Can I charge a LiFePO4 battery with a normal charger, or Is it possible to charge a lithium battery with a lead-acid charger? This is a question that we often receive from our customers. However, it is important to understand that lithium batteries are not the same as lead-acid batteries, and not all battery chargers are suitable for lithium batteries.

Brief Understanding of LiFePO4 Batteries

A fully charged 12V lithium iron phosphate battery should have a voltage of around 13.3-13.4V, while a fully charged lead-acid battery should have a voltage of approximately 12.6-12.7V. When the battery is at 20% capacity, a lithium battery will have a voltage of about 13V, while a lead-acid battery will have a voltage of approximately 11.8V. As you can see, the voltage difference between using a lithium battery and a lead-acid battery is quite small, and may differ by less than 0.5V at 80% capacity.

The LiFePO4 charger is a voltage-limiter, similar to the lead-acid system. However, it differs from the lithium-ion battery, in which each battery has a higher voltage, stricter voltage tolerance, and no trickle or float charge when the battery is fully charged. Although lead-acid batteries allow a degree of flexibility with voltage cut-off parameters, LiFePO4 battery manufacturers exercise caution when setting charging parameters due to the sensitivity of lithium-ion batteries to overcharging. There is no perfect charger that can miraculously prolong battery life and increase capacity through pulse charging or other methods. LiFePO4 is a clean system that can only absorb what it can manage.

Lithium chargers use the CV/CC (constant voltage / constant current) charging algorithm, which limits the current to a predetermined level until the battery reaches the desired voltage. As the battery reaches maximum capacity, the current gradually decreases. This system enables fast charging while preventing overcharging, making it ideal for lithium-ion batteries, among others.

Back to the question “Can I charge a LiFePO4 battery with a normal charger”, the answer is yes, but it may not be fully charged. And we do not recommend long-term use, it will affect the performance and life of lithium iron phosphate batteries.

LiFePO4 and Lead Acid Battery Charging Curve

LiFePO4 Charging Mode

CC (Constant Current) Phase (T1)

In the beginning, a discharged battery will be charged with a constant current and voltage will be climbing steadily until reaching the constant voltage setpoint which varies for different charging methods.

CV (Constant Voltage) Phase (T2)

The battery maintains a constant voltage during this phase while the current gradually decrease to 2A (0.02C) which is also known as tail current. At this point, the charging is cut off and the battery is fully charged.

3 Reliable Ways to Properly Charge LiFePO4 Batteries

There are 3 reliable charging methods that LiTime sugguest to charge LiFePO4 batteries. They are using LiFePO4 battery chargers, generators and solar panels.

 Method 1: Using LiFePO4 Battery Chargers

 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.

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.

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.

Method 2: Using Alternator/Generator

Another method of charging LiFePO4 batteries is by using an alternator or a 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.

LiTime battery can be charged by an alternator or generator.

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.

Method 3: 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. 

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?

Best Practices for Parallel Charging of Batteries

When connecting your lithium batteries in parallel, it is recommended to charge each battery individually before making the parallel connection(s). After charging, check the voltage of each battery using a voltmeter a few hours later and ensure that they are within 50mV (0.05V) of one another before parallel connection. By doing this, you can minimize the probability of battery imbalance and achieve optimal system performance. If you notice a reduction in battery bank capacity over time, disconnect the parallel connections and charge each battery individually before reconnecting.

Best Practices for Series Charging of Batteries

Connecting lithium batteries in series is similar to parallel connection, and it is advisable to charge each battery individually and ensure the voltage of each is within 50mV (0.05V) of each other before making the series connections.

Using a multi-bank charger to charge lithium batteries in series is highly recommended. This means each battery is charged simultaneously but is independent of each other in the charging process. However, in some cases, multiple batteries in series may not be feasible, and LiTime offers 24V and 48V batteries to reduce the need for multiple connected batteries.

Can I Charge LiFePO4 Battery in Cold (Under Freezing Temperature)

LiFePO4 batteries can be safely charged within a temperature range of 0°C to 45°C (32°F to 113°F).

LiTime has self-heating series LiFePO4 battery. The LiTime self-heating series comes equipped with a built-in heating system that utilizes proprietary technology, drawing power directly from the charger - no additional components required. The process of heating and charging is seamless; once charging below 0°C is initiated, the heating system automatically activates, and it deactivates when no longer necessary. The heating system does not draw power from the battery, but rather from the charger, preventing battery discharge. Simply plug the battery into the lithium charger, and the internal heating and monitoring systems will take care of the rest.

Visit LiTime Cold-Weather batteries where batteries have low temperature protection function. When it's below 0℃，batteries would cut off the charging to protect the battery. 

Conclusion

LiFePO4 batteries require specific charging methods to ensure their optimal performance and longevity. While it is possible to charge a LiFePO4 battery using a normal charger, it is not recommended for long-term use, as it may negatively affect the battery's lifespan and performance.

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.

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