5 Reasons Why Lithium Batteries Should Not Be Fully Discharged

In our daily life, we use a lot of rechargeable lithium batteries. They allow us to get rid of the constraints of wires and enjoy sufficient energy anywhere. Maybe you have noticed that some manufacturers recommend that you do not use the battery until it is completely exhausted before recharging. Why is that? This article will explore the 5 major reasons to help you use lithium batteries better.

1. Risk of Battery Damage

The principle of lithium battery discharge is to react with the chemical material wrapped in it. For example, the lithium-ion 21700 battery relies on the flow of lithium ions from the negative electrode to the positive electrode to generate current. After full discharge, the chemical substances in the battery may undergo irreversible changes, resulting in a significant decrease in capacity. This phenomenon is called “deep discharge” and will greatly shorten the service life of the battery.

Conclusion: Avoiding full discharge helps extend the life of the battery.

2. Battery Management System (BMS) Protection

Most lithium battery packs are equipped with BMS, which monitors the health of the battery and prevents overuse. When the battery reaches a point of near exhaustion, the BMS will stop the battery from supplying power to protect it from damage. Full discharge may cause the BMS to not work properly.

Conclusion: BMS plays a vital role in preventing full discharge damage and ensuring stable battery operation.

3. Safety Concerns

Over-discharging lithium batteries not only affects their lifespan but also introduces safety risks. When the battery voltage gets too low, it may lead to overheating or swelling, which can be dangerous. In extreme cases, the battery could catch fire or even explode, especially in high-power batteries like the 21700.

Table: Comparison of Battery Discharge States and Safety Risks

Over-Discharge Deep Discharge Conclusion: Keeping the battery from over-discharging helps lower the safety risks.

4. Capacity Loss

When lithium batteries are fully discharged, the chemical reactions inside the battery can change, directly affecting its capacity. For example, if a 21700 battery is over-discharged, its usable energy will be significantly reduced, leading to shorter usage time, and it may not be able to fully recharge to its original capacity.
Three Common Causes of Capacity Loss:

• Irreversible Chemical Reactions: Over-discharging can cause some of the chemical materials to degrade.
• Increased Cycle Count: Each deep discharge accelerates the wear on the battery’s capacity.
• Faster Aging: Extreme discharge speeds up the aging process of the battery;

Conclusion: Avoiding full discharge helps maintain the battery’s capacity and prolongs its useful life.

5. Reduced Charging Efficiency

Lithium batteries charge more slowly and less efficiently when their charge is extremely low. After a full discharge, it takes much longer to bring the battery back to a normal voltage. The charging process becomes unstable, and the battery may not recover to its optimal performance as quickly.

Conclusion: Keeping the battery at a moderate charge level improves charging efficiency and reduces charging time.

The Consequences of Leaving a Depleted Battery Uncharged for a Long Time

Leaving lithium batteries without charging for a long time can cause them to enter a state of “deep discharge”. This means that the battery voltage drops below safe levels and permanently damages the battery. The battery will not be able to store 100% of its power when it is recharged.

Worse still, batteries that have not been charged for a long time may not be able to hold a charge and enter “sleep mode”, where their voltage cannot be restored without professional intervention.

When Your Device Indicates That the Battery Is Out of Power, Is It 100% Depleted?

When a device signals that the battery is out of power, it doesn’t necessarily mean the battery is completely drained. Devices are typically designed with a small reserve of energy that prevents complete depletion to protect the battery.

This reserve ensures that the battery doesn’t enter an overly discharged state, which could cause permanent damage. The “empty” battery warning is generally triggered when the battery reaches a critical threshold (around 5-10%).

Final Thoughts

The above are the reasons why it is not recommended to fully discharge lithium batteries. When batteries are fully consumed, they may no longer be as healthy as before. Using some tips can extend the life of your battery. If you are looking for a professional lithium battery manufacturer to get high-quality batteries, please feel free to contact PKNERGY. We will answer all your questions about batteries.