How to Fix a Lipo Battery with 1 Weak Cell


Lithium polymer (lipo) batteries are commonly used in a wide range of applications, including remote-controlled models, drones, and smartphone accessories. While lipo batteries offer high energy density and lightweight properties, they are prone to certain issues that can affect their performance and lifespan.

One of the most common problems with lipo batteries is the presence of a weak cell. In this article, we will provide detailed guidelines on how to fix a lipo battery with 1 weak cell.

Brief Explanation of Lipo Batteries and their Common Issues

Lithium polymer batteries are rechargeable power sources that use lithium-ion technology. They have several advantages over other types of batteries, such as higher energy density, longer lifespan, and lower self-discharge rates. However, they also have some disadvantages that can affect their performance and safety.

One common issue with lipo batteries is over-discharging, which occurs when the battery is discharged below its minimum recommended voltage level. Over-discharging can cause irreversible damage to the battery cells and reduce their capacity.

Another issue is overcharging, which happens when the charger fails to detect when the battery is at full charge. Overcharging can cause gas buildup inside the battery cells and lead to swelling or even explosion.

Additionally, lipo batteries are prone to developing imbalanced cells due to variations in their internal resistance or capacity. Imbalanced cells can result in one or more cells having a lower voltage than others in the same pack leading to a weak cell.

Focus on the Problem of a Weak Cell in a Lipo Battery

A weak cell in a lipo battery refers to one or more cells that have been discharged too much or charged too little compared to other cells in the same pack causing it not to discharge or charge similarly. A weak cell can significantly reduce the overall performance and capacity of the battery pack, and in severe cases, it can lead to a fire or explosion. A weak cell may be identified when cells in a fully charged battery pack have different voltages.

For instance, if a 3-cell lipo battery is charged to 12.6 volts (4.2V per cell), but one of the cells is reading only 3.8 volts while the other two read 4.2 volts each, then you’ve got one weak cell. Furthermore, when discharging a lipo battery pack, you might notice that it reaches its discharge cutoff voltage sooner than usual, indicating that one or more cells in the pack are weaker than others.

It is essential to identify and fix a weak cell in a lipo battery as soon as possible to avoid further damage and ensure safe operation of your device. In the next section, we’ll discuss how to understand this problem better before taking action on fixing it.

Understanding the Problem

What Causes a Weak Cell in a Lipo Battery?

Lithium polymer (lipo) batteries are widely used in various applications, including remote control cars, drones, and even smartphones. These rechargeable batteries are known for their high energy density and lightweight design. However, they are also prone to certain issues that can affect their performance and safety.

One of the most common problems with lipo batteries is a weak cell. This occurs when one of the cells in the battery pack becomes weaker than the others due to several factors such as overcharging, over-discharging, or physical damage.

When this happens, it can cause a voltage imbalance between cells which can lead to further problems such as reduced capacity or even cell failure. If left unchecked, a weak cell can also cause overheating or swelling which can pose serious risks like fire or explosion.

The Dangers of Using a Lipo Battery with a Weak Cell

Using a lipo battery with a weak cell is not recommended because it poses serious risks to both property and personal safety. A weak cell cannot withstand high loads or discharge rates compared to fully charged cells which may result in sudden voltage drops that could damage your device. A lipo battery with voltage imbalance can also lead to thermal runaway where heat generated in one cell causes other cells to overheat resulting in an explosion or fire.

In addition to causing physical harm, overheating from using faulty batteries can damage your electronic devices beyond repair leading to additional expenses. It’s important that you don’t use any battery packs if you suspect they have any defective cells before diagnosing and fixing the issue.

So what should you do if you detect any signs of weakness in your lipo battery? The next section will guide you through the steps necessary for fixing this issue.

Tools and Materials Needed

Fixing a lipo battery with one weak cell requires the use of specific tools and materials. It is important to have all the necessary items on hand before starting any work on the battery pack. Here is a list of what you will need:


A multimeter is an essential tool for identifying which cell in the lipo battery pack is weak. It measures voltage, current, and resistance and can be used to ensure that the battery pack has been correctly re-soldered after fixing the weak cell. When using a multimeter, be sure to follow all safety precautions, including wearing gloves and eye protection.

Soldering Iron and Solder Wire

A soldering iron is required for removing the weak cell from the lipo battery pack as well as re-soldering all connections after replacing it with a new cell (if necessary). A good quality soldering iron should have adjustable temperature control to ensure that it does not overheat or damage other parts of the battery pack. Solder wire, preferably made of lead-free material, should also be used.

Balance Charger

A balance charger is needed to charge and balance the repaired lipo battery pack after fixing a weak cell. A balance charger ensures that each individual cell in the pack receives an equal amount of charge during charging, which helps prolong overall lipo battery life span.

Replacement Cells (if necessary)

If one or more cells in your lipo battery are dead or beyond repair due to permanent damage such as swelling or puncture, then they must be replaced with new cells. Replacement cells must be identical in terms of type (such as LiPo), capacity (mAh), voltage (V), discharge rate (C), and size (dimensions).

