After using your smart watch for a certain period of time, the performance of your smart watch may decline due to the chemistry change in the battery. You may notice that your battery cannot last as long as it used to. This article will walk you through the circumstances under which you should replace the watch battery, and provide you a detailed step-by-step guide on how to replace watch batteries.

 

Importance of Lithium Batteries in Smart Watches

Provide energy guarantee: Smartwatches are rich in functions, such as real-time monitoring of heart rate, blood pressure, exercise data, etc. They also have the functions of receiving notifications, making calls, playing music, etc. The realization of these functions all requires power support. Lithium batteries can provide a stable power supply for smartwatches, ensuring their normal operation.

The design of smartwatches aims for compactness and lightness to ensure comfortable wearing. Lithium batteries have a high energy density, meaning they can store a considerable amount of electrical energy in a relatively small volume and weight. This enables smartwatches to obtain sufficient energy supply without significantly increasing their volume and weight, meeting the strict requirements of smartwatches for space and weight.

Ensure long battery life: Users hope that smartwatches can be used for a long time without frequent charging. The performance of lithium batteries directly affects the battery life of smartwatches. High-quality lithium batteries can enable smartwatches to work continuously for several days or even longer after a single charge. For instance, some smartwatches that adopt advanced lithium battery technology have significantly enhanced their battery life, providing convenience for users and reducing the trouble caused by frequent charging.

Ensure fast charging: Lithium batteries support fast charging technology, which can charge a large amount of power to the smartwatch in a short time, allowing the watch to be quickly restored to use. This is very important for users, especially when they are out or in an emergency. The fast charging function can ensure that the smartwatch is always available.

When Should You Replace a Watch Battery?

Most smartwatches will prompt "Battery health has declined" or "Suggested repair" when the battery health drops below 80%.

1.Significant decrease in battery life
The most obvious sign of battery aging in a smartwatch is a significant reduction in battery life. For instance, if your watch could have been used normally for 3 to 5 days when fully charged, but now it can only last for a few hours, even under normal usage conditions, it might be due to a decline in battery performance and you need to consider replacing it. It even suddenly shuts down when the battery level shows 30%-40%.

This situation is usually due to the fact that after long-term charge and discharge cycles, the chemical activity of lithium-ion batteries decreases, resulting in a decline in their power storage capacity. Generally speaking, the battery life of a smartwatch is about 2 to 3 years (or approximately 500 complete charge and discharge cycles). If the usage frequency is high or it is often charged in extreme temperature environments, the battery will deteriorate at a faster rate.

2. Difficulty in charging or extremely slow charging speed
If you notice the following problems when charging your smartwatch, it might be a signal that the battery needs to be replaced:

The charging time has been significantly extended: it used to take 1-2 hours to fully charge, but now it takes 3-4 hours or even longer.

Poor contact: It is necessary to repeatedly adjust the position of the charging base or charging cable before starting charging. After ruling out the charger fault, it may be due to aging of the battery interface or battery expansion causing poor contact.

When charging, if the battery level does not increase but decreases instead: After plugging in the charger, if the percentage of battery level does not rise or even continues to drop, it indicates that the battery can no longer store electricity normally.

3. The watch is not functioning properly
Some functions of the watch, such as heart rate monitoring, GPS positioning, and Bluetooth connection, may not work properly, or it frequently experiences lagging or freezing during use. This could be caused by unstable battery power supply.

When the battery performance deteriorates severely, it may not be able to provide a stable voltage output for the watch, causing the device to suddenly shut down during operation, especially when performing high-power operations such as GPS positioning and sports mode monitoring. In addition, some watches may frequently restart when the battery is low (such as 20%-30%), which is a typical manifestation of unstable battery voltage.

4. Battery swelling or abnormal appearance
If you notice that the back cover of your watch is bulging, the gap between the cases is widening, or the back cover gets abnormally hot during charging, it might be due to battery swelling (commonly known as "bulging"). When lithium-ion batteries are overcharged or discharged, exposed to high temperatures or physically damaged, the internal electrolyte decomposes and generates gas, causing the battery to expand in volume. This situation is extremely dangerous and may cause leakage or combustion. Use must be stopped immediately and the battery replaced.

5. The system indicates that the battery health condition is poor
Some smartwatches (such as Apple Watch and some Wear OS devices) will issue a warning when the battery health is lower than 80%, indicating "The battery needs repair" or "the battery life has significantly decreased". This type of notification is based on the test results of the battery management system (BMS) by the manufacturer and has a relatively high accuracy. It is recommended to handle it in a timely manner.

How to Replace a Watch Battery

Take Fitbit Sense 2 as an example.
First of all, choose a dust-free and clean environment. Because the internal structure of a watch is complex and precise, even the slightest dust or fiber can affect its timekeeping. Before replacing the battery, it is recommended to clean the watch body and remove the fitbit sense 2 bands. When opening the back cover, clean the dirt in the gap of the cover.

The gap between the Fitbit Sense display and the watch case is very thin and lined with adhesive. Therefore, it needs to be heated vigorously, and then the back cover should be pried open with a plastic sheet. Then carefully remove the ribbon cable and separate the upper and lower parts. There are screws on the green motherboard. Remove the screws as well. Pry open the green motherboard. The battery is right beneath it

When replacing the battery, put insulating finger cots on your thumb and index finger to avoid direct contact of your fingers with the battery. Gently pull it out with a screwdriver or a needle, remove the old battery and replace it with a new one. The battery can be directly removed. If the side of some battery slots is surrounded by metal and cannot be pushed apart, do not force it.

After the battery is replaced, you can apply waterproof paste. Evenly apply a small amount of waterproof paste to the waterproof gasket on the back cover of the watch. Be careful to control the amount used and do not apply it to the battery. Waterproof paste plays an auxiliary and enhancing role in waterproofing. If you find that the waterproof ring is aged, hardened or loose, be sure to replace it in time by yourself. When closing, be careful to press with both thumbs at the same time. Make sure the position is appropriate and the force is even. Generally, it can close smoothly. If it really cannot be closed, do not force it. Do not bite or strike with a hammer. You can purchase a capping tool by yourself or find a professional watch repairman.

Conclusion

Seeking help from a professional technician may cost you both time and some money. Actually, with necessary tools and methods, it’s entirely possible to do it yourself. We hope this passage can help you understand how to replace watch batteries safely and effectively.