Why Do Lipo Batteries Swell? Causes & Prevention Tips

What Is Lipo Battery Swelling?

Lipo batteries, or lithium polymer batteries, are rechargeable batteries that use lithium-ion technology. Unlike traditional lithium-ion batteries, Lipo batteries use a polymer electrolyte, which allows for higher energy density and a lighter weight, making them a top choice for portable devices. They work by moving lithium ions between the positive and negative electrodes to store and release energy. However, when something goes wrong inside the battery, swelling can occur.

Lipo battery swelling happens when gases build up inside the battery, causing the outer casing to bulge. Normally, Lipo batteries have a soft, rectangular pouch design, but when swelling occurs, the battery may puff up and lose its regular shape. You might notice signs like a visibly bulging surface, difficulty fitting the battery into your device, or reduced performance, such as shorter battery life. This issue not only shortens the battery’s lifespan but can also pose risks to both your device and personal safety.

Causes of Lipo Battery Swelling

Lipo battery swelling can result from various factors, including improper use, environmental conditions, and the battery’s quality. Here are the main causes of Lipo battery swelling.

Overcharging and Over-Discharging

Overcharging and over-discharging are among the most common reasons for Lipo battery swelling. Overcharging occurs when the battery is charged beyond its safe voltage limit (typically 4.2V per cell). This excess voltage triggers chemical reactions inside the battery, breaking down the electrolyte and producing gas. Similarly, over-discharging happens when the battery is drained below its safe voltage (usually under 3.0V per cell), which can destabilize the battery’s internal chemistry and also generate gas. Both overcharging and over-discharging increase internal pressure, leading to swelling.

High Temperatures

High temperatures can have a significant impact on Lipo batteries. These batteries perform best at temperatures between 59°F and 77°F (15°C to 25°C), but exposure to heat above 140°F (60°C) can speed up the breakdown of the electrolyte, creating a large amount of gas. Leaving your battery in direct sunlight during summer or using it in a hot device (like a drone after extended flights without cooling) can cause swelling. While low temperatures (below 32°F or 0°C) don’t directly cause swelling, they can reduce battery performance, indirectly increasing the risk of over-discharging or overcharging.

Physical Damage

Physical damage is another frequent cause of swelling. Lipo batteries have a thin outer casing and a delicate internal structure. If the battery is dropped, crushed, or punctured, it can cause an internal short circuit or electrolyte leakage. A short circuit triggers intense chemical reactions that produce gas, leading to swelling. For example, a drone crash or a device falling can damage the battery, increasing the likelihood of swelling.

Poor Quality or Aging Batteries

The quality of a battery directly affects its safety and reliability. Some low-quality Lipo batteries may use substandard materials or manufacturing processes, such as impure electrolytes or defective separators, making them more prone to chemical reactions and gas production. Additionally, even high-quality Lipo batteries degrade over time with prolonged use. As a battery ages, its internal materials break down, potentially causing the electrolyte to decompose or the electrodes to deteriorate, which increases the risk of swelling.

Dangers of Lipo Battery Swelling

Lipo battery swelling doesn’t just affect usability—it can also lead to serious safety hazards. Here are some of the key dangers associated with swelling.

Fire and Explosion Risks

A swollen Lipo battery has built-up internal gas, which increases pressure. If you continue charging or using it, this can cause an internal short circuit. A short circuit generates heat and may ignite the electrolyte, resulting in a fire or explosion. The risk is especially high if you squeeze or puncture a swollen battery. There have been documented cases of fires caused by swollen Lipo batteries, particularly in drones and electronic devices.

Device Damage

Swollen batteries can cause physical damage to your device. Since Lipo batteries are often housed inside devices (like a drone’s battery compartment or a phone’s back panel), swelling can expand the battery’s size, putting pressure on internal components. For instance, a swollen battery in a drone might deform the battery compartment, compromising the device’s structure and rendering it unusable.

