Can I charge a lithium battery with a lead-acid charger? We often receive this question from our customers.

The answer is: Not recommended. It is not recommended to use lead acid chargers for long periods of time as they may affect the performance and lifespan of lithium iron phosphate batteries.

In the following you will find out why and how to charge LiFePO4 batteries correctly.

Table of contents

• Part 1: LiFePO4 battery charging logic
• 1.1 LiFePO4 battery charging mode
• 1.2 lead acid battery charging mode
• Part 2: 3 Recommended Ways to Charge LiFePO4 Batteries
• 2.1 Using LiFePO4 battery chargers
• 2.2 generator / alternator
• 2.3 solar energy
• Part 3: Charging LiFePO4 batteries in winter
• Part 4: How long does it take to charge lithium batteries?

Part 1: LiFePO4 battery charging logic

The material properties of the LiFePO4 battery mean that its charging curve differs significantly from that of a lead-acid battery. Compared to a lead-acid battery, the LiFePO4 battery has a simpler charging process and mode. Therefore, it is recommended to choose LiFePO4 as the charging mode.

1.1 LiFePO4 battery charging mode

Image source: Power Queen

CC (constant current) phase (T1)

Initially, a discharged battery is charged with a constant current and the voltage increases steadily until the constant voltage setpoint is reached, which varies between different charging methods.

CV (Constant Voltage) Phase (T2)

The battery maintains a constant voltage during this phase while the current gradually decreases to 2A (0.02C), also known as the final current. At this point the charging process stops and the battery is fully charged.

1.2 lead acid battery charging mode

Bulk / Boots Phase (T1)

Initially, a discharged battery is charged with maximum current and the voltage increases steadily until the setpoint for the absorption voltage is reached. (This phase essentially corresponds to the CC phase when charging LiFePO4 batteries).

Absorption phase (T2)

The battery reaches the absorption voltage set point and keeps the voltage constant while the current gradually decreases until the battery is full (within 10-20%). Generally, absorption does not last longer than 3 hours to avoid overcharging. (This phase essentially corresponds to the CV phase when charging LiFePO4 batteries).

Floating phase (T3)

After the absorption phase, the battery voltage drops to the set point for the float voltage and the current is also reduced to a low float mode to prevent battery discharge and compensate for any self-discharge. If the battery becomes more discharged, the controller can switch back to bulk/boosts or absorption to replenish the lost energy as long as energy is available. (LiFePO4 batteries do not have this charging phase.)

Part 2: 3 Recommended Ways to Charge LiFePO4 Batteries

Power Queen recommends three reliable charging methods for LiFePO4 batteries: using LiFePO4 chargers, generators and solar cells.

2.1 Using LiFePO4 battery chargers

Using LiFePO4 battery chargers is the most efficient and convenient way to charge LiFePO4 batteries. These chargers have been specially developed for LiFePO4 chemistry and ensure optimal charging performance and safety.

They provide the correct voltage and current values ​​required for efficient charging without damaging the battery cells. LiFePO4 battery chargers are often equipped with advanced features such as overcharge protection, temperature monitoring and automatic shutdown, further increasing battery longevity and safety.

See the table below for information about the voltage specifications of different LiFePO4 batteries and systems.

	Optimal charging voltage	Charging voltage range
12V(12.8V)	14.4V	14.2V~14.6V
24V(25.6V)	28.8V	28.4V~29.2V
36V	42.4V	42V – 42.6V
48V(48V)	54.0V	53.25V~54.75V
51.2V	57.6V	56.8V~58.4V

Charging tips:

Connect the charger to the battery before connecting it to the power supply to avoid sparking.

It is recommended to disconnect the charger from the battery after fully charging.

2.2 generator / alternator

In situations where electricity is not readily available, e.g. b For outdoor activities or remote locations, generators can be an excellent option for charging LiFePO4 batteries.

If you use an alternator or generator to charge your LiFePO4 battery, it is important to ensure that the charging voltage and current are compatible with your battery's specifications. If the alternator or generator supports a DC output, a DC-DC charger must be connected between the battery and the generator.

This ensures that the LiFePO4 battery receives the correct charging conditions and possible damage is avoided.

Power Queen's LiFePO4 batteries can be charged via an alternator or generator, thus offering a flexible charging option for various power sources.

2.3 solar energy

Solar modules harness the power of the sun and offer a renewable and sustainable way to charge LiFePO4 batteries. The solar energy is converted into electrical energy by the photovoltaic cells present in the solar modules. This energy can then be used to charge the batteries directly or stored in a separate energy storage system for later use. When selecting solar panels to charge LiFePO4 batteries, factors such as wattage, efficiency, weather conditions, and installation requirements must be considered. It is also advisable to use a charge controller to prevent overcharging and optimize the charging process.

A 12V 100Ah LiFePO4 battery can be charged with the 300W solar panels. The battery can be fully charged in one day (with effective sunlight exposure of 4.5 hours)./Day).

There are also removable versions, such as: b the portable solar panels from Power Queen, which feature a convenient foldable design and come with a portable case. These panels do not require complicated installation procedures and can be set up effortlessly in no time.

Part 3: Charging LiFePO4 batteries in winter

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

To ensure optimal charging in winter, you should note the following information:

Charge the battery indoors or in a temperature-controlled environment to avoid extreme temperature fluctuations.
Warm up the battery before charging if it has been exposed to very low temperatures.
Use a charger that is specifically designed for LiFePO4 batteries or that offers adjustable charging settings suitable for colder conditions.
Monitor the temperature of the battery during charging to prevent it from exceeding the recommended range.
Avoid overcharging by using chargers with appropriate safety features such as overcharge protection or automatic shut-off.

Power Queen 12V 100Ah Smart has protection against low temperatures. The intelligent BMS enables built-in low temperature protection to interrupt charging and prevent damage when the battery is charged at a temperature below 32°F. If you need to charge the battery at low temperature, press the button to disable the protection and charge the battery for emergency use.

Power Queen also has self-heating series for cold winter days. Power Queen LifePO4 Self-Heating Battery fulfills the upgrade self-heating function based on the previous battery. When the charging temperature falls below 41°F/5°C, the self-heating function will automatically activate. The heater will stop when the temperature reaches 50°F/10°C and then the battery will charge normally. Don't be afraid of the coming winter.

Part 4: How long does it take to charge lithium batteries?

Charging time for LiFePO4 lithium batteries may depend on several factors, including battery capacity, charging current and state of charge when charging starts. However, as a general estimate, LiFePO4 batteries typically take around 2 to 6 hours to reach a full charge.

It is important to note that charging time may be affected by the specifications and capabilities of the charger. Some chargers can offer faster charging speeds, allowing LiFePO4 batteries to reach full capacity more quickly.

To determine the exact charging time for a particular LiFePO4 lithium battery, it is recommended to consult the manufacturer's guidelines or documentation. These sources typically contain information about recommended charging current, estimated charging times, and any specific considerations or precautions for optimal charging.

 

Note: 12V 100Ah mini LiFePO4 battery as an example

Remember that charging LiFePO4 batteries within manufacturer recommended limits, using compatible chargers, and monitoring battery temperature during charging are essential to ensure efficient and safe charging while maintaining battery longevity to obtain.

Conclusion

Finally, we advise against charging LiFePO4 batteries with a lead-acid charger as this may cause damage to the LiFePO4 batteries. The LiFePO4 charger is a better choice. You can also learn how to store LiFePO4 batteries to extend their lifespan.

Power Queen offers qhigh quality LiFePO4 batteries and chargers. If you have any questions, please contact us at service.de@ipowerqueen.com.

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