Hi acracing16,
We see you have a question about your battery and that you've already checked out the maximum capacity. When you check Settings > Battery > Battery Health, does it mention anything about performance management being enabled? iPhone Battery and Performance - Apple Support
"Preventing unexpected shutdowns
With a low battery state of charge, a higher chemical age, or colder temperatures, users are more likely to experience unexpected shutdowns. In extreme cases, shutdowns can occur more frequently, thereby rendering the device unreliable or unusable. For iPhone 6, iPhone 6 Plus, iPhone 6s, iPhone 6s Plus, iPhone SE (1st generation), iPhone 7, and iPhone 7 Plus, iOS dynamically manages performance peaks to prevent the device from unexpectedly shutting down so that the iPhone can still be used. This performance management feature is specific to iPhone and does not apply to any other Apple products. Starting with iOS 12.1, iPhone 8, iPhone 8 Plus, and iPhone X include this feature; iPhone XS, iPhone XS Max, and iPhone XR include this feature starting with iOS 13.1. The effects of performance management on these newer models may be less noticeable due to their more advanced hardware and software design.
This performance management works by looking at a combination of the device temperature, battery state of charge, and battery impedance. Only if these variables require it, iOS will dynamically manage the maximum performance of some system components, such as the CPU and GPU, in order to prevent unexpected shutdowns. As a result, the device workloads will self-balance, allowing a smoother distribution of system tasks, rather than larger, quick spikes of performance all at once. In some cases, a user may not notice any differences in daily device performance. The level of perceived change depends on how much performance management is required for a particular device.
In cases that require more extreme forms of this performance management, the user may notice effects such as:
- Longer app launch times
- Lower frame rates while scrolling
- Backlight dimming (which can be overridden in Control Center)
- Lower speaker volume by up to -3dB
- Gradual frame rate reductions in some apps
- During the most extreme cases, the camera flash will be disabled as visible in the camera UI
- Apps refreshing in background may require reloading upon launch"
Let us know what you find. Take care.
