Your Apple Watch is designed to deliver an experience that is simple and easy to use. This is only possible through a combination of advanced technologies and sophisticated engineering. One important technology area is battery and performance. Batteries are a complex technology, and a number of variables contribute to battery performance and related Apple Watch performance. All rechargeable batteries are consumables and have a limited lifespan—eventually their capacity and performance decline. As batteries age, it can contribute to changes in Apple Watch performance. We created this information article for those who would like to learn more.
About lithium-ion batteries
Apple Watch batteries use lithium-ion technology. Compared with older generations of battery technology, lithium-ion batteries charge faster, last longer, and have a higher power density for more battery life in a lighter package. Rechargeable lithium-ion technology currently provides the best technology for your device. Learn more about lithium-ion batteries.
How to maximize battery performance
“Battery life” is the amount of time a device runs before it needs to be recharged. “Battery lifespan” is the amount of time a battery lasts until it is no longer useful. One factor affecting battery life and lifespan is the mix of things you do with your device. No matter how you use it, there are ways to help extend your device’s battery lifespan. A battery’s lifespan is related to its “chemical age,” which is more than just the passage of time. It includes different factors, such as the number of charge cycles and how it was cared for. Follow these tips to maximize battery performance and help extend battery lifespan. For example, keep Apple Watch half-charged when it’s stored for the long term. Also avoid charging or leaving Apple Watch in hot environments, including direct sun exposure, for extended periods of time.
When batteries chemically age
All rechargeable batteries are consumable components that become less effective as they chemically age.
As lithium-ion batteries chemically age, the amount of charge they can hold diminishes, resulting in shorter amounts of time before a device needs to be recharged. This can be referred to as the battery’s maximum capacity— or, the measure of battery capacity relative to when it was new. In addition, a battery’s ability to deliver maximum instantaneous performance, or “peak power,” may decrease. In order for Apple Watch to function properly, the electronics must be able to draw upon instantaneous power from the battery. One attribute that affects this instantaneous power delivery is the battery’s impedance. A battery with a high impedance may be unable to provide sufficient power to the system that needs it. A battery's impedance can increase if a battery has a higher chemical age. A battery’s impedance will temporarily increase at a low state of charge and in a cold temperature environment. When coupled with a higher chemical age, the impedance increase will be more significant. These are characteristics of battery chemistry that are common to all lithium-ion batteries in the industry.
When power is pulled from a battery with a higher level of impedance, the battery’s voltage will drop to a greater degree. Electronic components require a minimum voltage to properly operate. This includes the device’s internal storage, power circuits, and the battery itself. The power management system determines the capability of the battery to supply this power, and manages the loads in order to maintain operations. When the operations can no longer be supported with the full capabilities of the power management system, the system will perform a shutdown to preserve these electronic components. While this shutdown is intentional from the device perspective, it may be unexpected by the user.
Battery and performance management
Apple Watch Series 5 has new built-in software and hardware systems that help reduce performance impacts that may be noticed in certain conditions such as a battery with a low state of charge, a high peak power situation, or a chemically aged battery. The system is automatic, always-on, and works to provide the best possible performance of the Apple Watch Series 5. Power needs are dynamically monitored, and performance is managed to address these needs in real time. The system allows Apple Watch Series 5 to balance and reduce performance impacts as much as possible. The user may or may not notice effects on device, which may be temporary. Depending on the device battery state and the tasks that your Apple Watch is handling, some examples of these effects may include longer app launch times, lower frame rates, reduced wireless data throughput, screen dimming, lower speaker volume, or missing heart rate data during a workout.
If your device performance has been impacted by an aged battery and you would like to get help with a replacement Apple Watch, contact Apple Support.