battery percentage

What is your battery health?

Go to Settings > Battery > Battery Health to find out. If it's near or less than 80%, it's time to change your battery.

iPhone Battery Repair & Replacement - Apple Support

Hello,

There is no way to disable this alert, but I did come up with a method to prevent the popup using Shortcuts. 

In the Shortcuts app, create a new personal automation in the automation tab. Make the trigger battery level, when the battery level falls below 25%. Then set the action to turn low-power mode on. Now, when your battery level falls low, your iPhone will automatically enter low power mode and not show the prompt!

I hope this helps, and if you need a more detailed explanation, please let me know.

Thanks for reaching out!

-Drake