Swollen LiPo Battery? Why It Happens & Safe Disposal Guide

Anybody who uses lipos will eventually encounter a puffy or swollen battery.

And the first question that inevitably comes up is “What should I do?”

This post is all about what causes that swelling and what to do when it happens to one of your lipos.

The Critical Danger of a Swollen LiPo Battery

LiPo battery swelling is primarily caused by gas generation within the battery cells. This isn’t just due to abuse; even normal use can contribute to this process through something called electrolyte decomposition.

Here’s a breakdown of what happens:

Electrolyte Decomposition: A LiPo battery consists of an anode (negative), a cathode (positive), and an electrolyte – a chemical solution that allows charged ions to move between the anode and cathode. During normal operation (charging and discharging), this electrolyte chemically breaks down over time. This process accelerates significantly if the battery is over-discharged, overheated, or overcharged.
Gas Formation: When the electrolyte decomposes, it produces lithium and oxygen. The lithium forms lithium oxide on the electrodes, but the excess oxygen doesn’t adhere and instead forms gas within the sealed battery cell. This trapped gas is the primary reason for the battery swelling. Oxygen, as you know, is highly combustible, significantly increasing the fire risk. Other gases like carbon dioxide (CO2) and carbon monoxide (CO) can also form during these chemical reactions, contributing to the internal pressure.

What is electrolyte decompostion?

Simply put, a battery is made of three things: the anode, the cathode and the electrolyte. The cathode and the anode are the positive and negative terminals on your battery.

The electrolyte is a chemical inside the battery that allows charged ions to flow from the anode to the cathode during discharge (and the other way during charging).

Electrolyte decomposition is what happens when that electrolyte chemically breaks down. So in a lipo battery, as the electrolyte breaks down you end up with lithium and oxygen. This forms lithium oxide on the anode and cathode (depending whether you are charging or discharging).

But what you also end up with is excess oxygen that doesn’t adhere to the anode or cathode. This excess oxygen is part of what causes a battery swell. And oxygen likes to burn. See here for more details. He also goes over some other reasons a battery might swell.

Other gases that can be found in the battery during the normal chemical reactions of a battery are carbon dioxide (CO2) and carbon monoxide (CO). For a technical overview of this, see this paper.

Can You Fix a Puffed LiPo Battery? (Spoiler: No!)

The shortest, safest answer to “How to fix a swollen LiPo battery?” is: Don’t.

Attempting to “fix” or recondition a swollen LiPo battery is extremely dangerous and ill-advised. The internal structure is compromised, and the risk of fire or explosion is too high. Do not try to puncture, press, or discharge it rapidly in an uncontrolled manner.

Your only safe course of action is proper disposal. Saving a few dollars on a new battery is simply not worth the risk of personal injury or a catastrophic house fire.

Safe Disposal of Swollen LiPo Batteries

Properly disposing of a puffed LiPo battery is crucial. The key is to fully discharge the battery before taking it to a recycling center. This eliminates any remaining electrical energy, making it safe for transport and handling.

Here are the two main methods for safely discharging a damaged LiPo battery:

The Light Bulb Method:

Connect the swollen battery to a low-wattage incandescent light bulb (e.g., a 12V, 20-watt halogen bulb).
Solder lead wires to the bulb and attach appropriate connectors for your battery.
Allow the battery to discharge completely until the bulb no longer lights up and the battery voltage reads 0V.
Safety Note: Perform this in a fire-safe area, away from flammable materials. You can connect multiple bulbs in parallel for a faster discharge rate if needed.

The Saltwater Bath Method:

Place the swollen battery in a non-conductive container (like a plastic bucket).
Fill the container with saltwater. Use approximately 2-3 tablespoons of salt per gallon of water.
Submerge the battery completely. The saltwater will slowly discharge the battery. This process can take several days or even weeks for larger batteries.
Safety Note: Ensure the battery is fully submerged and keep the container in a safe, outdoor location away from anything flammable, and out of reach of children or pets.

Once the battery is completely discharged (0V reading on a voltmeter), take it to a specialized battery recycling drop-off point. Always call ahead to confirm they accept damaged or fully discharged lithium polymer batteries.

Preventing Swollen LiPo Batteries: Best Practices for Battery Longevity

Prevention is always better than dealing with the dangers of a puffed LiPo battery. By following these best practices, you can significantly extend the life of your batteries and reduce the risk of swelling:

Use a Quality Charger & Follow Proper Charging Protocols:

Always use a reputable LiPo-compatible charger and follow its instructions meticulously.
Crucially, always charge your LiPo batteries inside a fire-resistant LiPo safety bag. These inexpensive bags (often around $10) are essential insurance; if something goes wrong during charging, they can contain the fire.

Avoid Over-Discharging:

Never let your LiPo battery voltage drop below its minimum cut-off voltage (typically 3.0V per cell, though 3.3V-3.5V is often recommended for longevity). Over-discharging is a leading cause of internal damage and swelling.

Manage Battery Heat:

Heat is a LiPo battery’s worst enemy. Avoid using or charging batteries when they are excessively warm.
After heavy use, allow your batteries to cool down to ambient temperature before recharging. Similarly, after charging, give them a short break before putting them back into action.

Proper Storage is Key:

Do not store your LiPo batteries in hot environments, such as the trunk of a car on a sunny day.
Store LiPo batteries at their recommended storage voltage (typically around 3.8V per cell). Research shows that storing batteries at a full charge (above 80% state of charge) for even a few hours can significantly accelerate gas generation and swelling.

Conclusion: Prioritize Safety with Your LiPo Batteries

Puffed LiPo batteries are a clear indicator of internal damage and a serious fire risk. While electrolyte decomposition is a natural process, misuse accelerates it dramatically. Understanding the causes—especially over-discharging, overheating, and improper charging/storage—empowers you to prevent this dangerous issue.

Remember, once a LiPo battery is swollen, it’s compromised. Your safest course of action is always proper, complete discharge followed by responsible recycling. By adopting safe charging, usage, and storage habits, you can enjoy your lithium polymer batteries for longer and, most importantly, safely.

For more in-depth information on all aspects of LiPo battery care, check out our comprehensive LiPo Battery Guide