Can I charge a lithium battery with a lead-acid charger? We often get this question from our customers.
The answer is: Not recommended. Prolonged use of lead-acid chargers is not recommended as they can affect the performance and lifespan of lithium iron phosphate batteries.
In the following you will learn why and how to charge LiFePO4 battery properly.
Table of contents
- Part 1: LiFePO4 battery charging logic
- Part 2: 3 Recommended Ways to Charge LiFePO4 Batteries
- 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 with a lead-acid battery, the LiFePO4 battery has an easier charging process and mode. So it is recommended to choose LiFePO4 as 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 differs 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, charging stops and the battery is fully charged.
1.2 lead-acid battery charging mode
Bulk / Boat 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 target absorption voltage and keeps the voltage constant while the current gradually decreases until the battery is full (within 10-20%). In general, the absorption lasts no more 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 float voltage setpoint and the current is also reduced to a low float mode to prevent battery discharge and compensate for any self-discharge. If the battery drains further, the ESC can switch back to bulk/boosts or absorption to replenish lost energy while 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 Use of LiFePO4 battery chargers
Using LiFePO4 battery chargers is the most efficient and convenient way to charge LiFePO4 batteries. These chargers are specially designed 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 on the voltage specifications of different LiFePO4 batteries and systems.
Optimal charging voltage
charging voltage range
42V - 42.6V
Connect the charger to the battery before connecting to the mains to avoid sparking.
It is recommended to disconnect the charger from the battery after it is fully charged.
In situations where power 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 are using 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 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 avoids possible damage.
Power Queen's LiFePO4 batteries can be charged via an alternator or generator, providing flexible charging options for different power sources.
2.3 Solar Energy
Solar panels 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 choosing 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 to optimize the charging process.
One 12V 100Ah LiFePO4 battery can be charged with the 300W solar panels. The battery can be fully charged in one day (with 4.5 hours of effective sunlight)./Day).
There are also removable variants, such as e.g. B Power Queen's portable solar panels, 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).
In order to ensure an optimal charging process in winter, you should observe the following instructions:
Charge the battery indoors or in a temperature-controlled environment to avoid extreme temperature changes.
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 charge settings suitable for colder conditions.
Monitor the battery temperature during charging to prevent 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 the built-in low-temperature protection to stop charging and prevent damage when the battery is charging at a temperature below 32°F. When you need to charge the battery in low temperature, press the button to disable 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 meets 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 be activated automatically. 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 can 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 faster.
To determine the exact charge time for a specific LiFePO4 lithium battery, it is recommended to consult the manufacturer's guidelines or documentation. These sources usually include 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.
Finally, we do not recommend charging LiFePO4 batteries with a lead-acid charger as it 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.
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