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Understanding Defects in LiPo Cells and their Impact


Lithium-ion polymer (LiPo) batteries have become increasingly popular due to their high energy density, lightweight design, and versatility in various applications. However, like any other technology, LiPo cells are not without their flaws. This article aims to explore some common defects found in LiPo cells and their potential consequences.

Lipo Cell Swelling

One of the typical defects in LiPo cells is cell swelling, also known as bloating or puffing. This occurs when the internal components of the battery expand, causing the battery to increase in size. Swelling can be caused by factors such as overcharging, high temperatures, manufacturing defects, or physical damage. Cell swelling is hazardous as it can apply pressure on internal components, leading to decreased performance, reduced capacity, and in severe cases or rupture.

Thus we need to prevent lipo battery swelling as much as we can. To prevent LiPo battery swelling, it is crucial to follow a few key practices. Firstly, use a charger designed specifically for LiPo batteries and adhere to the manufacturer’s guidelines for charging. Avoid overcharging by monitoring the voltage during the charging process and removing the battery once it reaches the recommended limit. Never leave batteries unattended while charging. Additionally, control the temperature by charging, discharging, and storing the batteries within the specified temperature range. Handle and store the batteries safely, protecting them from physical damage and keeping them away from flammable materials. Regularly inspect the batteries for signs of swelling or damage, and replace any faulty or worn-out batteries promptly. By following these preventive measures, you can maintain the optimal performance and safety of your LiPo batteries.

Lipo Cell Capacity Loss

Another significant defect in LiPo cells is capacity loss over time. It refers to the gradual reduction in the battery’s ability to store and deliver charge, resulting in decreased overall capacity. LiPo batteries have a limited number of charge-discharge cycles before their capacity starts to degrade. Factors contributing to capacity loss include high operating temperatures, overcharging, deep discharging, and aging. Capacity loss results in reduced battery life, shorter runtime, and decreased overall performance of devices powered by these cells. Then how to stop it? Here are some tips:

  • Follow proper charging practices: Use a suitable charger and adhere to the manufacturer’s guidelines to avoid overcharging or overdischarging the battery.
  • Control temperature exposure: Operate and store LiPo batteries within the recommended temperature range to minimize the acceleration of capacity loss.
  • Avoid extreme charge levels during storage: Before storing LiPo batteries for an extended period, ensure they are at around 50% charge, as this is considered optimal for long-term storage.
  • Monitor battery health: Regularly inspect the battery for any signs of swelling, damage, or abnormal behavior. Replace worn-out or damaged batteries promptly.
  • Maintain a moderate usage pattern: Avoid subjecting LiPo batteries to extreme discharge or rapid discharge rates, as this can accelerate capacity loss.

Lipo Cell Internal Shorts

An internal short in a LiPo (Lithium Polymer) cell refers to an unintended electrical connection between the positive and negative electrodes inside the battery. This connection bypasses the normal current flow through the external circuit, creating a shortcut within the battery itself. Internal shorts can occur due to various factors, including manufacturing defects, physical damage, or electrode deterioration over time.

When an internal short occurs, it leads to a rapid release of energy within the battery, resulting in increased heat generation and potentially causing the battery to swell, vent, or even catch fire. The short circuit may be caused by a tiny metal particle, a damaged separator, or a breakdown of the electrode structure.

Internal shorts are dangerous because they can lead to thermal runaway, a self-perpetuating and uncontrollable increase in temperature within the battery. This can cause an escalation of chemical reactions, known as a thermal runaway reaction, which releases more heat and accelerates the failure process. In extreme cases, it can result in a fire or explosion.

Lipo Cell Self-Discharge

Self-discharge refers to the gradual loss of charge or capacity that occurs in a battery even when it is not being used or connected to any external circuit. LiPo (Lithium Polymer) batteries, like other types of rechargeable batteries, experience self-discharge over time.

The self-discharge rate of LiPo cells is generally low compared to some other battery chemistries, such as NiMH (Nickel-Metal Hydride) batteries. However, it is still important to be aware of self-discharge, especially if the LiPo battery is intended for long-term storage or infrequent use. Self-discharge rates can vary between different LiPo chemistries, but it generally occurs due to chemical reactions within the cell. Factors such as high temperatures, prolonged storage without maintenance charging, or poor battery management systems can exacerbate self-discharge. This defect can impact the usability of LiPo cells in applications that require long periods of inactivity.

If you plan to store a LiPo battery for an extended period, ensure it is stored in a cool (but not freezing) and dry environment. Extreme temperatures can accelerate self-discharge and degrade the battery’s capacity. Before storing a LiPo battery, it is recommended to charge it to approximately 50% of its capacity. A fully charged or completely discharged battery is more prone to self-discharge and may be more susceptible to irreversible capacity loss.

If possible, it is beneficial to use and recharge the LiPo battery periodically. Regularly cycling the battery helps counteract self-discharge effects and maintains its overall health.

Lipo Battery Thermal Runaway

Thermal runaway is a critical and potentially hazardous condition that can occur in LiPo (Lithium Polymer) batteries. It refers to a self-perpetuating increase in temperature within the battery, which can lead to a violent reaction, fire, or even an explosion. Understanding thermal runaway is essential for safe handling and usage of LiPo batteries.

Thermal runaway in LiPo batteries typically begins with an internal short circuit, which can be caused by various factors such as manufacturing defects, physical damage, or electrode degradation. When a short circuit occurs, it creates an unintended pathway for electricity to flow directly from the positive to the negative electrode within the battery, bypassing the external circuit. This creates a shortcut for current flow and generates heat within the battery.

As the internal short circuit generates heat, it can cause neighboring battery components to undergo further chemical reactions. This results in the release of more heat and accelerates the failure process, leading to a vicious cycle known as a thermal runaway reaction. The temperature rises rapidly, causing the battery to swell, vent gas, rupture, or even catch fire.

Thermal runaway in LiPo batteries is a dangerous condition that can result from an internal short circuit and subsequent temperature escalation. By handling LiPo batteries safely, avoiding physical damage, following appropriate charging practices, and monitoring their condition, the risk of thermal runaway can be minimized, ensuring safer usage of these batteries.


While lithium-ion polymer (LiPo) cells offer numerous advantages, they are not free from defects. Understanding and being aware of these defects is vital to ensure proper handling, storage, and usage of LiPo batteries. Manufacturers, users, and researchers should work together to improve LiPo cell technology, enhance safety measures, and develop better battery management systems to minimize these defects and maximize performance, safety, and lifespan.

Remember, proper maintenance, adherence to manufacturer guidelines, and avoiding abusive practices can significantly reduce the occurrence of defects and prolong the life of LiPo cells.

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