Safety Gear

It is important to wear proper safety gear when working with lipo batteries. This includes gloves, eye protection, and a fireproof surface to work on. Lipo batteries are flammable and can cause serious burns or fires if not handled carefully.

Having all the necessary tools and materials will ensure that you are able to safely and effectively fix a lipo battery with one weak cell. It is important to have a good understanding of each tool’s function before beginning any work on the battery.

Step-by-Step Guide to Fixing the Weak Cell

Step 1: Disassemble the Lipo Battery Pack

To begin the process of fixing a lipo battery with one weak cell, the first step is to disassemble the battery pack. Carefully remove all of the outer packaging from around the cells, including any plastic wrap or shrink tubing. Keep in mind that some batteries may be glued together, so you may need to use a gentle heat source such as a hairdryer to loosen any adhesives.

Once you have removed all of the outer packaging, separate each cell from one another and lay them out in a safe location. Make sure you keep track of which way each cell was oriented within the package so that you can reassemble it correctly later on.

Step 2: Identify Which Cell is Weak Using the Multimeter

Using a multimeter set to measure voltage, test each individual cell to determine if any are weaker than others. Cells with voltages lower than 3.0 volts are considered weak and should be replaced immediately.

To test each cell, place one multimeter probe on its positive terminal and another on its negative terminal. Read and record each voltage measurement for future reference.

Step 3: Remove The Weak Cell From The Pack

Once you have identified which cell is weak, it’s time to remove it from the battery pack. Use a soldering iron with a thin tip and carefully desolder all connections that attach this weak cell to adjacent cells in your pack. Take extra care not to damage any surrounding cells during this process as they can be easily damaged by excessive heat or careless handling.

Step 4: Replace The Weak Cell With A New One (If Necessary)

If necessary, replace your weak lipo battery with a new one. Make sure the new battery has the same voltage and capacity as the others in the pack. Be sure to match the polarity of your new cell with that of the other cells in your battery pack, or you risk damaging both your battery and any connected electronics.

Step 5: Re-Solder All Connections

Once you have replaced any weak cells, it’s time to reassemble your lipo battery pack. Solder all connections carefully, making sure all positive and negative terminals are connected properly. Take extra care not to create short circuits during this process as they can be dangerous and may even damage your newly replaced cells.

Step 6: Reassemble The Pack

Once all connections have been made, reassemble your lipo battery pack using tape or shrink wrap. Be sure to wrap each cell separately before reassembling it into a final assembly.

Step 7: Charge And Balance The Pack Using A Balance Charger

The final step is to charge and balance the newly fixed lipo battery using a balance charger. This will ensure that each cell in the pack is properly charged and balanced so that they all discharge at roughly the same rate during use.

A fully charged lipo battery should read around 4.2 volts per cell, although some chargers may vary slightly from this norm. Be patient throughout this charging process, as it can take several hours for a full charge depending on how depleted your batteries were before beginning this process.

Tips for Maintaining Lipo Batteries

Understanding the Importance of Battery Maintenance

One of the most important things you can do to prolong the life of your lipo battery is to maintain it properly. By following some simple guidelines, you can avoid many of the common problems that plague lipo batteries.

The key to proper maintenance is to understand how your battery works and what factors can affect its performance. For example, overcharging, undercharging, or storing your battery at an incorrect voltage can all cause damage that reduces its capacity and shortens its lifespan.

Charging and Discharging Your Lipo Battery

One of the most important aspects of maintaining a healthy lipo battery is charging and discharging it correctly. Overcharging or undercharging your battery can cause significant damage over time, so it’s essential to use a high-quality balance charger that’s capable of properly charging each cell in your pack.

In general, you should aim to charge your lipo battery at a rate that is no more than 1C (the capacity rating in amp-hours of the pack). Discharge should be kept below 80% and balanced regularly if not using for an extended period (more than a few weeks).

Storing Your Lipo Battery

How you store your lipo batteries is also crucial for maintaining their health. Ideally, you want to keep them in a cool, dry place where they won’t be subjected to extreme temperatures or humidity.

When storing batteries long term (more than several weeks), they should be stored at around 40% charge which has been shown by studies as preserving their longevity. Otherwise after storage for months they may have swelled cells inside from degradation.

Handling Your Lipo Battery Safely

Lithium polymer batteries are volatile and can pose significant risks if mishandled. The most common risk is fire, which can occur if the battery is punctured, overheated, or damaged in any way.

To minimize the risk of fire or other damage, it’s important to handle your lipo batteries with care. Ensure you do not puncture the battery and avoid heating them to more than 60°C when charging or discharging.


With proper maintenance and care, a lipo battery can last for years without any issues. By following these simple tips on maintaining and handling your battery pack, you’ll be able to enjoy longer run times and better overall performance from your RC equipment.

Remember to always use a high-quality charger designed for lipo batteries and store them in a cool dry place when not being used. Additionally, handling the battery with care will ensure its longevity.