Lithium iron phosphate (LiFePO4) batteries play a crucial role in various devices, ranging from small electronic gadgets to large-scale energy storage systems, and have become an indispensable part of our daily lives. Ensuring the effective charging and discharging of these batteries is of utmost importance for their performance, durability, safety, and environmental impact.

Improper charging and discharging can lead to battery damage, reduced lifespan, and even safety incidents. In this article, MeritSun guides you through the proper procedures for lithium battery charging and discharging to enhance your understanding and ensure optimal battery utilization.

Grasping Fundamental Principles and Constraints

Lithium-ion batteries consist of two electrodes, a positive electrode, and a negative electrode.

• Charging: This refers to the battery sending electrons back to the anode and reintroducing lithium ions to the cathode, thereby restoring the battery's capacity.

• Discharging: It is the process of using stored energy, where electrons move from the anode to the cathode externally.

Charge and discharge mechanism of a lithium-ion battery (Image by: Dreamstime.com)

In simple terms, during charging, electrons flow out of the battery through the current, while ions move from one electrode to another. It's like the electrodes "breathing" during the charging and discharging processes, exchanging ions. like the electrodes "breathing" during the charging and discharging processes, exchanging ions.

The charging of lithium iron phosphate batteries is divided into constant current charging and constant voltage charging.

• In the constant current charging stage, the battery is rapidly charged to the set voltage at the maximum allowable current.

• In the constant voltage charging stage, the voltage remains constant, and the current gradually decreases to ensure the complete embedding of lithium ions into the positive electrode.

For example, consider a 24V battery system (with a maximum float voltage of 28V) discharged to 15V. When the discharged battery (15V) is connected to a power source, the battery will begin charging at a preset constant current level. The current will remain constant until the voltage rises to 28V. At this point, the power supply will switch to constant voltage mode, and as the battery becomes fully charged, the current will decay to zero. The entire charging process needs monitoring to ensure safety and performance.

Efficient Lithium Battery Charge Tips

1. Answering the Question: Does Fully Discharging Lithium Batteries Affect Charging?

Many individuals harbor misconceptions about battery maintenance, often wondering whether they should wait until the battery is completely depleted before recharging. This concern may stem from a belief in memory effects or fears of limited charging cycles. However, this notion does not align with the actual situation.

Experts advise against consistently waiting for batteries to fully discharge before deciding to recharge them. The best practice is to connect the charger immediately after the battery is depleted. In reality, the battery's lifespan is related to the depth of discharge. Even if the battery is routinely discharged by only 10% before each use, it can undergo thousands of charging cycles. In contrast, there is a significant difference in charging cycle numbers between a battery that discharged almost 50% and one that discharged only 10%. Routine discharge before charging can prevent the growth of sulfate crystals, thereby enhancing battery performance and lifespan.

2. Impact of Charging Capacity in Lithium Battery Health

For ternary lithium batteries, it is recommended to control the charging capacity between 80% and 90% to extend the battery's lifespan. Excessive charging can lead to overcharging issues, directly affecting battery performance and longevity. Therefore, unlike other types of lithium batteries on the market, charging ternary lithium batteries to 90% is the optimal choice.

As for lithium iron phosphate batteries, whether charged to 90% or 100%, there are no significant issues. However, to more effectively prolong battery life, we advocate charging them to 90%. Additionally, when employing the shallow charging and discharging method, regularly conducting complete charging and discharging cycles (i.e., 100% charging and discharging) is recommended.

This process helps the Battery Management System (BMS) to update and accurately calibrate the State of Charge (SOC), thereby comprehensively enhancing battery performance and reliability.

Overcharging lithium batteries can generate excess heat and reduce battery life. It is crucial to charge lithium batteries to the correct voltage, avoiding overcharging. The peak charging voltage for most lithium-ion batteries is 4.20V per cell. However, reducing the peak charging voltage by 0.10V per cell can double the battery's cycle life. For example, charging the battery to 4.10V per cell can extend the battery life to 600-1,000 cycles.

3. Temperature Management Strategies for Optimal Lithium Battery Charging

Lithium-ion batteries are influenced by temperature during operation, with high temperatures accelerating degradation and reducing lifespan, while low temperatures may compromise performance. Overheating can lead to the risk of thermal runaway, potentially causing fires or explosions. To optimize performance and lifespan, it is recommended to use batteries within a moderate temperature range of 32°F (0°C) to 95°F (35°C) and manage the heat generated during charging and discharging to ensure safe operation.

①　Avoid High Temperatures:

Lithium batteries are heat-sensitive, and exposure to high temperatures may reduce battery life and pose potential safety risks. It is crucial to store and operate lithium batteries within the recommended temperature range. Low temperatures can impact the performance of lithium batteries, so it's essential to shield them from extreme cold. If possible, avoid exposing batteries to extremely cold temperatures. When not in use, store them in a temperature-controlled environment. Typically, the safe temperature range for lithium-ion batteries is 5°C to 20°C or 41°F to 68°F.

