage, and the current gradually decreases as the battery reaches full charge.
  • When the current drops to a preset cutoff level (around 0.02C, typically 2A for a 100Ah battery), charging stops.
  • No trickle or float charging is used, as LiFePO4 batteries do not require it and can be damaged by continuous charging.

B. Lead-Acid Battery Charging Stages

Lead-acid batteries use a three-stage charging process:

(1) Bulk Charge (T1)

  • Similar to LiFePO4’s CC phase, this stage supplies maximum current while the voltage rises.
  • This is the fastest phase of charging.

(2) Absorption Charge (T2)

  • When the battery reaches a pre-set voltage (typically around 14.4V-14.7V for a 12V lead-acid battery), the charger switches to constant voltage mode while the current gradually decreases.
  • This stage ensures that the battery reaches full charge without excessive gassing.

(3) Float Charge (T3)

  • Unlike LiFePO4, lead-acid batteries require a float charge to maintain capacity.
  • The charger lowers the voltage to a maintenance level (~13.2V-13.8V) to counteract self-discharge and keep the battery topped up.

C. Key Differences

Feature LiFePO4 Charging Lead-Acid Charging
Stages 2 (CC → CV) 3 (Bulk → Absorption → Float)
Charge Time Faster Slower
Float Charge Not needed Required
Overcharge Sensitivity High (must avoid trickle charge) Tolerates minor overcharging
Efficiency 95-98% 75-85%
Self-Discharge Rate Low Higher (requires maintenance charging)


Potential Risks of Using an Incompatible Charger for LiFePO4 Batteries

1. Incomplete Charging

Lead-acid chargers may not reach the full charge voltage required for LiFePO4 (typically 14.6V for a 12V battery). This results in reduced capacity and shorter runtime, as the battery never fully charges.

2. Overcharging & Battery Damage

Some chargers apply a float charge after reaching full capacity, which LiFePO4 batteries do not need. Continuous overcharging can stress the battery, leading to overheating, cell degradation, and reduced lifespan.

3. Incorrect Charging Algorithm

LiFePO4 batteries require a CC/CV (Constant Current / Constant Voltage) algorithm. Standard chargers might use pulse charging or float charging, which does not work with lithium chemistry and may damage the battery.

4. Reduced Efficiency & Performance

Using the wrong charger leads to higher energy loss and inefficient charging. The battery may take longer to charge, or worse, may not charge at all.

5. BMS Shutdown or Failure

Most LiFePO4 batteries have a Battery Management System (BMS) that protects against overcharging, over-discharging, and short circuits. An incompatible charger could trigger the BMS protection, causing the battery to shut down. In extreme cases, repeated stress can lead to BMS failure, making the battery unusable.

Conclusion: Use a Dedicated LiFePO4 Charger

To maximize performance, efficiency, and lifespan, always use a LiFePO4-compatible charger designed with the proper voltage limits, current control, and charging algorithm.

To maximize performance, efficiency, and lifespan, always use a LiFePO4-compatible charger designed with the proper voltage limits, current control, and charging algorithm.

How to Properly Charge LiFePO4 Batteries

Charging LiFePO4 batteries with LiFePO4 battery chargers, is considered one of the safest and most reliable methods. These chargers are specifically designed to charge LiFePO4 batteries with the correct voltage, current, and charging algorithm, ensuring that the batteries are protected from overcharging and undercharging.

LiFePO4 battery chargers often have advanced features such as built-in temperature sensors, which allow the charger to adjust the charging current according to the battery temperature, ensuring optimum performance and prolonging the battery lifespan.

protections of litime lifepo4 battery

Moreover, LiFePO4 battery chargers are capable of balancing the cells of the battery pack, which is necessary to prevent cells from draining faster than others during charging, thereby preventing the risk of cell damage

A single LiFePO4 battery cell has a nominal voltage of 3.2V and a recommended charge voltage range of 3.50V to 3.65V. It is important to note that exceeding a charge voltage of 3.65V can damage the battery cell due to its sensitivity to over-voltage and over-current.

Over-voltage can significantly harm the battery's performance, cause inflation, and even lead to damage and reduced lifespan. Therefore, lithium battery packs are typically equipped with a built-in BMS that provides protection against over-voltage. All of LiTime’s LiFePO4 batteries are built in battery management to protect the battery from over-voltage, over-current, over-charging, over-discharging and high temperature.

Please consult the table below for information regarding the voltage specifications of various LiFePO4 battery packs and systems.

lifepo4 battery charging voltage 

Charging Tips:

  • Connect the charger to the battery before connecting it to the grid power in case of sparks.
  • It’s recommended to disconnect the charger from the battery after fully charging.

