Message about my battery

Kindly reach out to the Store/Individual/Agency from whom you acquired your iPhone 11. They would be best equipped to confirm whether the device has undergone servicing by an unauthorized service provider.

In case you recall not encountering this message at the time of purchase and it surfaced after an update, it's important to note that this message is visible specifically on iOS 15.2 and subsequent versions. It might be beneficial to inquire about any recent updates or changes made to the device's software configuration that could have triggered this notification.

Understanding the circumstances surrounding the appearance of this message could provide insights into any alterations in the device's service history or software updates that have brought about this notice.

Parts and service history

With iPhone 11 models and later, excluding iPhone SE (2nd and 3rd generation), using iOS 15.2 and later, you can go to Settings > General > About for the parts and service history of your iPhone. You can also find out if the display has been replaced. If the repair was done using genuine Apple parts and processes, "Genuine Apple Part" will appear next to Display.

• An Unknown Part  message will appear if the display installation is incomplete or if the display:
• Was replaced with a nongenuine display
• Was already used or installed in another iPhone
• Isn't functioning as expected

An additional message might appear that says "Apple has updated the device information for this iPhone." This means that Apple has updated the device information maintained for this iPhone for service needs, safety analysis, and to improve future products. 

These messages don't affect your ability to use your iPhone.

Learn more about iPhone parts and service history.

The only way to get the notification removed is by replacing the ingenuie parts with a genuine Apple Parts through an Apple Authorised Sercvice Center.

Take your device to an Apple Retail Store or Apple Authorized Service Provider, or contact Apple Support:

Apple Repair and Repair Status Check - Official Apple Support

Apple Authorized Service Provider

Find Locations - Location Selector - Apple

Contact Apple for support and service - Apple Support 

Tornado_0323 Said:

"Message about my battery: Completed update and got alert that there may be a battery issue"

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Provide a Screenshot of this Message:

So what does the message read? Providing a screenshot of that message would most certainly help: Take a Screenshot on iPhone - Apple Support

Troubleshooting iPhone Battery Draining:

A. Battery Drain Info:

The iPhone battery will drain, unless it is plugged in and charging. With lots installed, the charge would be slower. As for how fast it would drain the battery, that would depend on the battery health and the volume (sound) you use.

1. Go Here: iPhone Battery and Performance - Apple Support
2. Scroll Down: to "Your battery's maximum capacity"

B.. Troubleshooting the Battery:

• iPhone Battery and Performance - Apple Support

• Charge and Monitor the iPhone Battery - Apple Support

• About the Battery Usage on your iPhone - Apple Support

• About Optimized Battery Charging on your iPhone - Apple Support

• If you see "Your iPhone Battery may Need to be Serviced" - Apple Support

• Use Low Power Mode to Save Battery Life on your iPhone - Apple Support

C. Give Apple Feedback:

Do your Part: Provide Apple with feedback on this, letting them know about this issue.  Apple may not get back to you directly, but the more feedback they receive on this, the more they will know what is occurring, and what bug fixes to include in updates to come.

1. Go Here: Feedback - iPhone - Apple
2. Select: "Bug Report" for the "Feedback Type"
3. Comment: that this all began after installing an update. Include the URL of this post
4. Proceed from there as necessary