②　Provide Adequate Ventilation:

When charging or discharging lithium batteries, ensure there is sufficient ventilation to dissipate heat. Avoid placing devices or batteries in enclosed spaces, as this may lead to overheating. Proper ventilation helps maintain temperatures within a safe range and prevents excessive heat buildup. When not in use, store lithium batteries in a cool, dry place. Avoid placing them in extremely cold environments, such as leaving them outside in cold temperatures. Storing batteries in a temperature-controlled environment helps preserve their performance and extend lifespan.

③　Charge at a Moderate Rate:

Charging at a reasonable rate helps manage the generation of heat. Fast charging or using high-current chargers may generate more heat and potentially damage the battery. It is advisable to charge lithium batteries at a rate of 1C or lower, where C represents the battery's capacity. For example, if the battery capacity is 2000mAh, charging at a 1C rate means a charging current of 2000mA or 2A.

④　Monitor Battery Temperature:

Some devices and chargers have built-in temperature monitoring systems to help prevent overheating. If your device or charger has temperature monitoring features, pay attention to any temperature warnings or alerts. If the battery becomes too hot during the charging or discharging process, it is recommended to pause the process and wait for the battery to cool before resuming.

⑤　Choose the right battery product:

Currently, the majority of lithium batteries on the market lack an effective temperature management system. However, at MeritSun, we are committed to addressing the electricity needs in cold regions with the introduction of a fully automated temperature management lithium iron phosphate energy storage system – the 12V/24V Low-Temperature Heat LiFePO4 Battery.

This product boasts enhanced temperature tolerance and intelligent heating functionality. Even in frigid environments (below 0°C), the battery automatically detects the ambient temperature before charging, employing internal heating components to raise the temperature to a normal level (10°C). This ensures the stability, health, and safety of the battery during charging and discharging. Additionally, the battery features intelligent Bluetooth app monitoring, advanced Battery Management System (BMS) to enhance battery performance, automatic balancing, and soft start functions, among other advantages.

Learn More: https://www.meritsunbattery.com/en/product-p7739.html

Lithium Battery Discharge Tips

Discharging lithium iron phosphate batteries involves addressing a series of crucial issues and considerations, including temperature impact, current control, complete discharge, depth of discharge (DoD), and self-discharge. The following summarizes key discharge tips based on the provided information to ensure efficient battery performance and extend its lifespan.

①　Temperature Impact:

In extremely low temperatures, electrode contraction and a decrease in electrolyte conductivity may hinder ion release, affecting battery performance. Conversely, at high temperatures, electrode expansion may damage the electrode structure. To ensure efficient lithium-ion exchange, users should maintain appropriate temperature conditions.

②　Current Control:

The Battery Management System (BMS) controls discharge current and has a maximum operating current limit. While using current within the BMS-specified range is safe, discharging at lower currents can optimize battery capacity and cycle life, contributing to prolonged battery usage.

③　Complete Discharge:

Lithium iron phosphate batteries typically have a charging voltage level around 3.65V and a complete discharge voltage around 2.0V. Complete discharge may lead to battery damage, so users should avoid over-discharging to maintain normal battery operation and lifespan.

④　Depth of Discharge (DoD):

DoD refers to the discharge portion of the charge/discharge cycle, directly impacting battery cycle life. Shallower discharge depths significantly increase the number of cycles the battery can provide. Therefore, avoiding deep discharge, whenever possible, helps extend battery life.

⑤　Self-Discharge:

Self-discharge is a non-linear characteristic of batteries over time, closely related to temperature. At higher temperatures, self-discharge rates accelerate, while at lower temperatures, self-discharge rates are relatively lower. The monthly charge loss ranges between 0.5-3%, and the impact of self-discharge on battery capacity, especially in high-temperature environments, should be considered.

⑥　When using lithium iron phosphate batteries, consider these factors :

Comprehensively can better maintain battery performance and extend its lifespan. Users should closely monitor factors such as temperature, current, and discharge depth, taking appropriate measures to ensure optimal battery performance in various environmental conditions.

Final Words

Proper charging and discharging practices and management are crucial for protecting lithium batteries. We encourage users to follow these tips to ensure long-lasting and efficient operation of their devices, while also reducing adverse environmental impacts. By better understanding and managing lithium batteries, we can collectively contribute to sustainable energy use and lifestyles.

In addition to proper charging and discharging practices, choosing suitable, high-quality lithium batteries can also provide peace of mind. MeritSun's energy storage systems utilize in-house developed A-grade lithium iron phosphate cells, industry-leading BMS systems, and intelligent remote monitoring channels. Choosing MeritSun means choosing peace of mind, offering a more convenient, advanced, and superior experience for your energy storage needs.

Learn More: https://www.meritsunbattery.com/

By George

MeritSun Power Limited

export-10@MeritSunpower.com

MeritSun was founded in 1999, we have 24 years of professional experience in energy and integrated solution services. We have 100+ R&D teams,1368 employees,48 fully automatic production lines, and a 150,000 square meters factory, become the industry pioneers in battery suppliers through effective management.