How to Charge LiFePO4 Battery without Charger

Method 1: Using Alternator/Generator

 This method is mostly used when you're out on a camping trip or an extended road trip. Although it's not as specialized as the LiFePO4 battery charger, it's still a good alternative if you can't get your hands on a charger.

To charge a LiFePO4 battery with a generator, you will need a portable generator that has an output voltage and current compatible with your battery specifications, and a charge controller to regulate the amount of charge going into the battery.

To use an alternator or a generator to charge your LiFePO4 battery, you will need to ensure that the charging voltage and current are compatible with your battery's specifications.

One of the significant benefits of using an alternator or generator to charge your LiFePO4 battery is that it allows you to charge your battery while on the go. For example, if you're camping in a remote location and don't have access to an electrical outlet, you could use a generator to charge your battery.

If the alternator/generator supports DC output, a DC-to-DC charger needs to be added between the battery and the generator; if the alternator/generator supports AC output, please refer to the recommendations in “Battery Charger” above to add a suitable battery charger between the battery and the generator.

Steps:

1. Connect the battery to the alternator through a DC-DC charger.

2. Ensure the voltage does not exceed 14.6V.

3. Monitor charging to prevent overcharging.

Method 2: Using Solar Panels

Another method of charging LiFePO4 batteries is by using solar panels. This method is becoming increasingly popular, especially among outdoor enthusiasts and professionals, thanks to its convenience and eco-friendliness.

Solar panel charging is easy and straightforward. You only need a solar panel with an output voltage and current that is compatible with your LiFePO4 battery specifications. 

charge lithium batteries with solar panel

Once you've selected a suitable solar panel, connect it to your battery using a charge controller. The charge controller is essential because it regulates the amount of charge going into the battery, preventing overcharging and damage.

One significant advantage of using solar panels to charge your LiFePO4 battery is that it's highly sustainable. Solar power is clean and abundant, so you don't have to worry about running out of fuel or cutting down trees to get power. Additionally, it can save you a lot of money and energy bills, especially if you use it regularly.

Furthermore, solar panel charging is convenient for people who are always on the go. Whether you're camping, fishing, hiking, or working outdoors, you can easily carry a portable solar panel with you and set it up to charge your battery. You don't have to rely on electrical outlets or generators, which can be noisy and emit harmful fumes. Suggest reading: What Size Solar Charge Controller Should I Choose?

Steps:

1. Connect the controller to the battery.

2. Connect the charge controller to the solar panel.

3. Set the charge controller to LiFePO4 settings (typically 14.4V–14.6V for a 12V battery).

4. Monitor the charge level to prevent over charging.

Tips: Connect the Negative terminals first, then Positive terminals.

FAQs about Charging LiFePO4 Batteries

1. Can I charge a LiFePO4 battery with a car charger?

Yes, it's absolutely possible with the proper equipment. A DC-DC charger serves as the ideal solution, enabling safe charging while preserving your battery's health and maximizing its lifespan.

2. Can I charge a LiFePO4 battery while using it?

Not recommended. While you can charge your phone during use, the same practice with LiFePO4 batteries is not advisable. Charging while discharging can generate excess heat, reduce charging efficiency, and cause voltage fluctuations that may damage connected devices. For optimal performance and longevity, it's best to fully charge the battery before use, ensuring all cells are balanced and functioning effectively.

3. Can you charge a LiFePO4 battery with a trickle charger?

No, using a trickle charger for a LiFePO4 battery is not recommended. Trickle chargers are designed for lead-acid batteries and continuously supply a low current to maintain charge.

However, LiFePO4 batteries do not require a float or trickle charge once fully charged. Leaving a trickle charger connected can lead to overcharging, triggering the battery management system (BMS) to shut down the battery or potentially shorten its lifespan. Instead, use a LiFePO4-compatible charger with a proper CC/CV charging profile.

Conclusion

LiFePO4 batteries require specific charging methods to ensure their optimal performance and longevity. 

By following these best practices and using the correct charging methods, LiFePO4 batteries can maintain their performance and lifespan, providing reliable power for various applications.

For more charging guide, follow on:

Lithium Batteries Not Charging? Trouble Shooting and Best Practices

Full Guide on How to Charge Batteries in Parallel

Comprehensive Guide on Charging Batteries in Series

David Lee
David Lee
David Lee is a renewable energy consultant with global experience in off-grid systems and battery applications, especially in golf carts. A graduate of the University of Sydney, he shares insights on sustainability through his writing.

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