Chemical Leakage

If swelling causes the battery casing to rupture, the electrolyte inside may leak out. Lipo battery electrolyte contains organic solvents and lithium salts, which are corrosive and toxic. This leakage can damage your device, irritate your skin, harm your respiratory system, and pose environmental hazards. Leaked chemicals can also create health risks if not handled properly.

How to Prevent Lipo Battery Swelling?

By using and maintaining your Lipo battery properly, you can significantly reduce the risk of swelling. Here are some practical tips to prevent it.

Charge Properly

Charging is a critical part of using Lipo batteries safely. Always use the original or a compatible charger, ensuring the voltage and current match the battery’s specifications (typically 4.2V per cell at full charge). Avoid overcharging by using a charger with a balancing feature to keep each cell’s voltage even. Don’t leave the battery charging unattended for long periods, and disconnect it once fully charged. For batteries you won’t use for a while, discharge them to a storage voltage (around 3.8V per cell) to minimize stress.

Avoid Extreme Temperatures

Lipo batteries are sensitive to temperature. Keep them in an environment between 59°F and 77°F (15°C to 25°C) during use and storage. Avoid exposing them to high heat, such as inside a car on a hot summer day or in direct sunlight. After use (like after flying a drone), let the battery cool down naturally before storing or charging it. Similarly, using a battery in very cold conditions (below 32°F or 0°C) can degrade its performance, so consider warming it up gently before use in chilly weather.

Regular Inspection and Maintenance

Regularly checking your battery’s condition is a key way to prevent swelling. Before using it, inspect the battery for signs of bulging, deformation, or leakage, and stop using it immediately if you notice any issues. Evaluate your battery’s performance every six months—if the battery life drops significantly or charging seems abnormal, it’s time to replace it. When storing batteries, keep them in a dry, well-ventilated area and use a fireproof bag to reduce risks.

Choose High-Quality Batteries

When buying Lipo batteries, opt for reputable brands and trusted sellers to avoid low-quality products. High-quality batteries are made with better materials and manufacturing processes, often including safety features like a built-in Battery Management System (BMS) to enhance safety. This can significantly lower the risk of swelling. Also, make sure the battery’s specifications match your device to prevent issues from mismatched parameters.

What to Do If Your Lipo Battery Swells?

If you notice your Lipo battery has swollen, take immediate safety steps to handle it. First, stop using the battery—don’t charge or discharge it further, as this could worsen the swelling or cause a fire. Avoid squeezing, puncturing, or disassembling the swollen battery, as these actions could lead to electrolyte leakage or an explosion. Place the battery in a safe container, like a metal box or fireproof bag, away from flammable materials. Then, contact a local professional recycling center or battery disposal facility to dispose of it properly. Never throw a swollen battery in regular trash, and absolutely do not burn it, as this could trigger a serious fire or explosion.

Frequently Asked Questions

1. Can I still use a Lipo battery after it swells? No. A swollen Lipo battery poses safety risks, including fire or explosion, and should not be used. Stop using it immediately and dispose of it properly.
2. How can I tell if my Lipo battery is starting to swell? Look for signs like a bulging surface, deformation, or difficulty fitting the battery into your device. Reduced performance, like shorter battery life, can also be a warning sign.
3. Does the brand of a Lipo battery affect swelling? Yes. Low-quality batteries are more likely to swell due to poor materials and manufacturing. Choosing a trusted brand like HIMAX Electronics can greatly reduce this risk.
4. Do I need to monitor my Lipo battery while charging? It’s a good idea to keep an eye on it. Lipo batteries can swell due to overcharging or faults, especially with non-original chargers, and leaving them unattended might mean missing early warning signs.
5. What’s the best storage temperature for Lipo batteries? The ideal storage temperature is 59°F to 77°F (15°C to 25°C), with humidity below 60%. For long-term storage, keep the voltage at 3.8V per cell and use a fireproof bag.
6. Why do Lipo batteries swell more easily in high temperatures? High heat speeds up the breakdown of the electrolyte inside the battery, producing gas that increases internal pressure and causes swelling. Avoid using or storing batteries in hot environments.

Choose HIMAX Electronics for Safer Lipo Batteries