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Lithium Battery Cut-off Voltage And Current Setting: Balance between Safety And Performance

Views: 0     Author: Site Editor     Publish Time: 2024-04-30      Origin: Site


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As an important energy storage device, lithium batteries are widely used in modern electronic products. In order to ensure the safe operation and optimal performance of lithium batteries, it is very critical to properly set the cut-off voltage and current. This article will discuss in detail the setting principles, standards and related factors of lithium battery cut-off voltage and current.

Internal connection cables of energy storage equipment system

1. Working principle of lithium battery

Lithium batteries work based on the movement of lithium ions back and forth between the positive and negative electrodes. During the charging process, lithium ions are released from the positive electrode and migrate to the negative electrode through the electrolyte solution. At the same time, electrons flow from the external circuit to the negative electrode to achieve battery charging. The discharge process is the opposite. Lithium ions return from the negative electrode to the positive electrode, and electrons flow from the negative electrode to the external circuit.

2. Setting of cut-off voltage

1. Discharge cut-off voltage

The discharge cut-off voltage refers to the lowest voltage that the battery can reach when discharging. Setting an appropriate discharge cut-off voltage can prevent the battery from over-discharging, thus extending the battery life. Generally speaking, the discharge cut-off voltage of lithium batteries is usually set between 3.0V and 3.2V. The specific value depends on the battery type, application scenario and manufacturer's requirements.

A lower discharge cut-off voltage allows the battery to release more energy, but it also increases the risk of battery loss and shortened life. A higher discharge cut-off voltage can extend the life of the battery, but may sacrifice some battery capacity. When setting the discharge cut-off voltage, there is a trade-off between energy output and battery life.

2. Charge cut-off voltage

The charging cut-off voltage refers to the highest voltage that the battery can reach when charging. Setting the charge cut-off voltage requires consideration of several factors, including battery chemistry, safety, and lifespan.

The charging cut-off voltage of general lithium batteries is usually set at around 4.2V. This voltage value is determined based on the battery's rated voltage and charging characteristics. Charging beyond the charging cut-off voltage may cause the battery to overcharge, causing problems such as electrolyte decomposition and heating, and may even cause the battery to explode or catch fire.

In order to ensure the safety and adequacy of charging, constant current-constant voltage charging mode is usually used during the charging process. In the constant current charging stage, the battery is charged with a constant current until the voltage reaches the charging cut-off voltage. Then switch to the constant voltage charging stage, charging at a constant voltage until the current drops to a certain value, at which time the battery is considered to be fully charged.

3. Setting of cut-off current

The cut-off current refers to the current value that is considered to be the end of charging when the current drops to a certain value during the charging process. Setting an appropriate cut-off current ensures that the battery is fully charged while avoiding overcharging.

National standards usually stipulate that the charging cut-off current shall not exceed 0.01 times the battery capacity, that is, 0.01C. For example, if the battery capacity is 2000mAh, the cutoff current should not exceed 2mA. Such a setting can ensure that the battery reaches a higher charge level at the end of charging and improves the battery's capacity utilization.

4. Influence of other factors

1. Temperature

Temperature has an important impact on the performance and safety of lithium batteries. In high-temperature environments, battery life may be shortened, and the risk of overcharge and over-discharge will also increase. When setting the cut-off voltage and current, temperature factors need to be considered and corresponding temperature control measures must be taken.

2. Battery aging

As a battery is used and aged, its performance may change. Aged batteries may require lower discharge and charge cutoff voltages to ensure safety and performance. During battery use, appropriate adjustments need to be made based on the actual condition of the battery.

3. Load characteristics

Different load characteristics may have an impact on the battery's cut-off voltage and current settings. For example, a higher discharge cut-off voltage may be required to meet power requirements under high load conditions, while the discharge cut-off voltage may be appropriately lowered under low load conditions to extend battery life.

5. Things to note

Correct cut-off voltage and current settings are very important for the safety and life of lithium batteries. Improper settings may cause battery damage, safety risks, or shortened battery life. When setting the cut-off voltage and current, it is necessary to follow the relevant standards of the battery and make reasonable adjustments according to the specific application, which is an important measure to ensure battery safety and performance.

6. Application of battery management system (BMS

Battery Management System (BMS): In some complex systems, such as electric vehicles or large energy storage systems, a battery management system may be used to monitor and control the status of the battery. BMS can automatically adjust the cut-off voltage and current according to the battery's temperature, voltage, current and other parameters to ensure the safety and optimal performance of the battery. Its function is as follows:

1. Battery status monitoring: BMS can monitor the voltage, current, temperature and other parameters of the battery in real time to ensure that the battery is within the normal operating range.

2. Battery protection: When the battery encounters abnormal conditions, such as overcharge, over-discharge, high temperature, etc., BMS will promptly cut off the power supply or take other protective measures to prevent battery damage.

3. Battery balancing: The balancing function of BMS can avoid battery inconsistencies during use, thereby improving the overall performance of the battery pack and extending its service life.

4. Battery usage optimization: BMS can reasonably allocate power according to the actual situation of the battery, optimize battery usage, and improve battery utilization.


7. Summary

Setting the cut-off voltage and current of lithium batteries is a complex process that requires comprehensive consideration of factors such as battery performance, lifespan, safety, and application scenarios. Following relevant standards and specifications and making reasonable adjustments according to actual conditions can ensure the best performance and longest life of lithium batteries. At the same time, users should also pay attention to the correct charging and discharging methods when using lithium batteries to avoid overcharging and over-discharging to ensure the safety and stability of the battery. This article is only for knowledge sharing and not a reference basis. If you have any questions, it is recommended to follow the recommendations and relevant standards of battery manufacturer experts.

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